Properties of Zamak components for the textile industry

 In previous posts in this blog we described the properties of Zamak for the application in different industries, including: lighting, building, electronics, electromechanical, household appliances. As we have already observed, the chemical and physical properties of the raw material and the surface and finishing treatments to which the components can be subjected therefore make Zamak a versatile material, capable of satisfying various types of aesthetic, mechanical or safety requiremensts. For applications on textile machineries also.

The properties required to Zamak components for textile machineries are mainly mechanical: the components must be able to dampen the vibrations of the machinery on which they are installed, to resist the strong wear caused by the sliding of the wires on them and they must have, already during the casting phase as to reduce costs, a precision with very narrow tolerances of the shapes.

In this sector of application also, the fluidity of Zamak is therefore fundamental because it allows to obtain a high degree of detail and complex shapes directly during the casting phase. Moreover, it is also fundamental the excellent surface quality of the Zamak die casts.

Let’s now see in detail these three characteristics of Zamak that are so important for textile machineries components.

Anti-vibration property

 In the textile industry Zamak components are employed in rotor spinning with a single spinning head technology: a technology that can overcome the limits of belt drive and in which the use of antivibration materials is essential. Textile machineries of this kind can in fact have rotor rotation speeds up to 180K revolutions per minute, with an output speed of up to 300K thousand revolutions per minute. This is why it is fundamental to employ HIDAMET (High Damping Metals) raw materials, such as zinc alloys, to make components subjected to this kind of stress. Zinc alloys, in fact, have an excellent damping capacity and this is why they prove to be a perfect choice for this field of application.

To find out more on the anti-vibration properties of zinc alloys we suggest to read the essay of I. Ritchie, Z. Pan e F. Goodwin, Characterization of the damping properties of die-cast zinc-aluminum alloys that can be found here.

Wear resistance

 Wear resistance is a fundamental requirement for components installed inside textile machineries. The sliding of the yarn on the component in fact subjects it to strong stresses which, over time, could damage it by eroding it.

Wear resistance in Zamak components is achieved through different strategies. First of all, the die-casting technology with which the zinc alloys are treated allows to obtain a surface layer, called “foundry skin”, of about 0,2-0,3 mm. The dense fine-grained microstructure of the “foundry skin” gives the zinc components a wear-resistant surface, as reported in the table below.

The tests were conducted on cylindrical specimens of 15 mm in diameter pressed on a hard cast iron disk, dampen with water carrying fine sand with a variable load. After a number of turns corresponding to a path of 10K cm, the thickness of the removed layer is measured. The value, expressed in tenths of a millimeter, provided the relative abrasion data. Zamak alloy, in the conditions in which the tests were carried out, is less consumable than ordinary brass while it is lower only than the 90/10 bronze. (The reported data derive from: L. Andreoni, Quaderno della colata a pressione delle leghe di zinco, Le leghe di zinco, Zama, ed. Edimet, Brescia, 1998).

Another strategy to increase the resistance of Zamak components for textile machineries is to subject them to specific surface treatments. In this case the components are placed on a tray immersed in a chemical bath where, thanks to the rotation given to the tray, they are able to absorb the chemical agent which, depositing itself on the surface, turns into a protective coating.

Possibility to obtain complex shapes and surface quality

The fluidity of Zamak allows to fill even the smallest cavities of the mold obtaining, already during the casting phase, small details and complex shapes. This property proves to be fundamental in an industry, such as the textile industry, in which the tolerances are very narrow and the components, to fulfill their mechanical function, are assembled together.

To deepen your knowledge on these themes we suggest you to read Thin walls thickness: a competitive advantage in zinc die casting.

Surface quality is also an important requirement for components intended for textile machineries. In fact, surface defects such as irregularities, bubbles or burrs could damage the yarn breaking it. Even in an industry such as the textile industry, where the requirements for the components are mainly mechanical, the possibility of obtaining an excellent surface quality directly during the casting phase and of being able to carry out various types of treatments and processes is therefore important.

To find out more on the surface treatments that is possible to carry out on Zamak components we suggest to read Coating, plating and other kind of surface treatments and Processing techniques for metal finishing.

Review of Zamak components for textile machineries

After analyzing the charateristics that make Zamak an excellent raw material for the production of components for the textile sector, let’s now examine some products that allow us to shed further light on the applications of zinc alloy die casting useful in this sector.

Adapter

The adapter is part of the spinning unit of rotating frames. In detail, it is installed on the machines that produce the type of cotton thread called “open end”: a thread intended for thick fabrics such as those of jeans or some shirts and which is opposed to the finer thread that is obtained in two phases, a first phase in which short pieces are made and a second in which the pieces are spliced generating an endless thread.

The component is placed in series on machines with 300/500 units, each independent in the production of cotton thread starting from cotton that is washed and centrifugated in order to make it homogeneous.

All the properties illustrated above are fundamental for this component: the anti-vibration property allows to dampen vibrations and it prevents the thread from slipping, the wear resistance allows the surface not to deteriorate, the fluidity of Zamak allows to obtain, directly during the casting phase, the details that are visible in the image of the post while the surface quality proves to be fundamental for keeping the yarn intact.

Feed Tray Bracket

Feed tray brackets are component derived from the assembly of two articles: feed table and holder.

Both the feed table and the holder have holes inside which magnets are installed, the assembly is therefore possible by magnetic force. The feed tray bracket, differently from the adapter, does not come in direct contact with the yarn and for this reason no particular surface qualities or resistance to wear are required. Zamak, in this case, was chosen for two fundamental reasons: the anti-vibration property and the possibility of obtaining a high degree of detail directly during the production phase.

