Hole Wizard holes "Feature" and Rapid Prototyping

[odmullen]

Any user who plans to make prototypes using rapid prototyping methods, and to use tapped holes in a part, should be aware that the Hole Wizard tapped holes are nothing but revolved cuts with a hole callout annotation assigned. This would be fine, except that the hole diameter is the MAJOR DIAMETER of the thread unless you check the option to add cosmetic thread to the hole.

Read the Help on Hole Wizard PropertyManager - Type Tab carefully. The "feature" is correctly documented. No rationale is offered, but I suspect it has more to do with programming objects and classes than it does with machine tools and processes....

 

[ctopher]

That is why most users use thread inserts in their rapid prototypes.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[Theophilus]

Yeah, I've been stung on that myself with some SLA parts (which don't tap well anyway, as Chriss alluded to regarding inserts). However, tapping SLS parts, with a little CA glue treating the surface before tapping, normally works great.

Anyway, it's a good point you're making. I definitely believe the default should be the minor diameter, since material can always be removed, but never replaced.

Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe trumps reason.

 

[odmullen]

Chris
Just don't spec a hole tapped to receive a threaded insert... Or was your observation sardonic humor?

I have used press-in metal inserts in the past, and used drill-size holes per the hardware specs to receive them. Works fine. Got just what I expected.

Jeff
ANother engineer here has tapped holes in FDM ABS parts with reasonably good results. The core of the parts is porous and the threads aren't as strong as in a solid part, but if one makes allowances it works fine for lightly-loaded bits.

Dennis

 

[ctopher]

humor

The materials are getting better these days so you can tap the material.
I have seen parts created with no holes or a point to start one, then drilled to match for a tap or whatever is needed.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[odmullen]

Chris
The idea in this case was to exploit the denser shell of the FDM part by molding the holes to pilot drill size, so the threads would fall in the dense shell area. It didn't occur to me that the Hole Wizard Tapped Hole would be modeled to MD size. Limited imagination, I guess...

Dennis

 

[Theophilus]

odmullen, that's where the CA glue comes in handy. It fills the porosity to create a fairly durable resin that's great for cutting (and holding) threads. Use the thin stuff. My favorite now is the Zap brand (I used to be a model-maker when interning a long time ago and found this trick works great for improving strength).

Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe trumps reason.

 

[odmullen]

Jeff
Thanks. Seems like a practical approach if you don't want to model the pilot holes or need to add holes not planned. Do you use CA on ABS FDM parts? Does it have any deleterious effect on the ABS plastic?

I've used epoxy saturation to strengthen wood parts this way, especially plywood edges.

Dennis