What kinds of mold insert are there?
They are named by where they sit and what they do. The types Materion lists as main uses for its MoldMAX alloys are:
- Core and cavity inserts: form the inside and outside surfaces of the part
- Parting-line inserts: sit where the two mold halves meet
- Sliders and lifters: moving pieces that form undercuts and side holes
- Hot runner tips: where hot plastic enters the cavity
Why do some inserts run hotter than the rest of the mold?
Because some spots cannot take a cooling channel, or not close enough: long slender cores, thin ribs, deep corners. Heat from the plastic builds up there, that region of the part cools more slowly, and the whole cycle has to wait for the slowest spot. The temperature difference also makes the part shrink unevenly or warp.
Why make inserts from beryllium copper?
Because beryllium copper mold alloys pull heat out of these spots much faster than steel while staying hard enough for service. Materion says MoldMAX HH matches standard tool steels in hardness and strength while conducting heat four to six times better, and that MoldMAX inserts in steel molds cool hot spots, reduce or remove the need for cooling channels there, and even out mold temperatures for tighter tolerances and less post-mold shrinkage and warping.
For the very hottest spots, PROtherm is the option Materion describes as having the highest conductivity of any alloy with tensile strength above 100,000 psi.
Besides cooling, what else suits beryllium copper to inserts?
- Excellent machinability and high impact strength (per Materion), so complex inserts are easy to make
- Good polishability for cavity surfaces that must be smooth
- Galling resistance and wear resistance in plastic injection service
- TIG weld repair with Materion's WeldPak or WeldPak XL filler metal
For the numbers against P-20 steel see Mold steel vs beryllium copper, and every grade is on the MoldMAX page.
How do you choose the insert material?
Choose by what that spot needs most. If it must resist wear and take load as well, start with MoldMAX HH; if heat removal comes first, look at PROtherm; for a copper alloy without beryllium there are MoldMAX V (Cu-Ni-Si-Cr) and MoldMAX XL (Cu-Ni-Sn). Give the insert size and resin in your quote request so the grade and available sizes can be confirmed.
Frequently asked questions
- How is a mold insert different from the core and cavity?
- The core and cavity are the parts that form the inside and outside of the plastic part. An insert is a way of making those parts as separate pieces fitted into the mold plate, so they can be replaced or made from a different material.
- Can beryllium copper inserts go into an existing steel mold?
- Yes. Materion says MoldMAX used in steel molds cools hot spots and reduces the need for cooling channels where they are hard to drill. The fit and assembly design should be checked by the mold designer.
- Can a worn beryllium copper insert be repaired?
- Yes. Materion offers WeldPak and WeldPak XL filler metal for TIG repair of beryllium copper MoldMAX alloys, with welding fume controlled as the SDS requires.
- Does every MoldMAX grade contain beryllium?
- No. MoldMAX HH and PROtherm are beryllium copper; MoldMAX V is Cu-Ni-Si-Cr and MoldMAX XL is Cu-Ni-Sn.
References
Sources read on 5 October 2026. Producer data changes; confirm values against the current datasheet before design.