The anti-vibration property is essential because the component is inserted in a jack rotating at 180K revolutions per minute and, if not able to dampen vibrations, it would risk hitting the other components with which it is in contact causing damage and breakage. The possibility of obtaining a high degree of detail results important for the making of the features of the object, such as, for example, the housing of the magnets that allow the assembly of the article.

Conclusions

In this post we analyzed some Zamak components that can be made for textile machineries, solutions that allow to illustrate the properties of zinc alloys and that result as a winning choice for this kind of mechanical applications.

For more information and updates subscribe to our blog, if you wish to consult our technical office to find out more applications of zinc alloy die cast components for the textile sector fill out the form.

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Introduction

In a previous post we discussed the importance of the metrology laboratory in a zinc alloys die casting productive plant. The metrology laboratory, in fact, assures the quality of the products throughout the production chain by guaranteeing the compliance to the requirements of the customer from a dimensional, structural and chemical point of view. The activities of the metrology laboratory described in the post Dimensional measurement: production control and reverse engineering are:

– Constant monitoring of each production cycle
– Fast checks of new projects and sampling
– Checks of projects that have undergone changes over time
– Control of parts incoming from external suppliers
– Reverse engineering, both on the product and the mold

To deepen these themes, we suggest you to read the post.

In this post we will instead examine different devices paying special attention to the need to choose the most appropriate tool on the basis of the characteristics and the requirements of the product.

Importance of the metrology laboratory

The presence of a metrology laboratory in the production plant is not enough to guarantee the quality of the products: in fact, this result can only be achieved through the employment of appropriate tools for the component to be tested. The set of devices must be up-to-date, advanced and comprehensive of different technologies, in order to allow the minimization of risks that is necessary to meet the requirements of the customer.

This is particularly true in a plant that employs zinc die casting technology for products intended for different market sectors: the variety of products corresponds to a diversification of the tools and of the technologies that the metrology laboratory needs in order to carry out its analysis.

To be specialized in different market sectors allows the competences acquired in a sector to be transferred in another and this is also true for the tests of the metrology laboratory. The choice of the tool in fact is not only determined by the requirements of the customer or by the necessary documentation in the different stages of a project, but it is also defined by the necessity to obtain the most indicative and effective data for the assessment of the compliance of a component with the design standards. The expertise acquired in the measurements of the components intended for a sector can then be transferred to the analysis that are necessary in another sector with advantages that affect the entire production chain.

The tools of the metrology laboratory

After depicting the importance of the metrology laboratory let’s now analyze the tools that allow the metrology tests to be complete and effective.

Industrial computed tomography

The technology of industrial computed tomography, referred to zinc alloys die casting, has a double usefulness. In fact, it allows defect analysis on the internal structure of the components aimed at detecting defects in the internal distribution of the material and thus at identifying porosity and air inclusions. Moreover, thanks to tomographic analysis, it is possible to evaluate the success of the assembly of components. In the case of the assembly of different materials the tomographic analysis allows a functional evaluation of the clearances between assembled parts and the verification of the absence of flaws such as air inclusions or deformations.

3D Scanner

3D Scanner is particularly suitable in the case of components with complex shapes. The device is less accurate than a Coordinate Measuring Machine (CMM), but it allows the capture, without contact, of all the visible surface of the measured object and it makes the comparison with the theoretical model possible. For this reason, whereas a test with CMM would be too time-consuming for the necessity of a complete reconstruction of the shape of the object, the 3D scanner allows the result to be obtained rapidly and effectively.

CMM

In a metrology laboratory CMM is surely the most common technology. The machine allows the selection of the desired areas and the execution of very accurate checks to be performed. For this reason, it is particularly suitable for the measurement of elements of components with simple shapes for which the tolerances are very narrow. However, the CMM does not guarantee the same results with different materials. In the case of zinc alloys, it is particularly suitable because the metal, differently from other materials such as plastics, does not run the risk of deforming during measurement.

Polyworks

Polyworks is the Innovmetric software that allows the tools of the metrology laboratory not only to be complete, but also complementary. What previously said about CMM and 3D scanner must not suggest that, during testing, a measurement method is to be chosen rather than another one. In fact, thanks to the software, it is possible to make the acquired data interact and to overlap the measurements of the 3D scanner with those of the CMM. For this reason, the software, allowing different data to interconnect, makes it possible to the metrology laboratory to unify its technologies for a complete and detailed final result.

UTM Machine

The Universal Testing Machine is the device employed in order to test tensile and compressive strength of a component. It is a very versatile machine that makes it possible to perform different kinds of tests on a wide range of materials and components. For example, concerning tests on zinc alloy die casts, the UTM is fundamental to work with the automotive sector. The verification of the resistance of products intended for this sector is in fact a fundamental part of the documentation that is necessary for the approval and the good outcome of projects.

In-line machine for the 100% dimensional control of production

This in-house designed and developed machine is intended to the verification of the compliance with the dimensional tolerances of automotive components. The device uses a camera for the detection of dimensions, volume and superficial quality of the components and a profilometer. The profilometer, thanks to laser technology, allows the reconstruction of the profile of the measured component and it is particularly useful for the reconstruction of the profile of complex shapes such as threads.

