Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Design seamless platsic housings

Design seamless platsic housings

Design seamless platsic housings

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

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.



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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


White Paper - Effects of AIA Quick Guide to UL 489 or UL 1077
The function of a circuit breaker is to provide overload (thermal) and short-circuit (magnetic) protection to a circuit and its downstream components. A circuit breaker functions like an airbag in a car, protecting circuit components and people by tripping the circuit to interrupt the current flow if it detects a fault condition in the control system. Download Now
White Paper - Guide to Integrate Large-Format Additive
As with any new technology, getting into large-format 3D printing begins with investigation. The first question may be a simple one: what does “large-format” mean? For 3D printers, “large” is a relative term. Many extrusion-based (FFF) 3D printers are referred to as desktop machines, because they fit on table space. Some of these have very respectable build volumes – but when it comes to “large-format,” the machines will need their own dedicated floor space. Large-format 3D printers have significant build volumes and are most often found in professional settings, like manufacturing facilities and R&D centers. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close