Injection Molding Bioabsorbable Medical Implants

April 21, 2009 in Bioresins, Engineering/Medical Grades, Injection Molding, Plastics / Resin by brentb | 1 comment

Medical grades of biodegradable/bioabsorbable PLA, PLGA, and PLG resins can sell for upwards of $1,500 USD per pound. This and the delicate nature of biopolymers can send shivers down the spine of any injection molder. Really though, the standard precautions and best practices of any high level molding operation familiar with running engineering-grade resins similarly apply to the processing of these bioabsorbable resins. Every aspect of the manufacturing process must be closely monitored, and proper procedures strictly adhered to.

Mold construction must take into account the rheology or flow characteristics of the resin, shrinkage, and venting requirements. Due to the relative infancy of the bio-materials there is little data available from the resin makers, so all mold construction should be steel safe. Selection of mold material should keep corrosion resistance in mind.

Cleanliness, of course, is paramount. There can be no contamination present in an implantable device. Purging an injection unit after a run with a different resin, no matter how thorough, is not enough. The screw must be pulled and all residue removed from the screw and barrel physically. Don’t use copper gauze (here we differ slightly from the standard molding procedures) for fear of fragmenting and heavy metal contamination. A plastic abrasive cloth would be better, and the unit should be wiped, dusted, and blown or vacuumed free of any minute debris after cleaning. Having a dedicated injection unit is a better option, with a dedicated molding machine, dryer, and loading system being the best case scenario.

The molding machine really is not specialized. Usually a general -purpose screw is fine with about a 3:1 compression ratio and 20:1 length over diameter ratio (again, a general – purpose unit). Clearances should be tight in the injection unit, and the check ring non-return valve should be in good shape. Bioresins are not very heat or shear stable, so sizing the barrel capacity of the machine to the intended shot size is very critical, and high compression screws are not advisable. Since the resins are so costly, any scrap will immediately affect the bottom line. Savvy molders start and stop the run with a “commodity” bioresin with similar flow characteristics.

PLA/PLGA/PLG for implantables, like most bioresins, are slow to give up their heat and also can be slow to obtain optimum crystallization, so cooling times and pack/hold times can be quite long which lead to longer cycle times. Here, corners can’t be cut by running a colder mold in quest of faster cycles because you risk endangering the end characteristics of the implant.

In addition to shear and heat degradation, bioabsorbable resins are susceptible to hydrolytic degradation. Careful drying is important, with drying in the cleanroom next to the molding machine being advisable. Minimum out-of-dryer/in-molding-machine hopper time is also essential. Like many engineering resins, bioabsorbable resins must be dried and maintained at or below 250ppm (0.025%) moisture. A moisture analyzer is mandatory.

It is important to fast-track the process building and optimization portion of any injection project for PLA implants, if only due to the resin costs. One tool for this is DOE, or Design of Experiments. Here again, process building with a commodity PLA resin and final tuning with the PLA implantable resin is advised.

The implantable device must be made, handled, and packaged under the strictest of cleanroom conditions. Packaging must protect the implantable and be hermetic to keep it from picking up ambient moisture. Vacuum packing with laminated foil pouches is an option, and inclusion of a desiccant in the master carton is also popular. Sealing options include vacuum and heat sealing. Finally, sterilization methods and their impact on product end characteristics must be cautiously considered.

Care must be taken with these expensive and fragile resins; but the discipline is good for a molder, and the results for following good methods and procedures can be quite rewarding.

Written By:

Brent G. Borgerson
Senior Process Engineer (Older Molder)

Avoiding the Consequences of Molding with Wet Resin

February 17, 2009 in Injection Molding, Plastics / Resin by brentb | 3 comments

In a recent blog posting we discussed the consequences of molding with wet engineering and commodity resins. The best way of dealing with these consequences is to avoid them entirely. In the posting we discussed our procedures and test equipment for assuring that the dryness of the resin is in the correct range. The most important aspect of resin drying is, of course, the dryer and the maintenance of the dryer.

