Hey, new member here.

I have a 3 axis mill i built from scratch...my own design and first thing I need to say this CNC stuff is pretty cool, it's kind of addicting.


I'm slowing bringing all the features I want online. Everything seems to be working pretty good except for the soft limits. I startup my machine, run the homing program and turn the soft limits on... They work when jogging slowly, but if I'm jogging it quicker (75 ipm or more) will blow right past them and crash into the hard stops.

any thoughts? I searched but couldn't find the same intermittent issue.

Thanks for the help

when jog and stop then start the deccleration ,and this movment you not take in acount
what we do ,we limit the jog to 10% speed ,actualy if you create yours m function well ,you not need any jog ,mayby only to find part origion
but all other ,like go home ,go rest.... bater create yours mfunction

Hi,
I think Kaatz is right, when you are jogging, say in the +X direction the controlled point is advancing 1001, 1002,1003 etc. But your Soft Limit is 1010 say....well Mach will
stop the jogging when it gets to 1010 alright....but it will take some time to decelerate to a stop.

SoftLimits works pretty well on my machine, but then it hs quite high (0.15g) acceleration so that even if the Soft Limit triggers the machine will stop almost instantly.
What machine accelerations do you have?. If they are pretty tepid then you can expect overrun.

May I suggest an experiment...try a MDI, something like g0x400, when in fact you know your X Sift Limit is only 300. I would Mach to say 'No, you bloody plonker, that exceeds
Soft Limits'. If it says this then I think Mach is doing what it is supposed to. Actually Mach does not say 'you bloody plonker'....but I feel it should .

Craig

thanks for the ideas... but i seem to be having a different issue. Your correct, there is some travel over run when stopping and i expected to see this. My issue is it doesn't even try to slow down... no "soft limit" fault is shown, and even if i set up the soft limit early so there is lots of room for it to slow down it keep on moving at full speed.

Any other things to check? thanks

and yes, if i use the MDI and tell it to run past the soft limit it will tell me it can't make that move

What acceleration , deceleration do you setup? Can send the trapeze photos?

I've attached the photos you requested of the motor acceleration and velocity graphs. let me know if you need anything else.

Thanks

Hi,
your accelerations are very low, about 0.04g, and that is contributing to your problem.

The best toolpath following occurs at highest possible acceleration. Acceleration requires torque from your axis motors and given that the torque is limited so will your accelerations.
You should try increasing the acceleration until you start missing steps or stalling, then back off by 25% or so. Try to get the acceleration to 0.1g or better if you can.

I see also that you complain that above a certain speed the machine overruns the Soft Limit and hits the stops? Why don't you just reprogram the Soft Limits to be 1/2 inch
'inside' the stops....surely your machine will decelerate and stop BEFORE hitting the physical end stops.

Craig

Thanks, I'll try and bump up the acceleration tomorrow morning and see if that helps.

And the overrun issue does not bother me when the soft limits are working. its minimal and i can work around it... or like you said, just back them off a little so there is an acceptable amount extra room to travel past the soft stop.
the real issue is when it totally ignores the soft stop.

I'll do some adjustments and report back tomorrow.

Thanks again for the help.

Hi,

the real issue is when it totally ignores the soft stop.

It should not do that ...ever. If it does then there is a fault no no amount of fiddling with acceleration or shifting the Soft Limit trigger points will solve.

Craig