15m Industrial Plasma Cutter

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01 Aug 2019 12:51 #141101 by Jarman

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01 Aug 2019 13:13 #141104 by rodw
Replied by rodw on topic 15m Industrial Plasma Cutter
I don't think anyone said steppers. As Tommy said, keep the gantry as light as you can.
And yes, Linuxcnc supports max and min limit sensors as well as homing sensors. The gantry is squared during homing in software based on home offsets. I use PNP proximity sensors on the gantry for limits and homing. I have one shared home/limit switch on the Z axis

You'd really need to calculate some weights and see what size motors you need to achieve target velocity and acceleration.

There are some notes here
linuxcnc.org/docs/devel/html/plasma/plasma-cnc-primer.html

and also the plasmac manual
linuxcnc.org/docs/devel/html/plasma/plasmac-user-guide.html

I actually like the idea of having everything on the gantry... Say a 105 amp Hypertherm or 120 amp Thermal Dynamics is not that heavy and both would romp in with 12 mm. The Hypertherm has the advantage of amps and pressure being controlled by software except presently this would require a RS485 cable back to the PC but I think soon this might be able to be managed by a remote control card.
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01 Aug 2019 13:39 #141106 by tommylight

The thinnest material to be cut is 8mm. The other is about 12mm.


???????
Those do not come in a roll ! Never.
If that is what you actually need to cut, at 15meters length, only the material for the table to carry that will cost you over 3000 plus work and welding.
You must mean 0.8 and 1.2mm, or ????
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01 Aug 2019 13:45 #141108 by tommylight

I don't think anyone said steppers. As Tommy said, keep the gantry as light as you can.


I did.
A 1.5 meter gantry can be made very light and sturdy and with reduction even some stronger Nema 17 motors on both sides can move it at over 18 meters/minute. Done that at 2.7 meters gantry and 22 m/m, gantry consisting of a 2mm thick metal bent to C shape with a single HGR25 and a single carriage, with floating head.

Now there is some contradicting info here so the answers are going all over the place.
Please check what exactly is needed and let us know.
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01 Aug 2019 14:11 #141109 by Jarman
Replied by Jarman on topic 15m Industrial Plasma Cutter
Sorry about that, my mistake.

You're right, the thicknesses are 0.8mm and 1.2mm.

Other than that I think the information is correct:


15m x 1.25m with a thickness of 0.8mm - 1.2mm.

Thanks for all of your help. I'll look into Mesa cards and THC.

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01 Aug 2019 14:37 #141111 by rodw
Replied by rodw on topic 15m Industrial Plasma Cutter
Mesa cards with ethernet.

For steppers 7i96 is a good card for plasma but you probably need to share limit switches on one input.. Also the 7i76e has a lot more inputs and is what I use. But the 7i96 was not around then.

For servos, the card of choice is the 7i77 but it is not an ethernet card so you need to connect it via a 7i92.

All of these cards have virtually unlimited expandability via the smart serial interface (up to 1024 inputs and 512 outputs from memory)

For smaller plasmas you need to look for something capable of 100% duty cycle at 40 amps from Hypetherm or Thermal Dynamics/ESAB. You probably will need a 60-80 amp one for that performance.

The THCAD-10 board is a voltage to frequency converter designed for the electrically noisy environments like plasma cutting. Each board is individually calibrated. It is connected to an encoder interface and we decode the frequency back to a voltage in software. Its remarkably accurate.
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01 Aug 2019 15:20 #141115 by tommylight

Sorry about that, my mistake.

You're right, the thicknesses are 0.8mm and 1.2mm.

Other than that I think the information is correct:


15m x 1.25m with a thickness of 0.8mm - 1.2mm.

Thanks for all of your help. I'll look into Mesa cards and THC.

