fluid processing applications - pvdf injection molding

Slide rule no moreEngel, which had supplied customers with a slide rule for quick calculations, now has an app performing much the same function but in a decidedly more mobile format. The Austrian supplier of injection molding machines and automation said in a release that its e-calc app contains materials data for typical thermoplastics, including thickness factors, temperature conductivities, de-molding temperatures, permissible peripheral screw speeds, enthalpy values, and guidelines for processing loss.

Stillman: This depends on the design intent of the part. Over and above the standard dimensional checking and our statistical process control, we measure surface roughness to single-digit nanometer deviations for optical parts. We assess mechanical strength for safety-critical parts. For in-mold decorated parts, we assess chemical resistance and scratch resistance of the artwork. We do peel strength testing for overmolding.

“Solving the problem of quick COVID diagnostics testing is one of our priorities at Rosti,” says Karl Stillman, regional sales director at Rosti Group. “We are delighted that our 72-hour 3D printing capabilities made it possible for our customer to produce test kits quickly and cost effectively.”

This is a critical success factor when engineers are trying to push design limits. We live in a world where if you are not progressing, you are going backwards. This process allows designers to “fail forward,” to iterate designs quickly and at a fraction of the traditional costs for molded parts.

Stillman: One of the key steps in any new project is fact finding. In many cases, we’re only molding the parts, which will be assembled at the customer’s site. However, it’s very important to know the eventual assembly method, because that enables us to add value to the design. Knowing the downstream value chain and operations is key in our analysis.

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"An update for iMoulder is currently in the planning stage it will include a new user interface, a expanded material library and updates to the trade name and suppliers database," Hague said. User feedback is guiding some other potential changes, including:

iMoulder has been a hit with users, pulling in 4.5 stars on Apple, with six reviews, and 4.8 stars on Android from 56 reviewers, with 49 giving it a full five stars. Apart from some suggestions, users offered up glowing comments, ranging from "use it almost every day" to "I love this app, thank you."

"We see great potential for our customer service, and in the long term for our training departments, in app technology," Wolfgang Degwerth, head of the customer service division at Engel Austria said in a release. "Thanks to e-calc, we have again simplified communication between Engel and our customers, and are now entering a totally new service era."

However, that’s just the tip of the iceberg. We have learned from past experience that part designs do not always behave the same way when we transition from printed prototypes to molded parts. There are a number of reasons for this. The print material does not behave the same as the molded resin. The layering process results in anisotropic properties, which are not as homogeneous as molded parts. The molding process results in shrinkage and molding stresses in the parts.

Stillman: These test can predict, on a statistical basis, whether our prototypes or our production processes are going to exceed the product’s quality requirements. We strive to be 100 percent confident in our process setup prior to production. In fact, we have developed a six-step process to qualify parts with as wide a process window as possible to ensure production stability. We also monitor the injection molding process.

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The company’s portfolio includes everything from beverage caps to currency cassette modules for ATMs. Recently, we sat down with Karl Stillman, regional sales director at Rosti, to talk about part design and how to with contract manufacturers.

We are a service provider. In theory, anyone with injection molding machines can do what we do. What makes us stand out is our customer intimacy and continuous improvement attitude. Rosti is only successful if our customers are satisfied and profitable, which translates to repeat business for us.

iMoulder app serves up mobile injection molding expertiseKeith Hague, director of Imtech Design Ltd., a U.K.-based Moldflow Gold Certified injection molding consultancy, created the iMoulder app in 2010, with versions for Apple and Android. Described as a "Plastic injection molding trouble shooter and materials guide," the app has three main areas:

Stillman: Yes, this happens several times per year. It’s all about understanding the boundary conditions of the parts, such as geometric envelope, usage conditions and assembly processes. From there, we dive into the design to realize a workable solution. This may result in significant design changes. There might be material changes, process changes or one part may have to be separated into two parts. We always find a solution by working closely with the customer.

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At the same time, Hague said his wife, who is a children's author, had begun looking at eBook platforms and he seized on the potential for an electronic version of this trouble shooting guide. Hague estimated that there have been 40,000 downloads since the app's June 2011 launch, with 1000-1200 new users added every month, split evenly between Android and Apple.

Finally, we think about assembly. What are the tolerance stack-ups? How do moving parts interact? Can the parts be easily assembled? Can error-proofing features be added?

We look at many areas of the part design. Is it feasible for injection molding? If not, Rosti will redesign the part and send an updated 3D CAD file back to customer with comments and a design analysis report showing before and after images and explaining the rationale for our suggestions to modify the design.

Rosti Group has helped a global molecular diagnostics company to begin manufacturing a COVID-19 saliva test, providing laboratory-quality results in 15 minutes. This will allow nonmedical personnel to obtain fast, on-site detection of the coronavirus at the point of need.

Stillman: Other than variation in costs, different materials have different properties. For example, polycarbonate should not be used with alkaline aqueous solutions or aromatic and chlorinated hydrocarbons, since these would degrade and weaken the part. Whenever we work with multi-material assemblies, we assess the chemical compatibility to ensure that there will be a chemical bond between them. In cases where chemical bonding cannot be achieved, and the materials cannot be substituted, we would recommend design changes to facilitate mechanical bonding.

