It is currently Fri Oct 19, 2018 9:35 am

 

Seeking some help on "drifting" X axis

CNC Plasma Cutters are amazing and there is always plenty of knowledge to share and discuss. Use the CNC plasma cutters general forum for this purpose.
patiencemetalfab
Posts: 3
Joined: Mon Aug 27, 2018 12:39 pm

Seeking some help on "drifting" X axis

Postby patiencemetalfab » Mon Aug 27, 2018 12:56 pm

We recently got a table second hand that had only been used a couple times. We got this table from an estate sale so the past user is of no help. It literally only had a couple cuts on it based on the tray below it.

First few cut files we ran were fine, but they were very basic shapes of plate (square, triangle, rectangle). Recently we tried cutting a file that had a series of holes in it and it seems to cause the X axis on the machine to "drift" to the right. In the picture below, this was the cut file run with a marker and cardboard to really see what was going on. The file was run 3 repeated times with each run time started from the finish position of the last run. You can see in the circles that it DOES NOT drift a consistent amount or with a consistent pattern each time-the hole overlap is not the same (thinking it rules out motor teeth count is wrong in setup). We already swapped X and Z motor output cables from the control box to the motors and reassigned the pin locations on the parallel cable to reflect that-the problem stayed in the X. Also threw a new parallel cable at it just to check.

The computer is an older gateway running XP and IS NOT connected to the internet in any way
Using sheetcam for cam and nesting and Mach3 licenced under CandCNC for control.
The table is a Precision Plasma LLC, kit table that someone put together with a Gecko g540 board.

Open to any thoughts at this point!!

Image

Mtw fdu
Posts: 197
Joined: Sat Dec 20, 2014 3:12 am
Location: Barossa Valley, South Australia

Re: Seeking some help on "drifting" X axis

Postby Mtw fdu » Mon Aug 27, 2018 4:39 pm

First thing I would be is to check and make sure everything like bolts etc are tight. Could be something loose somewhere.

Secondly, go into Mach 3 and reset the steps per inch/mm (whatever you are using) on each axis. See if any changes after running the file again like you have using the marker pen first.

It may help.

Mtw fdu.
Camcutcnc 2 x 2 plasma cutter with UC 100 Motion Controller
Powermax 45 with Machine Torch
Bobcad V27 and Mach 3
Proma THC
Now with Rotary Axis

patiencemetalfab
Posts: 3
Joined: Mon Aug 27, 2018 12:39 pm

Re: Seeking some help on "drifting" X axis

Postby patiencemetalfab » Tue Aug 28, 2018 3:08 pm

Mtw fdu wrote:First thing I would be is to check and make sure everything like bolts etc are tight. Could be something loose somewhere.

Secondly, go into Mach 3 and reset the steps per inch/mm (whatever you are using) on each axis. See if any changes after running the file again like you have using the marker pen first.

It may help.

Mtw fdu.


Thanks for the thoughts. First thing we thought was something was loose too, but after checking everything, we know it's not that. I will go in and revisit the steps/in, but I have my doubts that its where the issue is because its such a randomly occurring issue-but I will definitely check into it.

Mtw fdu
Posts: 197
Joined: Sat Dec 20, 2014 3:12 am
Location: Barossa Valley, South Australia

Re: Seeking some help on "drifting" X axis

Postby Mtw fdu » Tue Aug 28, 2018 4:42 pm

Cheers!

Keep us updated on your progress.

Mtw fdu.
Camcutcnc 2 x 2 plasma cutter with UC 100 Motion Controller
Powermax 45 with Machine Torch
Bobcad V27 and Mach 3
Proma THC
Now with Rotary Axis

User avatar
acourtjester
Elite Contributing Member
Elite Contributing Member
Posts: 3151
Joined: Sat Jun 02, 2012 6:04 pm
Location: Pensacola, Fla

