From Metal to Plastic, Silicone to TPE: Cut Cost, Enhance Performance

Learn how Enplas’s engineering and manufacturing expertise helped a major pharmaceutical OEM convert a test instrument component from metal and silicone to rigid plastic and TPE, enhancing the component’s functionality and usability, and reducing overall manufacturing cost.

THE PROJECT: CONVERTING A FOUR-CHANNEL PIPETTE AIR DISPLACEMENT DEVICE FROM METAL TO PLASTIC AND TPE

Enplas was approached by a global pharmaceutical OEM to manufacture a four-channel pipette air displacement device it used in biotech test instruments. The device consisted of a brass body, four stainless steel tubes, and four silicone molded seals. The goal was to redesign this whole assembly into a single plastic part.

The final single plastic part consisted of overmolded TPE seals and a plastic substrate. This redesign enhanced the device’s functionality and usability while significantly reducing its overall manufacturing cost. The project combined two of Enplas’s strengths: expertise in manufacturing thermoplastic fluid seals and a long history of helping customers convert metal parts to plastic.

Metal to Plastics Conversion

 

GOALS

The goals of the redesign were:

  • To reduce the cost of the device’s materials
  • To eliminate the need for assembly and reduce the number of fixtures used in the assembly
  • To eliminate the risk of damage from sub-assembly (i.e., components damaging each other during assembly)
  • To eliminate recurring maintenance issues in normal operation (e.g., sub-assembled components loosening slightly)

FUNCTIONAL REQUIREMENTS

The redesigned device needed to maintain the same precise dimensions of the original. In addition, the device’s elastomer seals need to be consistently air-tight against its inlet ports and maintain a product life of at least 1,000 cycles of pressurization.

ENPLAS’S APPROACH

Enplas began this project by understanding the original device’s performance requirements and assembly consideration with surrounding components. This enabled Enplas to recommend the best materials to use (both elastomer and rigid plastics) to meet the client’s goals. To ensure reliable sealing, material considerations included hardness, compression set, and chemical bonding characteristics.

Enplas also analyzed the physical design of the elastomer fluid seal to ensure secure contact with the consumable. The size and shape of the device’s contact surfaces is critical to ensure its air-tight sealing performance when pressurized against inlet ports.

The practice of Design-for-Manufacturability (DFM) was adhered to throughout the project to ensure the consistent and efficient production of quality parts for both injection molding and assembly with other components.

Finally, Enplas provided quality manufacturing services for the redesigned device, which included injection molding the rigid plastics and overmolding the TPE seals. All manufacturing at Enplas Life Tech undergoes our rigorous process validation practice to ensure quality and consistency.

SOLUTION: CONVERTING FROM METAL AND SILICONE TO PLASTIC AND TPE

Enplas successfully manufactured the redesigned component and exceeded the original device’s performance in several critical areas:

  • The device’s separate metal parts were replaced with a single component made of injection-molded plastic substrate. The device’s silicone seals were replaced with overmolded thermoplastic elastomer (TPE) seals. This resulted in over 70% cost savings due to lower material cost and elimination of manual assembly.
  • The device was required to perform up to at least 1,000 cycles. The redesigned device achieved over 7,000 cycles during endurance and functional tests without leaking.
  • Sub-assembly damage has been eliminated.
  • The new device exhibits no quality or maintenance issues during manufacture or operation. Recurring maintenance issues in normal operation have been eliminated.

For product conversions or enhancement projects, it is important to engage an expert manufacturer with a reliable engineering team that can recommend the best materials and manufacturable designs to achieve your performance goals, ensure reliable quality, and maximize manufacturing efficiency to reduce costs. Contact Enplas early in your design process to allow necessary modification to achieve best results like the above. Contact us now for your next project!

To learn more about whether silicone or thermoplastic elastomers (TPE) might work better for your project, download our comparison sheet.