At Matrix Plastic Products, we have a dedicated dryer for each molding machine that runs hygroscopic engineering resins. The dryers are of two types:

1. Desiccant hot-air dryers
2. Compressed air dryers

Key to dryer effectiveness is maintenance. If the dryer goes down, the molding machine might as well be down. At Matrix, we take a multifaceted approach to dryer maintenance.

Visual Inspection: Dryers are visually inspected daily for hose condition, clamps, and kinks. Controls are scanned for dew point and temperatures in the proper range. Air flow cones are inspected as are the air flow filters.

Monthly detailed inspection: This includes the moving parts, testing desiccant condition, and confirming dew point meter readings on the dryer with a hand held dew point meter.

All monthly inspections and maintenance are documented on a preventive maintenance spreadsheet, developed here at Matrix Tooling/Matrix Plastic Products. This sheet covers PM for most common injection molding room equipment and is available for free at: http://www.plasticstoday.com on the maintenance forum and also on Bill Tobin’s WJT Associates website: http://wjtassociates.com/site/.

Since the sheet was developed here at Matrix, it will soon be available on our main website, again, for free. The PM sheet has been used all over the world and is a great tool for any molder to have in his or her kit. So avoid the consequences of molding with wet resin and maintain those dryers!
Written by:

Brent Borgerson
Senior Process Engineer (Older Molder)

Job Losses in Manufacturing

November 14, 2008 in Manufacturing Industry by paul | No comments

Much is published about currency manipulation, unfair trading practices, and low cost offshore labor as primary reasons for the large loss of high paying manufacturing jobs in the USA. One thing rarely mentioned is the concept that the introduction of computer controlled machines and automation have had a significant impact on USA companies need for manual labor. Requirements for labor today are far different than in days past as manufacturers now need higher skilled people, but less of them. Special interest groups often look for easy targets when determining the reasons for job losses, but the bottom line is that in many cases, companies need fewer people to do the same amount of work as before. And as labor costs continue to climb, it’s the first place a manufacturer will look to reduce his overhead expenses.

Paul Ziegenhorn
President

Creating a Hybrid Quality Management System for ISO 9001 & 13485 Dual Certification

October 24, 2008 in ISO / QMS by annez | No comments

When Matrix Tooling, Inc. 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.

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 almost expected; a prerequisite for doing business in almost any industry.

Over the years, Matrix has increased our focus 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 cross-sectional scanning (“CSS”) technology.

But we also discovered that the quality standard specific to the medical device industry is ISO 13485, not ISO 9001. Though its structure is based on 9001, 13485 contains 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.

To date, our customers have not required us to become ISO 13485 certified. However, we have decided to pursue it anyway. We feel that aligning our QMS with our customers’ requirements will make us an even more reliable supplier. It will also differentiate us from our competition. We like that idea.

As we adapt our ISO 9001 QMS to comply with ISO 13485, we plan to implement risk analysis, process validation, and product recall procedures as well as incorporate device master records & device history records into our quality control plans. The end result will be a more robust, hybrid QMS that will enable us to apply for dual certification (we were pleased to learn that our current registrar handles both).

Why maintain dual certification? For one thing, ISO 13485 doesn’t mean anything to our non-medical customers. Secondly, we find it interesting to note that ISO 13485 does not require an organization to demonstrate continuous improvement or monitor customer satisfaction. These are key components in ISO 9001 – components we certainly would not want to dismiss in a competitive environment where things like customer satisfaction and continuous improvement are just a couple of the reasons why our customers keep coming back to Matrix.

Written By:

Anne Ziegenhorn
Document Control Coordinator

The Consequences of Molding with Wet Resin

July 29, 2008 in Injection Molding, Plastics / Resin by brentb | No comments

Drying engineering resins is crucial to obtaining desirable end products with these high–performance and often expensive resins. Thermoplastic resins are being called on to be as strong as metal and to survive in harsh environments. To achieve these end properties, a resin must be processed correctly, and one area of proper processing is to ensure that the resin is molded at or under the manufacturer’s specified maximum moisture content (%).