Other devices

Eventually, other common but fundamental devices in a Zamak die casts productive plant are the spectrometer, the density scale and the electronic microscope. The spectrometer allows the chemical composition of Zamak to be analyzed and it is of fundamental importance when, on the same machine, the mold is changed, and we move from the production of a component to that of another in different alloy. Thanks to the spectrometer in fact it is possible to verify that Zamak bath is concluded and that all the material employed in the process is the new one. The density scale is used to verify the compactness of the component and to exclude the presence of air inclusions or other similar flaws. Finally, the microscope makes it possible to detect superficial defects that would not be identifiable at sight, proving to be a valid aid in detecting cold laps, laminations, cracks and lakes.

For further information on the most common die casting defects we suggest you to read the article Die casting defects: internal and superficial.

Other tests

The various tests carried on in a metrology laboratory are aimed at measuring the dimensions of the components, their weight, the internal distribution of the material and their resistance. Moreover, other kinds of tests can be carried out, such as for example salt spray testaimed at evaluating the resistance of the component to environmental corrosion or the leak test that through the employment of dedicated tools, aims at verifying the absence of air inclusions in the component.

Conclusions

With this brief overview on the tools of the metrology laboratory we wanted to focus the attention on the importance of this department.

If you are interested in this theme and you want to be updated on the news of the sector we suggest you to visit Metrology News web site, an important online review rich in information on metrology tools and their employment in different industrial sectors.

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Products have been chosen on the basis of different principles: we privileged variety, selecting components that are produced for different sectors and complexity, in order to communicate our expertise and competence in satisfying the client’s requests.

Here the list of the videos:

• Die casting for household appliances: coffee machines
• Die casting for automotive: electronic steering wheel lock
• Die casting for automotive: sunroofs
• Die casting for building industry: windows and doors
• Die casting for household appliances: hinge for washing machines

Let’s give the floor to our experts.

Die casting for household appliances: coffee machines

In this video we show the production of a component for coffee machines and we describe the technical solutions implemented to obtain a perfect chrome finish.

This product is the bottom section of a coffee machine for the consumer market. It is an aesthetic component that comes into view and in contact with the end customer: for this reason there are specific technical and quality aspects to consider. During analysis stage, indeed, we have faced technical and process difficulties caused by the particular shape of the component, which could invalidate the requested standards thus reducing the quality of chrome finish.

It is exactly the particular geometry of the piece that does not allow the working of the internal surface and it is for this reason that, after careful analyses of the production process and considerations on the shape of the component, we decided to obtain a surface that was suitable for chroming process already after casting phase.

In order to reach this aim we have undertaken virtual and physical prototyping and simulation activities that have allowed the definition of optimal parameters for the production of the component. Thanks to simulation and prototyping we have identified two properties on which we have specifically focused our attention: roughness and surface quality. To achieve the expected result already during casting stage we tried to take the most out of production parameters. The lapping of the mold has been the chosen solution to obtain surface roughness already during casting phase; simulation and tests during production phase allowed us to modify the mold in order to obtain the requested surface quality and standards.

The adoption of these technical solutions and the modified parameters have therefore allowed us to obtain a product suitable for polishing and chroming treatments.

The polishing stage is carried out on still rough pieces, whose external surface is smoothed so that the subsequent chroming process has a good result. The next stage is indeed chroming phase. Chroming process is an aesthetic galvanic process that gives to the die cast a charming and protective aspect: the chrome surface, indeed, protects against corrosion. It is a process composed of various passages where the products are immersed in aligned tanks to receive sequentially processes of degreasing, copper plating, nickel plating and chromium plating. It is this final stage that gives, thanks to the extremely brilliant aspect, an important added value to the component, making it a distinctive element of coffee machines.

Die casting for automotive: electronic steering lock

In this video we present an automotive component whose mold has been designed in an unconventional way and on which it has been introduced an automatic threading system.

This component of the electronic steering lock has required an unconventional mold design because it is characterized by a complex shape. Indeed, the inner section of the product, which is designed to hold an electronic card and to contain sliding parts, has caused the main difficulties in mold design. Therefore, the structural complexity of the component, connected with the production process, has determined the necessity to obtain a considerable level of accuracy during mass production.

Considering that the product is designed to internally contain an electronic card and further functional elements, it is necessary the total lack of die casting defects (for example burrs) that could compromise the functionality of the product or of the elements inside the component. In order to achieve the requested precision and quality standards, mold has therefore been designed with an unconventional approach. The configuration with which it has been designed is indeed the opposite of the traditional one. The piece is picked up by its external part and not by the internal part as it usually happens: in this way we avoid both burrs and extractors in the internal part of the product.

After the optimization of mold design we also introduced during production cycle an automatic system for threading. This system, integrated into casting area, allows both the cutting of sprue runners and the simultaneous threading of two M8 holes. There are two important benefits that result from the implementation of this system: first of all we avoid manual operations (so the operator is free to deal with activities with greater added value) and, moreover, we obtain productive efficiency and continuity, with a resulting cost and time saving. Die casting technology, in particular die casting for electronic steering lock, thanks to our innovative approach and to the technical expertise of our engineers, constitutes a great choice for the production of automotive components because it ensures production accuracy also for the most complex products.

Die casting for automotive: sunroofs

In this video we present a component for automotive industry characterized by very close tolerances and complex geometries.

This part is a component for car sunroofs that has a complex shape and is characterized by very thin areas. Therefore it requires a high level of detail and accuracy. To meet the requests of the costumer we have adopted specific technical solutions that have assured the functionality of the piece and, at the same time, have allowed us to obtain a product free of every minimal deformation.

