Double check the length of 906A DO NOT use a 30mm bolt, use 35mm+ This can cause a catastrophic failure.
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Gene Weber's PM-728VT CNC Conversion
- Thread starter gene_weber
- Start date
- Joined
- Aug 12, 2022
- Messages
- 40
Good to hear this thread is helpful! @GB21, thanks for the heads up on the length of 906A.
I've been working on the controller box, and haven't posted much lately because the progress has been a bit slow. A number of parts were 3D printed, which is fun, but takes some time. I created them in Solid Works, and my son-in-law printed them. For example, the IPC-5 power supply has mounting holes on the top to accept a 40mm fan, or on the side for an 80mm fan. I'm using a 220v 60mm fan, so created a 80mm to 60mm adapter.
Also created a dual fan mount for the Raspberry Pi, a holder for voltage displays, a fan cover, vent covers, DIN rail clips, voltage labels, door hinges, and a door latch. As I said, fun to create, but eats up some time.
I actually had some blue spray paint that was pretty close to the mill stand color. So after cutting and drilling all the openings and holes needed, the controller box was changed from John Deere yellow to "Precision Matthews" blue.
You may recall that I ground the welds off and removed the heavy steel door. I'm replacing it with a plexiglass door so I can see inside the controller box. I had build a deck out of Cumaru, an extremely dense South American wood that is harder than oak. I found pieces of Cumaru in my scrap wood pile that were perfect for the frame. The groove already in the wood was a perfect fit for the plexiglass, and the dimensions were great for a frame. Sometimes a pack-rat just lucks out.
I simply rounded over some edges on the router table, cut some 45s, and made a frame. I want to be very clear here, please don't ever use wood when making and electrical box! The shape of this particular box shields the wood frame. Cumaru is also difficult to ignite, and it's coated with paint. But the key is that it's shielded. Please never mix electrical and wood.
Also spent time being cheap. There is a DIN mount that fits the Teknic IPC-5 power supply. I bought an inexpensive metal DIN rail mount and mated it with a piece of scrap aluminum to make a DIN mount. But hey, I like doing stuff like this. If you're in a hurry, buy the mount they list in the manual.
The controller "card" I'm using is a Mesa 7C81 FPGA card with a Raspberry Pi 4B. Here it is in the DIN mount with the cooling fans installed.
This is what the Controller box looks like today. A lot of wiring still to do.
I've been working on the controller box, and haven't posted much lately because the progress has been a bit slow. A number of parts were 3D printed, which is fun, but takes some time. I created them in Solid Works, and my son-in-law printed them. For example, the IPC-5 power supply has mounting holes on the top to accept a 40mm fan, or on the side for an 80mm fan. I'm using a 220v 60mm fan, so created a 80mm to 60mm adapter.
Also created a dual fan mount for the Raspberry Pi, a holder for voltage displays, a fan cover, vent covers, DIN rail clips, voltage labels, door hinges, and a door latch. As I said, fun to create, but eats up some time.
I actually had some blue spray paint that was pretty close to the mill stand color. So after cutting and drilling all the openings and holes needed, the controller box was changed from John Deere yellow to "Precision Matthews" blue.
You may recall that I ground the welds off and removed the heavy steel door. I'm replacing it with a plexiglass door so I can see inside the controller box. I had build a deck out of Cumaru, an extremely dense South American wood that is harder than oak. I found pieces of Cumaru in my scrap wood pile that were perfect for the frame. The groove already in the wood was a perfect fit for the plexiglass, and the dimensions were great for a frame. Sometimes a pack-rat just lucks out.
I simply rounded over some edges on the router table, cut some 45s, and made a frame. I want to be very clear here, please don't ever use wood when making and electrical box! The shape of this particular box shields the wood frame. Cumaru is also difficult to ignite, and it's coated with paint. But the key is that it's shielded. Please never mix electrical and wood.Also spent time being cheap. There is a DIN mount that fits the Teknic IPC-5 power supply. I bought an inexpensive metal DIN rail mount and mated it with a piece of scrap aluminum to make a DIN mount. But hey, I like doing stuff like this. If you're in a hurry, buy the mount they list in the manual.
The controller "card" I'm using is a Mesa 7C81 FPGA card with a Raspberry Pi 4B. Here it is in the DIN mount with the cooling fans installed.
This is what the Controller box looks like today. A lot of wiring still to do.
- Joined
- Feb 23, 2016
- Messages
- 424
That’s good to hear, they must’ve changed the kit. When I did my conversion, PM were delivering metric couplers which of course did not adapt to (some) US motors.
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- Joined
- Aug 12, 2022
- Messages
- 40
I need some input from people with CNC machining experience.
To complete the controller box I started reading more about LinuxCNC and realized I was overlooking some hardware required for spindle control. So I want to take a step back and make sure I incorporate everything in the controller box that is needed. Therefore it's necessary to know what the machine's capabilities will be in the end.
