12x12 F8 Z Axis Problem

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12x12 F8 Z Axis Problem

Postby bwillemo » Sun Feb 21, 2016 3:25 pm

Hi,

I originally bought the 12x12 F8 3D machine. Was quite happy with it, but 3D printing wasn't my thing to start with, so when the kit arrived with the aluminium gantry arrived I mounted it on my machine.

At that time, I started to work on milling PCB's. The machine was making very nice traces, but I had problems with missing steps.

Couldn't get it right... Out of frustration I bought another machine... thinking the grass is greener on the other side. Machine was German and double the price...

After one year - I have to admit - the fine 0.1 mm traces with a v-bit that the Zen Toolworks is making are awesome and I haven't seen it coming out of another machine yet.

Now after taking the ZTW online again... the problem on the XY - the missing steps - seem to be gone... The problem actually moved the Z Axis.

Does anyone has an idea where to start looking. Machine start milling the PCB correctly, but the more the process advances, the deeper the machine starts to cut... After minutes the machine is cutting through the bottom plate of the machine.

Thanks in advance, BW.
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Re: 12x12 F8 Z Axis Problem

Postby bjmxr88 » Mon Feb 22, 2016 1:25 pm

Hi BW,
Are you running the Mach3 Controller or the Arduino?
My first thought when I here your z axis is dropping into the material is a couple of things...
1) Be sure the Z-Axis remains locked or "enabled" during the cut process. If not, it iwill have a very hard time holding it's position.
2) This one seems very simple I know, but I have seen this sort of thing happen when the bit is not tight enough. IT tends to slip downward out the spindle collet.

Is your Z-Axis functioning properly otherwise? When your just jogging around before running a gcode file?
Does the z-axis height start out at the proper depth and then as the machine starts moving, it gets deeper and deeper into the materiel?

Thanks for posting your question. I hope we can help resolve it quickly for you.

Best,
B.J.
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Re: 12x12 F8 Z Axis Problem

Postby bwillemo » Mon Feb 22, 2016 5:48 pm

BJ, Hi,

I am using Mach3. I also have the 3 Axis Board.

http://wiki.zentoolworks.com/index.php/ ... iver_Board

1. I am not sure what you mean by locked/enabled? Is that something in Mach3?

2. I have broken at least 10 bits already trying to find a solution to the issue... Double checked the spindle - no problems found - at least not mechanic?

All axis are working nicely actually - they are very smooth. I did try jogging around to see if it missed steps, but couldn't see anything. Was also holding the lead screw to try to feel something, but no...

I have cut out a whole piece of MDF to be sure the PCB was level. Did cut out 1.5 mm... worked like a charm. Actually only problems with the PCB for now cause the Z Axis goes up and down all the time... In the beginning (first minutes) it seems to be fine... later on it sinks deeper into the PCB till the bit breaks.. Shouldn't go lower than 0.9 mm...

Strangely I had the problem on the X axis before... Now it moved to the Z.

Can it be the stepper motor board? The pcb-gcode software?

Bye, BW.
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Re: 12x12 F8 Z Axis Problem

Postby bjmxr88 » Mon Feb 22, 2016 6:01 pm

Okay,
It's starting to sound like a possible issue with your gcode. Could you possibly send me a sample of a file that you have had this problem with?
zentoolworkshelp@gmail.com
If you were able to mill your entire board without any issue and are only seeing the issue when the z axis moves up and down it usually is one of two things...
1.) Your acceleration may be set too high in the MAch3 motor tuning settings. This would mean when given the command to move up, the motor losses a few steps, so when it comes back down it actually goes deeper than before.
2.) When given the command to go up, the z-axis is hitting its limit (in the "up" direction). This would cause the motor to loose a few steps and like before when it comes down it will go deeper than it should.

What are your motor tuning settings set at currently for your Z-Axis?

Thanks,
B.J.
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Re: 12x12 F8 Z Axis Problem

Postby bwillemo » Mon Feb 22, 2016 6:42 pm

Hi,

I have sent the gcode to the e-mail address. Can't be simpler than that... it's just a micro controller with a couple of traces... Quite some pins, so going up and down a lot. Also 2 passes if I remember well, so - yes, this one isn't milling till the end on my machine.

For the other questions, unfortunately I am not home this week - going back on Friday...

