Messages

821

Mach3 under Vista / Re: xml file for 3020T-DJ engraving machine

« on: October 01, 2016, 04:36:36 PM »

Post your xml files for the mill and the plasma.

RICH

822

Mach4 General Discussion / Re: Rename A axis to U axis?

« on: October 01, 2016, 04:29:47 PM »

Speaking out ignorance ..............

I would say that Mach controller is designated to industry standard for a 6 axis machine with primaries / rotary  of  X/A, Y/B, Z/C.
If it was 9 axis then it would have a supplemental secondary axes of U,V,W and thus related  X/U/A, Y/V/B, Z/W/C were U,V,W
are parallel to X.Y.Z.

dah........, only know what Smid  says,  

no pop corn left....going for the chips
RICH

823

General Mach Discussion / Re: Machine settings and getting started

« on: October 01, 2016, 03:41:00 PM »

Did you post about this over 6 months ago?

RICH

824

Mach3 under Vista / Re: xml file for 3020T-DJ engraving machine

« on: October 01, 2016, 03:20:44 PM »

NigelW,
Have you purchased Mach and have it installed?

RICH

825

General Mach Discussion / Re: Backlash...

« on: September 30, 2016, 02:52:14 PM »

belts could maybe be tighter as that would be another source of lost motion

Timing belts are surprisingly accurate....even when home made timing gears are used and driven axis movement may be off a little but it's repeatable / rather consistent per revolution.

Been a long time since we did testing of timing belts.
Basis was measured computer and driver output pulses as compared to varing belt tensions to see the affect on an encoder output connected to the axis side to see the differences between the three pulses. Difference were small values of steps per unit as they  relate to axis movement.
 

RICH

826

General Mach Discussion / Re: Machine had a another brain fart.

« on: September 30, 2016, 11:20:14 AM »

Think your steppers are skipping.

The problem is just what is causing it.

A stepper can skip and continue with a small change in position OR just go totally out of control.
Usually you can hear the skip. If repeatable when running a program it could be easy. If random it can be a real PITA.

First know what you max velocity and acceleration values are and reduced them by 50% or more.
See if that helps, it could be velocity or accel and that is also related to the system components.

If not would need to ask for a lot of info to see if could pinpoint the problem.

I just went thru this with another user.

RICH
  

827

General Mach Discussion / Re: Backlash...

« on: September 30, 2016, 11:01:49 AM »

I quess you have what you have and until you upgrade components BC can help improve accuracy.
The best approach is finding just what each component adds to the backlash.
One needs to isolate the component, and test each, adding the numbers should approx the total backlash.

Usual mechanical items that cause some degree of backlash:

- Motor coupling - anything other than hard coupled will add to the BC, it's just a matter of how much
                   torque is applied to it.
 
- Thrust bearings - Can approach zero play, but will never be "zero"

- Screw - lost motion can be anywhere, vary, and linearity different along the screw and may not be
          the same in the oposite direction

- Screw Nut - it is what it is

- Older Machine - One could fix / replace all of the above but conditon of the different machine surfaces
                  can affect accuracy.

Just some comments:

I hard couple the motors to the screw shaft. Requires good alignment, but, have found that over time the
bellows and rubber type can cause problems in repeatability of movement.

Thrust bearings are something that a lot of folks just don't pay attention to. They need to be preloaded
properly such that they minimize play with the least force / torque required for movement. I measure
the installation to confirm.

I have never used the screw mapping in Mach so don't know how well it works for a worn screw.
To profile a screw can be a PITA, rather easy on my end because I have the equipment to do it
opticaly and very accurately in rather short order. What would you do if you found that linear tolerance
spec is not over the length and is all in a small section of the length? OR Accuracy is different in the
travel directions?

For "hobby" use adjustable ball screw nuts are an option such that it is easy to minimise any play.
You pay for good quality screws and nuts. The accuracy of your machine is only as good as the components
used. For a lathe I recommend the best quality screw one can rationalize buying for the X axis ( the smaller
the more expensive they seem to be ).

Practicaly speaking on a retrofit, one can replace the axis components and find that the a machine surface
causes inaccuracies or even installation problems.  

Just some thoughts,

RICH

828

General Mach Discussion / Re: Backlash...

« on: September 29, 2016, 04:59:55 PM »

For the time being can you clean / lube / and re pre-load the thrust bearings?
See how much they  contributor to backlash.........

Load up the bearings so movement requires some torque / hard to turn the screw ( one can call that zero play). Measure with torque wrench. then reduce pre-load by 1/2 the torque value and see what the difference the bearing contributes to the total  backlash.

Just a thought,

RICH

829

General Mach Discussion / Re: Machine had a another brain fart.

« on: September 29, 2016, 04:48:44 PM »

Are you using one of those Chinese 6030 controllers?

rich

830

General Mach Discussion / Re: Backlash...

« on: September 29, 2016, 04:31:01 PM »

Yes, the compensation can help.

Here is a link to some info worth looking at and play with the settings to see how things work for
your machine:

http://www.machsupport.com/forum/index.php/topic,29149.msg204717.html#msg204717

I will assume that you checked the backlash at different feedrates and different places along the axis travel.
So the "stable" numbers you mention reflect the above.
You may be able to optimise the adjustment of the table gibs and thrust bearings.... just note that you can't
have no backlash since the table won't move and as you take out play you also will use up motor torque to move
the axis.

For now,

RICH