We consider the resin, too. Is it suitable for the purpose? Will it achieve the cosmetic and functional requirements that the customer has specified or, in the absence of such a specification, what Rosti engineers envisage to be the critical functional and quality requirements.

Stillman: It’s had a huge impact. 3D printing can get designs from the screen into the designer’s hands quickly and cost-effectively.

Estimates of the total number of applications for Android and Apple vary, with some pegging Apple with more than 1 million apps in its App Store, while others estimate 775,000 for Apple and 800,000 for Android, but in any case, both now have injection molding programs mixed in among the Angry Birds and Words with Friends.

That makes creating molds for prototype parts a gamble. It can take four weeks and tens of thousands of dollars to produce traditional molds for prototype parts. As a result, engineers must be confident in their designs before committing the time and resources to make molds.

Stillman: The most common input is on part design for moldability. Rosti’s core competence is injection molding. We have an extensive knowledge base that we draw upon for every new project. As a contract molder and manufacturer, we have exposure to many different designs and materials, so we are well-versed in what works and what does not work. With the help of our certified Autodesk Moldflow engineering team, we can quickly identify areas that will result in molding defects and proactively design these out.

We pay considerable attention to cosmetic defects. This is one area that design engineers do not understand well. There is a lot of information on designing mechanical structures, but aesthetics is often overlooked.

Hague told PlasticsToday the iMoulder's genesis dates back nearly a decade. "About 10 years ago I developed a simple injection molding process condition chart for a range of common materials, and this was well received by my customers," Hague said. "In the plastic consulting business, we get asked similar questions over and over from different customers, so I decided to put together a simple trouble shooting guide but was struggling to work out how to publish it and keep it pocket sized."

That got us thinking: How could we get molded parts quicker and cheaper in the development phase? The answer was to print the mold, as well! It took a lot of development work, but we have perfected the process of 3D printing mold tooling. As a result, we can take a customer’s design from print to part in 72 hours. That includes design analysis, mold-flow analysis, part prototyping, tool prototyping and injection molding.

Stillman: To be honest, the occasions where we do not offer design recommendations would be an easier number to quantify. The truth is, we provide recommendations and suggestions to our customers more often than not.

"The main concept behind iMoulder was that the app should contain all the information on the device and not rely on internet coverage so the user can access information equally well standing next to a molding machine on the shop floor or back at the office," Hague said.

Hague told PlasticsToday that several material and hot runner suppliers have told him iMoulder is now standard field kit for their tech service engineers, which makes sense given its all-the-time accessibility.

Our top two priorities are always safety and quality. These are at the forefront of all our design and process verification protocols.

Stillman: First, we need to clarify what the customer’s objectives are. Is the product manufacturable? What can Rosti do to optimize cost to customer, operational performance for Rosti, and sustainability for all.

Cost optimization is another key area that we evaluate. Rosti has implemented many creative solutions over the years, including alternative materials, part consolidation, swapping metal parts for plastic ones (and vice versa), and the elimination of post-processing steps.

For example, we conduct finite element analyses on snap fits, load-bearing members and pressure vessels. We can simulate various bonding technologies, welding methods and mechanical fasteners under dynamic loading conditions. We like to take a holistic view of the assembly process and the product’s operational conditions. Only by understanding risks can we advise our customers and add value to the product.

Beyond machine setup calculations, Engel envisions e-calc as a new extension of its existing customer service and training offerings.

Stillman: We have customers ranging from manufacturing immaturity to international corporations that have as long a history in plastic parts as Rosti does. That said, we do have customers that surprise us and have been able to teach us about a particular design or material application. We value these interactions, as nothing is ever black and white. There are always compromises and trade-offs to be made. Conversely, we also have customers that believe they have “been there and done it all,” so extra care must be taken to prepare supporting evidence for our proposals. This would include simulation data, past product data, theoretical calculations, prototype tooling and other information.

Rosti’s Digital Innovation Laboratory used 3D printing to create prototype injection-molding tools, which allowed engineers to have prototype parts for the test within 72 hours. Production tooling—32-cavity molds—was ready just five weeks later, and the diagnostics company began serial manufacturing of the test under ISO-13485 conditions.

e-calc app is available for Android smartphones in German and English, with versions for iOS and Windows Phone under development.

Based in Malmö, Sweden, Rosti Group is a global injection-molding company and contract manufacturer to some of the world’s leading manufacturers in the packaging, consumer appliances, business machines, home automation, medical and automotive sectors. An exhibitor at the 2020 virtual ASSEMBLY Show, Rosti operates production facilities in China, Germany, Malaysia, Poland, Romania, Turkey and the UK.

Estimates of the total number of applications for Android and Apple vary, with some pegging Apple with more than 1 million apps in its App Store, while others estimate 775,000 for Apple and 800,000 for Android, but in any case, both now have injection molding programs mixed in among the Angry Birds and Words with Friends.