Newbie- EMC2 mesa 5i22 with linear encoder, Does it work?

[jbcj]

For all that know and are willing to help,

I don't see much information on the Mesa 5i20-5i22 setup with emc2. This is one of the options I am looking at for a retrofit on my bridgeport mill. I will be replacing a heidenhain tnc 135. I have linear scales on XY and Z axis. I believe that I have stepper motors on all tree axises as well. I am not sure about encoders as the control is limited in it's capablities.

Is the code/hardware implementation of this ready for prime time?

Am I able to use my linear encoders to improve precision?

Will I need to add rotary encoders to the motors if I do not have them?

Where do I find more information on this setup (googled alot not much detail out there)?





Thanks to all who know and answer......

Jim

[PCW_MESA]

Originally Posted by jbcj For all that know and are willing to help, I don't see much information on the Mesa 5i20-5i22 setup with emc2. This is one of the options I am looking at for a retrofit on my bridgeport mill. I will be replacing a heidenhain tnc 135. I have linear scales on XY and Z axis. I believe that I have stepper motors on all tree axises as well. I am not sure about encoders as the control is limited in it's capablities. Is the code/hardware implementation of this ready for prime time? Am I able to use my linear encoders to improve precision? Will I need to add rotary encoders to the motors if I do not have them? Where do I find more information on this setup (googled alot not much detail out there)? Thanks to all who know and answer...... Jim

For either the 5I20 or 5I22 you would use the HostMot2 configuration.

The HostMot 2 hardware stepgen configuration is basically "beta" now. Some people are using it with success, but its likely that a few bugs remain.

Using encoders (linear or otherwise) with steppers to improve accuracy is possible but right on the bleeding edge and quite involved. (using the step motor as a velocity mode servo is probably the best approach) In other words: not for the faint-at-heart

[chester88]

There has been a driver for 5i20 for a long time. It is mainly useful for servo systems.
The newer hostmot2 driver works for many of mesa's cards and has multiple firmware options each. Primetime ? - It is still being tweaked but is functional. It works for servos and / or steppers. There are example configurations included with EMC2.
If your motors are steppers you don't need to add rotary encoders to them.
Using the linear encoders (with steppers) will not give you any more precision as EMC (and most cnc controls IFAIK) do not close the loop with steppers.
The wiki is a good place to start:
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl
The online manual is there.
EMC hosted trial forum:
http://www.linuxcnc.org/component/option,com_kunena/
There is a mail list and irc as well.

[acondit]

Jim,

Unless you really want to be on the bleeding edge as Peter mentioned, Chester is correct that the linear encoders will not improve your accuracy if you are using steppers. Your accuracy with steppers is basically determined by the steps per rotation of your steppers (usually 200) and your gearing (screw pitch plus motor to screw gearing or direct drive). From what I have read you can't rely on microstepping to really increase your resolution, it is really just to smooth out the rotation at slow speeds.

I would suggest going for the simple approach to get running, then later when things are farther along you can explore other alternatives. Initially then your linear encoders will just serve to provide additional fault protection if the steppers loose steps. Using the Mesa hardware will provide a lot of flexibility without having to change as much hardware in the future.

Alan

[MrWild]

Those are the most Servo looking steppers I have ever seen. Yes, you can use linear scales and has been done before. You could run into dithering problems if the ball, screws have a lot of lash. If the table is off a little, the drives will correct, then overshoot a little, correct again and again causing a sort of buzzing whine when at a stand still. I have linear scales on my Crusader M and it whines a bit. I think Al suggests that enoders are the best way to go, but some have used the scales with success. Do a search for Crusader M retrofits and there is a guy that did it with his with good results. If you turned those servos into steppers, it'd be bleeding edge indeed

[chester88]

If they are servos, For EMC the best route is to add encoders to the servo motor or ball screws. You can still use the linear encoders to help with accuracy. Here is a small general write up:
http://jmkasunich.com/cgi-bin/blosxo...-02-20-08.html
With a heidenhain control there may already be encoders on the motor. What is wrong with the original control just as a matter of interest?

[samco]

Can you take a picture of the motors? I would have to agree that the look like servos. I would be a bit odd to have scales and steppers. (not that it hasn't been done)

sam

[jbcj]

Thanks All,

As far as the existing controller it only does straight line milling. IE moves 1 axis at a time thru a single drive . From my understanding Heidenhain uses the linear scales to create a matrix of the table if you will. This allows them to do a lookup to see how many steps or ticks on the counter are needed to go from X1 to X2(simple but effective). I think they also use them for other things as well.

It is suposed to have ball screws and low usage.....

I will have more concrete info when it arrives on the truck Monday/Tuesday.

I will take more detailed pictures and have a look at the electronics.

Jim

[chester88]

Do you know the full model number or the serial number I was looking up the docs for it on heidenhain website.

[jbcj]

All that I have for now is Heidenhain TNC135.

Jim

[chester88]

After reading a couple of manuals, I am pretty confident they are servos.
I have read a fair amount about heidenhain over last few years and have never come across anything about stepper controls. I wasn't sure about much older stuff like the TNC 135. The operating instruction doesn't say servos directly put talks about closed loop positioning which is almost exclusively servo.
do a search for 'tnc%135%' at this web site:
http://hesispub.heidenhain.de/hesis/hesis
if you are interested.
I downloaded the operating instructions: 214275

[jbcj]

Thanks for the link,

The manuals are dry but browseable.......
Based on what I read it looks like I will need drives as I most likly have only one.
Any sugestions?
Jim