Two types of temporary insert

3D-printed inserts

The cavity inserts are printed in resin and run on the micro injection molding press. A printed insert is the quickest temporary tool to produce, and a revised insert can be printed when the design changes. Insert life depends chiefly on the plastic: resins that are molded at lower temperatures and without glass fill allow the most parts per insert.

Insert life: 10 to 1,000 parts, depending on the plastic

Best suited to: A first evaluation of molded parts while the design is still changing

Aluminum inserts

The cavity inserts are machined from aluminum. Aluminum can be cut considerably faster than hardened steel and withstands more cycles than a printed insert, so it suits builds that require more parts or a longer test program.

Insert life: Hundreds to a few thousand parts

Best suited to: Test builds, pilot runs and early market quantities

Comparison with production tooling

Tooling	Insert life	Design changes	Typical use
3D-printed inserts	10 to 1,000 parts, depending on the plastic	A revised insert is printed	First molded parts and early design iterations
Aluminum inserts	Hundreds to a few thousand parts	A revised insert is machined	Test builds, pilot runs and early market quantities
Hardened steel (production)	Production volumes	Costly once the cavity is finished	Released designs and validated production

Selecting the type of insert

The plastic

Melt temperature and glass fill determine how quickly a temporary insert wears. Commodity and engineering resins molded at moderate temperatures suit printed inserts. High-temperature or glass-filled resins wear printed inserts rapidly and are generally better served by aluminum.

The number of parts required

A handful of parts for a fit check or a first bench test can come from a printed insert. A test build, a pilot run or a quantity for early customers generally calls for aluminum.

How settled the design is

If several revisions are expected, a printed insert keeps the cost of each revision low. Once the design is stable and more parts are needed, aluminum becomes the more economical choice.

The question the parts must answer

Temporary tooling answers questions about fill, gate location, weld lines, snap fits and assembly. Final dimensional qualification should be performed on parts from the production steel, for the reasons set out below.

What prototype tooling can and cannot show

Parts from a temporary insert are formed by injection molding. They show how the plastic fills the cavity, where the weld lines fall, how the gate affects the part, and whether snap fits and thin walls survive molding. A printed or machined prototype cannot show any of these.

A temporary insert does not conduct heat in the same way as hardened steel. Aluminum removes heat faster; printed resin removes it far more slowly. Cooling rate influences shrinkage, crystallinity and cycle time, so dimensions measured on prototype parts may differ from those of production parts. Future Micro Mold therefore treats prototype tooling as a means of settling the design, and qualifies dimensions on the production tool.

The prototype tooling process

Submit the CAD file

A STEP file is preferred, together with the intended plastic and the number of prototype parts required. Future Micro Mold provides a quotation and a tooling recommendation within 48 hours.

Design for manufacturability review

An engineer reviews draft, wall thickness, corners, undercuts and gate location, and recommends a printed or aluminum insert based on the plastic and the quantity required.

Insert production and first shots

The insert is printed or machined and run on the micro injection molding press. Prototype tooling requires 3 to 5 weeks, or 2 weeks on an expedited schedule.

Revision or production tooling

If the parts reveal a problem, the insert is revised and the parts are molded again. Once the design is settled, the production cavity is cut in hardened steel.

Before tooling is quoted, the shrinkage calculator indicates whether a tolerance is achievable in the chosen plastic. To begin, submit a request for quotation or discuss the part with Marve.

Prototype tooling for injection molding