Not sure if I’m saying this right but instead of making the z axis at the legs. Wouldn’t it be better to put the z axis at the gantry similar to the MPCNC? Or would that make it too heavy? I have had issues with my z slipping and falling during a few cuts so I was curious if it would be better by locking the legs in a rigid position and having the end plate adjust z height.
Thoughts??
I’m just guessing here, but if you had the feet stationary, they would need to be larger, and the router would have to reach down.
It would almost certainly be lighter to do it that way, and the Z would be lifting less. There are a lot of cnc machines that do it that way.
What that does is lock you into a size. With the LR you can have a 1/4" Z axis or a 8" Z on the same machine with no penalties to either. If you make it the other way an 8" Z build cutting a 1/4 will suffer, or a 1/4" build can’t cut 8"
Thanks for explaining Ryan! Do you have any tips on avoiding missed steps in the Z Axis? Just slow it down?
It should not skip steps, if it does something is wrong and speed is one of the factors. The more aligned the whole machine is the faster the Z axis can move.
When you say skipped steps - what are the z steppers doing? Are they spinning backwards and dropping when they should be raising?
If that’s the case, you may be under driving the steppers in the firmware. Do you know what your current is set to in the firmware?
You can check for Z binding by seeing if the carriage falls under it’s own weight while the platform is in the middle… make sure the lead screw nuts are not bolted tight to the 3d printed mount they need to wiggle. Some super lube on the lead screws can help. Also check your stepper drivers make sure they are not getting too hot to touch. Once that’s resolved you can lower max Z acceleration and feedrate a lot and your problem should go away. If it does, just tweak them up bit by bit until it fails again and bring it back down 10% or so as a safety margin. You will never get the Z axis zipping up and down as fast as you might like just because it’s lifting to much weight.
Some of the heavier CNC home builts use gas springs like on your car trunk to make the Z ‘weightless’ and get more speed, might be a fun hack to try sometime.
Greg, thanks for the few tips! I will definitely try a few of the tips you suggested. It seems like I have a feeling it might have something to do with the Motor and Lead Screw coupler. I am going to mess around with it tomorrow to see if that is the case. It only happens to my right side. The left side seems to hold its own fine.
Perhaps your printed Y Bottom part which holds the screw nut bends under the load of the gantry. I designed a support for my Lowrider2. Perhaps this could solve your Problem
How do I go about lowering the max z acceleration? Is that a value that I can change and then save with M500?
You can set max accel with M201… if you have eeprom enabled you can set with M500 otherwise just make sure it’s at the top of your code file.
Thanks