Newbie converting a PM-728VT

All things related to the Centroid Acorn CNC Controller

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DesertRider
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Re: Newbie converting a PM-728VT

Post by DesertRider »

I have a KP-3 probe on order from Centroid, and am wondering what it's like to use it. The video I saw shows th probe in a toolholder, then you swap out the whole toolholder. Is it possible to use a BT40 or similar tool holder in the PM 728?
martyscncgarage
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Re: Newbie converting a PM-728VT

Post by martyscncgarage »

DesertRider wrote: Fri Mar 12, 2021 7:16 pm I have a KP-3 probe on order from Centroid, and am wondering what it's like to use it. The video I saw shows th probe in a toolholder, then you swap out the whole toolholder. Is it possible to use a BT40 or similar tool holder in the PM 728?
PM728 specs say it has an R8 spindle taper. Do you have something different?
Just load the KP-3 into the correct size holder and leave it set up in it.
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
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DesertRider
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Re: Newbie converting a PM-728VT

Post by DesertRider »

I just turned the mill on for the first operation, and when I give an MDI command of 'S1400 M3', it spins at about 2200 RPM.
I have previously done the Wizard calibration, using 3000 and 0 as limits, ran the spindle bench test and entered the voltages (1.66 etc), hen set the speed limits to 4250 and 50 which are specific to my mill.

How can I correct this to ensure the correct RPM? Thank you.

Attaching the report.
martyscncgarage
Posts: 9912
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Re: Newbie converting a PM-728VT

Post by martyscncgarage »

DesertRider wrote: Sat Mar 13, 2021 3:53 pm I just turned the mill on for the first operation, and when I give an MDI command of 'S1400 M3', it spins at about 2200 RPM.
I have previously done the Wizard calibration, using 3000 and 0 as limits, ran the spindle bench test and entered the voltages (1.66 etc), hen set the speed limits to 4250 and 50 which are specific to my mill.

How can I correct this to ensure the correct RPM? Thank you.

Attaching the report.
report_64CFD94395CA-1116203993_2021-03-13_12-47-46.zip
What does it do when you call
S50
S2125
S4250
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
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DesertRider
Posts: 56
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Re: Newbie converting a PM-728VT

Post by DesertRider »

s50: nothing happens, no spinning at all
s2125: 3252 rpm
s4250: 4400 rpm

s100 doesn't spin either
s200: 170-180 rpm
s230: 230rpm (it varies a few rpms of course)
s250: 270rpm
s300: 400 RPM
s500: 900 rpm

Wouldn't the encoder loop back and change the voltage as needed? Otherwise what's the point of the encoder?
Last edited by DesertRider on Sat Mar 13, 2021 5:57 pm, edited 1 time in total.
martyscncgarage
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Re: Newbie converting a PM-728VT

Post by martyscncgarage »

DesertRider wrote: Sat Mar 13, 2021 5:52 pm s50: nothing happens, no spinning at all
s2125: 3252 rpm
s4250: 4400 rpm

s100 doesn't spin either
s200: 170-180 rpm
s230: 230rpm (it varies a few rpms of course)
s250: 270rpm
s300: 400 RPM
s500: 900 rpm

Wouldn't the encoder loop back and change the voltage as needed? Otherwise what's the point of the encoder?
No. The encoder does not close a spindle loop. The encoder is for slaving the Z axis to the current spindle speed.

You should set the bottom end speed for 200. You'll have to cut back the high end speed on your spindle drive. Look for a max adjustment. You will have to experiment with your drive settings
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
DesertRider
Posts: 56
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Location: Phoenix, Az

Re: Newbie converting a PM-728VT

Post by DesertRider »

I will be first to admit my complete ignorance about electronics, but I did the centroid measurement to map commanded and measured voltage with the benchmark range (0-3000) then adjusted in the Wizard the range to my actual spindle speeds. So I would expect that the Acorn will command 10 volts if it wants to get top speed (4200 in this case) and would command a proportionately lower voltage in the range 0-10 to achieve lower speeds. So for example, would send 5V to get 2100 RPM, etc. What am I missing here?
martyscncgarage
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Re: Newbie converting a PM-728VT

Post by martyscncgarage »

DesertRider wrote: Sat Mar 13, 2021 9:52 pm I will be first to admit my complete ignorance about electronics, but I did the centroid measurement to map commanded and measured voltage with the benchmark range (0-3000) then adjusted in the Wizard the range to my actual spindle speeds. So I would expect that the Acorn will command 10 volts if it wants to get top speed (4200 in this case) and would command a proportionately lower voltage in the range 0-10 to achieve lower speeds. So for example, would send 5V to get 2100 RPM, etc. What am I missing here?
All you did was the spindle analog output bench test. It proves that Acorn analog output is functioning properly.
Check your voltage at the spindle drive as you call those speeds. What DC voltages are you getting?
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tblough
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Re: Newbie converting a PM-728VT

Post by tblough »

You are not missing anything on the Acorn. If you check the voltages at the analog out again (without anything connected) with the max spindle speed set to 4200. You will see 10V at 4200, and 5V at 2100, etc.

Now, what you need to do is set up your VFD, so that 10V in causes the motor to turn at 4200 rpm.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
martyscncgarage
Posts: 9912
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Re: Newbie converting a PM-728VT

Post by martyscncgarage »

I believe that machine has a brushless drive.
Didn't explain what the encoder is used for. Displaying actual speed and for rigid tapping on a mill.
CNC12 does not close a spindle speed loop.
As Tom mentioned if you disconnect the analog output wires from your spindle drive, when you call your max spindle speed from MDI, you'll likely get 10 volts or very close to it.
It's a good test.
I asked out of curiosity what the voltage measured was with the analog output connected to your spindle drive. It should be close. Please post a picture of your cabinet wiring and explain what wire you used to connect from Acorn analog output to your spindle drive.
As Tom mentioned, if you had a VFD you would "tune" it, in your case, provided you used good wiring practices to wire your drive, you may have to adjust it. Hopefully you have a manual for it. (Usually, there are potentiometers for Min and Max speeds...I don't know about your drive.)

Again, I'm assuming you have a brushless DC motor for a spindle motor. I think that's what those machines come with.

Marty
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
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