BLOG: Design for Manufacturability (DFM): The Basics

If you are part of a product development team working on a product that may reach millions of parts, or are a growing start-up about to ramp up production volume, this article is a refresher on basic design for manufacturability, or DFM. At Enplas Life Tech, we believe that DFM is a collaborative process between our customers to enhance their original part designs. Read on to learn how injection molding engineers can help ensure your components are manufacturable and cost-effective at scale.

Design for manufacturability is the process of designing products to facilitate the manufacturing of components. DFM is especially critical for mass produced components and assemblies. It safeguards quality, it saves time, it saves money—and most importantly, it can prevent potential problems down the road.

Although there are many dimensions to DFM, the most basic goals ensure that:

  • It’s physically possible to manufacture your part, and
  • The manufacturing process is streamlined to be simple, efficient, and robust.

Basic Design for Manufacturability for Injection Molding

Due to the nature of the injection molding process, there are guidelines to follow when designing components. In injection molding, you have two molds enclosing a cavity that is filled with plastics to form the component. After the heated liquid material is injected into the cavity, cooled, and solidified into the part, the molds separate to eject the product. (This is a different process from 3D printing, a popular prototyping process. A part that can be 3D printed may be impossible to be produce via injection molding.)

Injection Molding

Below are a small portion of the many basic DFM considerations required to ensure that the final part design is possible to manufacture. Without proper consideration, the part may have defects or be vulnerable to breaking. These considerations include:

  • Undercut: A simple mold like the one shown in Figure 1 cannot open when there is an undercut. Certain undercut features could still be injection molded with special tooling, which would make the tooling more complex and costlier.
  • Draft: To ensure the molds open smoothly, products need draft. A product’s draft angle is a slant that is applied to each side of an injection molded part. The angle is positioned to run toward the direction of a mold’s pull and parting line; this helps to release the part from the mold. Draft considerations are important to meet your quality standards. Without it, major problems can arise that increase production time and cost.
  • Wall Thickness: Something seemingly as simple as wall thickness can have a remarkable effect on a product’s success. For instance, thinner walls require less material and cool faster. This reduces a mold’s cycle time (increasing the number of units that can be made per period) and input costs. But go too thin, and the product becomes brittle and unreliable. Too thick? Your process is not optimized. Another major consideration is the uniformity of wall thickness; a lack thereof can cause weakness and unsightly “sink marks.” Optimizing wall thickness is a basic—yet critical—consideration for your injection-molded product.
  • Rib Ratios: Walls that are thicker or non-uniform by necessity of design can sometimes cause problems. To counteract these issues, ribs are used. Ribs are thin structures that add support and rigidity to injection-molded parts. This solution, however, can cause problems of its own. To prevent these problems, rib design must adhere to certain proportions. For example, if your product’s ribs are too tall, breakage can occur during use or during ejection from the mold. Rib ratio must be carefully planned and evaluated for success.

Design for Manufacturability for Assembly and Overall Product Performance

In addition to ensuring that your part is injection moldable, other DFM considerations contribute to the function or overall assembly process of the product. For example, the addition of measured features could make the assembly process easier and less costly further down the road. Combining two components in one is another way to simplify overall assembly. Read our blog on advanced DFM for more information about DFM that enhances product performance and simplifies assembly at the same time.

Failure Mode and Effects Analysis (FMEA)

Any basic DFM done well should also include a failure mode and effects analysis (FMEA). This is the process of identifying the risk of possible modes of failures while a product is still in the development phase, and the development of measures to mitigate those risks. FMEA is a critical part of the initial phase of process validation for our projects.

At Enplas Life Tech, we believe design for manufacturability is a way to solve difficult engineering challenges collaboratively with our customers. DFM enhances component designs by improving product manufacturability.  Enplas Life Tech has a long history of successful collaborations with engineers at market-leading, global OEMs and innovative start-ups alike, in the medical, diagnostic, and biotech industries. Have a design ready for production? Contact us.

Design Development Beyond Basic DFM for Product Performance

If you’re reading this article, you’re probably already aware of the basics of design for manufacturability (DFM): the process of designing products to facilitate their manufacturing.

