Hole with Threads and Supports

[CCRN]

Good Morning,

I thought up a project yesterday to hold supplies that help us reduce central venous line infections in the ICU. I want to print my prototype design, but I have never printed models with threads before. I am not sure how to best orient this and if the supports in the threaded hole are going to cause issues with the threads.

I am considering printing this with the threaded hole side down on the bed but I would still have supports in it to support the end of the clamp.

Here is a screen shot.

Thanks,
jerold

[CCRN]

Or would this be a better choice.

[Hugs]

Just my $.02 but I wouldn't focus on printing the threads. I'd take the 1st option, rotate it 180° on the Y-axis to eliminate all support and make much smaller pilot holes for proper reaming and tapping.

You're not using Slic3r so I don't know if Cura or S3D has a similar feature...but in Slic3r, I would make a modifier mesh with 100% infill around the area where the finished reamed/tapped hole would be. Then drill and ream to size, and tap the hole.

[ednisley]

printed models with threads

Size the holes to fit an appropriate knurled brass insert, epoxy 'em in place, and move on:
https://softsolder.com/2016/02/03/knurl ... c-inserts/
https://softsolder.com/2016/02/16/knurled-inch-inserts/



You'll get better retention, much better durability, no random plastic fragments, and a good fit. They're cheap & readily available on eBay / Amazon (or spend more at a reputable supplier like McMaster):

https://www.ebay.com/sch/i.html?_nkw=kn ... ass+insert
https://www.amazon.com/s/ref=nb_sb_noss ... ass+insert

Then you can orient the part to get rid of (most of?) the support structures; flip it upside-down to put the smaller flanges on the platform and I think it won't need any supports at all.

Also, don't put supports in the holes. Make them hexagonal, put a flat side on the top so the slicer can bridge it, and a brass insert will make it perfect.

[CCRN]

Hi Ed,

So the holes should be sized so the inserts just drop in with epoxy? Or do you put them in when the plastic is still warm?

Thank you,
jerold

[ednisley]

holes should be sized so the inserts just drop in with epoxy

That's about the, ah, size of it. I use OpenSCAD with a version of nophead's polyholes() function to produce a hexagon exactly fitting the insert's OD, which makes for a light push fit. Your CAD package probably has a hole generator that does the same thing: make the hole circumscribe the insert and add about 0.2 mm to compensate for small-hole shrinkage:
http://hydraraptor.blogspot.com/2011/02/polyholes.html

Keeping the hole snug holds the insert in the proper alignment, but I generally thread a stud into the insert and shove it in place with a drill press:
https://softsolder.com/2016/03/07/vacuu ... a-platter/



I tried melting the inserts into smaller holes, which is the way they're supposed to be used with injection-molded parts. Epoxy is less exciting, more consistent, and produces better retention, at least for my one-off parts. It also eliminates the need for specialized and spendy insertion tools.

[CCRN]

That helps. Thanks.