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Why is the 'X' axis moving
« on: November 23, 2010, 07:01:40 PM »
This is my first post on this forum.
I have built a "home built CNC" from ply-wood. And this may not even be the place to ask for help. But I have about run out of ideas. I tried the other forum sites and have not found an answer to my problem.  My CNC is a Blacktoe V4 2X4 w/ chain drive on the X & Y axis. Z axis has a 1/2" 10 x 5 start lead screw.
I have been having a problem getting my motor to run smoothly. And keeping Z axis motor from stalling.
 
Saturday, I setup a simple gcode to test the motors as listed in Mach3 manual. The gcode runs in a loop and moves the gantry X axis up & down the table 50 times. I also added more moves to the gcode. Giving it a move across the 'Y axis', a move across from X0,Y0 to X20,Y12 and a move in the 'Z axis' of 4 inches up & down. Here's what it was doing while making an air cut. Everything was running fine, with just a small knock once in a while. Then the shocker, when the Z would try to move from Z0 to the + it would move about 2 or 3" and stall making a loud buzzing noise then start moving again. I tried changing the Velocity & Acceleration settings up & down but could not stop the Z motor from stalling. Of course when the Z motor would go into a stall it would throw the rest of the gcode off and start at a different spot in the code. When I stopped the program and returned to "Home" 0,0,0, it would be way off of 0,0,0 and 'Z' would drive into the table top. NOT GOOD!!!
The Z motor stalling has been going on sense day one, I kept thinking that the anti-backlash nut would work its way in, but still, it is not that tight. And YES I have been lubing it.
I tried changing the velocity & acceleration. After experimenting with the settings, the only way I could come close to having the steppers run smooth was to lower the setting on the velocity from 700 which what the math says it should be, to a lower setting.  Set X= steps @ 1420.682271 which is the setting that were set by the auto "Set steps per unit" by Mach3. Velocity @ 400, acceleration @3, step pulse @4, Dir pulse @5. Set Y= steps @ 1422.456593 (set by Mach3) velocity @ 450 acceleration @ 3. . Z= steps 1602 velocity @ 100, acceleration @ 10. I would let the loop run an air cut for a while and listen to the motors. I air cut this loop program about 15 or 16 times.  Most of the time they were running smooth, but then there would be a noticeable bump and knock like a motor skipping a step. The knocking sound has been very persistent.  And the knock and bump is coming sometimes from the X motor and sometimes from the Y motor. There is no pattern to the bumps. When I would stop the loop and go to home zero.   0,0,0 would be off, sometimes by as much 0.18 to X+ side. And a couple of times at 0.06" to the X- side of Zero. 
Here's the question: Is it likely that I have motors that are undersized and or bad? They should be 382 in oz. but here are no markings on the motors. Just a small paper tag with a couple of numbers. I put markers on all the sprockets and lead screw, and there is NO movement.
I had noticed before that sometimes when the gcode made a change in the 'Z' level is when the trouble would start.
The photo shows how much the X axis moved is one of my test cuts. Good thing it was scrap wood.


Offline Hood

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Re: Why is the 'X' axis moving
« Reply #1 on: November 23, 2010, 07:15:55 PM »
Have you run the driver test to see what the graph looks like?
Hood

Offline ger21

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Re: Why is the 'X' axis moving
« Reply #2 on: November 23, 2010, 07:54:45 PM »
What drives and power supply?
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Why is the 'X' axis moving
« Reply #3 on: November 23, 2010, 09:40:51 PM »
.
Have you run the driver test to see what the graph looks like?
Hood

Hood,
Please tell me more about testing the drivers. My drivers are KL-4030 w/ 36 volt power supply. And the C-10 breakout board. The motors have no name on them, but they should be 382 oz in, of course made in China.

P.S. You live in a very beautiful part of the world. My Grand-son's , Grandfather is from Dundee & lives in Lenzie..... And you have some of the world's prettiest women in Scotland. ::)
« Last Edit: November 23, 2010, 09:44:22 PM by gene8522 »

Offline Hood

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Re: Why is the 'X' axis moving
« Reply #4 on: November 24, 2010, 03:20:29 AM »
Dundee is only 12 miles from where I live.

If  you close Mach then look in the Mach3 folder you will see an icon named Drivertest.exe, double click on that and see if the pulse looks smooth, if there are large spikes or the line is very rough then you have pulsing problems.
If that is the case then it might be worth doing the optimisation steps, they are detailed in a file at the bottom of the Mach download page.
Hood

Offline Mogal

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Re: Why is the 'X' axis moving
« Reply #5 on: November 24, 2010, 01:44:23 PM »
things to look into:

If your loosing steps, slow the machine right down. I was hoping for 150+ out of my machine,
but I lose steps around 80ipm. I currently run 60ipm max, and I haven't lost a step since.
(I need some harmonic balancers - and need to do more tweaking)

Could also look into the wiring for posible electrical interferance. Was shielded cable used?

Possible binding in the rails... did/does the gantry travel freely without the leadscrews attached?
Could we see some pics of your machine?

Hope you get it sorted out, cuz these things are great once you get them working!

Chris
Re: Why is the 'X' axis moving
« Reply #6 on: November 24, 2010, 04:35:57 PM »
Believe it or not it was because of this post that I think I have found my problem. I was looking at the photo i posted and could not believe what i saw.  If you look at the dip switches maybe you will see what I saw. SWITCHES SET WRONG!!!!!. Set for 2.7A instead of 3.0A.  Reset the dips, ran an 8800 line gcode 5 or 6 times that had been giving me problems and guess what.  The tool return dead on "Home 0,0,0" at the end of each air cut!!! Funny how the more you look for a problem the easier it to over look it. Now after about 3 weeks I can get down to some real CNC work.
Here are some more photos of my build:






Offline Hood

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Re: Why is the 'X' axis moving
« Reply #7 on: November 24, 2010, 04:39:50 PM »
Good to hear and great looking machine :0
Hood

Offline Mogal

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Re: Why is the 'X' axis moving
« Reply #8 on: November 24, 2010, 05:04:18 PM »
Nice! Grats!
Thanks for the picks looks Great!

Chris
Re: Why is the 'X' axis moving
« Reply #9 on: November 24, 2010, 05:33:23 PM »
I am still getting a small bump and knock, but only when I drive the gantry up and  down the table at full velocity.

Hood have you figured out how my Grandson's, Grandfather can be from Dundee?

I live in Texas, close to Houston...................

Gene