Recommanded good stepper motor with encoder for plasma CNC

Hello,

I am currently designing my own 2x1m plasma table, with maybe a dual head with a wood router. This table would be used in my workshop.
I think I will go with LAM drivers, and I am looking to use closed-loop with stepper motors and encoders. I have seen a lot of steppers, with or without encoders. And I wonder if I should add encoders on motors, or go with motors already fit with encoders.
I have seen LAM motors with already fit encoders on mechapro.de. That seems good but are really expensive. I have no sufficient knowledge on stepper motors to know which one is a good bang for the buck, and which one not...

What stepper motor brand would you recommend going with the LAM drivers ?
If those motors are not fitted with encoders, which encoders brand would you recommend ?

Any tips are welcome
Thanks in advance.
 

Plasma has no cutting forces and will only loose steps if the motor gets hot from working outside its comfort zone becasue the velocities and accelleration settings in your config are too high. If your motor selection has been poor and they do get too hot, you can just reduce these settings (mostly acceleration) in your config.

Those of us using Lam are using their open loop drivers (eg DS1076/DS1076A and DS1073/DS1073A or their open frame LS equivalents) . Some of us use the Lam boost feature to reduce the current to the drives when at constant velocity as power requirements when not accelerating or decelerating and be as low as 15% of what is required when the motor is working. This lets the motor cool and perform at (much) higher levels without overheating and loosing steps.

Also the Lam open loop drivers have an alarm output that can be connected to Linuxcnc to signal when either the drive or the motor have faulted (most often overheated) before steps are lost.

If you were to go to the Lam closed loop drivers or add encoders, you would probably achieve the same result for less money if you used servo motors.

Of course using a premium driver like Lam means you really should be using premium Industrial grade motors. Lam, Moon, Motion King and Sanyo Denki are a few that spring to mind.

 

Thanks Rod for those precisions.

I think I have misspoken, and what I want to do is not called "closed-loop". Let me explain.

Despite all the careful I will take in my workshop, as I could do a lot of other activity around the plasma table, there is a risk of an object falling or blocking the gantry displacement. Dust could be an issue too if it blocks carriages on rails. So I would like to have a system that know when steps are lost and stop itself, signaling the issue.

I want to use LAM drivers' Boost feature too. And I thought it was possible to use the f-error on LinuxCNC, via a Mesa board, to trigger an alarm when a high f-error threshold is reached. Threshold set to correspond to step losses. Reading this Tommy's post , it seems possible. But maybe is not possible, and maybe LinuxCNC can not adapt the movement to compensate lost steps ?
As I will maybe add a wood router tool on the head in addition of plasma tool, it would be even more important to know when steps are lost.


I will take a look at Lam, Moon, Motion King and Sanyo Denki.

If something falls on the table it will be becasue of you so it should be you who removes it
Do your homework. Plasma and routers have totally different design parameters (light and fast vs big and heavy) so they are not compatible....
With Plasma velocity and acceleration is king, routers are not so fussy!

rodw wrote:

If something falls on the table it will be becasue of you so it should be you who removes it
 

Yes, of course, but if an object fall on the table when the gantry is moving, it can block the movement and break something before I can reach it and remove it. Whereas, if the system can detect a lot of lost steps, it can stop forcing on object.
If it can be done easily, why don't implement it ? Does it seem useless to you ?

rodw wrote:

Do your homework. Plasma and routers have totally different design parameters (light and fast vs big and heavy) so they are not compatible....
With Plasma velocity and acceleration is king, routers are not so fussy!
 

I have done my homework . I know plasma and router have very different needs and are not compatible. But I think there are some tricks to be able to mount both on the same table.
My idea is to have the router spindle removable, and not mounted when the plasma is cutting. It will be mounted only if needed. And as a router for wood or plastic do not need a lot of force while moving on X and Y, a plasma table frame may have sufficient rigidity.
This router would be used on wood or plastic sheets of 50mm thick or less.

From my inexperienced point of view, it seems compatible. What do you think about it ?