Replace change gears with a stepper?

And a video of the ELS -II in action.
 
jwmelvin said:
This looks great. I’ll likely do something similar with my G0602. I’d like to look at your code if you can put it somewhere accessible.
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jwmelvin,

Attached are the schematics some other documentation and the source code in a ZIP file. Please feel free to contact me if you have any questions about what I've done. I know that taking other people's software can be a challenge.
 

Attachments

  • Lathe Leadscrew Controller.zip
    1.5 MB · Views: 9
How about some follow up to this? How is it working out? Do you have any examples you can post.

Robert
 
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rwm said:
How about some follow up to this? How is it working out? Do you have any examples you can post.

Robert
Click to expand...

Robert,

I've been using the stepper system for a couple of months now. It's nice to be able to switch to very slow feed speeds without having to stop and change the gears. The lathe is quieter and gear train wear is eliminated (since they are disconnected). With a 3 N-m stepper there is no shortage of torque on the lead screw. I'm in the process of modifying the whole software system to do threading. It will thread US or Metric threads equally easily.

Modifications to the current system include: changing the 24-slot spindle sensor to 64-slots with a Top Dead Center (TDC) indicator, new tachometer software, new stepper speed calculation software, a new user interface and new cabling from the spindle sensors to the controller. The software will measure the spindle speed 64 times per revolution, averaging over 4 slots each time. The stepper speed will be adjusted 64 times per spindle rotation. The stepper will start a threading pass after the third TDC signal. This ensures the spindle is up to speed. For each threading pass the carriage must start from the "Home" position which is monitored by software. The first 1/4 to 1/2 turn of the lead screw (less than 0.030 travel) will be dedicated to acceleration of the stepper so the Home position must be off the end of the thread.

I started the threading software by researching Phase Locked Loop (PLL) techniques and implementing a second-order Sigma Delta PLL. The complexity rapidly got out of control. I believe that as long as the stepper has enough torque and doesn't miss any steps, a simple synchronized, open-loop system will be sufficient. Of course experiments in the shop will verify that it actually works.

I hope to have the prototype up and running within several weeks. It's pretty hot in Texas so shop time is limited to mornings.

Glen
 
gzoerner said:
I've been using the stepper system for a couple of months now. It's nice to be able to switch to very slow feed speeds ... It will thread US or Metric threads equally easily.
Click to expand...

There's other threads (like on glass jars, and that nice soap dispenser that got its pump broken) that I'd like to be able to cut,
which aren't notably US or metric, that would likewise be better done with such a system. Eventually, there'll be
a thermos cap or other oddball that you'll want to match, and sticking to standard threads (and threadforms) won't
be advantageous.
 
whitmore said:
There's other threads (like on glass jars, and that nice soap dispenser that got its pump broken) that I'd like to be able to cut,
which aren't notably US or metric, that would likewise be better done with such a system. Eventually, there'll be
a thermos cap or other oddball that you'll want to match, and sticking to standard threads (and threadforms) won't
be advantageous.
Click to expand...

While I'm going to stick with standard threads (US and Metric), it's a simple matter to change the User Interface to accept any thread pitch. It's just a (non-integer) ratio that drives the stepper control routines.

Glen
 
gzoerner said:
While I'm going to stick with standard threads (US and Metric), it's a simple matter to change the User Interface to accept any thread pitch. It's just a (non-integer) ratio that drives the stepper control routines.

Glen
Click to expand...
I am guilty of making odd thread combinations just to confuse someone in the future, a CNC lathe will turn any thread lead within it's accuracy.
One may single point a 1"-7 63/64 TPI thread if desired, I would never do such a thing (-:
 
This guy did it. Andy Pugh shows his mini-mill synced to his lathe. Its quite impressive. He built the encoder which fits his mill and synced it to the spindle/stepper he mounted on the lathe.
I wish he went into more specifics. But it shows that with a bit of ingenuity it can be done.

 
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