These solutions have been implemented in mold design phase and during the simulation of the filling flow, while the implementation of the injection channel, tilted sliders and ejectors has been managed in every detail to achieve complex shapes. For the simulation we have used Magmasoft software, which has allowed us to optimize filling flows in the entire die cast and in particular in the thinnest areas. The outcome has been a uniform and homogeneous filling. In addition, to increase even more the accuracy of the result, we have employed the vacuum technology, a tool designed and realized here in Bruschi to guarantee dimensional stability.

The technical solutions devised by the engineers have allowed us to achieve a product that has excellent technical features, compliant with our production process and that meets the complete satisfaction of the costumer. For the automotive industry, in this case for the production of sunroofs components, die casting technology allows the achievement of products with close tolerances and complex shapes that fully meet strict standards of the sector.

Die casting for building industry: windows and doors

In this video we show the production of the cover of the opening and closing system for windows and doors.

The component is part of the opening system for windows and doors: so it is characterized by functional and aesthetic properties. On the one hand, the functional properties are determined by the fact that the component contains in its inside other elements of the opening system. The aesthetic properties, on the other hand, derive from its nature of external element that comes in contact with the end costumer. For this reason the piece must have an optimal surface quality.

Therefore, to design and produce this component, we have considered various different aspects and we have found solutions able to ensure aesthetics and functionality. As regards aesthetics we focused on avoiding the formation of air entrapments in the die cast to obtain a surface suitable for powder painting. To obtain this kind of surface quality we used simulation software and the vacuum valve: these solutions permitted us to reduce painting scrap from 30% to about 0%. Concerning the functionality, instead, we have developed in collaboration with the costumer a re-design activity of the internal part of the component, aimed at reaching thin wall thickness that would maintain the properties of the product unchanged. Thin wall thickness, in windows and doors opening system, are important because the component has in its inside the fixing and the sliding system of opening mechanism and the reduction of thickness improves its functionality. The benefits provided by the reduction of thickness are considerable and concern less quantity of raw material and cycle time reduction. However, the production of the component does not confine itself to casting process. Indeed we have designed and realized an automation for the threading of 6 M5 holes. The threading phase is immediately after casting stage: the product passes through a vibrating device and after on a rotating table with three threading stations. The implementation of this automatic threading system has resulted in a considerable reduction of timing of the secondary processes.

Years of experience in die casting for windows and doors, technical skills and know how, have made it possible to produce a component characterized by specific aesthetic and functional properties and able to satisfy the costumer’s requests.

Die casting for household appliances: hinge for washing machines

In this video we show the production of the hinge for washing machine and the technical solutions adopted to guarantee the functionality of the product.

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The connection between the injection system and the shot entry is composed of two main elements: the feed and the runner. Their structure and size have a crucial impact on the casting flow, since different shape can bring about different results and help in reducing the risk of defects in the die casted product.

Runner positioning

To define the ideal position of the runner it is necessary to keep in mind that molten metal should cover the shortest distance possible to avoid premature cooling. Because of this, it is usually suggested to direct the flow towards the smallest side of the cavity, or to take advantage of ribs and branches to ease cavity filling. When dealing with more than one shot entry, it is important that flows are not convergent, since that would cause an energy loss and the formation of turbulences and air trappings: therefore, it is best to design the runner to obtain parallel or divergent flows.

Runners position it is also crucial to keep under control the distribution of shrinkage porosity. It is impossible to avoid porosity, but it is possible to manage it. In fact, in order to obtain a disperse and uniform porosity the shot entry should be placed in correspondence to the thinner parts of the casting, while in order to obtain a reduction of the porosity in a massive zone the shot should be placed next to the thicker parts of the casting.

Moreover, the flow should be directed towards those zone with high quality requirements: to obtain a high surface quality it is needed that the cast should be as direct as possible. These precautions lead to a better control of shrinkage porosity and thus to a casting process optimization.

Design and dimension of runners

Another important element to consider is the shape of the runners. Normally the most used shape is trapezium, but for some high tolerance alloys, such as Zamak, runners with circular cross-sections can be used: this reduces energy dissipation, thus preserving flow’s temperature.

During the designing phase, the ratio between the runner’s section and the shot entry should be kept in mind, but there is no universal rule: the choice depends on the wanted result. Smaller runners allow for a saving of both material and energy, but require more power from the injection system and are more subjected to premature solidification. On the other hand, larger runners require more material and energy, but have higher hydraulic efficiency and increase the thermic value of the mold. Therefore, they require also a longer cooling time which could have a negative impact on the cycle time.

Moreover, the cross-section of the runner should be decreasing in size through their whole length, and this applies also to branches:  the entering section should be equal or larger than the exiting one. If the main branch splits to two runners with the same cross-section, the resulting runners should also be of the same size, and their sum should be equal or smaller than the main branch.

Another issue regarding the design of the runner could be the presence of sharp edges and the discontinuity of flow deviations, the most critical points in the design of the runners. They should be avoided to prevent the formation of turbulences. When working with compound dies a particular attention should be given to construction and assembly errors, because the formation of bottlenecks and bulges could damage the metal flow. This kind of mistakes can be fixed in the tool shop, allowing for a recovery of the original functionality of the mold.

Finally, it is important that the volume of the runners will let the metal flow in the cavities at the same time, and that is why their length must be constant.

To allow the casting to be evenly distributed in all the cavities, it is necessary to attach the main runner to the injector with a feed.

