I’m making the last adjustments to the “monsterCNC” (2800x2000mm). It works very well. but there are things to improve. One of them is that when the motors are de-energized, the entire z-axis falls off. It does not fall evenly, it falls more on the side that has more weight. I am using t8 rods with a pitch of 2mm. I do not know if exist with a smaller step, which would be the solution. or someone has already implemented another solution. I imagine it is a common problem.
Another thing that I would like to improve, is that the CNC has a lot of force on the X and Z axes, but the Y axis has only one motor. Then, if it is demanded, so that it cuts deep, the Y axis is the one that can get to lose some step. I have planned to change this engine for a nema23, or, in some way add another engine to this axis.
It should not, check your step rate, bit quality, DOC.
I have all three drivers in 0.7volts. If I try to stop the X-axis with my hand, I really have to do a lot of strength. the same with the Z axis. When it goes up not so much, but when it goes down the wheels get up before losing steps. But to lose steps to the Y axis I have to do very little force. I imagine about 3 kilograms.
If I increase the current I will surely give it more strength. with 0.7v the stepper is barely warm. With this machine I plan to do work that can take several hours. So I do not think I can give more strength to the stepper by increasing the current.
In what way can the step rate affect the strength of the stepper?
I don’t want to cause confusion, but I think the problem is that when they eventually fall, the side closer to the router falls faster or more. I think the risk is it binding up.
If you have a park spot, as Ryan does, you can go there before turning off the motors. A different pitch would increase the steps per mm needed, which can limit your max Z speed, but somewhere in between the T8 and allthread makes sense to me…
As for the Y motor. IDK. Larger nema 17? More current, but you’re risking an overheat, which would suck on hour 2.5.
If your reasoning is to make it as strong as X and Z, that’s not a terribly good reason. Those axis are doubled up because it’s needed to move both ends in step. If the Y is really skipping, then it would make sense to look for an improvement, but each bigger part makes the rest weaker.
I like Ryan’s idea of parking the router after the job is done. That means you need to manually add a line of gcode at the end of the that will move the router somewhere safe.
I am currently experimenting with that same idea with a fun electrical trick. I have created an electric kill switch for the router using a standard electric light switch. Here is a short video that shows how it would work. The basic idea is I will place the switch in a location that the machine (an MPCNC in my case) can flip the switch. Then I add gcode at the end of the file so the machine moves and turns off the switch. In the video I have it set as a high X location. I want to move it to X0 so I just send the printer back to home or X0 and it will turn off the spindle. Or I could somehow place the switch somewhere so the Z axes could turn the switch off. I don’t know.
That’s the idea. I don’t have it all figured out yet but there it is.
I don’t know fusion’s postprocessors, but the M18 command is what will disable the motors. It’s probably being added to the bottom of your file. Even if you’re not on a low rider, M18 is a bad idea. If you split your jobs into multiple files, you’ll lose your origin as soon as you disable the motors.
The other thing to look at is that the firmware isn’t disabling the motors after a timeout period with no movement. Ryan’s firmware has it on for a few minutes after the last command, so when a job finishes, you’ve got time to turn off the spindle, part the router, turn it off manually, or whatever. I have disabled the auto off feature all together in grbl.
If you do this, make sure you remove the M18. Otherwise, it will turn off the motors, then get the command to move to your home position, but have no idea where it was (because the motors turned off).
Pretty sure we are on Version 9 and 10 (different creators I have only used V9 and don;t use fusion CAM). I do believe the release steppers is hard coded into some of the early post processors. Look at the last few lines, but first move to one of the current versions.
