Design Guidelines for Plastic Industrial Parts
The wall thickness of a thermoplastic part depends on several factors. These factors include the type of thermoplastic used, mechanical stress on the part, electrical performance requirements (if any), and more.
The following are general rules of thumb:
The main wall thickness of the part should be uniform
Avoid rapid thickness transitions. Instead, use a gradient thickness transition of 3 to 1.
The gate for injecting the thermoplastic should be in the thicker section
Wall Thickness Considerations
When designing plastic parts, several factors should be considered to determine the wall thickness of the part. These factors include:
Application requirements such as:
The formability of parts includes
Material flows to the narrowest point
Number and location of doors
Design requirements for registration bodies such as UL or RTI
The design of the part should include consideration of the location of the parting line, also known as the parting line. The design of the part should also have draft (the angle of the vertical component) and closure.
The location of the parting line should appear on the main feature plane. When a stepped parting line is required, a draft angle of 7° is preferred, with a minimum of 5°.
Radius and fillets
The inside radius (r) of the corner should be 25% to 60% of the wall thickness. The outer radius (R) of a corner is the sum of the inner radius plus the material thickness (t). R = r+t.
The fillet radius is the same as the inner radius, with a minimum of 0.020 inches (0.508 mm). If the feature is load bearing, a larger radius is required.
Sharp corners should have at least 0.005 in (0.127 mm) clearance.
The rib that intersects the wall should be 50% – 60% of the wall thickness with a fillet radius of 0.015 in (0.381 mm). The maximum height of the stiffener is 3 times the wall thickness.
Typical draft for ribs is 1° to 1.5°, with at least 1/2° on each side.
The minimum spacing between ribs is twice the wall thickness.