Blackwell Plastics partners with OEM manufacturers and sub-tier suppliers in South Texas including Houston, San Antonio, Austin and Corpus Christi to provide plastic injection molding and plastic extrusion of engineering grade resins that satisfy demanding industrial applications. Blackwell Plastics supports plastic injection molding and plastic extrusion projects from design to fulfillment.

Monday, January 23, 2012

Simple Challenges - Simple Solutions

The most frustrating problems are often the simplest solutions once you find them.

The life of a custom molder is full of adventure and daily challenges that can be frustrating at times, but also provide learning opportunities and great satisfaction when accomplished. Recently, we were running a general purpose natural ABS that was colored with color concentrate at the press. The material was dried and tumbled with the color and supplied to an autoloader at the machine. The process technician set up the machine and supplied first article samples to our quality department which were accepted for production. Soon thereafter the operator notices streaking in the color and notified QC.
Problem: Streaks and inconsistent color in the parts.

Initial Trouble shooting: The process technician noted concentrate in the site glass and in the feed section of the screw. The barrel was purged and restarted. It was noted that there was no evidence in the parts or purge that the material was wet. Following the purge and restart production parts were approved and resumed. Within the hour the problem resurfaced.

Second Trouble shooting: The process technician considered an incompatible melt index in the material and color concentrate that caused materials not to mix properly. Data sheets were reviewed and a melt index test was done to confirm that material and color were to specification. The machine was restarted and started running good parts. Within the hour the problem resurfaced again.

Third Trouble shooting: Scratching our heads we shut the machine down to tackle the next day. Upon coming in the morning the process technician was inspecting the equipment in preparation for another run and when he lowered the vacuum hose color concentrate spilled on the floor. The first clue to our problem.

Solution: It was determined that the specific gravity of the color concentrate was slightly greater than that of the ABS. As a result as the material travelled through the vacuum hose the heavier concentrate settled in the corrugations of the hose and starved the machine of color. Color concentrate was visibly present in the material presented to the throat of the press, but at the ratio blended prior to the vacuum loader. Upon recognizing the issue the vacuum pressure was increased to move the material with more force through the corrugated tube and the problem was resolved.

Sometimes the most frustrating and challenging problems are solved with the simplest of solutions. We hope you may park this experience in your memory bank and look like the smart guy when this happens in your shop. At Blackwell Plastics we believe it is important to do what you love and love what you do. If we can be of assistance, feel free to Ask an Engineer at or call us at 713 643-6577.

Jeff Applegate

Friday, December 2, 2011


At Blackwell Plastics “A challenge to conquer” inspires learning and yields satisfaction and pride in our work when we have accomplished our goal. Today’s challenge was an 8 cavity clear rectangular part that presented a weld line or flow line in the face of the part. Upon analysis each cavity was gated at the corner and vented at end of fill in the opposite corner. We completed a number of shots to progressively fill the cavities and confirm that the cavities were balanced and filling properly. Process Engineering quickly ruled out material rheology or the tool geometry as a cause of the defect. The root cause was determined to be a venting issue. We considered three options to address the problem.

1. Perimeter venting – This strategy would involve a modification to the cavity of the mold to vent the entire perimeter of the cavity.

2. Static vent pins in the cavity – This strategy would involve putting static vent pins in the cavity area where the weld line was generated to allow uninhibited flow to the vent thereby eliminating the visual weld line.

3. Coining Technique - This strategy would involve filling the cavity with a relaxed toggle at low pressure allowing the part to vent along the entire perimeter. Upon 96% fill we would clamp, pack and cool. This would be similar to option 1, perimeter venting, but would not require a modification to the mold.

We tried the coining first to avoid modifications to the mold and after the progressive fill to ensure balanced filling we shot at 96% fill, clamped, packed, cooled and ejected. For today’s challenge the “coining” of the mold solved the problem without modifying the mold. The result was a part with less stress in the part and elimination of the weld line.

