New Pocket NC X and Y axis not calibrated.

[David Farmer]

I went through the tutorial and was able run the test part, although i did it slightly different than the tutorial. The part did not come out correctly, it seemed like maybe the x and y axis weren't correctly calibrated, but they did home correctly. I cut the feature on the side with the A axis at 0 degrees, and i found that the features(hole, slot, square and triangle) were shifted -0.015 Relative to the x axis. The most obvious was the hemisphere on the top. I roughed it out with the B axis at 0 degrees and then did the radial cut with the B axis at 90 degrees. I can clearly see the translation, and the features don't match up. Before I made this post I decided to do a bit of inspection, so I chucked up a 1/2in piece of carbide in the table, and ran an indicator on it.

B axis with 1/2" carbide shank run out: +- 0.0035

I checked the run out on the spindle too with a 1/4 carbide shank: +-0.0015

This is fine, with this much stick out and this tool holding method that is acceptable for both.

I aligned the B axis to the mid point of the run out and checked to see if there was a gap between the 1/2in shank in the table chuck and the 1/4 shank in the tool holder. I sent the commands as follows G0 A90 B90 Y0.375. Then I slowly advanced the shanks together. I was able to fit a .0125 piece of shim stock between with minimal friction. I backed the spindle off and tried the bottom. I sent the code G0 Y-0.400. I subtracted twice the thickness of the shim and moved the spindle to the bottom. The friction was similar. 

Y axis needs to be offset: 0.0125

I did the same for procedure for the X axis.

X axis needs to be offset: -0.0075

Here are the pictures of the part:

The biggest give away was the hemisphere, you can see the operations clearly aren't aligned. I have attached the fusion 360 file. I don't believe this error would be caused by anything I did in the fusion file. I double checked the origin position and verified that the same origin was used for all of my operations, but maybe I missed something. Because of the measurement I took(shown above) I believe the machine is not properly calibrated on the x and Y axis, and that is the cause of this issue. I also took a video of machining this part, however I dont have anywhere to upload such a long video.

Can I calibrate the machine myself, or would I need to send the machine back in? I bought this machine for my work with the expedited fee, and we already have several projects lined up so time is of the essence.

Thanks! Looking forward to getting this working properly and making some parts.

[David Farmer]

Heres the link to my fusion file with the cam and everything.

https://a360.co/2JnfmwV

I also attached it here as well.

[Q Rothing]

Hi David,

I am going to look into this and will get back to you via email as soon as I can.

Thanks!

Q Rothing

Pocket NC

[David Farmer]

Thanks! I just found the linux CNC portion of the web interface, but I'm not going to change anything just yet.

[David Farmer]

I had to break some of the links in the file, so i have attached that version here.

[David Farmer]

I went into the Linux CNC server settings, and adjust the AXIS_0 HOME_OFFSET by +0.0219 and the AXIS_1  HOME_OFFSET by +0.0023. I rigged up a test indicator into a tool holder, and verified that the inside bore of the b axis was concentric and the parallel(to the best of my ability) with the spindle. Then I swept the indicator around(just like using a 4 jaw or dialing in on a hole or pin) and moved the machine until the indicator moved only from the surface finish of the bore. The I took the inverse of those numbers and added them to the home offsets in Linux CNC. Then I re-homed everything, and swept the bore again. Now I believe the X and Y axis are properly Calibrated. 

I do have one other issue, The Y axis Cable chain binds and the chains come undone. I took a look at the mechanism and in my opinion the cable chain shouldn't be used in this way. Basically its fixed on end to the y axis carriage and floating on the other end. The Y axis carriage shoves it down around the corner into its place. I don't think the cable chain is intended for this kind of use, which is why I believe it binds. It also doesn't have much in the way of clearance which doesn't help. Anyways there doesn't seem to be much that can be done about it, but ill keep trying to think of a solution.

[Q Rothing]

Hi David,

You should receive an email from me regarding these issues. 

Thanks!