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3D model - control drawings

Hi group,

I have a question for the plastics oriented people in the group.

For years, we've been doing business with a select few local mold houses. We know these vendors real well, and they know what we expect from them. What we usually do is supply them with a 3D model and a control drawing that shows critical dimensions and tolerances. This arrangement has worked out pretty well, in most cases.

We now find ourselves in a client driven situation where we need to specify an overall tolerance, relative to the model, for those features that aren't specified in the control document. The parts may be freeform shapes and would require a 3 axis CMM to measure.

Have any of you had to deal with a similar problem ?? If so, how did you solve it ?

Regards

Mark

Reply to
MM
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Mark,

What you could do is set a note for what tolerances are possible from the mold shop and agree to a tolerance range xyz as well as flatness and positional tolerance per hole or datum feature for inspection. So, the inspection or scanned data will have to apply these xyz ranges from a set of datums or datum targets, primary, secondary and tertiary or similar to datums applied to a casted part..

For instance, a tolerance range for an inspection or scanned inspection could be added to the notes below. (btw, these values could have a deviation per the life of the tool,

100K, 200K,.. 1mil.)

NOTES: (UNLESS OTHERWISE SPECIFIED)

  1. THIS DRAWING IS A SUPPLEMENT TO THE 3D DATABASE FILENAME XXXXXX..XXXXXX. FEATURE AND PRODUCTION TOOLING INFORMATION SHALL BE DERIVED FROM THE DATABASE. ALL DIMENSIONS SHOWN ARE FOR PART INSPECTION/ QUOTATION PURPOSES ONLY. IN THE EVENT OF A CONFLICT BETWEEN THE DATABASE AND THIS DRAWING, THE DATABASE SHALL GOVERN UNLESS SPECIFICALLY NOTED OTHERWISE.

  1. MATERIAL: PC/ABS, NO REGRIND

  2. COLOR: PANTONE BLACK 6C, OR EQUIV.

  1. TEXTURE: MT #11010 OR APPROVED ON EXTERIOR SURFACES.

  2. ALL UNSPECIFIED RADII TO BE .010".

  1. FINISH: SPE/SPI #3 OR BETTER ON ALL UNTEXTURED SURFACES.

  2. NOMINAL WALL THICKNESS TO BE .080.

  1. ALL DIMENSIONS TO THEORETICAL INTERSECTIONS. TOLERANCES ARE +/-.005

  2. + DIMENSION INCREASES WITH DRAFT. - DIMENSION DECREASES WITH DRAFT.

  1. THE FEATURES FOR THIS MODEL SHALL BE LIMITED TO THE TOLEARANCE RANGES SHOWN BELOW PER THE A, B, AND C DATUMS SHOWN. UP TO 0.25", +/-.001" TO 0.50", +/-.0015" TO 1", +/-.0025" AND +/-.0015" ADDED PER INCH UP TO 8" OR +/-.010" AT 8" ADD +/-.005" PER INCH UP TO 12" OR +/-.020" AT 12" THE LONGEST SPAN SHALL NOT EXCEED +/-.020". PLANAR SURFACES TO HAVE A FLATNESS OF .005" PER 1", NOT TO EXCEED .015" OVER THE ENTIRE SURFACE.

Reply to
Paul Salvador

It sounds like the customer is asking you to tolerance their part/drawing. Can you put that responsibility back on them?

Ken B.

Reply to
mold.dude

If the design concern is that parts must fit together, namely your plastics along with their freeform shapes, you may be able to use a go/nogo inspection procedure. Your plastic parts would be checked as fitting a sample supplied by your client. This could be a "dumbed down" piece that concentrates on the shapes involved rather that color, etc. The molder would check his parts against these "gauges" to within an acceptable level of deviation... such as holes must line up within ".xxx" or visible seam in this area not to exceed ".xxx" etc.

I've done this many times to overcome issues of having manufactured parts fitting sculpted or "freeform" parts as you stated.

- Eddy

Reply to
Eddy Hicks

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