Understanding the conditions and events in the cavity from the perspective of the plastics allows our process engineers to solve problems. The idea of getting in to your work has a whole new meaning when solving problems outside the two plates of steel. Doing what you love and loving what you do is a joy that few get to experience and are at the heart of what makes our team go. If we can help you solve your problem, feel free to contact one of our engineers at

-Jeff Applegate

Thursday, October 27, 2011

Mold Maintenance: Hidden Costs Often Overlooked – Jeff Applegate

Injection molds are a big investment and in many circumstances represent a substantial portion of assets on the balance sheet of a company. Tooling assets are similar to a car that is used for transportation. Maintenance is essential to keep the vehicle running efficiently and continuing to be dependable transportation. Injection molds are like any other mechanical asset requiring maintenance to ensure efficient and dependable performance.

When water lines become clogged, vents become blocked, or mechanical parts begin to wear, the efficiency, quality and overall performance of the tool begins to decline. In an effort to produce parts process technicians may make adjustments to the manufacturing process such as increasing pressures or extending cycle times to accommodate normal wear and poor maintenance. Seldom does the loss of production efficiencies get noticed and are more often are overlooked as minimal variances to the process. There is truth in the saying that “small leaks sink ships” and the accumulation of many of these variances add up to big dollars.

It is not uncommon for shops to simply blow out the water lines and spray down the cores and cavities with rust inhibitor and call that maintenance. For the purpose of this article I will address the two general terms referring to maintenance that take place in most shops.
Preventative Maintenance – Routine maintenance that is done on a tool that is out of the machine. Preventative maintenance is routine and should be prescribed by the individual tool. Materials processed, moving parts, complexity of part are some of the factors that will influence the maintenance interval. Typical tasks in routine mold maintenance include:
• Cleaning and descaling of the water lines
• Disassembly of the tool to inspect and Lubricate the ejector pins and leader pins
• Inspection and lubrication of slides or moving components of a mold
• Inspection of cores and cavities for wear or damage
• Cleaning of vents
• Inspection of hot runner systems

Predictive Maintenance. – This is typical of high volume production tools to ensure that there is minimal unexpected downtime. Predictive maintenance accounts for predicted life cycle of components and production performance history of the mold. The idea is to study and record the performance of a mold so that you can predict the normal wear patterns. Once these are identified an intelligent preventative maintenance program can be implemented. This program would include all of the above PM as well as the specific plan for critical wear or performance components.

There are many programs that can help manage the preventative maintenance for tools. At Blackwell Plastics we use a Preventative Maintenance software package that is an added option to the IQMS ERP system. This system allows us to create a custom PM plan for each tool that automatically triggers a work order upon reaching the prescribed number of cycles. Companies such as Tooling Docs also have Preventative Maintenance software and training that can do this as well. Tooling Docs also offers valuable training programs in maintenance, repair and management of the tool shop.

Don’t let “small leaks sink your ship”. Investing in Preventative or Predictive maintenance is described as a “last frontier” in improving performance and profitability. Proper maintenance will yield consistent processing, consistent quality, and consistent profits.

For more information on injection molding, mold building or mold maintenance, please contact Blackwell Plastics engineering 713 643-6577, email: or our website at

Monday, September 12, 2011

Product Design

Navigating the path to bring a new product to market often leads you to unchartered territory and treacherous decision points that can lead to costly if not tragic results in bring a new product to market. A general overview of bringing a product to market would cover these milestones.
• An unmet need
• An innovative idea
• Good Industrial Design/Engineering working with all available collaborative technologies.
• Material selection
• Tooling
• Manufacturing

You need all of these disciplines working together and need experts in those fields that are best suited for the product because of their specific experience. Finding the right designer and engineer with a history of designing similar parts is key to the success as you can build on the experience of others that have gone before you and benefit from the good and bad lessons learned and realize efficiencies gained by following in the path already blazed by another. In some instances you may need to work with a couple design firms to get all the expertise. For example one design firm may be great at the creative and mechanical aspects of the design, but does not have electronics and reliability engineering in house.