That is more like it, thank you.
That brings us back to what some of us mentioned above and excludes some other.
To recap :
-Very light gantry made with a single square metal tube 80X80 or 100X100 mm, with a single square rail and a single carriage, HiWin HGR 15 or 20, 25 is the upper limit, belt driven preferably with some reduction, Nema 23 motor ( 17 will do just fine if above 1.2A ). Total weight with all motors should not exceed 50KG.
-Floating head, also as light as possible, screw driven with Nema 17 motor, all-thread M6 or M8 will do just fine but at slower speeds ( if you can budget it, use 1605 or 1204 ballscrews), drawer slides with ball bearings are very good for this, magnetic torch holder ( use magnets from old hard drives ), and very sensitive float switch so it triggers if it hits parts of material without breaking the torch.
-2 motors with reduction driving pinions on both sides of the gantry, Nema 23 2NM is more than enough. Ignore the 3:1 ratio, that will depend mostly on the pinion you use, so try to find the smallest pinion first, then calculate the reduction ratio to get 10 to 20mm per MOTOR revolution. You might end up needing 10:1 so buying 3:1 reduction might prove a bad investment.
-mounting the computer and controls and the plasma on the gantry is a very valid idea, but will greatly limit the maximum speed and acceleration.
-buy a small plasma, something like a Hypertherm 45, inverter as they are lighter, but do not buy a chinese one.
-Mesa 7i76E and THCAD
- supported round rails for the long axis on both sides, fi20mm are fine but use 3 carriages per side, 50 to 60cm total length for the carriages. You might want to use fi30 with 2 carriages per side but the price difference at 32 meters is quite big.
-you do need 31 to 32 meters of rails in total for the long axis, gantry will take the above mentioned 50 to 60 cm on both sides.
-Shielded cabling is a must.
-Drives, get Lam technologies DS1076 from mechapro.de at a significantly reduced price for the X and Y axis, DS1044 for the Z axis. 1076 work with higher voltage so you get much faster motor speed. They are indestructible.
-Metal work, that is for you to decide, and you have a lot of freedom on that part.
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01 Aug 2019 20:47 - 01 Aug 2019 20:48 #141148 by rodw
Replied by rodw on topic 15m Industrial Plasma Cutter
Tommy is the master of budget plasma builds and really knows his stuff.

-buy a small plasma, something like a Hypertherm 45, inverter as they are lighter, but do not buy a chinese one

Just watch the duty cycle. 100% duty cycle is 32 amps which is probably enough for your work. Also check the power input requirements, Single Phase ones require something like a 50 amp circuit which is huge for a single phase supply. So the three phase ones are much easier to wire in (12 amps or so).
At 15 kg for the inverter with careful design you should still be within Tommy's 50kg. I think my 1.22m gantry weighs about 32 kg including motors and gantry ends. It uses a 40 x 80 aluminium extrusion and 2 x HGR 15 rails with pinion drive. If I did it again I would just use one rail and probably go up to a bigger profile Tommy suggests but if you look at the Hiwin engineering specs, a single HGR 15 should be enough and probably save some weight.
Last edit: 01 Aug 2019 20:48 by rodw.
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01 Aug 2019 22:15 #141155 by tommylight
Thank you Rod, and sorry i forgot to mention that you do need at least 30A at 100%, as Rod mentioned. It would also help if it has current regulation, that way you can fine tune the best cutting at the fastest rate.
On a 15m machine every second counts, so some design ideas mentioned here will save you a lot of time and nerves later when using the machine.
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01 Aug 2019 23:16 #141161 by rodw
Replied by rodw on topic 15m Industrial Plasma Cutter
So it sounds like the XP45 would be an ideal machine.
To control current via RS485, make sure you have a PC with a serial port for a RS-232 to RS485 adapter. I've not played with RS45 but somewhere on this forum I read the USB to RS485 adapters are not very robust!

So while Tommy has outlined a good stepper solution, you may also like to check out Bob's Servo Plasma build.
forum.linuxcnc.org/plasma-laser/36667-bo...lasmac-build?start=0

He shows the Mesa hardware he's using and a bit about the servos he uses. I have no experience with servos.
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