The feed

The feed is a junction needed to pass from the squared section of the injection channel to the thin one of the shot entry. There are many different types of feeds and each one has different advantages, but all have the same main functions: to make the passage between the channel and the entry more gradual, so as to contrast metal tendency to withdraw from walls, and to direct metal flow.

The most common models of feed are the fan feed and the double tangent feed:

• The fan feed creates a narrow flow with a higher speed in the middle. Because of this, it is more suitable for short and thick shot entries, and it is ideal for small angles;
• The double tangent feed produces a larger flow, with higher speed at the sides. Because of this, it is more fitting for long and thin shot entries and offers larger angles;

Independently form the chosen type of feed, the section should be linearly decreasing from the channel to the shot entry. This means that it is not enough to use a trapezium-based feed, but it will be necessary to curve either the base surface or the side’s surface.

Pro and Cons of a straight feed

The term “Straight feed” identifies those feeds with a straight trapezium base and curved sides. The main advantage of this kind of feed is that the opening angle is the same as the half-opening of the feed, making it easier to remove the runners, while the main disadvantage is the tendency to work with a cold shot entry. Moreover, the flow generated by this feed has a narrower leading front and thus the metal has a tendency to withdraw from the walls.

Pro and Cons of a curved feed

The curved feed is a feed characterized by straight sides and a curved base. It is ideal when it is necessary to have a stronger flow to the sides, but the opening angle is harder to calculate and it causes the formation of small parts that require removal. The flow created by this kind of feed has an higher speed in the middle and metal tends to stick to the walls.

After learning about their strengths and weaknesses, it should be clear that, just like the runners, the type of feed should be chosen depending on the wanted result, on the power of the injection machines and on other secondary conditions. By allowing a better control of the casting flow and reducing the risk of air trapping formations, the feed is a fundamental tool for casting process optimization.

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This is a widely discussed topic among the industry specialists: since the very first stages of mould filling various mistakes can occur, for example caused by a too quick metal solidification that can damage the final result. All of this can be forecasted and avoided thanks to HPDC simulation, thus improving the entire productive process and leading to consistent time and costs reduction.

The complexity of die casting process

When considering metal melting process a thermo-fluidodynamic biphasic simulation is needed, because metal processing process is composed of both kinetic and dynamic phenomena, heat transfer and phase transition from liquid to solid. In addition to that, the heat transfer is both of the convective kind, thus related to movements of the fluid, and the diffusive kind, determined by the heat shift between fluid and mould.

In order to face these issues the best solution is a simulation software.

Especially in the case of HPDC simulation (High Pressure Die Casting) mould complexity and machines parameters increase the number of variables to take in account during the simulation. Moreover, the productive process is continuous and based on quick cycles of high pressure fillings and cool down phases. These features, added to the intricate shapes and the shallowness of some products, highly increase the numeric complexity of the simulation.

After these premises, it is plain that the simulation process cannot be straightforward either: the equations used in the process can be solved only through an analytic approach only in a few and limited circumstances. For this reason is necessary to use a numerical methodology that requires a conspicuous use of computational resources. The numerical approach involves management of a discrete domain (the finite space in which the studied element lies) and a simplification of the equations.

The domain is turned into a so-called mesh: a calculation grid composed of different sized cells. A balance equation is written for each of these cells, to build up the global system and to be solved by the simulator. Higher the number of the cells and smaller their dimension, the more precise and lengthy will be the simulation.

The employment of specific programs plays a fundamental role to achieve the best possible results: programs like MagmaSoft, a CFD simulation software designed for foundries are based on a LES (Large Eddy Simulation) numerical scheme, enabling the user to compute without approximation the turbulence of vortexes of medium and large size, thus leading to quickly and precisely re-enact the studied phenomenon.

Why preliminary studies for die casting matters

Those who study the process of die casting through simulation cannot avoid the comparison with reality. Only the observance of the real process permits to identify defectiveness in the product and to classify them, so that they can be studied, reproduced and avoided, thus achieving better surface aesthetical quality. Furthermore, an in-depth and empirical analysis of the real-life phenomenon is fundamental for setting the boundary values. Their determination, in addition to being necessary for the closure of the numerical system, determines the closeness of the simulated model with reality.

Through the use of a HPDC simulation, the following defects can be studied and prevented:

• Porosity
• Cold Laps (due to low temperature in filling phase)
• Presence of air in the diecast
• Metallic inclusions determined by the presence of foreign bodies in the molten material
• Cavitation issues or mould erosion
• Scrap reduction

Each of these possible issues is linked to physical aspects of the system detectable in the simulation, such as speed, pressure and temperature: porosity, for instance, is caused by material distribution in the mould and is therefore linked to the speed of injection, to air pressure in the mould and to heat distribution during solidification. Through the use of simulation it is possible to foresee the formation of vacuum pockets that may decrease the solidity and aesthetic of the product. Click here to read about a case study of shrinkage porosity reduction in a component.

Another occurrence in which the simulations proves particularly efficient is in forecasting the possible damages caused to the mould by cavitation: there is a risk that the mould may undergo a major erosion if subjected to pressure variations. Because of this, it is necessary to analyze in depth the object geometry, drawing duct with strategical shapes and positions.

HPDC Simulation: comparison with reality

The expert should then research the causes of the anomalies in the physical qualities of the fluid, analyzing accordingly to the case and matching the mathematical data given by the simulation with the extra value of practical experience and know-how. By comparing the expected data provided by the simulation with the effectual results, two main goals are achieved:

• on one hand, it increases the understanding of the physical phenomenon causing the faultiness and helps the researcher with finding a suitable solution, for there may be many possible ones;
• on the other hand, it increase the interpretational ability of the researcher, leading to a better knowledge of which fields or combination of fields allow to identify critical values linked to faultiness creation;

The more experienced the software user is, the better the results.