Depending on the application choosing the right material can also be a critical decision in ending up with a product that meets all the requirements at a lowest cost. A good first question to ask is “can we make it in polyethylene?” If not then begin going up the engineering material chain to find the right material for the application. The material suppliers have excellent resources and can be invaluable partners in helping you select the right material and help in understanding the market.

The next hazard is developing the tooling. There are many niches in tooling companies. Some include prototype, bridge to production tooling, speed, cost, polish for lighting and reflectors, corrosive materials, multi-shot, coordinated automation, insert, etc. Choose the right tooling company that also has a track record of building tools for your type of application. This is most important when working on high volume or complex parts.

Last is finding the right processor. Whether it be injection molding, extrusion, blow molding or other process, finding the right supplier that fits for you is another critical area in making a successful project. Not all processors are alike. As with tooling there are niches such as prototyping, low volume, high-volume, engineering materials, clean room, highly automated or highly custom. A couple suggestions that will help you pick the right processor. When possible use a regional supplier that is close to you. Communication and transportation costs alone are just a couple items that make will make this relationship pay off. Certainly there are scenarios that competitive cost drives manufacturing to other regions, but proximity will be your friend as you work through the manufacturing challenges. Next look at their business and see if the majority of their business looks like yours. If you have a low volume custom product and they have a highly automated shop that manufactures long runs then it probably isn’t the best fit. Most importantly recognize that the processor is your manufacturing partner and as such communication is critical to your success. Having a partner that you can trust, communicate, and shares your passion for building your business will make your life much more enjoyable. After you meet all these criteria then work on getting pricing that works for both of you.

What makes the product development process so interesting and difficult is that the combination of these key relationships is rarely the same from product to product. No one supplier can be all things to all application, but finding the right fit in each of these critical "cogs" makes the product realization experience work well. Do your research, look at the portfolios of the Industrial Design firms, know the key characteristics of your tooling that will make your product successful, take advantage of the vast resources of the material suppliers technical and marketing expertise, visit the processors to see if their business is a match and find a relationship you can trust and enjoy the experience of building your product and your business.

For assistance in navigating this path and for identifying possible partners to collaborate on your product, please feel free to contact us at 713 643-6577 or email

Thursday, April 28, 2011

5 Product Development Mistakes…and how to avoid them

by Walter Carver M3 Design
March 2011

The odds of a major league baseball game ending with a "walk-off" are about 1 in 11. So why is it that most development schedules expect a game ending home run to succeed? 

These “success oriented” schedules put the project at great risk, eventually take longer to complete, cost more and compromise product quality. The good news is with proper planning, common product development mistakes can be avoided and the risks to cost, schedule and product quality can be minimized.


Mistake #1:  Starting the development phase too soon


Most product development processes can be reduced down to three basic phases: Strategy, Concept and Development. The Strategy phase discovers the product needs and defines the strategy for creating and delivering the product to market. The Concept phase takes the results of the Strategy phase and determines the optimal form the products should take. The Development phase takes the product defined in the Concept Phase, further develops and validates the design, and takes it into the supply chain for manufacturing.

When under schedule or budget pressures, it is temping to jump straight to the Development phase before the Strategy and Concept phases are started or completed. Why skip or rush through the Strategy and Concept phases when they provide the foundation for the Development phase? During these two critical phases, needs of the target market are identified, system-level architecture and product specifications are defined, and the product concept is selected. 

Product development costs increase substantially as the product moves from the Strategy to Concept to Development phases. Starting the Development phase before Strategy and Concept phases adds great risk, resulting in schedule delays and unnecessary increases in development cost.


Mistake #2:  Underestimating the back-end


Most of us are familiar with the “fuzzy front end” of the development process, but little is said about the “murky back end”. The development phase is not complete once engineering has completed the design and all of the specifications are approved. At this point, you are only 30% to 50% through the development phase and just entering the “murky back end”

During the back end of the development phase, the design must be validated and transitioned to the production supply chain. In addition, prototypes are built and tested to determine if they meet performance specifications and pass qualification and regulatory testing. 