At Matrix Plastics Products, we are very careful (almost to the point of being neurotic) about our resin drying and dryness assurance procedures. We take a multi-pronged approach to these issues including some of the techniques and procedures as follows:

  • •  Drying Time: We follow the manufacturers’ recommendations as a minimum for drying time before beginning molding as well as residence time in the dryer. These steps are carefully documented for accountability.
  • •  Drying Temperature: Again, resin makers’ guidelines are strictly followed.
  • •  Dew Point Monitoring of the Dryer: Our dryers feature dew point monitors and alarms which are consistently observed. The dew point on a dryer is the best indication of the proper function of the dryer, which allows us to foresee many impending problems.
  • •  Moisture Analyzer: Our Quality Inspection lab features an OMNIMARK Mark IV moisture analyzer which can be used to test and verify results. This is the last line of defense and is used whenever there is any doubt about the dryness of a resin. In the case of sensitive jobs, moisture analyzing test are routinely used and documented.

A part molded with wet resin (moisture content above the manufacturer’s suggested max percentage) may not be a cosmetically unappealing part, but it is almost always a structurally weak part. Hydrolysis – the result of heating moist resin – produces an action in the resin that is essentially akin to thermal degradation. The molecular structure and integrity are affected, and a weak and/or brittle part is the result. Some of these problems are not always readily detectable, especially during the early life of the product, but premature and unexpected failures can result from molding with “less-than-dry” resin. We try our best to avoid this situation.

Written By:

Brent Borgerson
Senior Process Engineer (Older Molder)

Pat Collins
Molding Operations Manager

The True Cost of Cheap Molds

July 1, 2008 in Design, Manufacturing Industry, Mold Making / Tool Building by brentb | No comments

A thermoplastic injection mold is like most anything you buy in life; you get what you pay for. If you want a throwaway mold with a limited life expectancy that produces simple parts and allows for generous dimensional and flash tolerances (and may require post-molding defect corrections like flash trimming), then by all means purchase inexpensive tooling from a low-cost supplier. But if factors like part consistency, uptime, conforming to quality standards, on-time delivery, low maintenance costs, long mold life, and fewer headaches are important to you, you’ll likely want to consider buying a quality mold upfront.

An injection mold is not a small purchase to be taken lightly, even for a tiny plastic part produced by a large corporation. It should be viewed as an investment, with each running cycle giving back a portion of your ROI.

For many of the molded parts of bygone years, an inexpensive mold might have been sufficient. Times have changed though and products have become more demanding. Their geometries and resins have demanded a more complex, precise and robust mold. An inexpensive mold won’t be able to give you these parts, at least not for long. What good is a cheap mold that breaks down in the middle of a production run, fails to make in-tolerance parts, or runs slower than the calculated cycle when the customer needs a steady stream of good parts promptly and consistently?

There will always be a place for simple and cheap molds in certain applications, but if there is any complexity to the part or tool, it would be foolish to build and design based on price alone. Overseas low-cost providers are an option, but that opens up potential issues with communication. Not only due to language problems, but time zones, local customs, and general business practices can add on top of that. Logistic issues and rising transportation costs should also be considered.

Reputable mold builders stake their reputations on every mold they build. They want a robust mold, built correctly with the best materials, that doesn’t come back for repair or adjustment. They want the customer to be there if at all possible for design reviews and samplings. All the teleconferencing in the world can’t take the place of personal meetings at times. These personal meetings are with the mold maker’s technical staff and design specialists, not some sales rep or consultant for a cheap offshore mold builder.

