Advantages of Plastic Injection Molding

Low cost and good repeatability. Extremely cost efficient in larger quantities.

Notes

You can arrange multiple pieces in one mold by connecting them with small bars ~0.1", however the sub-components must not have widely varying volumes. When the design does not allow for additional structures to improve strength, consider using a stronger material, such as glass fiber filled plastic. Consider specifying a fire retardant material when necessary. Contoured parts warp less than flat parts.

If desired specify the following:

• Where to place the gate - the location where plastic is injected - a small rough spot will appear at this location.

• Where to place the parting line - the location where the two mold halves meet - a thin line will appear at this location.

• What surface finish to use - polished, matte, textured.

A small slightly rough spot appears at the Gate. A thin line appears at the Parting Line. A circular mark appears at the ejector pin locations.

Living Hinges - A Living Hinge is a thin connection provided between two sections of a molded part so that it can be used as a hinge, e.g. a box, with a lid, molded as one piece. You can use living hinges in your Injection Molded parts.

Multiple parts in one design - In some cases you can design several different parts in one tool to avoid the cost of making separate molds for each part. Generally the limit is about four if the parts are fairly different and up to 24 if the parts are nearly identical. To have multiple parts in one tool, join the parts together with a narrow connecting channel. If desired, you can "Remove connecting links". Combining parts in one mold does not always decrease the cost - check pricing both ways.

Box seams - Since a seam between two halves of a box is difficult to fully hide, most designers make the seam pronounced - more visible - to make it look like it is decorative. Look at some molded products to see some styles.

Insert Molding - A screw driver with a plastic handle is an example of insert molding. Injection Molding is performed around a l (or another plastic) part. Additional examples include threaded l inserts and electrical plugs.

Material Selection

Material	Colors	Stiffness	Dimensional tolerance	Intricate design	Dark colors	Max wall thickness, mm
ABS	Many	High	Good	Good	Fair	5
Nylon	Many	High	Good	Fair	Fair	4
Delrin	Usually white	Med	Good	Good	Good	4
Polyethylene	Many	Low	Poor	Good	Good	4
Polypropylene	Many	Low	Fair	Good	Good	2
Polystyrene	Many (translucent, opaque, transparent, tinted)	Low	Good	Good	Good	5
Polycarbonate	Many (translucent, opaque, transparent, tinted)	Med	Good	Good	Fair	4