I can give you the parameters of my machine when I am in front of it...

Surely, I think my configured speed/acceleration is way below the one that should be possible on that model.

I did also use half acceleration on Z axis compared to the other axis, just to try it... Jogging around never missed a step... Have tried different values, and I think I know how it feels when it's too fast?

Appreciate your help to fix the issue.

Cheers, BW.
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Re: 12x12 F8 Z Axis Problem

Postby bjmxr88 » Tue Feb 23, 2016 1:49 pm

I took a look at the gcode. Overall looks very straight forward. The highest Z movement looks to be 12.7mm and as long as you are not starting too close to the top of your Z-travel to begin with, you should not hit the mechanical end of travel. Would be something to look at just in case though.
Your velocity/acceleration combination may work okay for jogging, but it doesn't always mean it will work for actually cutting. So it will be good to look at those settings just to be sure. Your velocity used in the gcode is very conservative, so if there is an issue it will be in your rapid movement.

Another thing I just thought about was that when you jog, it's typically only one axis at a time, so amperage draw is minimal. However when you are running gcode, you are using all 3 axis at once and amperage draw will be at its max. It may be possible that the power supply you are using is not able to keep up with the amperage draw. Possibly a faulty PSU unit could be causing the z axis to skip a few steps. Just another thought to consider.
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Re: 12x12 F8 Z Axis Problem

Postby bwillemo » Tue Feb 23, 2016 4:08 pm

Hi,

As I said - I will give you the motor tuning parameters later this week when I have access to the machine...

I have been doing quite some research before posting this message. Yes, the g-code is very conservative... I made so many tests - always making it slower (feedrate, acceleration, etc...), just in case it couldn't keep up... It's now quite slow, so I am a bit clueless... Machine is moving so smooth...

I will also check out the idea of the power supply. Actually I connected the controller and the motors to the same power supply first... I know, it's not recommended... but in the mean time I had spit it... I almost had the feeling the problem was gone... Maybe I have to check that way - it's a big power supply, but you're right it could be the problem. I have some replacement, I will try that out first.

Would like to try as many things as possible before changing controller, motors, etc... Not sure I really made good use of the machine yet. When it was 3d, the spindle was too high and I wasn't very happy cause I couldn't find good ways to attach my things on the table... anyway - would be great to be able to use it now... I don't doubt that it's an excellent machine...

I'll check all those things out on Friday and let you know.

Thanks for your help already, BW.
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Re: 12x12 F8 Z Axis Problem

Postby bjmxr88 » Wed Feb 24, 2016 9:18 pm

Sounds good. Always happy to help. Definitely good to check on each item and kind of work your way down the line. It may be also a good idea to try swapping drivers or motors to see if the problem follows as that would be a good indication of where the problem lies.

Best Regards,
B.J.
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Re: 12x12 F8 Z Axis Problem

Postby bwillemo » Tue Mar 01, 2016 6:00 am

B.J.,

My motor tuning parameters with my machine setup in mm are:

X: 200 steps, Velocity: 1000, Acceleration: 200
Y: 200 steps, Velocity: 1000, Acceleration: 200
Z: 200 steps, Velocity: 500, Acceleration: 100

I did tune everything down to make sure it wasn't a problem with the mechanical built.

But I think you found my problem. The power supply! I have to admit that I was a little lazy in the beginning... Did even connect the controller to the same power supply as the motors. Did split that before sending this e-mails, but now that you suggested that this could be an issue I replaced it by another 12V 5A power supply... and now it seems to work. Have only don e limited tests, but it seems the Z axis is not dropping/missing steps anymore. Will have to make some more tests to be sure.

Is 12V 5A enough for the motors or do I need more?

Thank you for your help, BW.
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Re: 12x12 F8 Z Axis Problem

Postby bjmxr88 » Tue Mar 01, 2016 3:26 pm

Okay,
I think the acceleration is somewhat high actually. Your velocities are pretty conservative. If you can get by with those numbers in your testing than great, but otherwise consider turning acceleration down to about 30mm/sec^2. Especially in the Z axis.

12V 5A is pretty good, if your stepper drivers are set to about 1.5A ea. That's only 4.5A total so should be plenty.

Keep us posted how testing goes and let us know when you have optimal working results.

Best Regards,
B.J.
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