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Losing steps or interference???

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fabguy
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Joined: Thu Aug 08, 2013 4:17 pm

Losing steps or interference???

Postby fabguy » Thu Jul 03, 2014 9:16 am

I am having problems with the gantry losing steps and getting in a bind. The motor tuning is set exactly the same for both. The gantry slides freely when the spring tension is released from the gear rack. I have CandCNC electronics; plazpack 1a, sheetcam, mach3, I also have a USB installed. The table is grounded as is the plasma cutter and each side of the gantry next to the drive motors and also the control cabinet. I did a dry run (TORCH OFF)of a railing insert with lots of detail and it runs perfect without any binding. When I actually try to cut this out it will cut fine for 5-10min. then the x and slave axis' have become so far out of square that the gantry binds up. I had the acceleration and velocity originally at 640 and 35 then slowed it to 600 and 25 but neither made a difference. I did notice that when the torch fired I could see faint lines or fuzz across the computer screen and went away when torch is off.
Tim

BTA Plasma
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Re: Losing steps or interference???

Postby BTA Plasma » Thu Jul 03, 2014 12:54 pm

That should tell you there is a problem with your shielding. What plasma cutter? Are you running the motor cable right next to the plasma lead?

fabguy
Posts: 16
Joined: Thu Aug 08, 2013 4:17 pm

Re: Losing steps or interference???

Postby fabguy » Thu Jul 03, 2014 1:20 pm

I have a TD A120, the plasma lead is in the igus chain with the motor cable on the gantry only.

Stout
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Location: Helotes, TX

Re: Losing steps or interference???

Postby Stout » Thu Jul 03, 2014 7:13 pm

You could confirm that it is a hi freq bleed over problem by running a complicated pattern that is continuous. So one start, and lots of cutting. If it runs fine, then break it up and put in a few starts. If you have problems, then I'd say the issue was related to the hi freq starts.

I was never able to solve this issue with my old Esab system. But it would display an error when it occured, so I would have to check table positioning whenever I got that error. The Hypertherm PM1250 does not use hi freq start, so no issues like that anymore.
Victor Simonis
Grey Forest MetalCraft
Helotes, TX 78023
210-872-2622
Sector Technologies Photon 5x10 water table machine with Hypertherm Micro Edge Controller, Powermax 105

fabguy
Posts: 16
Joined: Thu Aug 08, 2013 4:17 pm

Re: Losing steps or interference???

Postby fabguy » Thu Jul 03, 2014 10:54 pm

I removed the torch lead from the cable carrier, fired the torch and could still see lines on the screen so I removed the ground from the control cabinet and they went away. Tried to cut the same file and got the same results, gantry gets way out of square.

BTA Plasma
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Re: Losing steps or interference???

Postby BTA Plasma » Fri Jul 04, 2014 11:40 am

Typically a gantry that end up out of square is caused by a loose connection. A loose cable, gear, pulley..everything that can get loose will get loose. It could also be your operating outside of the power range for your motors and loosing steps on acel and decelleration. What are your motor tuning numbers? What kind of gantry do you have? What kind of reduction? any pics?

Metriccar
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Re: Losing steps or interference???

Postby Metriccar » Fri Jul 04, 2014 3:56 pm

I looked on their website and at least the new a120 does not have high frequency start.
Here's what it says:
Start Cartridge
High Frequency has been completely eliminated from the plasma system. A patented component called the ?Start Cartridge? sits between the tip and electrode. The Start Cartridge is in contact with the tip while the torch is inactive. When a start signal is given, air forces the cartridge to break contact with the tip and the pilot arc is started. This unique design allows the pilot arc to start without moving either the tip or electrode, resulting in better parts life, cut performance and reliability.

If it only happens when the plasma is cutting but not during a dry run it would suggest to me it's not a mechanical issue but an electronic issue. Only other thing besides what Stout suggested is trying to run the cut with the plasma lead temporarily out of the chain away from the motor wires.

Is it possible something in the motor itself changed to make it more prone to EMI?

fabguy
Posts: 16
Joined: Thu Aug 08, 2013 4:17 pm

Re: Losing steps or interference???

Postby fabguy » Sun Jul 06, 2014 7:54 pm

Problem solved. Power to the shop runs from the panel in my storage room out to the shop right next to the phase converter that powers the plasma cutter, all of the power to the shop is directed out from this point. I was getting interference from this only when the torch was fired. With the plasma unit powered up I would run the gantry a bit then check for squareness, all good. Then I would run the gantry with the plasma torch on and it would be way out of square. I tried to use power for the PC and cnc controls at different locations in the shop but none worked out. The last place I tried for a power source was in the office right next to the storage room, the electric is run directly from the panel in the wall and is 10 feet from the phase converter. I ran a extension cord from the office over to the PC and cnc controls and did the same tests on the gantry with the torch off and the torch on and it was square both times. I then loaded a railing insert to cut and let it do its thing, after about 20 minutes of cutting it was finished. It ran perfectly the whole time, checked for square and it was only out 0.008. Thanks for the helpful replies to my post.


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