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Low Volume, Cost-Effective Alternatives to Injection Molding

Plastics are an integral part of consumer products, everything from your smartphone and laptop to your car, contains some amount of plastic parts.

As a hardware startup, your product too, most likely relies on plastic for the electronics enclosure.

Injection molding is a commonly used process for manufacturing plastic parts, but the high upfront costs of the molds makes it viable only at high volumes. So if you are looking to develop only a few prototypes of your product, injection molding is not the right way to go, instead, here are the types of companies that can help you build physical product prototypes.

A startup developing a new product from scratch faces high uncertainty of whether their product will be successful in the market or not. Therefore, it is hard for them to invest several thousand dollars for injection molding of an unproven product idea.

Below are some alternatives to injection molding that allow manufacturing low volume parts(10s or 100s of), cost effectively so that you can test the market, receive feedback from users, present your product to investors, run promotions and more.

1) Urethane Casting

(RTV Casting/ Resin Casting/ Vacuum Casting/ Silicone Molding)

Urethane Casting is an excellent alternative to injection molding, but without the high upfront costs or long lead times of injection molding.

A 'master pattern' of the product is created using CNC Machining or high-resolution 3D Printing with the required surface finish. This pattern is then used to create a urethane or silicone mold into which a suitable resin can be poured in order to create multiple copies of the product. The mold typically lasts for around 20 runs.

This method provides a wide range of resins that can mimic 'production-grade' materials ranging from soft elastomers like silicone rubber to hard plastics like ABS, along with ‘production-grade’ quality.

This process is great for cost-effective production runs of 20-200 parts to test the market, gather feedback from early adopters and test the engineering and design requirements.

2) 3D Printing

3D Printing is suitable as a prototyping process and for very low volume production runs. It requires no upfront investment into creating molds and can provide lead-times as short as a few hours. This makes 3D Printing a preferred choice for quick iterations during the development of plastic products, and sometimes for metal and composite materials too.

3D printed parts inherently have a 'layered' surface due to the way 3D printing works. But this surface can be sanded and painted to achieve the desired surface finish.

The resulting parts can be used as 'appearance models', for marketing and promotional shots, presented to investors or potential customers. Here is a more in-depth guide to prototyping for hardware startups.

There are several different types of 3D Printing technologies both for plastics and metals with their own pros and cons. FDM (Fused Deposition Modeling), SLA (Stereolithography) and SLS (Selective Laser Sintering) are the ones that are most commonly used in product development.

SLA and SLS technologies are slightly more costlier than FDM, but provide tighter tolerances and better finishing. There are other specialized 3D printing technologies that allow printing with multiple colors or materials in the same part.

3) Thermoforming

Thermoforming involves creating a mold of your product over which a thin sheet of plastic is heated and formed using vacuum, pressure or mechanical force. The plastic sheet takes the shape of the mold and extra material is then trimmed off.

Since this process involves very low pressure and temperatures, the mold can be made from inexpensive materials like plastic or wood. Surface finish is important as the formed product picks up small details on the mold.

(Author: Colagor, via Wikimedia Commons)

Thermoforming, however, cannot be used to produce highly complex parts which the other processes can. It is therefore limited to 'relatively' simple products like packaging trays, large panels of appliances, vehicle door panels, dashboards, simple product housings etc.

4) CNC Machining

CNC machining is a highly reliable process and it is as relevant today as it was when first conceived in the 1950s. It is one of the most versatile manufacturing process in terms of the number of materials that can be processed in a CNC machine - plastics, wood, metals, ceramics and many more.

Due to the high tolerance, fast turnaround and wide range of materials available for CNC machining, it is used to create accurate molds, dies or patterns for other manufacturing processes involving molding, casting, forming or extruding.

Setup costs involved in CNC machining, especially for complex geometry, are higher than that of 3D Printing. It is therefore more suited for low to mid-volume production (upto a few hundred parts depending on part geometry) with fast turnaround times as opposed to one-off production.

In some cases, CNC machining is also used as a secondary operation in combination with another manufacturing processes. For example, CNC machining can be used as a secondary operation on 3D printed parts or metal castings to achieve tighter tolerances.

5) 3D Printed Molds

Using 3D printed molds as an alternative to metal molds in injection molding is a fairly new process. As the quality and surface finish of 3D Printing continuously improves, 3D Printed molds for low volume injection molding are being pioneered by companies like Stratasys with their Polyjet printing and Formlabs using their SLA printers.

3D Printed molds can prove to be a low cost way for testing production-grade materials and processes at low quantities but it is currently limited to small parts and yet to be adopted by the industry at large.

It should be noted that the cost-effectiveness of manufacturing process at a certain volume is highly dependent on the part geometry. For quantities approaching 300-500 parts, injection molding with lower quality steel or aluminum molds can be considered depending on the part geometry. It is a good idea to involve suitable engineering or manufacturing professionals who can guide you early in your product development process.

Outdesign Co is a product design, prototyping and product development company. We help startups as well as established businesses around the world bring new products to market. To discuss your project, click here to get a quote.

Outdesign Co is a product design & development company helping clients across 15+ countries turn their ideas into “World-Firsts” and award-winning products.

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