Nope. Unless they started opening on weekends again :-(
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G3616 Conversion.
- Thread starter jcdammeyer
- Start date
Not really a big deal. Unlike a servo that I can switch over to constant torque mode I have to be able to detect that the stepper motor has stalled with a specific power setting. If the stepper driver has resistors for setting current then it's pretty easy to use a relay to switch them based on the motor direction. 18 ft-lb for tighten. 20 ft-lb for loosen.
But most of the drivers I have use switches to set current. There is one where I think I can put a relay across the dip switch. But I also need to interface to a quadrature encoder so I can tell when it's stopped turning. Quadrature so if it's vibrating around the sensor edge that we also detect that.
I could use 1 PPR on the motor, which if stepping at say 10kHz with 2000 steps/rev I should see a pulse every 0.2 seconds. So if no pulse occurs after that time I will know it's stalled. Since it stalled at a higher speed and torque falls off on a stepper for higher speeds it's likely it will just buzz once stalled at that lower torque value. I could then step very slowly for another 1/4 turn (after reduction drive) to firmly tighten it.
To loosen, set higher current into motor, turn slowly for two turns. Then speed up if trying to remove R8.
This would be so much easier with a servo motor compared to a stepper.
Here are the two parts enlarged for the F03 specification size.
Planetary Gear output shaft size is 14mm with 5mm key. Screws are 5mm. Drive is 3/8" with a retainer pin hole that is 3mm diameter.
Planetary Gear output shaft size is 14mm with 5mm key. Screws are 5mm. Drive is 3/8" with a retainer pin hole that is 3mm diameter.
No. I don't have 5mm metric in stock. I have lots of Philips Pan head and the bolt diameter is large enough to clear the socket. Plus I might still mount a flat slotted encoder disk there instead of mounting an encoder on the back of the stepper motor.
I have a couple of US Digital encoders I pulled off my DC brushed servos because they were very unreliable. Switched to CUI for those motors. But likely for what I want on the draw bar it would be adequate. But making up an aluminum disk with slots using the slitting saw and indexing on the rotary table is pretty easy.
Or even just a disk with a ring of small holes which I can make LinuxCNC do without a rotary table.
Hence no socket head screw capability.
Attachments
And just for general interest. The 3D parametric CAD drawing took less than 10 minutes. The CAM using AlibreCAM took about 25 minutes which includes generating and zipping the G-Code .ngc files.
I'm not suggesting anyone use the files but if you are interested in what I did.
How I would use them would be to:
1. 0.042" aluminum sheet a bit larger than the diameter placed onto scrap plywood or MDF and held in the corners. Ensure that the center point sits over a T-Slot.
2. Run the G-Code that cuts out the middle hole.
3. Hand drill through the plywood and with a large fender washer and a bolt anchor down the middle.
4. Next run the G-Code that does the center drilling for the mount holes and encoder holes.
5. Run the G-Code that does the 4 mounting holes.
6. Screw self tapping screws into the wood through the 5mm mount holes.
7. Run the G-Code to drill the encoder holes.
8. Finally run the G-Code to cut out the outer perimeter.
9. Remove the outer clamps, screws and bolt.
10. use a deburring tool to clean the perimeter if the edge is ragged. Same with the 14mm center hole.
11. Depending on the state of the encoder holes deburr from the rear with a hand tool.
12. Mount to adapter.
There. A 12 step program...
I'm not suggesting anyone use the files but if you are interested in what I did.
How I would use them would be to:
1. 0.042" aluminum sheet a bit larger than the diameter placed onto scrap plywood or MDF and held in the corners. Ensure that the center point sits over a T-Slot.
2. Run the G-Code that cuts out the middle hole.
3. Hand drill through the plywood and with a large fender washer and a bolt anchor down the middle.
4. Next run the G-Code that does the center drilling for the mount holes and encoder holes.
5. Run the G-Code that does the 4 mounting holes.
6. Screw self tapping screws into the wood through the 5mm mount holes.
7. Run the G-Code to drill the encoder holes.
8. Finally run the G-Code to cut out the outer perimeter.
9. Remove the outer clamps, screws and bolt.
10. use a deburring tool to clean the perimeter if the edge is ragged. Same with the 14mm center hole.