However, a more product performance focused DFM does not simply make your product moldable: it can also enhance your product’s value in terms of its function, quality, supply stability, and manufacturing cost. We could even call this “Design for Functionality”.

Unlike many manufacturers, Enplas Life Tech goes beyond the basics to offer this advanced DFM when we see opportunities to help. Our customers—innovative medical industry market leaders—tell us again and again how they appreciate this customer-centric practice. 

For example, many companies approach Enplas Life Tech for the manufacture of elastomer fluid seals for diagnostic or medical devices. Given the intricacy in shapes and functions of fluid seals, the end product’s performance and quality may diverge greatly depending on whether it went through only basic thoughts of DFM, or a more rigorous, advanced DFM process.

The below image is a sample of an elastomer fluid seal between a fluid inlet (pipette) and a microfluidic chip. Customers’ original designs often come with two or more sealing ports with separate elastomer tips, each to be assembled as a secondary operation after injection molding. (See Figure 1 [note: this is a hypothetical design].)

Fig 1a. Pipette, interface with elastomer fluid seals, and microfluidic chip

Fig 1b.Two fluid sealing ports, two separate parts for each port

Conducting basic DFM would be sufficient to ensure that this design is compatible with all injection molding processes (e.g., no undercuts, appropriate draft, and material being compatible with the dimensions and wall thickness). 

After discussing the project with the customer, however, we develop a deeper understanding of their priorities for the product’s application: the seal must stay in place to avoid any leakage. Our goal is always to support our customers in achieving the best possible product value. Therefore, we might suggest the following change (see Figure 2):

Fig 2. Two sealing ports, one integrated part sealing both ports

This change in the design created a path (an “internal runner”) that enabled the thermoplastic elastomer to flow inside the rigid plastic and connect the two sealing ports. This change provides multiple benefits:

1) Function: Enhancing Fluid Seal Bond Strength

  • The internal runner performs as though it is “bolting down” the elastomer into the rigid plastic as opposed to simply being glued externally. This makes it significantly stronger and prevents it from peeling off. 
  • This uses a method called “overmolding. Overmolding takes advantage of the thermoplastic elastomers’ characteristic to chemically bond to rigid plastic surfaces. This also enhances seal strength and avoids the risk of the seal peeling off, decreasing the possibility of leakage or reagent loss.

2) Time and Cost: Eliminate Assembly Process and Reduce Lead Time to Lower Cost

  • By overmolding the part, the injection molding process alone will completely attach the two materials. There will be no need for additional assembly processes or adhesives—hence no problems from assembly or adhesives during mass production.
  • By combining the two tips into one elastomer seal, the mold/tools can be simplified. This also contributes to reducing cost.

Material choice is a significant consideration in DFM. In the past, Enplas Life Tech has suggested using a different type of elastomer, even though the original choice may have been sufficient to make the part. In this particular case, we recommend materials that are able to fill in molds more quickly due to higher viscosity. In these cases, the change in materials has improved the stability of production quality, avoiding chance defects. 

In order to suggest these changes, the injection molder must be well-versed in the characteristics of both rigid plastics and thermoplastic elastomers; have the sufficient expertise to build tools that can achieve the desired precision design; and, most importantly, have the dedication to work with customers and their complex requirements until the right solution is found. 

At Enplas Life Tech, we believe DFM is a way to solve difficult engineering challenges collaboratively with our customers to enhance component designs, improving product quality and performance. This makes life easy for all stakeholders: from our customers’ component design engineers and quality managers, to OEM customer production and assembly lines.

Enplas Life Tech has a long history of successful collaborations with engineers at market-leading global OEMs in the medical, diagnostic, and biotech industries. Have a design ready for mass production? Contact us

BLOG: Process Validation

If you’re a market-leading life sciences company searching for the right quality plastic parts manufacturer or custom manufacturing services provider, you already know how difficult it can be. Just trying to find a qualified provider you can trust can be time intensive and, well… frustrating.

At Enplas Life Tech, we know that trust is one of the most important services we can offer. We understand that your products’ success relies on the service providers you choose to trust.

