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Problems setting up Mach3 under chinese controller
« on: January 10, 2012, 05:30:55 AM »
I'm new here, recently I bought a small cnc router, the machine is all aluminum and very robust, after make some test I notice the week point and added some aluminum bars on the Y axis to remove some torsion, now I think is very good mechanically. Also I'm using screws with 10mm pitch and using microstep 1/8 in the controller.

Now the problem, when I start messing a round with the router and cut stuff I was not concern with precision and tolerances, but now I'm stuck.
For example I draw a 3mm diameter circle in autocad and currently i'm using mastercan x4 that i have in work to make the nc file and all the cam work.
I draw the 3mm diameter circle create the .nc file and load the file into mach3, and what is cut is a rough circle, and the actual cut diameter is no 3mm but 2.70 or 2.80mm.

Another test that I have made was drawing a rectangular box with 20mmx2mm and the result after cutting was 20x1,7mm, but this is not consistency some times it cut 20mm other 19mm, etc.

In my x and y axis I have this setting in mach3:
- steps per:160
- velocity: 600
- acceleration: 300
- step pulse: 1
- dir pulse:1
Machine kernel is at 25000Hz, but I think that I have tried almost all the speeds

When I use fine tuning the axis, the moved distance is always different in repeated movements, if I move 15mm after fine tuning the x axis for example, I measure difference of almost 1 or more mm, for me a tolerance of 0.25 to 0.50 is acceptable, but not 1mm or more mm.

The motor and axis move freely, I donĀ“t know what to change in setting now! Or even I just can tell if this is a problem for mach3 or the controller.

One more thing if I lower the acceleration, the circles came out even worst seem that the router make the circle by moving 4 times (1 time cut a quarter then stop, cut another quarter then stop.... if I put acceleration in 300 the movements of the router are fluid.

This ate my motors:
http://www.selectronic.fr/media/pdf/61574.pdf

My controller:
http://www.mycncuk.com/forums/attachment.php?s=f91a420683273a9cd02f37f9e73c77b0&attachmentid=1371&d=1262794611

Can some one give me a little help?
 

Offline Hood

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Re: Problems setting up Mach3 under chinese controller
« Reply #1 on: January 10, 2012, 05:54:28 AM »
First thing I would try is setting the pulse widths to 7 or so or maybe even enable Sherline mode.
How much backlash do you have? Have you got backlash enabled? If you do disable it and try again as setting backlash with wrong settings can make things worse.
Hood
Re: Problems setting up Mach3 under chinese controller
« Reply #2 on: January 10, 2012, 07:04:18 AM »
I will try to change the pulse widths to a bigger amount, thanks for the tip.

Regarding the backlash I've got it disable, never change any setting in backlash because a can't understand the change/effect... I will read the mach3 manual now  ;D
 

Offline Hood

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Re: Problems setting up Mach3 under chinese controller
« Reply #3 on: January 10, 2012, 07:12:41 AM »
Ha ha not sure if its in the manual, a search of the forum should help though as I think a few have described it, Rich I think is the one who normally does.

Best not to use it until you know if you have any or not, if you can test to see if there is any and then if there is try and get rid of it rather than using software. Backlash can be in screws, bearings, slack couplings, slack belts or even flex in bearing mounts.
Re: Problems setting up Mach3 under chinese controller
« Reply #4 on: January 10, 2012, 07:35:48 AM »
That I know, I have the backslash in the bearings, and just by turning the axle by hand I can't feel or see any backslash.

Can you advice me witch is the best microstep setting? probably I'm doing all wrong....

With my current setup I notice that  if I cut a big circle the end result is more accurate than a small circle, and the movement is more fluid.
 

Offline RICH

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Re: Problems setting up Mach3 under chinese controller
« Reply #5 on: January 10, 2012, 05:20:39 PM »
Quote
I have the backslash in the bearings

Post pictures of your axis in question and we'll go from there.
You need to address each cause of the backlash since each has a different influence. The bearings should be prelaoded and must be
installled correctly.

Once the bearings are initialy preloaded such that the backlash is minimized in them then you can check the screw and refine the axis as a total.

I used backlash compensation on my mill for a long time, and could do some nice work, but was never realy satisfied until I got rid of it.

RICH
Re: Problems setting up Mach3 under chinese controller
« Reply #6 on: January 10, 2012, 06:58:15 PM »
I've just made some test and with the pulse with to 7 the cnc work fluid, but the result of the cut part is almost the same.

After make a more detail test in the axis I think that probably I have a little backslash on the x axis.

So I decided to disassemble the machine, the result, the x axis screw is bend I tried to put it strait but is very difficult, do you think that is better to buy a new one or this will work, is almost strait, but still have a minor bend.
The part that connect the x axis to the y axis are bend too, I will make a new part from strong material.

Now the worst part I remove the bearing from the screw  :-[ now I have a pile of little metal ball and I don't have a clue how to put then inside  ??? it possible to reuse this bearings?

Rich, I don't have any photos now the machine is all disassemble, if you what I can take some photos of the machine disassemble.

Thanks for you biggggg help

Offline Hood

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Re: Problems setting up Mach3 under chinese controller
« Reply #7 on: January 10, 2012, 07:24:10 PM »
I presume you are talking about the ball nut rather than the bearing?
Some can be put back together easily enough, some not. All depends on the style. Also some have  two size bearings in them and often you need them in the right order.
Hood

Offline RICH

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Re: Problems setting up Mach3 under chinese controller
« Reply #8 on: January 10, 2012, 09:58:45 PM »
Not sure i can help at this point, since what you need to do is get the bent parts fixed, fix the ball screw or if you mean the axis support bearings replace them and put it back together.
Sorry for your troubles........remember this is supposed to fun.....

RICH