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Design seamless platsic housings

Design seamless platsic housings

(OP)
Many plastic housings that I see have a groove along the seam where the top and bottom of the housing meet. This groove is illustrated in the attached picture of a calculator housing(TI-89). First, is this groove there to prevent a lip that your finger can catch on? Also, is there any way to make the top and bottom halves meet with creating a lip and not needed the groove? Apple designers seem to have figured it.

RE: Design seamless platsic housings

I don't believe Apple did it as you said. What apple did is use metal and then hide the areas where the groove would be.

RE: Design seamless platsic housings

(OP)
Can you show a cross section of the plastic joint where there would be no seam? None of the plastic design guidelines show this kind of joint. If not, can you show a cross section of how you would design an esthetically pleasing joint? Thank You!

RE: Design seamless platsic housings

The gap is put there to hide any out-of-straightness of mating parts. Perfectly flat parts are virtually impossible to produce by moulding, even difficult by machining. If there was a face-to face contact, any small irregularities would be immediately obvious. Having a pre-existing gap effectively hides this from the eye.

Oh, and your example shows a pretty poor example. The gap is usually around 1 - 2mm.

H

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

RE: Design seamless platsic housings

Star for Pud, who got it right.

The groove hides mismatch of edges in a bolted joint, and also hides flash/extrusion in a bonded joint.

You can make an assembly with no groove at the joint, but you will spend a lot of money on hand trimming/ application of Bondo/ abrasive finishing to make the seam perfectly flush, and you will still get customer complaints about the edges cutting skin as they become re-exposed when the plastic changes shape from various aging mechanisms over which you have no control.


Mike Halloran
Pembroke Pines, FL, USA

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