[face_the_heat]

Hey everyone, this is my first post here I've taken on a project to complete a 2 axis plasma table. Looking for some help on questions I can't find answers to.There is a lot of knowledge here on this forum appreciate all the help I can get. Thank you in advance.

I have 4 x 8 ft table currently I have 2 motors, the track, a plasma machine with torch.

My current issue is locating a driver to run the steppers I have. The GeckoG540 is what I'm eyeballing currently. Its a great all in one unit. The only problem I have encountered is the high inductance of my motor. Specs are as follows:
2.1 A/P
1.70 Ohm/P
8,0mH/P
269 oz-in
Serial # MP-2302-S-21

The Gecko can only handle max input voltage of 50v ( http://www.geckodrive.com/images/cms...8%20Manual.pdf )

"The power supply voltage is determinedby multiplying the square root of the motor’s inductance by 32, as in the example below for a 2mH rated motor:32 * (√2) = 45VDC"

Therefore my 8mH needs 90 volts! Which leads to the question..can I successfully run these motors on 50 volts without compromising too much stepping speed?

[msimpson99]

I think you are overthinking it. I would question more a 269oz motor running on a 4x8 machine.

[face_the_heat]

I think you are overthinking it. I would question more a 269oz motor running on a 4x8 machine.

Ok so you think that i will be able to get enough inch/min of cutting speed withoit killing my drivers?
Also to be noted is that this is a older torchmate gantry setup, the motors are connected via belt drive to step down gearing i haven't calculated the ratio yet. Rough estimate is 6:1

[flyinwilly]

That 6:1 gearing is probably why you have such small motors on a 4x8. If you are planning to cut thin stock there is no way you will have enough speed and acceleration to give good cuts.It will probably be OK for thicker material (> 10 GA). With the numbers you gave, those motors will run at about 50% of the listed capacity with a G540.

I use a G540 with 425 Oz steppers and 2.8MH with a 48V supply so I get around 380 OZ. I use a 4:1 gearing on a belt drive and I can run at 250IPM (max) with OK acceleration. However, to get really accurate cuts, I usually run at 150 IPM on 16 GA steel and lower the cutter amps. I am currently building a new gantry that is less than 1/2 the weight of my current one and reducing the gearing to 2.4:1 to get more speed and have the steppers run at a lower speed (to get more torque for better acceleration).

The G 540 is a great driver but has it's limitations. I've been running for over 5 years and it's been bulletproof but new drivers are also on my shopping list.

I think you need bigger motors in any case (especially if you change the gearing ratio). I would also look for other drivers (like the G201, 80V, 7A). They would be $100 more than the G540 but all of your problems would disappear (with new motors).

Willy

[msimpson99]

Also keep in mind that acceleration plays a heavy role in plasma cutting. You need to keep those speeds up even on corners and circles. You should look for at least .3g acceration or else you will get poor quality on your corners.

Take a look at this video. Its cutting 1/8" steel at roughly 190IPM. Pay particular attention at the acceleration. In this vid I have the machine set to just above .3G.
https://youtu.be/bTc2v_qYARc

[Kerryfisher]

Neat jig!

[Torchhead]

The older TM tables were notoriously underpowered. They have a 3 :1 belt reduction but with the small motors they have poor acceleration. Voltage does not give you torque it goes you more RPM. They have enough speed but a practical cutting spped of about 150 IPM before you see toolpath deviations (corner rounding ) Course that table with no Z and no THC is only going to cut thicker material that does not bow so higher speed cutting may not be a need.
The G540 with the right t motors can triple the performance.