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Nagging software issue
« on: July 17, 2010, 06:17:02 PM »
Hi all,
A little background;-I have a no-name brand of CNC 2'X2'X4.5" router table made with:-Vexta PK266-02A step motors, 1.8 degree, 2A (one motor per axis)-Mechatronics Bi-Polar 3 axis micro step driver board. Initial run with Mach 3 program:-max velocity of motors was roughly 26 ipm -at any velocity in any axis, extremely rough movements, 2 axis movements were 2X as bad, to the point that it has worn out my comosite screw nuts after a mear 5 projects -Z axis would lose steps (simple 300 lines of code and Z would be up 0.060")-Roadrunner program would only cut 1/2 of it before the Z was above the piece and would be up about 0.150" at the end of the program

Things I have done: -Called company that made the table, they sent me a file called Easy3Mill.XML to be run inside the Mach3 program -Downloaded Easy3Mill.XML, NO CHANGE -Deleted the file Mach3Mill.XML, rebooted Mach 3 -Re-configured Port, Pins, motor tuning. Now I have max velocity of just over 60 ipm, very smooth operation in all 3 axis. I have run mutiple projects without issue using max velocity of 45 ipm on X and Y and 25 ipm on Z. BUT NOW IT"S BACK!!! Simple 28,000 lines of codes for a "V" router, after 17,000 lines the Z axis is up 0.060". Uninstalled Mach3 (not easy, over 60 files attached in various places after installation was done). Re-installed mach3, same issues as origanally, replaced Mach3Mill.XML with Easy3Mill.XML, worked ok, untill I reboot the program. Mach 3 rewrites the Mach3Mill.XML each time I reboot Tryed changing Kernal speed, using sherline mode, changed max velocity, changed voltage outputs to the motors from 2-4VDC.

My question is why does this Easy3Mill.XML file smooth out the movements, but still hasn't solved my Z axis issue????? How do I solve my "losing Z axis steps"?????? Am I doing something wrong?????

Offline ger21

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Re: Nagging software issue
« Reply #1 on: July 17, 2010, 06:25:10 PM »
Cut the accel on the Z axis in half. That should help your Z axis problem.

As for the smoothness, the only thing I can think of is they use a longer pulse width?
Gerry

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JointCAM Dovetail and Box Joint software
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Re: Nagging software issue
« Reply #2 on: July 18, 2010, 09:25:55 AM »
I currently have the X and Y axis set at max velocity of 45 ipm and accl of 15, and the Z at max velocity of 25 and accl of 8.5 all three axis have a total max of 60 ipm. I already have the Z in half of X and Y, So you think I should lower the Z accl in half again? 
thanks,
Will

Offline ger21

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Re: Nagging software issue
« Reply #3 on: July 18, 2010, 09:28:51 AM »
I have a 30x45 router, with Xylotex and 250oz motors. My accel and velocities are:

X axis: accel 10, velocity 155
Y axis: Accel 10, velocity 190
Z axis: Accel 5 velocity 55

My Z axis loses position doing 3D carving if the accel is higher than 5.
Gerry

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Offline RICH

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Re: Nagging software issue
« Reply #4 on: July 18, 2010, 09:51:08 AM »
Quote
worn out my comosite screw nuts after a mear 5 projects


- if your nuts a worn then you will have backlash in the z and thus it will affect the z position
- then it's time to replace the nuts or use backlash compensation

Quote
Easy3Mill.XML
- attach the original xml file
- i would compare the difference between the settings in the easymill.xml to what didn't work for you otherwise

Quote
worked ok, untill I reboot the program /  Re-installed mach3
- Did you run the driver test? delete the Mach3 driver which can be found in the device manager, then just run the drive
 test as that will reinstall it  since you may be using a different driver which exists on your PC

Quote
Mach 3 rewrites the Mach3Mill.XML each time
- yes, every time you change settings  it will rewrite

voltage outputs to the motors from 2-4VDC   
- if you look at Vexta's info on you motor they give info on preformance (1.4 A / 5V Series and 2A / 3.6  Unipolar ) so speed and torque
 depends  on  how they are wired, but note that for unipolar they give a curve for 24V. So at a lower voltage you will not get that  speed

Do as Jerry suggested  to start and keep lowering.

