Suggestions For Steering Clear Of Mistakes

Suggestions For Steering Clear Of Mistakes When Designing Injection Molded Plastic Components

Errors, which newcomers often make whilst beginning to design plastic parts can often be spotted by Rapid prototype components before commencing to manufacture an injection mold. I will highlight some generally made errors. I will moreover describe the effect that these kinds of mistakes will have on the finished components. I will in addition provide various suggestions which are fine design practices to understand while designing components.

One vital aspect in that plastic parts differ from other parts, e.g. metal parts, plastic injection mold maker
is that plastic components normally ought to have consistent wall thickness. Parts with uneven wall thickness typically cool irregularly and leave nasty shrink marks that are visible on the outer surface. Also, this can cause stress at the junction of high and low shrinkage and cause the part to warp.

Given that plastic parts are shaped by injection molding, they ought to be designed with a draft. A good description of draft is the angle of taper of a side wall or rib required to permit the molded plastic part to be detached from the metal mold. Lacking appropriate draft, plastic parts may be tricky to detach from the mold. Many mainstream devices use draft angles between 1.5 to 2 degrees.

An often used design element are ribs. Ribs can raise the rigidity of a component. Some guidelines must be observed, though, when adding ribs. The thickness of the ribs should not be too large to steer clear of shrinkage marks. Make the thickness of the ribs less than the wall thickness. Generally ribs are 60% to 80% of the wall thickness and spaced not less than 2 times the wall thickness apart. It is best to keep the height of the ribs below 3 times the wall thickness and rather add additional ribs rather than increasing the height of the ribs.

Bosses are another design element utilized for mounting and assembly purposes. Regularly, bosses are designed with thick wall sections that may influence the appearance of the plastic component and the finished product.  The ideal wall thickness around the boss is dependent on the nominal part thickness. If the thickness is less than 1/8 inches, the perfect boss wall thickness is around 60% of the part thickness. If the part thickness is more than 1/8 inch, the best boss wall thickness is about 40% of the wall thickness. As a rule of thumb, the height of the boss ought to be less than 2.5 times the boss hole diameter.

Sharp corners ought to be avoided when designing plastic components. Sharp corners can lead to stress risers. Those may cause part failures and decrease the strength of a part. The inside radius of ribs and bosses should be no less than 0.015. For other corners, pick an inside radius of a minimum of half the wall thickness and an external radius equivalent to the inner radius plus the wall thickness.

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This entry was posted on Pátek, Listopad 11th, 2011 at 8:33 and is filed under plastic injection mould maker. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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