Re: Seeking some help on "drifting" X axis

Postby acourtjester » Tue Aug 28, 2018 5:16 pm

The comment " The file was run 3 repeated times with each run time started from the finish position of the last run" this may not be a problem Mach will only do as it told. Now if you start from X 00 and Y 00 on the DROs that is a problem, unless your G-code has commands at the end to return to X00 and Y00 like (G1X0Y0, G1 X0 Y0 or G0 X0 Y0) it is not starting from the same start point.
DIY 4X4 Plasma/Router Table
CandCNC DTHC-IV & Feather Touch
Hypertherm PM65 Machine Torch
Drag Knife and Scribe
Miller Mig welder
13" metal lathe
Small Mill
Everlast PM 256 tig

tcaudle
Posts: 1036
Joined: Tue Feb 28, 2012 6:47 pm

Re: Seeking some help on "drifting" X axis

Postby tcaudle » Thu Aug 30, 2018 1:25 pm

Almost all positional problems that are not consistent (same on every run) are mechanical. The ONLY way to really cecked for backlash is to turnon the motors so they lock, walk to each one and try (hard) to move the axis back and forth. Any play will show up as changes in postion. Backlash can be from loose pullyes, belts, gears etc. Bad mesh on a gear to rack can cause problems. It the table is as unused as you say then it probably was never completely checked and calibrated. The other bane of cutting is lost steps. It ususally random and happens when a motor stalls from tryin gto move too fast with a given load. Feedrate and acceleration both factor into lost steps. Of course if there is any binding ( or the slave motor is not working or fighting the main motor there will be problems. That table and setup are capable of doing accurate cutting.

There are tests you can do to eliminate the electronics. You pull the motors, put them all facing you on a bench and with power off you roitate the shafts so all of them have the flat in the same position then you power them and zero the DRO's You then run a test g-code that sends the axis back and forth a bunch ot times at different feedrates and alwyas return to zero each time. At the end you take everything back to zero . All of the shafts should end up at the same place they started. Any thing that is off is a lost step.

If it's a CandCNC front end (electronics) and MACH3 profiles, then you can get support over on the CandCNC support forum.

patiencemetalfab
Posts: 3
Joined: Mon Aug 27, 2018 12:39 pm

Re: Seeking some help on "drifting" X axis

Postby patiencemetalfab » Fri Aug 31, 2018 3:53 pm

Thanks guys for all the info. I have been in the Mach 3 forum trying to get some help over there too. Seem to have everyone blaming the code, but I feel like if it was code, it would be an identical error, the same on every run. Ran a run again this morning with another piece and got video of it. The link is below and you can see in the corner of the Mach3 screen that it is commanding X to move (coordinates changing) but the torch is moving in a straight line along Y with no change in X as commanded. It starts at 26 seconds.

https://photos.app.goo.gl/zMLs8ZasSgLg1U129

Disregard the fact that the marker is off the work piece, I had changed the start position, but this time, you can see it's the same error as the piece it drew previously. So sometimes its a consistent error, and sometimes it changes like in the first picture posted...

By the way, what would cause a motor to actually loose steps? Bad motor? I locked the motors and tried to push the bridge and there was absolutely no movement so they are tight.

User avatar
WyoGreen
Elite Contributing Member
Elite Contributing Member
Posts: 675
Joined: Tue Mar 04, 2014 8:36 pm
Location: Cheyenne, Wyoming

Re: Seeking some help on "drifting" X axis

Postby WyoGreen » Fri Aug 31, 2018 8:44 pm

Several things can make a stepper motor lose steps. Trying to run it faster than it's capable of running, bearings binding, too much weight to move, electrical noise on the motor cables (usually caused by running the torch cable in the same carrier as the motor and/or computer cables), and if I thought enough I could come up with some more, but you get the idea. So yes, you could have the motor binding up, but that's pretty rare. Tom's suggestion about pulling the motors and running a test on your bench is about the only way to really be sure whether it's the motor or some other cause, such as electronics or mechanical.

Steve
Precision Plasma gantry
CommandCNC Linux controller w/Feather Touch & PN200 hand controller
HT-45 plasma cutter
Plate Marker
CNC Router table


Return to “CNC Plasma Cutters General Forum”

Who is online

Users browsing this forum: No registered users and 11 guests

Easyscriber engrave attachment for Hypertherm torch's