Prototype Injection Molding: When and Why To Use It

What is prototype injection molding?

Prototype injection molding, also known as rapid injection molding, is a process that incorporates rapid tooling (RT) method to produce injection-molded parts quicker than standard tooling times. This acceleration is achieved from using aluminium tools, eliminating certain complicated elements, or simplifying the tooling and manufacturing process. Due to the nature of the tool, it is also less expensive to make, which makes it suitable for rapid prototyping project budgets.

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While prototype injection molding offers cost and time advantages over standard tooling methods when compared with other rapid prototyping techniques like 3D printing, CNC machining, or vacuum casting, it becomes more time-consuming and costly for production quantities below 100. Project budgets are generally tight and deadlines are even tighter, so why would you invest in prototyping via injection molding? Why not go straight from you 3D printed prototype to production tooling?

Why use prototype injection molding (over other rapid prototyping techniques)?

Prototype via injection molding is a crucial step for several reasons, even when project budgets and deadlines are tight. While 3D printing and other rapid prototyping techniques offers a quick and cost-effective method for creating prototypes, transitioning directly from 3D printing to production tooling without injection molding prototypes can lead to various challenges. Here are six key reasons why prototyping via injection molding is essential:

1. Allows testing of parts in the production-intent material

While processes like vacuum casting does a great job at simulating injection molding resin properties, it cannot compare to 'true' injection molding materials. SLA-printed prototypes may also be fine for many parts, especially if they are mainly cosmetic. However, with prototype injection molding, you can use the same materials that will be used in the final production process. This ensures that the prototype accurately represents the material properties, including strength, flexibility, and durability, this is especially critical for functional parts.

2. Enables validation of the production process 

Injection molding is a specialized and complex manufacturing process. If you have not fully understood and tested these intricacies, you could open yourselves up to failure down the road. Parts manufactured via injection mold tooling can help you understand how the product will perform in the production process, validating the manufacturability of the design and identifying any issues related to tooling, parting lines, gate locations, and other aspects crucial for mass production.

3. Facilitates the testing of part builds

By using production-grade materials and manufacturing processes, these prototypes closely mimic the properties and performance of the final production parts. This enables engineers and designers to assess how the product functions in real-world conditions and identify design issues before committing to hard tooling.

4. Enables low volume production runs and market testing

As the parts are essentially the same as production components, you can use them in early builds for market testing or even introduce them to the market place and start selling. Just because it is called 'prototype injection molding' doesn't mean that it can only be used for prototyping purposes. It is also a viable and competitive option for low-volume production of 100 and over.

5. Allows satisfaction of initial demand while production tooling is being made

Production tooling can take many months to have built. Even then it takes time to ship to the injection mold and get up and running. Instead of waiting and losing that valuable time you could use the prototype tooling to supply parts for initial demand. And it is a good backup should your production tool be out of action for whatever reason.

6. Helps save on time and costs

While prototyping via injection molding may seem like an additional step, it often leads to time and cost savings in the long run. If anything is wrong, you can fix it before investing time and money into full-scale production tooling. 'Fail early' is a mantra of many production design development teams, and prototype injection molding allows you to do this in a relatively risk-free and inexpensive manner.

How to choose a prototyping method

Among today's manufacturers, both medical device prototyping and plastic injection molding for medical devices are viable options for producing complex plastic parts and components. While originally considered competing technologies, these techniques are now each largely recognized as having unique advantages and can even be used together to help optimize production efficiency.

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The prototype is usually processed with plastic or metal on a CNC machine or 3D printed or vacuum casting, making several samples. Generally, a prototype is provided to the customer for confirmation, and after the confirmation, the mass production starts. 

Through the prototype you can quickly find out the shortcomings of product design and then improve it, with a short production cycle, reduced waste of manpower and material resources in comparison with the mass production. 

However, the role of prototyping is not just this one, it plays a central role in production of plastic parts.

In the drive to production, it's important to understand the volumes involved, and align expectations of what your chosen production process, prototyping or medical injection molding, can achieve.

If you're wondering whether plastic injection molding or medical device prototyping is the right process for your next project, we'll explain when to use each technique and how they can be used collectively to support one another.

When to use prototyping techniques for your medical devices manufacturing?

Creanova considers prototyping as the perfect solution when annual volumes are very low, when the products do not have to be very accurately made and when the product's final geometry is still uncertain (think of prototyping and pilot versions of certain products). Of course, prototyping is also ideal if there is currently insufficient budget for (mould) investments. Tooling for any product can be very expensive, and without knowing how many will be sold, the return on investment (ROI) for the capital expense of tooling may fall into a grey area ' maybe the ROI will be acceptable if volumes are high, but maybe not if we don't hit the sales we think we could.

Please note that when switching from medical device prototyping to medical injection moulding, the properties of the product may change (e.g. the strength, stiffness, draft angles).

In brief:

• low production volumes (100 parts or fewer per year)
• designs with frequent changes
• uncertain annual volumes (investments can be deferred)
• products that are required quickly (some techniques needs only 1-2 weeks)
• Relatively small plastic parts or components

When to choose plastic injection moulding for your medical device manufacturing?

Plastics Injection molding for medical devices is a tried and tested technique that has been used by many Med-Tech companies around the world for a very long time. It is ideal for very small to very large components in medium-to-high annual volumes. Injection-moulded components can be made with an enormous range of plastics, and very high accuracies can be achieved.

Injection-moulding components can be finished with a wide range of fine and coarse surface textures. 

Once an injection mould has been made, a very large number of injection-moulded components can then be manufactured one after the other and at relatively high speed:

• products with a low unit price (this is then cheaper than prototyping in the long term despite the mould investment)
• injection moulding parts with high dimensional accuracy
• injection moulding parts that must withstand mechanical stress and special conditions
• Longer turnaround times (5-7 weeks for simple parts)
• Parts of any size or complexity

Medical device prototyping and plastic injection molding are both helpful processes in their own right. Prototyping has given engineers the power to make plastic designs real in relatively short time and with low initial investment. Medical injection molding, on the other hand, is the go-to for quality and value. It is commonly used to quickly and reliably produce high-volume runs of complex plastic designs. 

The use of prototyping in innovative and experimental scenarios has been grabbing recent headlines, but the reality is that the majority of today's plastic parts are manufactured using plastic injection molding. The choice is understandable given how the process helps to control quality, costs, and design complexities such as tight tolerances.

Creanova Medical Manufacturing Engineers have successfully launched many products, from small to high production volumes, guiding clients among the available medical device manufacturing technologies. 

Leveraging its 20 years of combined experience in prototype machining, CNC manufacturing, vacuum casting and injection moulding, Creanova serves Med-Tech companies with high quality medical devices which meet their specific needs and requirements.