I’ve been wondering what is preventing MR-1 from being able to rigid tap in case I wanted to modify it to do so? There are a few things that come to mind but looking for feedback from the gang on the forum. So things on my radar are:
G code limitation in cut control
Spindle reverse direction signal not hooked up to VFD
Spindle belt set up may require different tensioning set up
ground Z-axis ball screw for accuracy vs. existing threaded lead screw
ground Z axis ball screw would likely require servo motor with encoder + brake set up
Did I miss anything? Would the existing x axis set up and spindle belt work as is? I get why Langmuir left this feature off of the machine because it adds some cost and complexity without question. But if a guy wanted it what would a guy have to do?
The fact that CutControl will not entertain the VFD in reversing direction. That Langmuir probably has no intention of building this into CutControl software’s control strategy. Besides after using this machine for 6 months or so, I don’t believe the spindle has the power to perform this. Certainly the belt drive is a negative in this conversation.
Just a note… After using this machine with thread mills, I probably would never consider rigid tapping again. In my opinion the thread mill process is far superior.
Again, this is just my two cents.
The encoder position is not shared with the control, and that would be the first requirement. The control has pins for it, but they aren’t connected to the servo driver. I haven’t been able to get useful documentation from CWMotor (who makes the servo) to see if it is even exposed.
Once that is fixed you’d need control software that supports it. GRBL almost certainly does not, it’s a very minimal system.
I’m a fan of thread milling too … just not for tapped holes less than 1/4. I planning to use this instead of cut control/GRBL controller:
So hopefully GRBL limitations won’t be an issue. But I want to try to make sure there are no mechanical deal breakers I’ve over looked that will preventing me from rigid tapping. I’m very glad for everyone’s feedback so far. Looks like the drive belt is something I’ll have to figure out. For small taps I’m hoping MR1 has the torque I need though.
Rotator, I’m also curious about modifying the MR-1 to enable rigid tapping holes smaller than .25in. I imagine the difference between thread milling and rigid tapping is the cutter engagement. Since, thread milling is similar to single point threading on lathes there is less cutter engagement vice the full engagement of a rigid tap cutter. Is there any disadvantage with the MR-1 spindle belt causing issues with reversing the spindle for rigid tapping? How is your plan going to use the AcornSix CNC Controller?
Rigid tapping is on my list of things to do. I have the MR-1 converted to the Acorn controller and setup the spindle encoder to show actual RPM. I also have forward and reverse working. The only think I haven’t done is testing.
After I put the machine back together I found some QC issues that went mostly unnoticed. I have been working on fixing those first. I’d like to get rigid tapping working some time over the summer.
I’m going to start looking into the Acorn controller, myself as well. I have access to MasterCam and will take a look at the posted G-Code for rigid tapping. Your research and development will prove profitable as a conversion kit! I’ll keep in touch.
My post up there is really old. I did figure out how to get the encoder working with the stock spindle and drive and it’s documented here:
All of the encoder pins are available on the servo drive’s DB44 connector and I’m guessing it wouldn’t be too hard to get those working with an Acorn.
I never used rigid tapping myself. I’d want to do that at low RPMs, and the stock spindle isn’t really well suited to low RPMs. I ended up replacing the spindle to get tool changing and my new spindle can’t do rigid tapping and I’m okay with that.