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MatrixLogo horizontal white

Injection Molding and Moldmaking
with Surgical Precision

Injection Molding and Moldmaking
with Surgical Precision

Call us: (630) 595-6144

Call us: (630) 595-6144

By Patrick Collins and Brent Borgerson

October 15, 2009

Like many thermoplastic resins, nylon has its quirks and accompanying processing considerations. One of nylon’s most notable characteristics is its affinity for water. Nylon is extremely hygroscopic, a veritable sponge, absorbing any humidity in its environment. It is an efficient sponge; quick to suck up water, and slow to give up the moisture.

Moist nylon resin affects the end product, often producing brittle or dimensionally unstable parts. Cosmetics are also affected; splay being one notable cosmetic defect that can be caused by moist resin. If the processed resin is out of moisture specs, it is essentially degraded. This is called hydrolytic degradation, and the effects and symptoms are akin to thermal degradation. Desired characteristics of many nylon parts include toughness and impact resistance. Parts produced with resin that has been sub-optimally dried can lack these traits. Moist nylon resin can be hard to process. Nylon has a tendency to drool from the nozzle. Good heat control at the nozzle is important for molding nylons successfully and controlling nozzle drool or freeze-off, but wet resin can make this control almost impossible to achieve. In addition to drying nylon well, it is important to dry nylon consistently. The same nylon resin dried at different moisture levels will exhibit different melt viscosities, even though the moisture levels may be within the manufacturer’s specifications. Water acts as a plasticizer; therefore wet nylon will fill more easily than dry nylon. This is reflected in peak fill (transfer) pressure and can be reflected in fill times, especially visible in a pressure limited process. For good consistent molding results, especially in a product with demanding dimensional specs, the resin moisture level should be consistent from run to run. If nylon is allowed to stay in the dryer for too long (over the recommended time), the material can start to degrade as well.  Natural nylon may start to turn yellow.  The finished part may also be very brittle.  This is more common on nylons than most materials.

When inspecting nylon parts it is always good to allow the finished part to absorb the moisture in the air before you do your inspections.  Depending on the environment this can take a few hours or more.  Some nylon jobs require a fixed amount of moisture to be put into the poly bag that holds the parts.  This is common in the processing of nylon straps. At Matrix Plastic Products, we strictly follow manufacturers’ recommendations for drying temperatures and times to ensure dryness, and we have a moisture analyzer to verify the results. We have found that good, consistent drying gives consistent molding results.

By Anne Ziegenhorn

October 2, 2019

When Matrix first acquired ISO 9001 certification in February, 1999, our primary motivation was to increase our sales potential with a larger number of OEM’s. We were good at designing and building precision plastic injection molds and molding custom parts. The quality of our work and our responsiveness to customers had earned us a good reputation over the previous two decades. Our existing customers were pleased with our performance and were not requiring us to be ISO 9001 certified. But we decided to pursue it anyway on our own terms – and on our own timeline – to stay ahead of our competition.  So we became one of the first mold shops in the Chicago area to become ISO 9001 certified.

We quickly realized the internal benefits of modeling our quality management system (“QMS”) on the ISO 9001 standard. The consistency that ISO brought to all areas of the company yielded obvious improvements. We became more consistent in how our jobs were quoted, documented, designed, processed and inspected; this led to a greater degree of control and confidence throughout the company. Consistency in our purchasing methods and receiving inspections led to the virtual disappearance of vendor returns. Formal management review meetings took place at regular intervals, bearing targeted plans of continual improvement.

In short, ISO 9001 made us better while giving our sales force increased credibility with potential customers. Today, ISO 9001 certification is expected; a prerequisite for doing business in almost any industry.

Over the years,  Matrix continued to focus more heavily on medical device applications where our detailed micro-tooling, close-tolerance molding and advanced inspection capabilities provide a natural fit. We added a class 100,000 clean room and more advanced inspection technology.

But we also discovered that the quality standard specific to the medical device industry is ISO 13485, not ISO 9001. Though its structure was originally based on 9001, 13485 contained additional requirements for risk management, regulatory compliance, traceability, contamination control, and device history documentation.

Our medical customers come to Matrix with device design concepts and requirements for how their devices must function. Our design engineers are often involved in the development stage from a production perspective and make recommendations for resolving part geometry, material selection and other manufacturability issues. While we are technically a second-tier supplier, not the “specifications developer,” we are certainly invested and involved in the success of these products and consider ourselves a critical link in the supply chain. If a customer gets audited by the FDA, we want to be well equipped to fully support them and provide all the documentation and traceability they may need.

So in 2010, we decided to pursue ISO 13485 certification as well because we felt that aligning our QMS with our customers’ requirements would make us an even more reliable supplier. We also liked the idea that having the additional certification would further differentiate us from our competition. 

As we adapted our ISO 9001 QMS to comply with ISO 13485, we implemented risk analysis, process validation, and product recall procedures, as well as incorporated device master records & device history records into our quality control plans. The end result yielded a more robust, hybrid QMS that enabled to achieve our dual certification.

Today, of course, ISO 9001:2015 and ISO 13485:2016 are no longer structured in sync, so we now maintain two separate certifications. Why?  Because ISO 13485 certification is required by most of our medical device customers, and ISO 9001 certification is required by most of our non-medical device customers.  While the largest segment of our business is medical, we do want to continue serving other key industries requiring a similar degree of quality and precision. We find that by incorporating the best of both standards, we get the benefit of having a more comprehensive QMS that focuses on meeting both customer and regulatory requirements, risk-based thinking, customer satisfaction, and continual improvement - components we feel are just some of the reasons why our customers keep coming back to Matrix.

By Paul Ziegenhorn

March 21, 2011

As an ISO 13485 certified manufacturer, managing risk is always a priority. And the most basic concept of that management process is first understanding what those risks are.

Recently, the question was raised: "Can any trace mold corrosion be transferred to the final molded product?" This opened a spirited discussion because, while we've been building injection molds for over thirty years, nobody here had a definitive answer.

After consulting with others in the industry, as well as a metallurgist at our steel supplier, we came to the conclusion that while it's theoretically possible to transfer any contaminant from one surface to another, having a problem with bio-burden testing or introducing a contaminant into a product during plastic injection molding production is highly unlikely.

We are involved in a program that overmolds stainless steel with plastic. A stamped steel piece and a metal injected piece are both loaded into a tool steel mold, then overmolded with a high temperature nylon. The stamped piece is passivated; the MIM piece is as-molded and sintered. In speaking with our metallurgist, we learned that the main sources of corrosion on the mold cavities would be degraded resin coupled with high mold temperatures. Fortunately, as we are the molder on this program, we have control over both of these issues. Our processing and mold temperatures are both within manufacturers' specifications, so that helps control a major source of any corrosion. The metallurgist also explained that any corrosion sufficient enough to create a transfer problem would be visible to the naked eye.

The material we chose for this program was a high hardness, general purpose tool steel. We did this due to the fact that two metal inserts are being inserted into the mold cavity for overmolding. There are other grades with similar hardness and stainless properties available, but based on what we learned we do not feel it is necessary to change steel grades at this time. However, we have decided to add a visual check to our regular preventive maintenance plan for this job, a solution we now feel is sufficient to catch a problem before it occurs.

 

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