Injection Molding FAQs

At Biomerics, our medical contract manufacturing roots can be traced to the field of injection molding. For over 20 years, we’ve provided injection molding solutions to the medical industry’s leading companies, and in this time we’ve received a wide range of questions and inquiries regarding injection molding and tooling. In an effort to better support and assist our customers (current and prospective) who are in need of injection molding services, we asked our engineering team to provide us with answers to the most common injection molding questions we receive. You will find our in-depth injection molding FAQ focused exclusively on the medical device market below:

What types of medical products are ideal for injection molding?

“Thermoplastic injection molding is ideal for medical products and components that must be produced in a repeatable and consistent manner,” explained Kevan Beynon, a Process Engineer at Biomerics. “High volume items, products and components with tight tolerances, and parts that must be repeatedly produced in a timely fashion are all prime for injection molding.”

Bryce Smith, a Program Manager at Biomerics, added, “Almost any plastic product or component that must be repeatedly manufactured with little or no variation is ideal for injection molding. If you’re producing large volumes of the same plastic part, injection molding can often help you realize lower part costs and higher quality.”

What variables effect the cost of an injection mold?

“The size and complexity of the part being molded are the two variables that come to mind whenever I’m asked about mold costs,” answered Bryce. “The bigger and more complex your part, the more the mold itself will cost you. Also, bigger molds can result in additional per piece costs due to the fact that more material will be needed to manufacture the part.”

“The cost of the new mold, the cost of qualifying the mold (IQ/OQ/PQ), and the cost of materials (i.e. the plastic that will be molded) are the three biggest cost variables when looking at the overall injection molding picture,” added Kevan. “Together, these are known as the ‘startup costs’, because without them, the mold can’t be run and parts can’t be produced. Aside from these startup costs, there are also mold maintenance costs and, of course, labor costs. Building the mold correctly the first time, qualifying the mold according to regulatory standards, and choosing the correct material from the outset are the easiest and most impactful way to lower injection molding costs.”

Injection Mold

What are ‘mold classifications’? Why do they matter?

“Molds are classified according to SPI standards, and are organized by the amount of parts they are forecasted to produce,” explained Kevan. “The mold classification is important because it defines the type of material the mold must be made out of, which makes costs easier to predict and communicate. Essentially, the mold classification allows companies to accurately set cost and production expectations. Although there are several classifications, in the medical industry, we deal with:

  • Type 101 Molds – These molds are the most expensive because they are made out of the highest quality, highest grade material. Type 101 molds are intended for extremely high production (1,000,000+ cycles).
  • Type 102 Molds – These molds are typically high priced and are made out of high quality, high grade material. Type 102 molds are intended for medium to high production (500,000 cycles).
  • Type 103 Molds – These molds are the most popular and generally carry a middle-of-the-pack price tag. Type 103 molds are made out of moderate quality, moderate grade material and are intended for medium production runs (100,000 cycles).
  • Type 104 Molds – These molds are typically low priced as they are made with low quality, low grade materials. Type 104 molds are intended for low production (10,000 – 50,000 cycles).”

“It’s crucial that the mold is built to the correct classification,” added Bryce. “If not, you’ll end up paying too much—either you buy a mold designed for more cycles than you need and you end up paying a lot up front for higher grade tool material, or you buy a buy a mold that can’t handle the amount of cycles you need and you end up having to spend more money on another mold.”

Can the mold itself be modified? In what circumstances would that be necessary?

According to Bryce, “A mold can be modified, however, the modifications that can be made will be limited and small. Modifications are usually made to help the mold perform better, or as part of a cosmetic change. Modifying a mold can be very costly, due to the costs associated with physically modifying the mold and the cost of having the mold down, not producing parts.”

“Any modification has to be approved by the customer,” added Kevan. “Most mold modifications are made to reconfigure a part as part of a change request. However, there are minor modifications that must be regularly made to the mold to ensure that it is in good working order. These types of modifications generally fall under mold repair and maintenance.”

What is the difference between overmolding and insert molding?

