Plasma Cabinet Layout Questions

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dovrosenberg
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Plasma Cabinet Layout Questions

Post by dovrosenberg »

I am getting ready to put my plasma control cabinet together. It is a steel 24x24x8 cabinet. The right hand side is where the cables will come in thru wire glands. I added a fan on the lower left side. E stop is on the upper right side. Power comes in on lower right side.

Looking for feedback on the component layout. I have 3 NEMA34 and 1 NEMA17 closed loop steppers. Toroidal power supply for the steppers, the acorn board and acorn THC.

I put the THC TX board in the lower right near the big power supply. The THC RX board in the upper right

I also have some circuit breakers I’ll be adding to protect the internal power supplies and components on DIN rails

Will this layout minimize EMI?
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IMG_6857.jpeg


dovrosenberg
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Re: Plasma Cabinet Layout Questions

Post by dovrosenberg »

This is my final layout. I put the THC TX board in the lower right near the torodial power supply. I figure that should help shield any EMI that might leak from the plasma. I put the THC RX board in the upper left hand corner as far away from the TX board as I could. The stepper drivers are 1.5" apart from each other. Next step is to start wiring everything together and see if it works as expected.

The Acorn boards, power supplies, and circuit breakers are all DIN rail mounted. Have a 20amp overload breaker for the whole cabinet. The big power supply gets a 10a breaker, the acorn board power supply and TX power supply share a 2 amp breaker. All breakers are D curve.
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IMG_6862.jpeg


ShawnM
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Re: Plasma Cabinet Layout Questions

Post by ShawnM »

Layout looks fine, just make sure you have a good ground bus somewhere and ground EVERYTHING to this bus. Grounding is critical in a plasma build.

I’m guessing a 20A breaker is not sufficient for everything but you don’t list and details for your components. You have 4 stepper drives and the toroidal supply looks fairly small but tell us more. You should be supplying the drives as much power as they want. In other words if the stepper drive is rated for 48 volts don’t use a 24 volt power supply, use a 48 volt power supply. When you don’t supply all the power the drive can handle you leave lots of speed and torque on the table. You don’t necessarily need torque with a plasma cutter but you certainly need speed.


ShawnM
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Re: Plasma Cabinet Layout Questions

Post by ShawnM »

What’s the NEMA17 drive for? Don’t say the Z axis. The Z axis in a plasma build needs to be fast and “snappy” if you are gonna have a THC.


dovrosenberg
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Re: Plasma Cabinet Layout Questions

Post by dovrosenberg »

The torodial supply is a 1200W that outputs 65 vdc. The stepper drives can handle up to 110vdc. The NEMA 17 is for the z axis. it is 113 in oz closed loop stepper. The z axis is a ball screw. my old z axis NEMA 17 was only 75 in oz. What do you suggest for powering the Z?
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z axis
z axis


dovrosenberg
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Re: Plasma Cabinet Layout Questions

Post by dovrosenberg »

ShawnM wrote: Tue Feb 04, 2025 8:33 am Layout looks fine, just make sure you have a good ground bus somewhere and ground EVERYTHING to this bus. Grounding is critical in a plasma build.

I’m guessing a 20A breaker is not sufficient for everything but you don’t list and details for your components. You have 4 stepper drives and the toroidal supply looks fairly small but tell us more. You should be supplying the drives as much power as they want. In other words if the stepper drive is rated for 48 volts don’t use a 24 volt power supply, use a 48 volt power supply. When you don’t supply all the power the drive can handle you leave lots of speed and torque on the table. You don’t necessarily need torque with a plasma cutter but you certainly need speed.
I have a ground bus bar that I welded to the frame that everything will be running back to except the DC grounds
ground bus
ground bus


ShawnM
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Re: Plasma Cabinet Layout Questions

Post by ShawnM »

So, doing the math a 1200 watt, 65 volt power supply is capable of 18.46 amps at full load. That leaves 1.5 amps for everything else. I know you probably will never draw full load but a 20A breaker for the entire cabinet, including all the other devices is too small in my opinion. You running 120 or 240 into the cabinet?

If the drives can handle 110VDC and you supply them with 65VDC you will be getting half the rated performance.

Your Z axis is in my opinion the most important axis on a plasma and needs to be fast for THC machines. So it needs to have enough power to move quickly without any missed steps or drive faults.

Best practice is for ALL the grounds, AC and DC, to be on a single, common bus bar. Look at the Acorn schematic, the AC ground is tied to the DC power supply ground.


dovrosenberg
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Re: Plasma Cabinet Layout Questions

Post by dovrosenberg »

I was planning on using the 120VAC 20amp from my garage outlet. I have another 50amp 240 outlet I could use. My NEMA34 motors are these with the CL86T driver.

https://www.omc-stepperonline.com/s-ser ... tWsTJor0NI

The torodial power supply is this one
https://www.automationtechnologiesinc.c ... es/kl-6020

Regarding the DC ground - I thought I read somewhere that the DC grounds should NOT be tied to the main ground to avoid EMI.what about the shields from the control cables? it says only to ground the end closest to the motor and leave the other end open to avoid ground loops


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