After design validation, production ramp-up is performed to work out any remaining problems with supplier components, fabrication, and assembly procedures. Other issues dealing with product inspection, field support, shipping, inventory, returns, and product end-of-life need to be worked out during the back end.

Underestimating the back end is a common and costly mistake. The back end of the development phase can be a lengthy process taking 6 months or longer depending on the complexity of the product. Many of the back end items have lead times that affect the overall schedule and are not completely in your control. It is important that back end activities be carefully planned to prevent major schedule delays.


Mistake #3:  Not engaging suppliers early enough


Your product must not only meet performance specifications, but also cost goals. About 70% of manufacturing costs of a product are determined by design decisions early in the development phase. Waiting until the design is complete to engage production supply chain can be a costly mistake. Getting design feedback from your production supply chain will reduce manufacturing cost while improving product quality, reducing development time and shrinking development cost.


Mistake #4:  Trying to do too much with prototypes


Engineers and designers need to create prototypes or other working samples of the product they plan to produce. Engineers test these prototypes to verify that the design meets its specifications and design goals. In doing so, product design problems and their solutions can be identified early in the development phase to keep the overall project on schedule. However, schedule pressure will drive some organizations to try to get too much out of a single prototype.  

During the development phase, a number of prototypes should be built and tested. Even though they may not be made from production components, prototypes emulate the production design as closely as possible and help gain product confidence one-step at a time. These prototypes are necessary to determine whether the performance of the product matches the specifications, uncover design shortfalls, and gain in-the-field experience with the product in use. 

Combining these prototypes with product qualification, customer acceptance trials or other back end activities often seems like a good idea, but is often a mistake. Trying to get too much out of a prototype, such as using the prototype for product qualification, will defeat the purpose of the prototype. Prototypes should serve a specific need.  If the prototype is meant to address more than one need, (i.e. aesthetic and functional), it is best served splitting these functions into separate prototypes to reduce complexity, development time, and ensure the prototype serves its original intent – to solve or identify a problem.  


Mistake#5:  Misunderstanding regulatory requirements


Every industry has a myriad of regulations that govern product performance and safety. Discovering that your product does not meet one of these regulations during product acceptance testing in "the murky back end" can be costly. These costs will include time and labor to redesign due to construction or testing deficiencies, as well as product retest and re-evaluation at the laboratory. 

At the beginning of the development phase, due diligence with a certified testing laboratory and applicable regulatory agency should be performed to plan the compliance effort. The best way to gain confidence that the product will comply is to know the regulatory standards against which the product will be tested before you design the product. This will also avoid problems caused by insufficient design, uncertified components, incorrect or non-applicable test methods and so on.  You need to review, understand, and plan for the standards as early as possible in the design stage. It is impossible to learn all of the requirements just a few weeks before final production or distribution.  In addition, these standards may change on you mid-project, so keeping abreast of potential changes to standards is critical.

As the product certification process can be complex, it requires a great deal of preparation to ensure the product passes through a laboratory test regimen on the first try. Proper and early planning for the regulatory testing will go a long way towards ensuring smooth results.  




There will always be schedule pressures during the Development phase of a project. Therefore, it is critical that all factors that can affect the schedule are well understood and planned for in order to minimize development cost and maximize product quality.  The five common mistakes described above should be kept in mind before and during the product development process to ensure schedule, budget, and quality are met and the product is a success in the marketplace.

The path of Product Development is littered with unknowns and opportunities to make costly mistakes.  Collaborating with the Design Firm and key component manufacturers minimizes these mistakes and helps improve project success.  If we can help you with product development or for more information on product design and injection molded parts go to  You can also reach us at 713.643.6577 or email at

Thank you to our friends at M3 Design for providing the content for this article.

