March 2008 Design Tip

Protomold: It Isn't Just for Prototypes Anymore

Protomold has long been the place to go for fast, affordable, injection moulded prototypes. But for an increasing number of customers, Protomold is also a source of production parts in quantities of up to 25,000. Depending on the number of parts you need, Protomold can be significantly less expensive than a traditional moulder using steel tooling. And regardless of quantity, you still get Protomold's speedy turnaround for unmatched speed to market.

There are several ways that Protomold can help control cost and slash production time on large orders. Multi-cavity moulds, which produce up to eight copies of a part in each press cycle, increase tooling cost somewhat, but can more than offset that increase by reducing press cycle time and cost. The ideal number of parts per mould depends on various factors.

Obviously, part size can be a limiting factor, but even for small parts the ideal number of cavities per mould can vary. For example, a customer needing 24,000 identical small parts might maximize savings by using an 8-cavity mould. For a customer needing fewer parts, say 2,000, the lower tooling cost of a 4-cavity mould might be the better choice. "What-if" scenarios using the "cavities" option of the ProtoQuote® (see fig. 1) or Protomold's sales or customer representatives can help you choose the most cost-effective solution.

Fig. 1

Fig. 1: ProtoQuote® Cavity Specification

There are a couple of limitations to keep in mind as you consider the use of multi-cavity moulds:

  1. Side actions: Because they tend to use so much of the mould's maximum "footprint", multi-cavity moulds don't leave room for side-action cams and must be simple straight-pull moulds.
  2. Hot tips: Due to mould complexity issues, multi-cavity moulds cannot use hot-tip gates.

In addition, until the part has been thoroughly prototyped and tested, you should probably stick to single cavity moulds. Once your design has been proven, you may elect to convert to a multi-cavity mould for production.

Fig. 2

Fig. 2: Multi-Cavity Mould

If you have questions regarding the use of multi-cavity moulds for production parts, check with your Protomold sales representative, who will be happy to help you find the best and most cost effective solution.