11. Depending on the state of the encoder holes deburr from the rear with a hand tool.
12. Mount to adapter.
There. A 12 step program...
Attachments
I found in the drawings/XAxis folder all sorts of drawings and photos I had done a few years ago. Working with ordering parts from AliExpress for the Robot Arm I realized I should get after getting ball screws. The thing that put that project #42 on hold was not knowing whether to use a 16mm, 20mm or replacement 2505 sized ball screw to replace the 1" ACME 0.2" pitch screw.
I had a photo of the screw nut and where it went when I had the table off a few years ago.
But I really couldn't tell from those pictures whether the much larger ball nut and holder would fit. So first step is remove the RH side plate, wind the lead screw all the way over so the edge of the table lined up with the frame section in the photo above. Dangled a square over to measure to the screw center line.
Well lots of measurements. Sketches, then CAD drawings and finally taking the original ACME screw and nut assembly drawing I did in 2017 and adding it to the two parts I drew today.
Here's a perspective view.
So similar end view with the ACME screw centered on the X axis.
Looks like there will be plenty of room for a larger ball nut holder. Why not just go with a 16mm screw? Well the pulleys and bearings and spacers etc are all sized for the current 1" ACME screw. The cost of a 25mm over a16mm isn't that high and the rounded ends then match all my bearings and the pulley.
All I need to do is cast new end plates with the hub in line with the new ball screw center line. Easy to do since it was a two part pattern. Just move the hole up and use some wax to plug the old one.
All for now. Time to download the 1" double ball nut step file and model it with the parts done here.
I had a photo of the screw nut and where it went when I had the table off a few years ago.
But I really couldn't tell from those pictures whether the much larger ball nut and holder would fit. So first step is remove the RH side plate, wind the lead screw all the way over so the edge of the table lined up with the frame section in the photo above. Dangled a square over to measure to the screw center line.
Well lots of measurements. Sketches, then CAD drawings and finally taking the original ACME screw and nut assembly drawing I did in 2017 and adding it to the two parts I drew today.
Here's a perspective view.
So similar end view with the ACME screw centered on the X axis.
Looks like there will be plenty of room for a larger ball nut holder. Why not just go with a 16mm screw? Well the pulleys and bearings and spacers etc are all sized for the current 1" ACME screw. The cost of a 25mm over a16mm isn't that high and the rounded ends then match all my bearings and the pulley.
All I need to do is cast new end plates with the hub in line with the new ball screw center line. Easy to do since it was a two part pattern. Just move the hole up and use some wax to plug the old one.
All for now. Time to download the 1" double ball nut step file and model it with the parts done here.
Took the model of the 25mm ball screw I did a couple of years ago. Now that I have the table assembly modeled I created a ball nut holder and with some bevels on the holder.
I will have to cast new end plates and come up with a better method of locating the holes. Unfortunately the Chinese builders didn't put them in symmetrical locations. On the RHS the set is even turned CW a tad so the top of the holder isn't level.
I suspect they had some sort of jig that held the ends of the ACME screws so it was parallel in the two dimensions to the table and then they just pressed the end plates and used a centering punch to set where the holes go. That a plate pivoted slightly wasn't important...
I will have to cast new end plates and come up with a better method of locating the holes. Unfortunately the Chinese builders didn't put them in symmetrical locations. On the RHS the set is even turned CW a tad so the top of the holder isn't level.
I suspect they had some sort of jig that held the ends of the ACME screws so it was parallel in the two dimensions to the table and then they just pressed the end plates and used a centering punch to set where the holes go. That a plate pivoted slightly wasn't important...
Going down this route soon.
I'm finding it invaluable this time to do all the CAD up front. To make sure things fit. I know on the island if the mill is disabled there are a few people close by who can make some chips if I make a mistake. But I'd rather not have the mill that disabled.
For me the plan is some maintenance to see what wear hard CNC is causing and plan mitigation. Measure up and design mounts for the ballscrews. Assemble and continue work will setting up for next retrofit (without glitches one hopes).