If you want to keep up-to-date with die casting industry news, take a look at other simulation posts and please subscribe to the blog.

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Considering the metrology room as a part of production process is an advantage: it becomes an integral part of the process, such as the design of the die, machine setting or finishing, not just a post-production control.

In terms of production the metrology room inside of die casting plant allows to manage important activities, such as:

– Constant monitoring of each production cycle
– Fast check of new projects and sampling
– Getting an overview about projects that have undergone changes over time
– Control of parts incoming from external suppliers
– Reverse engineering, both for the product and the die

To achieve these goals, a complete range of tools and innovative machines is needed, complementing the precision of a traditional CMM system with a 3D scanning one, combined with the most advanced software for inspection and statistics, allows to accomplish a complete dimensional control.

Following, you can find an analyses regarding applications of a metrology room inside die casting process.

Constant monitoring of each production cycle
Pieces are dimensionally tested when they are still in the production cycle to ensure the correct quality. Products are taken directly from the die casting machine for dimensional and statistical controls: to cyclically evaluate the dimensional quality and, in general, to continue monitoring the reliability of the process.

Fast check of new projects and sampling
A constant dimensional control activity, especially in the project start-up phase or sampling phase, it is strictly necessary to reduce time and costs. Having a metrology room inside the plant allows real-time control of the pieces produced to immediately confirm the precision of the process or, in the opposite case, to have a real-time response in order to make changes or updates in production cycle.

Getting an overview about projects that have undergone changes over time
In case of dies or products previously designed and developed by a different supplier, it could be necessary to analyse and check them to ensure the dimensional quality required by the customer. In fact, without similar controls, the new supplier could face the same issues. This kind of analysis is essential to avoid this situation. Instead, by getting a complete analysis of the project, the new die caster will be able to act directly for updates, ranging from simulation software to machine settings.

Control of parts incoming from external suppliers
Having a metrology room inside of die casting plant could be also really useful in case of complex products, that need to be assembled with other components from a different supplier. In fact, in addition to the control of produced pieces, it is important check all the other parts of the product. This method assures to minimize risks for the customer.

Reverse engineering 
Dimensional measurements are very important in case of reverse engineering actions, both on parts and dies. It can be a helpful activity in order to analyse the market, or pieces already in production, or rebuild a component starting from the die. This methodology can be applied on different purposes, to speed up some projects.

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In order to enhance efficiency of the process, various topics can be explored:

• Design of the production process
• Risk analysis
• Choice of production tools
• Planning of activities

Design of the production process for Die Casting Cycle Time Reduction

The most advanced technology that is available for die casters today includes software that can simulate production and therefore optimize process parameters.

These include:

• Sequence of the casting process
• Shot curve
• Temperature of melt
• Thermal regulation

The results of the simulation can be represented in graphs or videos that show the various phases of the process: filling the die, solidification of the material and possible defects that could happen and that we will discuss in the next paragraph under risk analysis.

During the design of the process one shouldn’t forget additional operations to be performed after the die casting phase. Beyond their impact on time, which in such case will lengthen and must be included to establish the delivery date, additional wall thickness must be considered to maintain the tolerances as required by the customer.

Risk analysis

The possibility to simulate the entire die casting process provides a precious opportunity which allows to foresee possible defects and eliminate them by acting on the causes before production starts.

The most common defect is burr, requiring additional machining for elimination, increasing the production time and the cost of the final product.

Another aspect to be analyzed in the preliminary phase is the surface quality of the part: based on the more or less correct filling of the die, flow marks and cold laps could appear.

Shrinking of the material during the cooling phase must also be calculated: we are referring to porosity, being the appearance of cavities inside the die cast product while solidifying. The main cause of this defect is the differing speed of cooling and hence solidification in the various zones of the die. A preventive analysis of material flow inside the die allows to optimize this delicate effect and render speed and temperature the most homogeneous possible.

For the die caster, being able to identify defects and analyze them in each and every aspect (quantity, shape, exact location, etc.) is crucial because by establishing the causes of defects one can choose to modify the productive process or to modify the die.

In these cases, a choice that might seem more complex could induce a time and cost saving by eliminating additional machining.

The choice of production tools

In the die casting sector, when choosing a supplier it is fundamental to evaluate if they use cutting-edge machinery, if they effect periodical checks on the tools and if they offer the possibility to develop automation processes in-house.

An expert die caster is able to execute efficient implementation of automation even when involving third parties.

Numerical control of all equipment allows to intervene in every phase to optimize and reduce production time.

To this point, industry philosophy 4.0 foresees to make the entire industrial process digital. The die caster’s engineering team receives feedback from both the internal quality control department and from the client when product defects are identified. The analysis of the entire process also has the objective to make production times more efficient.

With data at hand, the analysis repeats itself the same way as in the preliminary design phases of the production process.

Planning of activities

The initial planning covers the definition of the technologies to use, the production phases and the process parameters such as which die to utilize, casting temperature of the material etc.

At a later stage one can be more precise and define:

• Runner design
• Gating design
• Detailed process parameters

From product co-design in strict collaboration between client and die caster, to simulation of the production to prevent defects, from die casting cycle times to reduction of additional machining operations and surface treatments, up to final in-house assembly avoiding additional manipulation, the whole productive chain can be analyzed and made to the highest level of efficiency.