Often, time to market is critical, and control of the project timeline is not always possible with an offshore supplier. When a cheap mold is late, produces out of tolerance parts, or breaks down, its low purchase price suddenly becomes very expensive. Many times a cheap mold that doesn’t perform like it should can end up being more costly to correct than a more expensive North American mold would have been in the first place. Losses in time and productivity are often just as costly and are even harder to recoup.

When the whole picture is looked at, you can see that in the purchase of an injection mold the old adage of “you get what you pay for” holds so true.

Written By:

Brent Borgerson
Senior Process Engineer (Older Molder)

Biodegradable Plastics: The Green Dilemma – Part 2

June 10, 2008 in Bioresins, Injection Molding, Plastics / Resin by brentb | No comments

In Part 1, we discussed the history and sources of biodegradable and compostable plastics – what we call “green resins.” They are here; they are with us; and they come with unique challenges in both the mold building and injection processing of these resins. Most are still in the developmental stages.

Bio-resins are formulated to give end properties mimicking well known thermoplastic resins, and in some cases the processing techniques of a bio-resin emulate the conventional resin for which it is designed to mimic, but in many cases they are processed quite differently.

Most bio-resins thermally degrade quite readily. Many run at a melt temp around 350°F or less, and even if kept at the recommended melt temperature, can degrade in the barrel or a hot runner system over time. Generally, the molder wants between 50-75% of his barrel capacity for each shot, and barrel or hot runner residence time shouldn’t exceed two minutes by much.

A good processing method is to begin and end the molding with an easy flow PE resin. While the PE is going through the barrel, the heats can be lowered to the bio-resin range. The hot runner can be purged with the PE either through air shots or by running parts. When shutting down this procedure is also followed. The mold and machine, after being cleaned with Polyethylene, are shut down with the PE in them. In addition to avoiding thermally degrading the bio-resin, this technique mollifies the tendency of the bio-resins, particularly PLA, to be corrosive, especially when degraded.

A well designed hot runner system with a well placed thermocouple for each drop, as well as manifold and sprue bushing thermocouples is needed to process bio-resins successfully. The hot runner system capacity should not exceed two shots.

A well fit sliding ring-type, non-return valve and a general purpose screw with a 20:1 or 22:1 L/D ratio will nicely plasticize most any bio-resin. Shear will greatly affect most of the bio-resins, so gate size can’t be too small, and fast injection speeds should be reserved only for the thinner walled parts.

Bio-resins should be well dried prior to processing. Most should be dried to under 0.010% moisture. Either desiccant, or compressed air dryers can be used. Temps can be moderate to low when compared to many of the common thermoplastic engineering resins.

Always consult the resin maker’s guideline literature before processing any resin, especially bio-resins.

Mold construction must be tight to successfully mold bio-resins without flashing. Vents are important, and care must be taken when cutting them. The experience gained from building molds for Nylons and LCP can be applied to constructing a mold for bio-resins. Again, the resin’s corrosive nature must be taken into account when selecting steels for the injection mold. Matrix Tooling has experience in designing, constructing, and running precision injection molds for bio-resins.

Bio-resins seem to be the wave of the future, and though new and a bit delicate, can be injection molded successfully with a little knowledge, care, and common sense.

Written By:

Brent Borgerson
Senior Process Engineer (Older Molder)

Biodegradable Plastics: The Green Dilemma – Part 1

June 2, 2008 in Bioresins, Injection Molding, Plastics / Resin by brentb | No comments

“Green” is all the rage now, and a major part of the green revolution is biodegradable and bio-compostable plastic resins. Our landfills are quickly filling up and a large portion of the contents are plastic items. These items remain in their state “forever.” Incineration isn’t an option due to air pollution and grinding the plastic only reduces the size but not the volume.

