hi,

been a long time since ive been to any message form, but im at a loss and could really use some help.

i am running mach 3 on one of my mills and have been for a long time now, however recently my old boards and drivers went out so i upgraded all, new nema23 motors are awesome as i finally have full travel on my mill again.

while cutting some parts i noticed something happening where when the x is cutting a curve its not smooth there's a small straight part.
after researching more i found whats happening as it gets to the middle of the curve and has to revere direction the motor is slowing down to reverse then it speeds back up. so as it slows down the y is still moving fine making that little bit of straight angle on the curve.

i tryed searching the net for answers, and found sites that it seams like at least 2 other people had problems like this but no answer.

has anyone here ever had that problem and know the solution? thank you for your time.

It could be you have a bit of backlash, so when the motor reverses the table doesn't immediately follow.  Check to make sure there is no play in the drive components, and you can measure backlash using a dial indicator.  Mount the indicator on something fixed with a block on the table, jog the block until the DTI indicates some convenient number.  Now use small jog increments (say 0.01mm) to jog the other way until you see the DTI needle just start to move. 

so i feel like a idiot right now, lol

when i set up everything i did use a dial indicator to ensure steeps were right, inch forwards and inch in reverse, all perfect. and no blacklas turned on.
how ever im not one to dismiss anyone's suggestion when im asking for help, so i just ran out to my shop and put the dial indicator back on, i did noticed when i quickly jog back and forth it was not moving the table, it was at that very time i was looking at the end nut to see it slow down that i noticed the a gab starting between the nut and the bearing, it was loose to the point i could turn it by hand, i don't think i ever really tightened it back down after that last break down and clean.

after tightening it, i threw some metal in and ran the same code, and although it was only 1 test, i did not see the issue that kept happening last night. ill have to do some more test tonight but its looking like it was a human error, lol

so john a big thank you for your time and help. ill try and post another update after i test more tonight, but it is looking like it was all my fault lol

We've all been there! Happy to help.