Speaking of surface finishing and surface treatment and again pointing to die casting cycle time reduction, the surface characteristics of the end product as requested by the client can be achieved in a more efficient way when the entire productive process is analyzed.

Starting with the client component design idea, some characteristics can be optimized to render the subsequent machining less complex and avoid issues with wall thickness or defects.

If the part needs to be delivered painted, for example, a chromate conversion coating is usually applied to prepare the surface for an improved life span of the paint finish. If a product with smooth finishing is needed, the surface of the product needs to be prepared before chromate conversion with a vibrating treatment.

Placing confidence in expert suppliers, you can count on a quality product at contained costs, because analyses to identify die casting cycle time reductions are included in all phases of the project to always guarantee an excellent result which is conform to the client’s expectations.

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Salt Spray Test (SST) is a really widespread corrosion method, applied in order to check materials and surface coatings corrosion resistance. This kind of test is an accelerated corrosion test which produces a corrosive attack to coatings to evaluate, after a pre-determined period of time, if they can be used as a protective finish. The duration of Salt Spray Test depends on coating corrosion resistance: if the coating has high corrosion resistance, the testing period is longer before the appearance of corrosion.

It can be used for different materials such as: zinc, phosphate surfaces, electroplated chromium, nickel, copper and tin and also for paint coating. Moreover Salt Spray testing is fundamental in order to evaluate product or component corrosion aimed at outdoor uses or in cold or wet environments.

Summarizing it is possible to say that Salt Spray test is used to:

• Analyze corrosive resistance of different materials and finishing
• Measure the corrosive inclination when a metal or coating is scratched
• Determine coating adhesion and corrosion creep
• Evaluate corrosion resistance in a marine environment

Products without SSL resistance would corrode under saline air influence.

Salt Spray Test application

Salt Spray test (SST) is really widespread because of its many advantages: it is quite inexpensive, multi material, quick, standardized and repeatable.

It is done using a salt spray chamber where inside are inserted parts or components to be tested. In fact Salt Spray test is used to predict which materials will resist corrosion in real conditions. The apparatus for testing is composed by a closed testing chamber, where salt water solution is sprayed due to pressurized air.

The classic Salt Spray test is atomizing salt solution into a chamber supported or suspended between 15-30° from the vertical. This solution is made of 5% of NaCI (Sodium Chloride), while the exposure zone is maintained at 35° C. The test is continuous for the entire period of test: the period can reach more than 1000h.

The consequence is an environment extremely corrosive made of dense salt water fog in this chamber where samples are exposed to it and to corrosive conditions.

Modified Salt Spray test

The majority of Salt Spray test are continuous, this means that the product under test is exposed to continuous salt fog for the entire test duration. However few product do not require such exposure: this one need a modified salt spray test. ASTM G85 is an example of test standard which contains different modified Salt Spray test.

There are different modified Salt Spray test, referred to in ASTM G85 as annexes A1 to A5. Many of these modified tests are related to particular industry sector depending on corrosion effect of environment.

• ASTM G85 Annex A1 – Acetic acid salt spray test (non-cyclic): this test is used to analyze corrosion resistance of decorative chromium plating for zinc die casting if exposed to an acetic acid salt spray climate at elevate temperature. Test samples are placed into a chamber and exposed to an indirect salt water spray solution.
• ASTM G85 Annex A2 – Acidified Salt Fog Test (cyclic): this test is normally used to test aluminum alloys corrosion.
• ASTM G85 Annex A3 – Seawater Acidified Test (cyclic): this test can be used to test corrosion of coated or uncoated metals if exposed to changing climate or acidified seawater spray followed by high humidity at an elevate temperature. Test samples are placed in the chamber system and exposed to a changing climate.
• ASTM G85 Annex A4 – SO2 Salt Spray Test (cyclic): this test can be used to test samples in a SO2 (sulfur dioxide)/salt spray/acid rain environment during their service life. These samples are placed in a chamber and exposed to 1-2 possible changing climate cycles.
• ASTM 685 Annex A5 – Dilute Electrolyte Salt Fog/Dry Test (cyclic): this test is used to test corrosion resistance for paints on steel product if exposed to changing climate of dilute electrolyte salt spray.

Zinc corrosion resistance

If compared to other materials, zinc is well known for its ability to resist to corrosive environments. However is not well known that its resistance depends on the formation of a surface barrier. Normally, when galvanized products are exposed for a normal use, for example in marine or road salt environments, zinc creates a protective layer of zinc carbonate: it resists salt attacks and ensures long-term corrosion protection.

For all the reason above mentioned, zinc is the perfect material to be used to produce automotive parts. 

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Die casting process: reducing costs

Why use zinc?

Zinc metal is the perfect choice for many reason, for its decorative and functional applications.

Zinc is a dense metal, really durable, strong and allows many die casting finishes compared to other materials. Furthermore is possible to die cast zinc at moderate temperature, for example compared to aluminum: this means saving in terms of energy and processing over other alloys.

These zinc characteristics are crucial for functional and aesthetic reasons: from surface improvement to design.

Zinc alloys can be the right materials to develop products or components because they can be finished in a variety of techniques however, in particular for functional parts, the majority are used without any surface coating. Due to zinc characteristics, this material is acceptable for uses in uncoated state: this allows an important cost saving.

But it is not just zinc making the difference. During zinc die casting process is fundamental a collaboration between client and supplier in order to improve the component or product. This can be done for example with a co-design activity. Zinc allows several morphological innovations, saving and mass production: the supplier expertise will do the rest.