This problem is a product of the disposable or throwaway society that we now live in. I can still remember families having one TV set, telephone, refrigerator, and radio per household. When these malfunctioned, they were repaired. People had one fountain or ball point pen, and they were refilled when the ink supply was depleted. Nuts, bolts and most everything else you used came from a bulk barrel and were wrapped in old newspaper or put into a brown paper bag which was then used for your lunch. There wasn’t such a thing as blister or clamshell packaging. You took your soft drink bottles back for deposit, and your empty milk bottles were picked up by the milkman. We live in a convenience-first throwaway society and plastics, particularly plastics packaging, play a big part in that convenience.

Enter biodegradable and bio-compostable plastics. With these two “green” families of plastics we can have our throwaway convenience without overfilling our waste disposal sites. There also is the advantage of deriving these plastics from renewable plant resources rather than finite resources based on crude oil and natural gas.
The earliest plastics were bio-plastics that were derived from cellulose (wood). Billiard balls were the first use. Later Henry Ford used soybean derived resins in his early automobiles. The Yo -Yo is cellulosic and most of today’s screwdriver handles are of this renewable resource, non-petroleum based plastic. This plastic won’t biodegrade though, and when disposed of becomes a permanent part of the landscape.

During the Arab oil embargo of the 1870’s, corn starch was used to extend polyethylene due to the lack of petroleum feed stocks. The resultant packaging which included milk caps and pails was functional though the resin was problematic to run. The products broke down into smaller pieces but never completely degraded as only about 25% of the product was corn starch.

My first exposure to a truly biodegradable, and in this case, bio-absorbable was at Matrix back in 2002. The resin was PLA (Polylactic acid). This was a corn based resin for a PLA encapsulated implantable radioactive “seed” for treating prostate cancer. This medical grade resin at the time of development was $1,500 per pound. Medical uses of PLA soon became a commonplace.

PLA continued to be developed, and commodity grades of the resin soon were made available allowing for prices to fall until it became a viable alternative to petrochemical resins.

Development of “green” plastics continued at a frenzied pace between 2003 and the present, and soon soy and milk (casein) based plastics reappeared and new resins came out based on the castor bean. Characteristics and properties of the new resins began to mimic the traditional resins that we are used to. Cutlery, plates, cups and clamshell packages for the fast food industry are becoming common. Writing instruments are being developed that are made from these resins, and even the pesky and environmentally ugly shopping bag as well as beverage bottles are being developed using biodegradable resins.

One developmental problem of these resins is combining the lasting properties of conventional resins with the biodegradable and compostable properties of the “green” resins. You want your pen to decompose in the landfill but not in your pocket. Your shopping bag must survive the trip home from the store; your plate or cup can’t leak all over you.

These bio-plastics, especially PLA have come under criticism though. Many people blame the rise in food costs largely on these bio plastics (and bio fuel). Defenders and makers of PLA say that they only use feed corn not consumer corn for PLA. Detractors say that the shortage of feed corn raises milk, egg, and chicken costs as well as red meat costs, and more land is diverted to feed corn for PLA and less to consumer corn.

New development in castor bean plastics makes use of this product which is poisonous to human beings. Soy based resins also take some of the pressure off of corn, though it puts the beneficial soy plant under pressure. Recent plastic resin and also fuel developed from biomass may prove the most promising development in “green” plastics and fuel. The corn kernels and soy beans can be used to feed the world’s people, directly or indirectly, and the once discarded biomass can be used to make the fuel and plastics we need to save the environment. Exciting new developments in this area are forthcoming.

At Matrix Plastic Products, we are involved in ongoing R&D projects involving “green” plastics. They require specialized mold building techniques and processing methods. It is exciting to be involved in projects that not only lessen our dependency on foreign oil, but are good for our fragile environment. I think the future will accentuate the positives and minimize the negatives of “green” plastics.

Written By:

Brent Borgerson
Senior Process Engineer (Older Molder)

Successful Mold Building: Technology or Art?