Tuesday, March 29, 2011

What is needed to get an Injection molding quote

Every time the phone rings I get excited. I never know exactly what to expect on the other end of the line. As a project Engineer I receive a lot of calls from prospective customers trying to understand how to get a quote to injection mold plastic parts. Prospective customers come from many different backgrounds. Some are seasoned veterans in the world of injection molding while others are still learning that there is more than one type of plastic.

Regardless of the individuals background the goal is always the same, get them an accurate estimate of the manufacturing cost based on the information they provide as quickly as possible. The key to providing a fast and accurate quote is the "information they provide". Typically we will ask for basic information such as the part files, material type, estimated EAU, physical requirements, and unique specifications for the product. However, a good quote begins with a thorough understanding of the application of the part. How will the part be used? How long do you need the part to last? What environment will the part be exposed to? Will the part be exposed to chemicals that may attack a plastic part. Will the part be used in sunlight with U.V. exposure? What are the mechanical requirements of the part? Does the part need to bear weight, withstand impact or be flexible in its application? How many parts are you going to use in a month, quarter or year? What are the dimensional tolerances for the parts? Expected production quantities and dimensional tolerances will drive number of cavities and specifications on tooling design that significantly impact tool cost, tool life, and unit price. Do you expect the design to change? If so, you may want to plan for this in the tooling to save tooling cost for changes or new tools in the future. Finally, don’t forget packaging. Packaging is important in protecting the parts and can add significant cost to manufacturing. These questions represent some of the initial information necessary to understand the application. A thorough understanding of the part allows the Project Engineer to not only give an accurate quote, but also allows the Project Engineer to apply their design, material, and processing knowledge to contribute valuable experience to the project possibly making the part perform better or reduce cost.

One scenario I often encounter occurs when prospective customer has an invention and would like to find out the cost to have it made. It is not unusual to find that part models or drawings do not exist and the prospect is only willing to give a rough description of the part out of fear that someone will steal their idea. Without drawings or information about the parts use and application we can not provide an accurate tooling quote or even suggest materials. It is important to know that it may take several hours of work to prepare an accurate and well engineered quote for a new part particularly if tooling is involved. An accurate quote for a custom part requires a coordinated effort with many outside vendors and suppliers. This effort takes time and requires resources from all involved. This is a fact that is often not understood or appreciated when a request is made for pricing. Unfortunately we are unable to help these individuals and request they contact us when they feel comfortable disclosing more details about there project.

A second scenario we encounter is when a prospective customer is able to provide us a description of the part and an understanding of the application along with a 2D print. In this scenario we can help suggest materials and discuss tooling options. While discussing the parts use we are often able to recognize requirements the customer may not be aware of. If we have a 2D part print and the general material type we can estimate the part weight and tooling with enough confidence to provide a solid budgetary quote. The final pricing would be dependent on the customer’s final part design and material selection.

In most circumstances prospective customers provide a 3D solid model and the exact grade of material. In this circumstance we can provide a very accurate quote quickly. A 3D solid model allows us to accurately predict the labor in building a tool. By using the mass properties of the part model and the density properties of the material we can calculate the part weight. The only variable we have at this point is the cycle time which can be estimated fairly accurately depending on the part design.

In summary, there are many aspects of requesting pricing on a plastic part that will help the processor provide an accurate and timely tooling and piece part quotation.
• Application - Be prepared to thoroughly describe the part including where and how it is used.
• Design – Having a 3D solid model produced in a software like Solidworks or ProEngineering will help expedite the process and provide more accurate pricing.
• Volume - Be able to provide information regarding the annual volume and the expected number of years parts that will be required.
• Materials – Do your research and come with a specified material or prepared to discuss material requirements.
• Tolerances – Dimensional tolerances can significantly impact unit price
• Packaging – Packaging is often not considered and can impact the unit cost.

The more information provided for a quote allows your processor to provide a more accurate and timely estimate.