Reducing costs in zinc die casting

There are several ways where is possible to save during zinc die casting process. For example, the most important are:

• Simulation phase
• Co-design service
• Work on surface treatments

Simulation phase

Cost reduction in simulation phase can be applied widening simulation phase. Simulation, developed at the very beginning of product design, is a key point of die casting process.

Simulation software, such as MAGMASOFT, have been allowed by a higher computing power and innovative algorithms. These tools help designers to avoid any defect and problem during the process and allow processes simulation of material inside mould cavity.

With these particular software is possible to modify the product and its performances already during the beginning of product design phase. This software allow the specialist to analyze real time data to identify critical points and, since the beginning, specialists can simulate defects and modify the die casting process in order to avoid issues. Everything is done in order to avoid material and time waste.

Co-design service

In order to reach a significant cost reduction zinc die casters can offer to their customers a co-design service. This service is done to improve product design or functionality, or reduce costs thanks to the collaboration between client and supplier.

Is fundamental for the supplier to take into account the entire production process. In this way is possible to improve products or components performances. Moreover every zinc die casting manufacturer should have a dedicate engineering department, focused on analysis and simulation. Die casting manufacturers should have the chance to do prototyping right inside the structure, using pilot tools.

This is an approach applied to guarantee the client a full support in order to improve components during product design phase.

Surface treatments

Surface treatments cycle need to be optimized in order to produce a finished product aligned with clients expectations. Often is the client who gives precise indications about the correct cycle, otherwise is the designer who, in strict collaboration with its client, suggests the most suitable process.

The process is normally divided into three steps: the first one is dedicated to polish parts and eliminate marks such as part lines, created during die casting process, the second one prepares the component for the real surface treatment choosing the most suitable solution for the product, the third one regard strictly surface treatments application.

Surface treatments done in the same plant as die casting allows the client to have finished or semi-finished products using only one supplier to cut costs and simplify the process.

All this process has to be done in order to avoid secondary and unnecessary operation which will raise costs.

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New goals and targets are constantly shifting to respond to market trends. It is essential to leverage multiple disciplines and competencies in order to be able to reach the global customers’ casting product expectations and manufacturing needs.

How Die Casting Simulation can lead to Savings

A smart casting process optimization requires flexible variables, with the ability to update information and data in order to adapt to the changing business environment.

Each team involved in the process must collaborate with other teams in order to identify and develop cost-effective, innovative, and simple to use methodologies; therefore, innovative thinking and creativity should be encouraged in order to facilitate solutions for difficult manufacturing situations.

Let’s now dive into die casting simulation issues.

The importance of the collaboration between suppliers and customers

When a supplier works closely with its customer and viceversa, each component of the process can be optimized to perfection:

– product or component co-design
– die casting simulation
– tooling
– manufacturing processes
– mould design
– complementary works
– shipment procedures

Such collaboration guarantees great results in terms of high quality production and cost optimization.

If the customer aims at getting better products at lower costs, the manufacturer needs to be selected carefully and involved early enough in the process to enable collaboration not only in the design, but also in the entire decision making process.

A joint effort between suppliers and customers is a win-win solution to meet the market needs.

This can be true for several fields, but in particular concern Zinc Die Casting. From design to finishing there are many variables to manage, therefore a good process design is crucial to reach product integrity and quality.

In fact die casting simulation is therefore a fundamental stage to ensure best results in the most efficient way possible.

In this post is underlined the first phase of product or component co-design from the angle of die casting simulation.

Die casting simulation allow the designer to foresee with a good precision all material reactions inside the mould cavity among a thermos-fluid dynamic analysis of the mould. This kind of analysis is called CFD simulation (Computational Fluid Dynamics).

Concerning mould temperature, using this kind of software, is possible to identify possible defects such as cold laps and hot spots, and is possible to simulate temperature exchanges during the solidification phase and mould opening.

Numerical steps, in this particular phase, are fundamental. For this reason is necessary to start with die casting simulation that can help specialists to identify the best mould design parameters since the very beginning, obtaining an important cost reduction.

A proactive approach of designer can avoid and anticipate problems such as flow marks and blisters, cold laps, porosity, shrinkage porosity, lakes, and shot to shot inconsistency.

It is important to say that simulation allows to identify the correct balance between speed and temperature and geometry of overflows and runners in order to prevent any issue or defects in high pressure die casting.

Tools for casting process optimization

There are several applications available nowadays to maximize both the profit margin and the quality of the casting process: the use of die casting simulation software improves the collaboration among designers and engineering team, ensuring that all components leaving the development department are suitable for casting and can be manufactured in an economical process.

This kind of technology offers a virtual version of the casting process from filling to solidification and porosity prediction, in order to obtain reliable and high-quality products avoiding the costs of trials and the production of expensive moulds or patterns.

The die casting simulation examines mould filling, solidification and cooling, therefore residual stresses and distortion, as well as microstructure formation and property distributions can be assessed.

Within the main benefits of simulation in die casting you can include:

– Avoiding defects that arise from gas porosity, shrinkage, turbulence, etc.

– Filling process optimization to provide a fast but smooth and controlled flow

– Time savings thanks to efficient gate design and sizing

– Material cost and waste reduction

– Reduction of cycle times and maintenance costs

– Minimization of start-up costs through modifications to patterns or tooling

– Improved communication within suppliers and customers

Having a comprehensive and effective simulation tool enables the implementation of smart processes and optimized casting layouts.

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