setting backlash in mach 3,solidcam

[chrispare]

ok so my homemade cnc has some backlash in it, in mach3 there is a setting witch I have figured out no problem. My issue it when I gcode a part in solidcam and import it into mach it does not compensate for this backlash,even though it is set in mach.
so is there a setting in solidcam where I can set the backlash??

thanks chris

 

[RonGinger]

What do you expect to happen with the backlash comp? there is no change to the gcode, and their is nothing a CAM package could do.

Whenever an axis changes direction mach will make an extra move to cover the backlash. There is no change to the gcode, but mach makes the move.

In my opinion this does no real good. Yes, mach will do the mathematically correct thing, but unless your motors can do infinite acceleration, there will be a short time when the table is unconstrained by the screw, and there is a good chance for the tool to grab and either break or gouge the work.

Backlash is bad and should be eliminated mechanically.

 

[warranator]

Well said, I couldn't agree more with Ron.

 

[Herbiev]

Me too 8)

 

[chrispare]

I am concerned with the z axis, and when I run gcode and thed go to mome the z is out the amount of the backlash.
I relize that I should eliminate the play but this is a brand new (chinese mill) so I am not going to spend loads of money on my first cnc.
When and if I get another it will be perfect, but for now as a hobbiest this is going to have to do.
So is there something that I am missing in mach and not turned it on or something?
If I jog manually it compensates for the backlash,but if I do code for just a straight z movement to say 2 inches and back to 0 it will be out. If then I go and jog manually 2 inches measured with a didital caliper and back to 0 it works out perfect, on the caliper and in mach.

Do It make sence?

 

[around]

I am assuming that you have stepper motors on the X, Y and Z axis.

Have you tuned the Z axis motor and confirmed that your speed and acceleration values for the Z axis are not causing you to miss steps? The Z-axis motor has to work fairly hard to move the mill head vertically. If you set it to the same speed and acceleration values as your X and Y motors, you may be asking for problems.

If slower manual jogs are working but higher feed rate moves are not, then I would check for missing steps.

Cheers,

Adrian

 

[chrispare]

I am assuming that you have stepper motors on the X, Y and Z axis.

Have you tuned the Z axis motor and confirmed that your speed and acceleration values for the Z axis are not causing you to miss steps? The Z-axis motor has to work fairly hard to move the mill head vertically. If you set it to the same speed and acceleration values as your X and Y motors, you may be asking for problems.

If slower manual jogs are working but higher feed rate moves are not, then I would check for missing steps.

Cheers,

Adrian

Yes they are steppers,and I am sure that it is set right.I have even tried to slow it right down while running code.

 

[warranator]

Try lowering your kernel speed. Your pc might be struggling to keep up. Seems very odd that you have so much backlash. How much backlash are we talking about? These Chinese mills come with anti-backlash ball nuts which are pretty crappy quality but they do work when the machine is new.

I bought a Chinese router and one problem I found was the z ball screw was relying on the coupler and not the bottom bearing to secure it from moving. See if you can move the z axis by hand, try to move the z axis up and down and see if there is any play.

If you can post a picture or the link of the machine it may also help.

 

[ruzzie]

Hi
You should try the Mach forum, I'm sure some of the users can help you out

http://groups.yahoo.com/group/mach1mach2cnc/

cheers
Paul

 

[blighty]

have a look at these vids....

[ame]http://www.youtube.com/watch?v=A27nOkTFYDY[/ame]

and this one might help too

[ame]http://www.youtube.com/watch?v=buXHZ_McbOY[/ame]

i have done this on my set up and it works fine, but the less mechanical backlash you have the better it works.