As noted previously, this machine is for me as a hobby machine in retirement. It's possible that I could come up with some widget that I make a couple hundred of and sell, but mostly I think I'll make one to a few of the things I draw up in CAD. I'm guessing that the majority of the milling will be aluminum or steel, and actually some hardwood.
Based on that I think:
- The machine needs limit and home switches on all 3 axes.
- The machine needs CNC control of the spindle speed and direction to coordinate feed and speed during milling.
- The machine should incorporate a spindle speed encoder to coordinate low speed spindle operation and Z axis feed for threading operations.
- I think I'd like to add a fourth axis for "A" rotation about the X axis in the future.
- I don't think I'll need an automatic tool changer or automatic flood or mist coolant control.
Since I have zero machining experience, please let me know what your experiences are. Am I overlooking something? Is there something you often use as a hobby machinist, or dearly wish you had?
Thanks,
Gene
To complete the controller box I started reading more about LinuxCNC and realized I was overlooking some hardware required for spindle control. So I want to take a step back and make sure I incorporate everything in the controller box that is needed. Therefore it's necessary to know what the machine's capabilities will be in the end.
As noted previously, this machine is for me as a hobby machine in retirement. It's possible that I could come up with some widget that I make a couple hundred of and sell, but mostly I think I'll make one to a few of the things I draw up in CAD. I'm guessing that the majority of the milling will be aluminum or steel, and actually some hardwood.
Based on that I think:
- The machine needs limit and home switches on all 3 axes.
- The machine needs CNC control of the spindle speed and direction to coordinate feed and speed during milling.
- The machine should incorporate a spindle speed encoder to coordinate low speed spindle operation and Z axis feed for threading operations.
- I think I'd like to add a fourth axis for "A" rotation about the X axis in the future.
- I don't think I'll need an automatic tool changer or automatic flood or mist coolant control.
Since I have zero machining experience, please let me know what your experiences are. Am I overlooking something? Is there something you often use as a hobby machinist, or dearly wish you had?
Thanks,
Gene
You could pass on the spindle encoder and just thread mill instead. Things I could not live without is a enclosure (huge mess and safety) power drawbar, and coolant or air blast to clear chips. If you end up making a few hundred widgets the line between "hobby machine" and "small production machine" starts to fade .
.
- Joined
- Jan 7, 2016
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- 3,279
- Joined
- Feb 23, 2016
- Messages
- 424
1. Yes to home switches -- mine are X-, Y- and Z+. Opposite limit switches are set in software. So you only need 3 and home=limit.
2. Yes to control of spindle speed otherwise you cannot properly do CNC-ing, as different cutters and materials will need different speeds, and I usually have different ramping vs cutting speeds.
3. Agree with @GB21 that threadmilling is way better than regular threading, so I hardly ever thread anymore. Three threadmills replace a full box of taps and dies. So the encoder is optional. That said, I have the Omron encoder and will be installing it on a new bracket in the next several days.
4. I am starting work on building a rotary A axis but that is crearly optional
5. You DO need mist coolant (I use a Noga) and it can be as simple as just air to cool and evacuate chips or can add the coolant as I do. The multi-nozzle liquid coolant you see the big boys use is a huge pain in the a** in the hobby shop, so I stopped use liquid and rely on air + Koolmist.
6. An enclosure is a MUST IMO -- again, in agreement with @GB21. My front panels are polycarbonate the sides are curtains with regular plastic and the back is regular home depot plastic.
Once a luxury is attained it becomes a necessity. So I could hardly imagine being without a touch probe (Centroid), tool height setter (home made), and power drawbar (Priest).
As you might recall I use a Centroid Acorn so their hardware + software + peripheral (touch probe) solutions solve most of the above questions and integrate the system nicely.
ATC with a carousel would be suuuper nice but seems way above my skillset.
As for hundreds of parts for sale -- that's not me, but I think special care to reproducibility, finish, efficiency will be huge there. I am strictly a hobbyist.
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- Joined
- Aug 12, 2022
- Messages
- 40
Thanks! I just watched a YouTube video on thread milling.
- Joined
- Oct 23, 2021
- Messages
- 27
I’m about finished with my conversion, have spindle control,last thing is to install my encoder for RPM’s and the air mist system. Mainly do threadmill but want the option for rigid as well.
Have two coats of paint to get on it and then will use self leveling epoxy on the inside of bottom. At the end of the day I’ll probably use air for chip cleaning with minimal mist.
Acorn controls and Teknic SDSK, absolutely loving it.
Homing is a must, 3 switch’s will cover homing and limit.
Have two coats of paint to get on it and then will use self leveling epoxy on the inside of bottom. At the end of the day I’ll probably use air for chip cleaning with minimal mist.
Acorn controls and Teknic SDSK, absolutely loving it.
Homing is a must, 3 switch’s will cover homing and limit.
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