I may try again with a more complete mixing. The alternative is to bind pieces that would otherwise use blind holes with epoxy, which is the preferred method with CFC. To get good tolerances, I would use the mill to scribe the lines where the parts go
Indeed, it pulled out with low effort. Retrying with better mix.
Tried again. Absolutely rock solid.
UPDATE: Several good suggestions in comments. I may try melting a stainless steel threaded insert into a hole with a soldering iron. This should be as tightly held as epoxy, maybe better. It to some extent, depends how well CFC melts and then freezes.
Depending on the nature of the failure, sometimes it is necessary to make the hole in the base material be not round, so it doesn't turn when you screw something into the insert. Other times you might need to undercut the edge of the hole, so it won't pull out under load.
ReplyDeleteEpoxy can be strong - I usually add one of the thickeners like silica - but it doesn't always form a strong mechanical connection to other plastics. Making sure the surface is rough is a 1st step.
Try a rivnut?
ReplyDeleteIt should work about the same as the epoxyed threaded insert. Thanks for letting me know of this critter.
DeleteOr maybe one of those furniture thread inserts with threads inside and out.
ReplyDeleteThreading does not work well in CFC. I mixed better and solved it.
DeleteI have found that cleaning the holes makes a very big difference. The tiny bits of swarf left can reduce the adhesion of the glues used. (I often just use a solvent to wash out the holes).
ReplyDeleteAdditionally, a tiny bit of work to make the bottom of the hole a few percent larger than the entry can make for much stronger insert installation. Just a few percent of taper give a lot more surface area to prevent pull-out.
YMMV depending on application.
I just bought an assortment of threaded inserts designed to be used with 3D prints. But the way they're designed to be installed is you make a slightly smaller hole, then you use a special tip on a soldering iron, sized for the insert you're using, and press the insert into the material. It melts around the insert and then cools, locking into the external features of the insert.
ReplyDelete