For more information on Blackwell Plastics and how we can help you bring your product to life contact us at

By Jason Mann

Wednesday, March 9, 2011

Invention and Opportunity are Alive and Well

 “Everything that can be invented has been invented.” - Charles H. Duell, Commissioner of the US patent office – 1899 

I write this article in a time of economic recession not to reveal a new technical discovery, but to encourage you that the entrepreneurial spirit is alive and well.  I want to encourage you that the drive for innovation and the opportunities that invention creates are bountiful in our region.  If Charles H. Duell could only see us now.  How many of you enjoy looking through Sky Mall, Sharper Image or Hammacher Schlemmer magazines for the new widgets, gadgets and innovative ideas?  What drives innovation? What inspires us to invention or to pursue cheaper, better and faster?  Irritation, inconvenience, inflation, war, greed, or unmet needs all inspire innovation. Competition and market incentive drives every industry to look at innovative ways to create new revenue, increase margins, maximize cash flow, and reduce inefficiencies. Competition to improve performance drives our engineers to challenge the status quo, solve difficult problems, find process improvements, and discover new inventions.  As a custom manufacturer in Houston, Texas, I see first hand the overflow of new inventions and opportunities in our city.  Inventions in medicine, chemistry, material science, information technology and energy are happening every day in our city. 

The plastics industry is a magnet for inventions and every week new ideas and innovations for all industries are coming to life in Houston.  Houston is home to the Texas Medical Center where more than $2 billion is spent annually in research and development and more discoveries, patents, and innovation are created than can be commercialized.  Houston also has the University of Houston, Rice, Houston Baptist University, St. Thomas and several other colleges and research institutions that are conducting research in every scientific discipline.  Houston is home to NASA’s Johnson Space Center, the capital of the U.S. energy industry, and our own massive chemical manufacturing facilities along the Houston Ship Channel. 

Without sharing details of customer proprietary secrets, we are seeing innovations in the medical device industry, energy, electronics, and aerospace industry.  Plastics are finding applications into many new product innovations.  We are participating in new products for electrical connectors, clamps, valves, meters, seals, medical devices, specialty pipe and tubing, and oil field testing and production equipment.  We partner with the resin manufacturing and compounding companies to match materials to these specialty products.  Some of our recent projects include the application of high molecular weight plastics, barriers for corrosive gasses and acids, water soluble materials, thermoplastic composite materials, materials with Kevlar rope to add tensile strength, and chemical resistant tubing suitable for bonding.  Invention and inspiration are alive and well in 2011.  It is these innovators that make it fun to come to work every day and this abundance of opportunity that gives us confidence in a strong economic recovery.  If only Charles Duell could spend a week in our shop, he would recognize that the opportunity for invention is limitless.

If you are an innovator and would like to pursue your innovation visit us at or call (713) 643-6577.

 Jeff Applegate
 Blackwell Plastics

Tuesday, January 4, 2011

Irish + Alcohol = Problem

What happens when you combine a large concentration of pubs, young Irishman, and street signage? A lot of broken signs!  One of our customers received reports from the field that there signs were having the metal support cables snapped. As it would turn out, the inebriated Irishman thought it was fun to rotate the signs on there bases until they snapped the internal cables holding the signs up.

To combat the problem we decided to re-design the base of the sign so the hooligans wouldn't be able to break the cables if they twisted them. The solution was a two piece self righting swivel base. The upper and lower were originally both going to made in Acetal, but having two like materials created wear issues. The upper was changed to a super tough Nylon for better wear characteristics.  The swivel design was successful in preventing the cable's from breaking, but the swivel still had one major issue. The drunken Irish would still twist the signs which eventually wore the points of the swivels down to a flat. Glass fibers in the Nylon increased the amount of wear on the leading edge of the swivels. Once the leading edges became worn flat they had a tendency to get stuck pointing in the wrong direction making the signs useless for pedestrians.

To overcome the problem many different ideas were tossed around. We considered metal plates on the tips, re-shaping the tips, and new materials to prevent wearing. In the end we decided to make two changes. The first change was to run the nylon parts with a hotter mold, this brings more plastic to the surface of the part and buries the glass fibers deeper in the plastic.  The second change was to add a self lubricating additive to the Acetal to lubricate the wear surface. As the two parts wear on each other the lubricant would migrate to the surface to prevent wear on leading edges.

