Prototype Before Injection Molding, Why and How
· 2 min read
Injection molding is the cheapest way to make a plastic part in volume and the most expensive way to find out your design was wrong. A mold is a five figure commitment that takes weeks to cut and is painful to change. Here is how we see Georgia startups and manufacturers use 3D printing to get to a mold they will not regret.
Three things a printed prototype proves before you cut steel
- Fit. Does the housing close over the board? Do the snap fits engage? Does the part clear the thing next to it? A dimensionally accurate print answers this in days, and if the mating part exists we scan it so the prototype fits reality rather than a drawing.
- Function. Does the hinge survive a thousand cycles? Does the clip hold? Does the gasket seal? Printed in the engineering material closest to your production resin, a prototype can be tested like the real thing.
- Market. Does anyone want it? Looks like works like prototypes go in front of pilot customers, investors, and a crowdfunding camera before any tooling money is spent.
Design for molding, checked on a print
A print will happily make geometry a mold cannot. Undercuts with no slide, zero draft walls, wildly uneven wall thickness. So we design the prototype the way the molded part will have to be made, with draft, uniform walls, and ribs instead of thick sections, and we flag anything that will not mold. That way the part that passes testing is the part the mold maker can actually quote.
Bridge production, the part nobody tells you about
Between a finished design and a finished mold there are typically six to twelve weeks. Printed bridge parts cover that gap. Tens to a few hundred end use parts in nylon, ASA, or polycarbonate let you ship product, fulfill a pilot, or stock a trade show while the tool is being cut. The same files, the same geometry, a different process for a few months.
When molding wins and when it never does
Molding wins on unit cost at volume. Where that line sits depends on the part, but if you need thousands of identical parts a year, a mold pays for itself. Below that, printing often stays cheaper forever, and for a part that will be revised every few months, a mold is a liability. We tell customers when they have crossed the line in either direction.
What to send us
A CAD file if you have one. A sketch and a description if you do not. The mating parts, if the prototype has to fit something that exists. Tell us the production resin you expect to use and we print in the closest engineering material so the test means something.