“The process of adding another layer of material over a polymer part or component is considered overmolding,” explained Kevan. “An example of this is overlaying a material onto a plastic substrate (e.g. extrusion) to form an introducer. In the medical industry, overmolding is commonly used to create catheter connecters, luers, and hubs.”

“Insert molding is the combination of metal and/or other plastics into a single unit,” answered Bryce. “In the medical industry, companies often use insert molding to add metal pins and bushings to a plastic part that has already been molded. They ‘insert’ the piece into the hub, handle, or other component.”

Over Molding

What advantages does injection molding offer over other fabrication techniques?

“Depending on the part and the volume size, injection molding can result in lower unit and capital costs,” explained Bryce. “If you’re running a large amount of volume on a single part that you need produced repeatedly and consistently, it would be hard to find another technique that offers any of the benefits injection molding does.”

“When it comes to manufacturing parts with precision, consistency, and repeatability, injection molding is usually preferred over other techniques,” added Kevan. “In these types of situations, injection molding typically offers lower costs, higher efficiencies, and less scrap, for ranging volumes of production.”

What types of materials can be molded?

“There are a wide range of materials that can be injection molded, even metal and ceramic can be injection molded. However, in the medical industry, we mostly see plastic injection molding,” explained Kevan. “Plastic injection molding can be broken into two categories: thermoset injection molding and thermoplastic injection molding.

“Thermosets are materials that cure through a chemical reaction that is spurred by heat and pressure. Thermosets that are commonly molded in the medical industry include silicone and rubber.

“Thermoplastics are materials that are heated until they reach the melting temperature, and then cooled until hardened. Thermoplastics can be melted and formed over and over again, whereas thermosets cannot. Thermoplastics that are commonly molded in the medical industry include nylon, polycarbonate, polypropylene, and thermoplastic polyurethanes.”

“Molding the two types of plastics require different equipment, capabilities, and material knowledge,” added Bryce. “It’s good to know the difference between the two, when designing a product and its corresponding mold. Lately, we’re beginning to see companies shift their products and components that once used thermosets to thermoplastic. Although we don’t know the exact reason for this, we know that it is partially due to the natural biocompatibility and additive compounding ability of TPUs and other thermoplastic materials.”

What three things should engineers be conscious of when they make an injection mold?

“Exactness, endurance, and expenditure,” answered Bryce. “Exactness has to do with precision. How precise does the part need to be? The more precise and complex the part is, the more the mold and part inspection will cost.

“Endurance has to do with the volume of the part. How many parts/cycles is the mold expected to produce? As I’ve stated before, underestimating or overestimating this number can result in additional, unnecessary costs.

“Finally, expenditure has to do with the overall cost of the mold. How much money is expected to be spent on the mold? This will effect many different things, but the most significant will be the quality/conformance of parts and the amount of parts that can be produced.

“Together, these three things can make or break the ability of the mold in meeting expectations.”

“Quality of the mold maker, quality of the mold material, and the mold manufacturer’s customer service system,” added Kevan. “A good mold maker will ensure that the mold is built correctly the first time, which will save you time and money because you won’t have to rework the mold or send it back.

“Selecting the correct grade and quality of material for the mold is also very important—you don’t want to have to buy two Class 103 molds when a single Class 102 mold would have done, and vice versa.

“Finally, a good mold maker should have an excellent customer service system in place—they should be able to clearly and effectively communicate and respond to any questions that may arise.

“Being cognizant of these three things can save companies looking to purchase a mold time, money, and stress.”

What injection molding solutions does Biomerics offer?

At Biomerics, we offer a wide range of injection molding solutions to meet the most demanding device needs. Our cross functional engineering teams utilize scientific injection molding principles to develop and optimize processes, components, and finished devices. Through our dynamic ISO 13485 compliant quality management system, we are able to partner with customers to design and validate processes and tooling used in medical injection molding. We specialize in high volume cleanroom molding, vertical overmolding, and low volume custom molding. Our vertical and horizontal presses (which ranging up to 900 tons) allow us to meet the injection molding needs of the most unique devices.

To learn more, send us an email (, give us a call (801-355-2705), or visit the Injection Molding section of our website.

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