I am a big fan of "plain old PLA" The problem is not the plastic you are using but the engineering design. The part looks like you are used to designing with metal or wood, where you start with flat stock and screw parts together. If you need good rigidity with 3D prints, then fill all the air space around the part with plastic. Use thick skin and 30% or more infill.
PLA is not "tough" because it is rigid and will not bend. So it breaks like glass. But as long as you do not break it, PLA has the least flex The other things I always say is to use compound curves. Think about the hood of a car. If the sheet metal were flat you could bend it up by hand but after it is stamped, hood shape it becomes rigid. It costs no more to make a curved part as a flat part with a printer. You want the skin to be curved and the infill prevents buckling. So what parts dos this fixture support? I would say to make the fixture bigger until it overlaps the other parts, then back off a few millimeters of clearance. If there is air inside the machine you are building, you are giving away strength. A for precision. You can't have that with printed plastic, make the holes undersize by 0.5mm or so then ream them on your mill. I have also bought bronze bearings and press-fit them into the reamed-out plastic. I've pressed in sealed ball bearings too. Brass threaded inserts are also very good. You install them with a soldering iron. You have to experiment with the heat setting and the hole size but the result is very strong and durable joints. Another trick to making a strong post, like a stub-axel in plastic. Make it a pipe, not a calendar, then add threads to the inside and put a long steel screw dowwn the center and use CA glue to keep it there and bond it. Now the plastic axel has the shear strength of a steel screw. I guess you could also epoxy in a steel rod, but screws are easy. Better to simply not have long thin structures n the design. NEVER use a design that look like a slab of metal and never use sharp 90 degree corners At the very least you can add the biggest fillets possible. But beter to rait the top of the bottom plat up to just before it contacts whatever is above it.. Don't worry, tripling the thickness does not use 3X more plastic, the inside is just infill. People are used to designing with metal where you have 10X more material strength so they don't need to bother with careful engineering. Maybe the simplest advice is to just say "pretend you are making the part with balsa-wood. No one would think of using a 1/8th inch baseplate of balsa for support. No. You'd start with a 4-inch block and only carve off the minimum about of wood. Every bit of balsa you turn into air gives away strength. The next step in sophistication after just following rules of thumb is to use FEA. Most CAD systems allow you to do a finite element analysis f the part and will show the most stress areas in red and the low stress areas in blue. Then you re-design to make the red areas go away. On Sat, Oct 8, 2022 at 9:18 AM gene heskett <ghesk...@shentel.net> wrote: > This is for Chris; > > I printed a new carriage for an Ender 5 plus, out of PETG+CF. But while > its working right now, "cold flow" seems > to be ruling the day. > > With enough pressure on the POM rollers to contain the head, the base > plate is warping, making the roller fit loose. > Is there a plastic that's more stable than PETG+CF? See png from > OpenSCAD, the POM rollers are the 4 corner holes. > > Suggestions? > > Cheers, Gene Heskett. > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/> > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
