In my searches, I didn’t find any DIY tangential or drag knife that have some properly bearing uses. The knife have an axial load from the pressure against the table, and radial and moment load from the knife drag, and there the knife rotation.
I have tried use a trust bearing for the axial load, ball bearings for radial load, moment load and axis rotation, and linear bushings for the up/down mouvements and moment loads.
The more problematic load seems the moment, so I have used 3 axis for linear up/down motion in a radial way so that moment is well spread no matter what direction is the drag.
Neat project! Already looked at stepperonline’s planetary gearboxes and dual shaft stepper for slimmer assembly (or encoder instead of dual shaft)? No idea if their 3:1 or 5:1 gearboxes can handle loads you’re targeting. Look forward to seeing how your project turns out.
That would be phase 2. It’s no bigger then a Makita router, and way much lighter…
Pulleys and belt should be fine here, the rotation load is not big. With a 1:3 pulleys ratio, it’s wa better then a direct coupling and no stress on the stepper…
I’ve look into the gear reducer stepper, it looks like a great idea! You’re talking about something like that? It would make it more compact but a bit taller… But it’s something to tinker with. In cost, I think it’s cheaper : pulleys and belt versus coupling and stepper/reducer…
It looks like the planetary gearboxes have some backlash. It seems less convenient for lots of small rotation changes in both direction. The cheap one from Aliexpress is ~2°.
I’ll stick with driving belt for the moments wich as near zero backlash.
I have received my tangential oriented cutting knife hardware parts orders, but they got the micro switch and the rods wrong, not my fault this time… So I can’t assemble anything since rods diameter are wrong.
But I did forgot to order the driving belt… Bugger !
I’ll unfortunately have to wait a little bit longer to do a full assembly…
I’ll keep this thread updated!
Just also found that trust bearing are the wrong size (my bad)…
I have tested assembly and found some interferences. So I still need to do some work on the model… But so far so good for the functionalities, looks sturdy and operational!
I’m pretty excited with the results, rotation is so smooth and knife is spring loaded on 3 linear axis. So ball bearings for rotation, trust bearing for axial force and linear rails for spring loaded motion!
3:1 ratio for stepper rotation axis with belt.
I’m still missing my homing micro switch with roller, received the wrong type again!
Next step is the actual Low Rider built, I really need to make some space for it in my garage and I’m depress by the mess I need to sort out for it!
I know I’ve started reversed, tool first then cnc, but I was looking a the garage like a kid looks at broccoli…
looks really nice. What are you planning to do with it? I use a drag knife to cur the base of my skis but the knife is much simpler. Are the instructions, list of components and stls available?
I could not be more aligned with this statement, haha!! I assembled my LR in the kitchen but haven’t officially set it up to try it out yet because I need to deal with my mess in the garage! I feel your pain!!
