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I am trying to fix the old lab volt cnc lathe at my school with an arduino and i got all of the motors running but i can't get autodesk hsm to export grbl turning programs. Does anyone have a solution to this? Or at least a different program i could use to create the g-code?
Try CNCL from the microsoft store, it is an easy way to do CNC on a lathe using GRBL
I looked on the store to see what it looked like and it says that CNCL can perform threading operations. The program says it works with Grbl, but Grbl does not have synchronized spindle motion. How is threading accomplished? Do you need a specialized modified version of Grbl?Quote:
Originally Posted by hfjbuis
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Originally Posted by 109jb
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Threading is accomplished by running the spindle using a stepper motor. The stepper motor is connected to GRBL Y-axis output. By engaging the stepper by a lever, it can be disengaged when not in use. I am very satisfied with this solution. Any GRBL 1.1 (or compatible) controller can be used. Check the "My Lathe" on this forum <a href="http://www.mwt.messageboard.nl/forum/index.php?" target="_blank">http://www.mwt.messageboard.nl/forum/index.php?</a> for detailed information and drawings.<br>Threading on a lathe is no magic, it is just turning two axis simultaneously. Mach3 uses spindle synchronization, but this only works if the spindle speed is constant. My lathe has a simple and cheap 500W DC motor that, due to its low torque, does not run at a constant speed. But this low torque also reduces the damage when i do something stupid.
I don't use Mach3, so can't say how it works, but LinuxCNC uses constant synchronization of the spindle, so if the spindle speed changes, so does the feed on the Z-axis. Having said that, you solution should work fine, but I have doubts about a stepper motor's ability to provide enough torque, particularly when cutting larger thread profiles in ferrous metals. Do you have any videos of your machine threading using the stepper on the spindle?
Mach3 requires a synchronization pulse, one per spindle revolution. The speed is also adjusted once per spindle revolution. Dat works OK if the spindle speed is "constant". Do you have a resolver on the spindle or like mach3 just a single pulse?
Torque could be an issue. I run my spindle stepper at 1/16 excitation just to reduce the noise. I mostly do small parts and run at lower speed to reduce the cutting forces and the deflection of the workpiece. The largest thread i have cut was M27 x 1.5 in aluminum and UNC 3/4 10 TPI in steel. That worked ok. At the end of this month i am going to cut (Collet holder) M32 x 1.5 in CrMo steel. I will then change the excitation to full step because i haven't enough steel to do it twice. Because the spindel speed never has been a bottleneck in cutting, i am going to change the gearbox to have more torque and will run the spindle at a higher speed to keep "the same" speed. My spindle is driven by a nema 23 stepper 1.9 Nm i could also try a bigger nema 23 stepper.
I have no videos at all, but it is on my to do list.
By the way, the most i like about this "CNC threading" is that the thread is always "perfect" without any adjustments and the ability to start en stop at the exact position.
I tried to record a video using my cellphone. I think for a first impression, it is OK. What threading would you like to see (tread type)