RICH
Re: Nagging software issue
« Reply #5 on: July 18, 2010, 09:53:29 AM »
Ok Thanks Gerry, I'll go out and try that this morning. I wish I had velocities like yours those would make my projects alot quicker. Another question, 10 tpi, max velocity of 60 ipm is a motor max rpm of 600, according to the manufactor graph the motors have a max rpm of 2500, I know that the toque goes way down but I should easily be able to get twice the velocity that I'm getting, here's the page with the chart
http://catalog.orientalmotor.com/image?cid=1002&imgname=pk266-02b_stc.jpg  
But if I try to increase the velocity more then 60 ipm the motors just sit there and chatter. I'm running at 1/2 step so 4000 step per inch. At full step, 2000, it's even worse, and if I go to 1/8 step, 16000, there is no difference from 1/2 step
Again, thank you for all the info,
Will
Re: Nagging software issue
« Reply #6 on: July 18, 2010, 10:06:03 AM »
Rich, I know I need new nuts, and have compensated for the backlash already, but if I start right at the material height Z at 0.0000" by the time I get done with the project it is up from the surface of the material, so that tells me that the backlash is not this cause, because of gravity, it's loosing steps as I run it. I'm going to try slowing it down, which I'm still a little upset at the slowness already, I thought it would be faster.
as for the file, there is HUGE differnces, the origanal file is only 41.4KB were the new Easy3Mill file is 141KB
Yes I ran the driver test, my computer is ONLY for this machine, the only program on it is the Mach3, I'm not even on-line with it, and the driver test is as perfect as anyone could ask for
OK, clarification, on the V-Ref settings I have changed from 2-4V to get the different Amps to the motors, 4 is the max, 2 is the conservitive so my driver board wouldn't heat up too much

Offline ger21

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Re: Nagging software issue
« Reply #7 on: July 18, 2010, 10:09:43 AM »
Another question, 10 tpi, max velocity of 60 ipm is a motor max rpm of 600, according to the manufactor graph the motors have a max rpm of 2500, I know that the toque goes way down but I should easily be able to get twice the velocity that I'm getting............

Not really. Realistically, with inexpensive drives and 24Volts, 600-800 is the realistic maximum. With a good drive like a Gecko running at 48V, you might be able to get 2000 rpm with the motor unloaded, but usable rpm will be no where near that.

My Y axis uses a 1/2-8 2 start screw (4 turns/inch), so it only spins at 760rpm. My X only spins at 620rpm. Also, I needed to make dampers to achieve these speeds. Without dampers, I had terrible resonance issues which greatly reduced the speeds I could get.

Another thing, if the drive has 1/8 stepping, try that instead of 1/2 stepping. It should run smoother.
Gerry

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

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Nagging software issue
« Reply #8 on: July 18, 2010, 10:12:24 AM »
OK, now looking at the motor specs, they are 166oz motors, well you know what, not sure on much of the technical info of all of this, so here is the link to all the info on my motors
http://catalog.orientalmotor.com/item/stepping-motors--1068/pk-series-stepping-motors/pk266-02a?

I think they still should go much faster then I can get them to go.
Thank you,
Will

Offline RICH

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Re: Nagging software issue
« Reply #9 on: July 18, 2010, 10:12:52 AM »
Will,
 All things considered then you have found the max velocity for "YOUR SYSTEM".
I don't know what the motor curve would look like at a reduced voltage, but as you have found out it is a lot less.
That said, play with velocity and accel and set for what will give you consistant preformance with no issues.
RICH