Rods "Spaceship" Scratch built Plasma Cutter build

Just curious, Is there any real world advantage to having such high acceleration?

My machine I am sure is slow compared to what you guys are talking about but performs fine with all of the parts I cut from 1.6 sheet to 25mm plate.

Is this more like chasing dyno numbers or in the PC world benchmark figures? Also would having such high acceleration put much more stress on the components? I am all for having nice things but I am just curious if this is something I should try to look at in the future?

Thanks Tom,

It sure is interesting to watch! It is pretty cool to see how much performance can be gotten out of something and with these steppers its also cost effective compared to servos.

There is something about doing things differently that I am drawn to - conventional logic says use AC servos but I am sure Rods stepper system will end up pretty close.

We'll see. I think Tommy has already proved steppers work. Its a bit of a leap from the cheap Chinese ones to those built for industrial use.

I was just looking at the maximum rated velocity for linear rails and its only about 5 m/s so no wonder Tommy's machine was horrendous But they can handle 300 m/s/s acceleration

thefabricator03 wrote:

Thanks Tom,It sure is interesting to watch! It is pretty cool to see how much performance can be gotten out of something and with these steppers its also cost effective compared to servos. .

I'm not sure its as cost effective as you might first think. I am close to $3k into this upgrade...Anyway, the end is in sight. Did I tell you I hate Microsoft now. It took at least 2 hours today to get the lam programmer up and running. But finally with some help from Chris, we got the 17 kg power supply box into place and the control panel back on the machine.



I did get motion and its satisfying to hear the motors clunk into action. I just have to finish off revised wiring to the motor enable signal. I was working on that when Chis arrived so only one is enabled. Its interesting to see that Lam actually have a true motor enable input. But you can invert the signals when programming it.On my old setup, I had a 5 volt stepper driver disable signal hooked to estop. It was fired by a 24 volt relay to switch the 5 volts. But now I can use 24 volts for all inputs so I am going to get rid of the relay and power direct from the 7i76e.

Tommy, after your post yesterday, I did some research. Linear rails are rated for velocities of 3-5 m/sec and we are driving them way beyond that. Thats why those 600 balls make so much noise complaining about being overdriven on a plasma machine!

There was nothing really wrong with the Spacehip before I tackled this upgrade. It was built on some motors and drives I had on hand and a 48 volt switch mode power supply that seemed popular and then some NEMA34's so I could use cheap premade belt reductions. I just got the smallest 34's I could find so my stepper drives could still drive them.

We still want to harness that low down torque Steppers have plus retain their simplicity for DIY builds. With the predictable forces on plasma tables (in the absence of cutting forces), there is not much benefit to be derived from moving to servos provided the whole package is engineered correctly. Thats actually much harder for steppers than it is for servo machines.

I struggle to see why stepper manufacturers have so many products in their lineup and it was hard to make a product selection from our engineering model output. Hardly any motors matched our requirements. The Sanyo Denki's were a bit opportunistic as I got them cheap as chips and they are a perfect match to our model output. Time will tell but one would think replacing $20 motors with $200 ones and doubling the voltage should make a difference!

The servos Bevins uses are an 80ST. If you Google "80ST servo" listings will abound.

Linear rails are rated for velocities of 3-5 m/min

Are you sure about the unit?

CPC rates their linear systems for 10m/s and acceleration beyond 500m/s²

and here an excerpt from Hiwin:

Reinhard wrote:

Linear rails are rated for velocities of 3-5 m/min

Are you sure about the unit?

CPC rates their linear systems for 10m/s and acceleration beyond 500m/s²

and here an excerpt from Hiwin:

Reinhard, my mistake, it should be m/sec when I review the source I was quoting. My bad! See:

www.rollon.com/IN/en/news-item/378-under...ed-and-acceleration/

... we are driving them way beyond that. Thats why those 600 balls make so much noise complaining about being overdriven on a plasma machine!

The noise comes from the balls scouring at each other. On cheap linear cariages the balls push each other when moving. That scratching makes the sound ...

Better systems provide a spacer between the balls (image taken from CPC, Hiwin and others offer similar):

with such ballchain the friction is lower and lifetime is longer.

At work a carriage was broken and needed to be replaced. But cheese-pairing support collegues bought a carriage without ballchain - now the machine screams like hell.

cheers Reinhard