Injection Moulding Mould Core/Cavity Materials / Processes

What materials are the mould cavities and cores commonly manufactured from?

I have head talk of such materials as silver-steel, and processes caled spark-erosion, and water-jetting, but I still know very little on this area!

Please could anyone give me a brief overveiw? I’ve reached the stage in my A-level project where I have to describe the processes involved in creating my product. Thank you very much!

Molds can be made out of alot of materials including composites. It’s mostly a function of hold many molding cycles does the mold have to survive. A single prototype, several hundred pieces… ?

There are other factors: physical size of the part, the temperature of the melt, the surface finish required, etc.

most are made from steel (stronger, cheap material (relatively speaking)), aluminum (+ soft, easily tooled; - soft, easily damaged if operator is a ham-fisted dolt).

try these for starters:

Our tool makers deliver two kinds, stainless and aluminum. Aluminum is much cheaper, but will only last a few thousand shots of polycarbonate thus ideal for prototyping. When it’s time to order 100,000 parts, we usually also get a 4 or 6 cavities done in some version of stainless.


yay! thankyou this information is perfect.

the mould is for high-volume production … at this level (im only 17! lol) i don’t tihnk we have to figure too deeply into specific volumes or details, but heres the best I could come up with:

The part is a circular sector radius 50cm, angle 45 degrees, about 5cm in depth

the material i want to use is a PC/ABS blend

the part requires little aesthetic quality, as it’s purpose is purely function, so an integral finish isn’t really necessary!

(… are we being lead to beleive you’ve had bad experiences with mould operators, Lmo?)

I’ve encountered few.

Story 1 - An aluminum mold was made to prototype a large part. The molding company owner was personnaly operating the machine while we were “dialing” in the first dozen parts. Everything was going remarkably well for a new tool. We were pushing a delivery deadline to supply ‘first articles’ for testing so he put his employee on the machine so we could take off for lunch. While we were gone the part started to develop a small amount of ‘flash’ at the parting line so the employee bumped up the hydraulic pressure to (in his estimation) decrease the ‘flash’ … destroyed the mold, blew the delivery deadline, lost the contract, AND had to eat the cost of the mold myself. It was a great lunch though…

Story 2 - Large, six cavity, polished, chrome plated, mold. The machine operator failed to carefully inspect the mold before closing it. A stainless steel threaded insert had fallen onto the surface of a thin-section in the mold and was crushed when the mold closed … thereby destroying the mold surface. This happened prior to mold “inserts” which are commonly used today so the entire mold had to be taken out of service for repair (and it never was quite right).

A mold insert is an individual, removable, cavity held into a larger frame.

See threaded mold insert at: