CNC moviment error

[Alex S.A]

Dears,

I have a doubt about CNC regarding to moviment.
Some peoples used to say that CNC accumulate moviment error so that to erase it is necessary restart the CNC then the error accumulate goes down to zero, if not the CNC accumate moviment error untill the machine generates a message error of displacement. Is it true? How does it work?

[Switcher]

I don't know what machine or control you have, you should be able to referance out your cnc machine, that is send everything back "Home" (X=0.0, Y=0.0, Z=0.0).

I doubt you would have to shut down & restart your machine, If it is running correct.



.

[Al_The_Man]

I think you are talking about two different things, a machine may accumulate error due to mechanical defects, scaling errors etc. As far the controller is concerned, every thing is OK so no error will occur, The only thing that will reset it is a re-home.
The other case is if the mechanics and feedback are in order, no accumlative error should occur, but if the machine is not in the position the controller thinks it should be, a following error results, but this is not accumulative.
I assume you are talking about closed loop controls, with feedback to the controller?
Al.

[Dale Heart]

It sounds like your talking about a system with no feedback... so all that is happening is things are moving about as programmed (and by that I mean the servos, steppers etc are doing what they are told)... but due to overshot from inertia or flat spot tracks or for whatever reason, each time the machine moves it's not exactly as required. So, if you sent the signal to move 100" the actual movement may be 100.01"... and over time there is an accumulated error... yes (I don't want to argue about this). The thing is, it only can build up from the start of a cycle and referencing will get rid of this accumulated error.

[Switcher]

I had a problem once at work, the (5-axis) c-axis encoder got coolant on it. The coolant kept messing with my referance point.

Once the encoder was cleaned, & everything sealed up, worked like new.


.

[Alex S.A]

The system I am using is with closed loop control. Servomotor, encoder, driver and CNC.
If I got the point, In this system the can accumulate if there is some mechanical problem, right?

[Al_The_Man]

You did not say wether there was any alarm etc with the error.
If you set a zero point up on the offending axis and use a dial guage zeroed at this point, then send the axis out an back the same amount, and repeat this several times, you will see if the error is accumulative by the axis not returning to zero as per the dial guage. compare this to the displayed position.
Al.