AllInOne Overheating? Oscillating

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johnballard
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AllInOne Overheating? Oscillating

Post by johnballard »

I have a Lagunmatic 250 10HP vertical knee-mill with AllInOne controller. It's been a great machine in my garage and I have machined more than 500 parts without issues. However, today there were two curious events.

I had been running a series of programs (five tool changes) to build 100 parts. Each part takes about 50 minutes of machine time. There is one operation that forms a contour on two posts that takes 30 minutes of continuous machining. I have ramped the feed rate to 750mm/min so the x and y axis are constantly moving. This operation finished and I changed the tool to a drill, started the program, ALT-S and WTF. It moved off the part by >50mm and the machine stopped - fault. Nothing crashed. I checked the positioning (x, y, z) and everything seemed OK, just that my program never would take the drill where it ended up.

I started the drill program again, deep-drilled the first hole, and while fast moving to the second hole the whole machine started shaking (before the drill had engaged my part - thank goodness). I pushed feed-stop immediately. Shaking stopped. It was like I had a disconnected or slipping encoder. I'm assuming it was the x-axis since the holes are aligned along the x-axis (no y movement).

I stopped my program. X, Y, Z axis displays were shifting maybe 0.001mm. Jog functions were fine. I checked x and y motors - not hot, very dry (coolant was on and recirculating fine) and sounded normal.

I shut down everything, cut main power, and opened the control box. It was 60F today (pretty cool for my region) so the temperature in the box was reasonable. The only elevated heat was on the AllInOne board. The heat did not seem excessive. All the VFD's were cool.

I have no idea what to look at now. Any suggestions?

I'm going to put a fan on the bottom of my control box so there's fresh air blowing through the AllInOne. What else can I do?
Attachments
100.nc
Includes contour - 45minutes machine time.
(370.1 KiB) Downloaded 13 times
report_0818141095_2021-04-02_22-30-54.txt
(141.34 KiB) Downloaded 15 times
Panduit covers off - sorry
Panduit covers off - sorry
Lagunmatic 250
polaraligned
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Re: AllInOne Overheating? Oscillating

Post by polaraligned »

I would check my PID motor tuning. In particular, if Kd is too low the motor can bust out into oscillations. As for overheating, that probably is not the case but I don't see a fan in that cabinet. You should have filtered fresh air coming in low and an exhaust fan high.
martyscncgarage
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Re: AllInOne Overheating? Oscillating

Post by martyscncgarage »

Agreed, I think its a servo motor tuning issue. You might post the make and model motors here and what the DC buss voltage is. Maybe Marc can suggest something with more information. (Post a picture of the motor label)
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cncsnw
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Re: AllInOne Overheating? Oscillating

Post by cncsnw »

Try reducing Ki on all axes to 0.002.

I would also double the Y axis acceleration time (from 0.107s to 0.215s), and cut its Ka in half to match.
johnballard
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Re: AllInOne Overheating? Oscillating

Post by johnballard »

Attached are the motor labels. The DC circuit is a full bridge fed by 120vac = ~170VDC. I did add a negative temperature coefficient thermistor 2R025 in series.

I'm surprised by the recommendations you guys made, but I will follow them; I know you are the experts. I will explain. I've logged hundreds of hours of machine time with no issues at all. I did perform the tuning process when setting up the almost-new controller and drives. It's just that these two events occurred after having run the mill >4 hours really hard. I was considering that the situation was an anomaly that occurred on a well-tuned machine, rather than a condition that is a machine not set correctly.
Attachments
y-axis motor.jpg
x-axis motor.jpg
Lagunmatic 250
polaraligned
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Re: AllInOne Overheating? Oscillating

Post by polaraligned »

That X axis motor is only rated for 100v - the voltage constant and max speed tell you that. Sometimes they printed the max voltage on the label, sometimes they didn't. I would replace that with proper motor for your supply voltage or use an step down transformer. The Y axis motor is a monster at nearly twice the stall torque as the X axis motor and probably overkill. I use this era Baldor servos on my Series II machine, and used them on a Series I machine that I have since sold.
johnballard
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Re: AllInOne Overheating? Oscillating

Post by johnballard »

Changed the parameters and the whole machine seems 'smoother' - that's a feeling, like after you've had a few Bourbon...

Been cutting lots of 4140. Spindle VFD fried - I think.

Not sure what happened. I have been milling pretty heavy parts, but yesterday I changed tools and then the spindle would not start. I have eliminated the Centroid control system, checked the resistance between all three phases (1.2, 1.1, 1.2ohms) but the VFD still displays err1 (overload). So I will change it. Initially, I though I heard fans in the VFD, but with the box shut I did not noticed when they stopped. They don't run now. The VFD itself was not excessively warm. It does not smell like something burned. The spindle drive was hot, but I could keep my fingers on it - so I don't think it got over 40C. I had it cranked to 75Hz in the operation before it stopped.

I need some advice.

The spindle is 7.5kW 3 ph wired 240v. I had it connected to a 7.5kW 1ph to 3ph vfd. The VFD was controlled by the Centroid controller. I had the max frequency set to 75Hz.

The mill does have a manual speed control, but I'd rather use a VFD to control the speed from the program rather than manually cranking a speed change when required.

What VFD do I need?
Attachments
Spindle nameplate.JPG
Lagunmatic 250
tblough
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Re: AllInOne Overheating? Oscillating

Post by tblough »

You need a VFD rated for 20A that will run on 230V single phase and will take an external 0-10V speed input. A VFD with sensorless vector control will give you much more low speed torque than one that is just frequency control. Hitachi WJ200, ABB ACS355, Yaskawa V1000, and Automation Direct VF4 are all good drives.
Cheers,

Tom
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polaraligned
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Re: AllInOne Overheating? Oscillating

Post by polaraligned »

The largest VFD that is designed to operate on 220v single phase is 5hp, and there isn't a wide selection out there. You could use a 3 phase converter and run it on single phase but you would need to upsize it by 200% or so as a general rule of thumb.
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Re: AllInOne Overheating? Oscillating

Post by tblough »

When sizing a VFD, ignore the "HP" ratings snd look at the Amp rating. That will give you a better picture. FLA motor rating = VFD amp rating. You have a 5Hp motor - the "7.5" rating is an overloaded rating good for a few minutes of run-time. This is a common ploy with "special duty" rated motors.
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.
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