Desktop Injection Molding Tips

Plastic will shrink from when its melted state to its solid form. To compensate and have the part be the correct size, the mold should be made slightly larger, so that it shrinks to the correct size. In addition, it should be noted that the mold will expand when it is heated very slightly, and for high precision situations, this should also be factored it.

Common Linear Shrinkage Values
Material Shrinkage Processing
Temperature
ABS- High Impact .005 - .007
ABS- Medium Impact .005 - .008
ABS-High Heat .004 - .006
ACETAL .020 - .035
ACRYLIC- General Purpose .002 - .009
ACRYLIC- High Flow .002 - .007
ACRYLIC- High Heat .003 - .010
ACRYLIC- Impact .004 - .008
NYLON- 6,6 .010 - .025
NYLON- 6 .007 - .015
NYLON- Glass Reinforced .005 - .010
POLYCARBONATE .005 - .007
POLYESTER .025 - .050 thick .006 - .0012
POLYESTER .050 - .100 thick .012 - .017
POLYESTER .100 - .180 thick .016 - .022
POLYETHERIMIDE .005 - .007
POLYETHYLENE- LDPE .015 - .035
POLYETHYLENE- HDPE .015 - .030
POLYPROPYLENE .010 - .030
PPO/HIPS (NORYL) .005 - .007
POLYSTYRENE- Crystal .002 - .008
POLYSTYRENE- Impact .003 - .006
POLYURETHANE .010 - .020
PVC-RIGID .002 - .004
PVC-FLEXIBLE .015 - .030
SAN .002 - .006

Plastic Resin for Injection Molding Suppliers and Distributors

The hardest part in doing desktop injection molding is finding a distributor who will sell you less than a truckload of plastic. One good supply source is ebay.

The other problem is custom color. Most plastics come in either natural (white) or black.

Resin Supplier Links: Colorant and Color Matching Supplier Links:

Plastic is typically manufactured in natural color or black. If you want a different color you need to add colorant. The colorant comes as pellets, and doesn't necessarily mix well in your machine. To get a good consistent color the plastic needs to be mixed, extruded, and chopped into pellets. Companies that do this for you are called compounders.
  • Accek Color: Custom formulated coloring systems for plastics. They mainly sell colarant, but they will do compounding, if you send the uncolored plastic to them. This cost was about $7 per pound for 100 pounds.
  • Chase Plastic: Full-service specialty engineering thermoplastic distributor serving plastic processors throughout North and Central America
  • Interfacial Solutions: Plastic additives and specialty compounded resins. Service based company.
  • Compounding Solutions: Specialty compounder for the medical industry. Min Quantity 25LBS. Nate Doyle. To compound a green ABS: 25LBS= $13.47, 50LBS = $8.74, and 100LBS= $6.74.
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