By using a lubricating additive and reducing the amount of contact with glass fibers in the parts we were able to reduce the wear characteristics of the parts . The parts will now be able to resist the constant twisting and abuse they will see in the field.  The signs will now allow sober Irishman the ability to safely navigate the streets of Ireland.  For help solving any of your issues please call 713.643.6577 or visit our website at

Monday, November 29, 2010

Happy Holidays

Many of us throughout our lives have had particular times when we have had a “special guest of honor” join us in our home. These times are usually during the holidays such as Thanksgiving or Christmas. The typical guests of honor list usually includes grandparents, children, or relatives who may be living a long distance from home-base, it could also be spiritual leaders such as your pastor, traveling evangelist, teachers, or the return of a long lost friend.

Whatever the occasion and whoever the quest we always strive to make the experience pleasant, we “bring out our best”. The air temperature must be perfect, the food must be the perfect texture and taste superb, the drink must be extra cold, and the dinner rolls extra fluffy. We also bring out the very best pots and pans for preparation; we get out the best plates, utensils, and our favorite serving dishes.

Have you ever wandered what sort of effort it takes to get just a small fraction of all the items you would need to prepare for such an occasion? Have you ever considered how many engineering hours there are in each and every item you will use in your dinner preparation? How many different materials are all of these various item made from?

There is a tremendous number of different metals, glass, stoneware, and ceramics, not to mention the large numbers of plastics.

There are literally hundreds of thousands of different plastic materials commonly used in the world today. Do you know which material you are using? Do you go out and research what materials are in a particular serving spoon before purchasing it? Do you know the upper temperature limitations before the spoon becomes too soft and weak to serve mashed potatoes for instance? What will happen to your serving spoon if you were to accidentally drop it on the ceramic tile, will it shatter into pieces, or will it just break into two pieces, or will nothing really happen to it?

I am certain that the majority of homemakers and cooks strictly rely on the “plastics professionals” to answer and research all of these questions. Understandably every cook does NOT research every utensil they buy, every pot handle, and every lid for each container of their plastic ware. So, as we celebrate the holidays take a moment to consider all of the plastic materials that you use. Consider the skills, technology, and professional collaboration that have come together over the last hundred years to bring these products to your holiday celebration. The design community uses the term human factors to consider how we humans interact with products. They design for fit, feel, function to improve the performance of these products. Developments in the science of materials expand the pallet for industrial designers to improve products. As plastics professionals we work to engineer the building blocks of the polymers, we compound these polymers into engineered applications and enhance with additives, colors and fillers to continue to extend the pallet for the designers. The tool makers and processors have worked together to complete this progression with the development of ingenious tools, machines and processes to transform these polymers into usable products. Possibly you have been to the plastics exhibit at Disney’s Epcot center where they highlight the use of plastics in the modern kitchen. There are plastic materials in your appliances that cook your meal, plastics in the trays and utensils that you serve your guests, plastics that make the pots and pans easier to clean, plastics in you decorations and even in your napkins and tablecloths. As you enjoy your ham or turkey this holiday season, account for the involvement of plastics in your celebration and consider your friends and colleagues that have worked together to make this possible. Take pride in the work we do to improve the quality of life and be encouraged by the work you do. At Blackwell Plastics we get the privilege to work with incredible customers every day to apply existing and new materials to create new products. It is a big part of what make it fun to come to work every day. If we can help you with your dream or idea to improve the quality of life with plastics you can reach us at or 713 643-6577.