That’s why Enplas Life Tech has an established quality control procedure built on proper industry-standard validation procedures: to statistically ensure that each part coming out of the line will fall within strictly-set standards for your project.

Precision quality parts from Enplas Life Tech are a trusted, reliable choice for your important diagnostic and medical devices. We know that your component production must continue without interruption. Therefore, we created a rigorous validation process that will enable us to provide you with an uninterrupted supply of the components critical to the shipment of your products that may ramp up volume over time.

Enplas Life Tech complies with the increased requirements of documentation and traceability in the medical industry. Our four-part process—DQ, IQ, OQ, and PQ—is the standard for validation and quality assurance in the medical/biotech industry. Enplas Life Tech took the basics of this standard process and added other procedures we consider necessary to have a truly rigorously validation process. These validation steps establish documented evidence of a high degree of certainty that the manufacturing process will consistently yield a product of predetermined quality. Enplas Life Tech records each step of the process and provides our customers with complete documentation in the form of the “Process Validation Protocol (PVP).”

Our validation process begins with the DQ (design qualification) stage. In this stage, our priority is to properly understand our customer’s unique, specific requirements and expectations. This includes areas such as production volume (e.g., including whether the production volumes might remain stable or increase with time, and resulting in decisions such as number of cavities), tool life, required levels of tolerance, and the minimum-required “CpK value”—a value that statistically indicates the capability and likelihood of the produced part coming in at required specifications. This information is used to determine how to build and set up the molds (e.g., what type of steel, which press, what support equipment is needed, cost, how many operators). All of the following processes—IQ, OQ, and PQ—are conducted to achieve the goals set in DQ. 

In addition, a failure mode and effects analysis (FMEA) is conducted as part of the design-for-manufacturability (DFM) process to minimize failure risk for critical functions or dimensions. 

The second stage is the IQ (installation qualification) stage. This stage is where the tools are built and evaluated, all production related equipment is set up, and various injection molding parameters are tested to determine a safe range of settings. It confirms that the tools are built to meet all inputs from the DQ stage and that the molding process is appropriately set up to begin producing sample parts with the injection molding machines. 

This stage marks the beginning of “scientific molding”: a practice to identify a range of injection molding parameters that would achieve the highest yield of precise parts. In other words, testing the limits of parameters to retain highest levels of quality in the products’ precision and dimension while running the presses in the most efficient manner. In the scientific molding process, data is collected from various studies (e.g., gate seal, cavity balance, back pressure, and melt flow) as outputs to create a “process window”—a general range of statistically-tested process parameters that produce products within the required tolerances. 

Other studies (such as the cooling study, used to determine the smallest amount of time required for the dimensions to become most stable) are also conducted.

The OQ (operation qualification) stage further refines the parameters to achieve certain operational performance requirements. OQ takes the data from the previous stages further: it obtains objective evidence that a defined, optimal process window allows the consistent production of acceptable products. A design of experiments (DOE) study is conducted, in which software statistically calculates many process variables to identify the optimal ranges. Following that, a full-dimension, first-article inspection derived from a set number of sample parts is conducted and the CpK is measured. If the CpK does not meet the initial goal set in the DQ stage, improvement plans are created and implemented.

PQ (performance qualification), the final stage, challenges the equipment similar to the OQ phase, but now does so under load. Finally, longer-run trials are conducted to confirm that key dimensions are maintained under a longer production period. Another first-article inspection and capability study are conducted on samples. The process is then officially validated to ensure it meets the customer inputs provided at the DQ stage. The degree to how much time and effort we devote to the PQ stage depends on customer requirements. We are happy to conduct the right level of validation to meet your specific needs.

Is your life sciences company searching for a quality plastic parts manufacturer or custom manufacturing services provider? Consider Enplas Life Tech’s engineering and design services and trusted validation process. Contact us today to learn more.

Want more proof of our dedication to product performance and quality? Download our TPE case study, “Life Science Diagnostic Device Development: Challenges and Solutions for Fluid Interfaces.”