Plastic and rubber moulding

Moulding makes plastic and rubber parts in volume from a mould: housings, caps, gears, bottles, tanks, seals and grommets. The mould is made once; after that each part comes out in seconds or minutes, so the price per part depends mostly on the material and the cycle time.

Injection moulding makes accurate plastic parts. Blow moulding makes bottles and hollow containers, rotational moulding makes large tanks, extrusion makes pipes and profiles, and thermoforming makes trays and covers from sheet. Rubber moulding uses compression or injection moulds for seals, gaskets and grommets.

The moulding workshop needs a machine large enough for the part and the mould. Some workshops make their own moulds; others use a mould maker, or run moulds that you own.

Materials commonly used

• PP, HDPE, LDPE and ABS
• Nylon (PA6, PA66), acetal (POM) and polycarbonate
• PVC and engineering grades such as PBT
• Rubbers: NBR, EPDM, neoprene, silicone and Viton

What to send with your requirement

• A 3D model (STEP) and a drawing with critical dimensions
• The material grade, colour and any additive (UV, flame retardant)
• The quantity per order and per year
• Whether you own a mould already, or one must be made
• Packing, printing or assembly needed after moulding

What affects the cost

• Material cost and the part's weight
• Cycle time and the number of cavities in the mould
• Machine size needed
• Mould cost if a new mould is needed
• Secondary work: printing, inserts, assembly and packing

Common mistakes to avoid

• Not stating the exact material grade, which changes shrinkage and strength
• Designing thick or uneven walls, which cause sink marks and long cycles
• Not agreeing who owns the mould and who maintains it
• Asking for a moulding quote without saying whether a mould exists

Frequently asked questions

I already have a mould. Can another workshop run it?

Usually, if their machine fits the mould's size and tonnage. Share the mould's dimensions, the material and the part weight in your requirement.

What is the minimum quantity?

Each workshop sets its own minimum, often because setting up a mould takes time. Matching on Diemeco checks your quantity against the workshop's minimum order.

Can I get a mould made and parts moulded together?

Yes, some workshops do both. You can also post the mould as a separate requirement under injection mould making.