Dane Kinchen 11-22-2010
Project Engineer/Sales Engineer
Blackwell Plastics

Tuesday, November 2, 2010

Medical device design

Everyday we encounter thousands of plastic injection molded products that we don’t give a “high value” too, but we expect these products to work flawlessly when we need them. Examples could be the living hinge on a plastic lid, a cap on a soda bottle, or a zip tie. When using these everyday products do you ever consider all that makes them work?  All of these injection molded parts perform simple functions and appear to be simple in design, but work because of decades of development in plastics material science and product design. Odds are you probably haven’t put much thought into their engineering unless you have been asked to design one.

Consider the injection molded zip tie example and think about all the factors that make the simple zip tie work. First you have the physical properties of the plastic material. The interface of the molded pawl (lever) and ratchet must be in perfect alignment to ensure they make contact. The angles and tolerances of the molded pawl and ratchet must be considered to ensure a positive lock. When you start to break down how the simple zip tie works you find it is not as simple as it seems. Now take understanding of the zip tie and place it with a first responder or hospital ER  and envision a doctor who must quickly secure the device while wearing gloves and working under pressure.  Recently I have been working on an injection molded medical device that serves as an endotracheal tube holder and provides a safe way to insert an orogastric tube into the esophagus of a patient.  This device design solves many problems for hospital and first responder medical technicians.  The device secures the ET tube assembly to the patient, eliminates the discomfort and risks of feeding tubes through the nose to access the stomach, and provides a bite block to prevent a patient from closing the air way.  The zip tie is a critical functioning component and many factors have to be perfect  for a zip tie to work in this environment.  We will discuss some of the challenges encountered with this design and the steps Blackwell Plastics took to solve the problems.

The illustrations show how the design planned for the assembly of the final product and how it would function. The device includes two components that would be bonded together. To assemble the final part, the tube from the lower piece is inserted inside the cylinder on the top piece and solvent bonded in place. The material originally chosen for this application was flexible PVC, with a higher durometer for the top section and a lower durometer (softer/ more flexible) part for the bottom section.

We recognized the critical variables that would impact the mechanical performance of these performing areas.  Before the tools were made we anticipated there might be adjustments to certain features so we stayed “steel safe” and inserted certain parts of the mold.  This allowed us the flexibility to make quick and easy changes if needed. We also built the tools in stainless steel to allow broader choices of plastic materials including PVC.  Following first shots the customer found that the “zip tie” would not hold the ET tube without it slipping. The pawl (lever) wouldn’t engage the ratchet (strap).  Under close observation we saw that the strap was deflecting away from the lever because the amount of clearance or  “play” behind the strap. We also noticed that the plastic lever would fatigue after a couple of uses and wouldn’t hold enough pressure on the strap to secure the lock.  After the problems where identified the mold was easily modified to take up the clearance and thicken the pawl to restrict flex movement. The improvements made the lever stronger, but the 90 durometer PVC material still allowed the lever to bend out of position. The material needed to be flexible enough for the strap to bend, but rigid enough for the lever to engage the teeth on the strap. We were asking the one material to perform as both a rigid and flexible material.  We elected to go with a LOWER DUROMETER MATERIAL to give flexibility we wanted in the strap and add material to the lever to pin it down and force it to make positive contact with the strap; this would allow a lower durometer material to make a positive lock.  The final adjustments made to the lever were enough to give it the strength needed. Finding the right balance between strength and flexibility was difficult but crucial to the part’s performance. This small example illustrates how difficult it can be to predict exactly how a design will perform when you take into consideration all the different factors that can affect performance.  In early stages of the project when planning for tooling it is important to anticipate design challenges and plan flexibility in the tool design so that modifications can be made to critical components without significant rework and cost.  

These challenges where only a few of the issues we encountered while bringing this plastic injection molded product to life. The parts have gone through several transformations since the first samples were molded. Early on we understood the design may need to be adjusted and we where able to plan accordingly.  Taking the proper precautions helped to save time and costly tooling changes. None of these changes happened overnight, and it took team work and the dedication of several people to make the product a success.  That persistence will now benefit those in the medical community and those who receive medical care.  If we can help you bring your product to life or for more information on product design and injection molded parts go to  You can also reach us at 713.643.6577 or email at