Originally Posted by
Cartierusm
I got my machine together with Mcmaster Carr Precision Acme Lead Screws and Dumpster CNC antibacklash nuts but I'm getting .01" backlash. That's a ton! I emailed him today and should recieve a response by tomorrow, I hope, but was wondering if this is normal. I tried his nuts, no pun intended, a few years ago and had the same problem but thought I'd give it another try as I couldn't afford ballscrews this time. With the nut mounted and everthing I can take the gantry and move it and see the nut shift. I wonder if I could use a heavier spring to push the part that grips the screws. Any help would be appreciated.
I don't see anything like this on my two machines that use DumpsterCNC nuts. The DumpsterCNC ABNs are spring loaded to keep the nut snug on the lead screw threads when reversing travel direction. Mine are already pretty snug on the 1/2" ACME rods with the included springs. Any tighter and they will probably just wear faster. The nut should not shift relative to the lead screw.
If the whole lead screw moves lengthwise then there is free play or flexing in the lead screw mounting system. Do you have the lead screw mounted so that it cannot shift but can easily rotate? Shaft collars and thrust bearings will be better than just letting the lead screws float inside the bearings.
Do not depend on the stepper motor alone to hold it steady. This will work on small machines with light cutting forces but will not work well on heavy gantries or higher cutting forces.
CarveOne
CarveOne
http://www.carveonecncwoodcraft.com