May 22, 2008 in Manufacturing Technology, Mold Making / Tool Building by brentb | 2 comments

Back in the early days of moldmaking, the product was the result more of craftsmanship than technology. A crusty old moldmaker with thick glasses, clad in a denim apron would take the project from a block of steel all the way to a finely-fit, fully-functional injection mold. The mold was his masterpiece. He took his time hand-fitting the components, and each mold, even for similar products, was often unique. Some tools took the moldmaker the better part of a year to produce.

Times have changed though, and the necessity of quick time to market and short product lives have shrunk lead time, while demanding resins and complex part geometries have dictated that robust and precise molds be built in much less time than in the past.

These shortened lead times are where technology has really stepped in to help. The crusty moldmaker has been replaced by a technologically savvy leadman, and each stage of the mold building operation is done under the control of specialized operators who are completely versed in the technology of their stage of the operation.

All steps of the mold building operation (design, steel milling, electrode cutting, wire and sinker EDM operation, turning, and grinding) are Computer Numerically Controlled and connected via a local area network. Many of these operations are palletized and robot attended, enabling lights-out operation to further reduce time to delivery of the finished mold. Direct access to 3D design models is available to every operator at every phase of operation. Time-tested standards like prints and setup worksheets are becoming a thing of the past. Even the progress of jobs and tracking records are maintained electronically.

Matrix Tooling, Inc. is now thirty years old. Having seen the mold shops of even twenty years ago, it would have been hard to imagine that today’s machining centers with their brightly colored computer displays, robotic arms, and servo motors have any relationship with the mold shops of the “old days” where craftsmanship was king.

But there’s no doubt craftsmanship still has its place. We’ve spent the last thirty years blending the best aspects of traditional mold making with state-of-the-art technology to produce a precise, top quality and robust injection mold as quickly and economically as possible. The first paragraph of the Matrix Tooling quality policy reflects this: “Matrix Tooling, Inc.’s mission is to combine traditional craftsmanship with state-of-the-art technology in designing and producing the highest quality injection tooling and molded products.”

Our team members have found the key to successful mold building and we take great pride in combining the latest technology with old-time craftsmanship into every build. Though the mold building business has evolved each team member takes the same pride in our end product as the crusty old mold maker with the denim apron.

Written by:

Brent G. Borgerson
Senior Process Engineer (Older Molder)

Lack of Apprentice Training

May 16, 2008 in Manufacturing Industry by paul | 1 comment

I’ve been involved in high school career education programs for much of the last 15 years. A good portion of that time was spent talking to educators and parents about careers in precision manufacturing being a viable alternative to the typical 4-year college program being pushed on our kids. Colleges have done a very good job of convincing us (and especially the parents) that the only way to a successful and rewarding career is to get a degree. I, for one, don’t agree. An apprenticeship can offer a young person another option; and the fact is that college is not necessarily the best choice for many high school students. Most teachers will agree with this logic. They know first hand which of their students are good candidates for advanced degrees and which are more likely to struggle. Most apprentice programs are struggling to attract talented young people, who by that time have had 12+ years of people telling them that they will need to get a degree in order to get a good job.

I know that the U.S. is not the only country with this problem. Much of Western Europe suffers from the same shortages. Many look down on those who work with their hands, but eventually, someone will need to learn and become the next batch of journeyman plumbers, electricians, toolmakers, etc. If not, homeowners better get ready to learn these skills or be ready to open up the checkbook.

I read an interesting article back in the mid 1990’s. In Germany (where an apprenticeship in a trade is still considered a viable career choice), the graduating number of architects outnumbered the number of apprentices from all skilled building trades combined. Think of how many architects it takes to build a home versus the number of workers needed from the various trades, and you’ll realize that something is seriously out of whack. Apparently the Germans, too, have spread the word that working behind a desk versus working with your hands is the way to go.

Hitting closer to home, we’ve struggled with finding quality candidates. Toolmakers today require skills far different than what was needed prior to the computer age, and the fact that few are training today makes for an unsustainable labor situation.

Written by:

Paul Ziegenhorn
President

« Older entries § Newer entries »