This article and youtube video shows how I calibrate the Phlatprinter with the Planet-CNC controller and software using an inexpensive digital caliper which can be purchased from Lowes or Home Depot for around $30.

Steps to digitally calibrate your X,Y, and Z axis using Planet-CNC software:

Tools Required: Digital Caliper (~ $30)


1. Place a sheet of MDF or other hard surface material on the Phlatprinter table. Substitute foam if you must, but remember you will want to be able to measure accurately, so a harder edge surface is preferred. You could glue a piece of Balsa on the end of a sheet of foam as an alternative.

2. Position the MDF or other material so that it lines up with the front of the table.

3. Zero the X,Y, and Z axis in the Planet-CNC software. Note: This is very important! Do this before starting to calibrate each axis!

4. Type in the GCode to move the X axis you are setting up into the text area bottom right side of the display.

For the X and Y axis we want to move them 2". For the Z, we will move it only .5 (upwards)"

G1 X -2.0 F10
or
G1 Y 2.0 F10
or
G1 Z .5 F10

5. Measure the actual distance traveled with digital caliper. See video for where to place caliper for each axis.

6. Repeat 3 thru 5 for each axis, recording the actual values measured.

7. Go to the File | Settings menu and click on the calibrate button. Select each axis and perform a measure function. Then input the actual value moved as read on your caliper.

8. Let the software figure out the new step values and accept them if they appear reasonable. Ensure the reverse check box for any axis calibrated remains where you had it. If it was previously checked, there is a good chance it will be unchecked when the new calibration values are accepted.

9. Repeat steps 3 thru 5 and verify the new settings produce near zero differences between your input and actual movements.

10.Save your settings by exporting to a file and then closing Planet-CNC software.

11.Reopen the software and repeat steps 3 thru 5 again to ensure the settings have stuck.

12. Generate a 2" circle in Sketchup and load the GCode into your machine. Cut the test circle and verify it is round, not oblong. If you are not missing steps and your feed rate is correct, you should get a perfect circle.

13. To ensure your drive rollers are not introducing skew along the X, you need to create a pattern of at least 12 inches by 12 inches. This pattern will ensure your rollers turn a full 360 degrees during the test cut. Make a copy and rotate it 90 degrees. Cut this out and put both parts together to see if they match. If so, your machine is now ready to do precision cutting.



Note: During the video, I did not write down the values I measured and my ole brain forgets easily so I had to wing it a bit, but you'll get the idea. Do the Y and Z like I show doing the X and follow the written instructions above and you should be good to go.

 

Excellent presentation on the video, in that it addresses specifically how to set the Planet-CNC controller and software, where to get to the calibration settings area, how to accurately measure your results and how to make the changes to your specific machine to calibrate the axes.
Great job, Larry!

And, now there's a specific thread to link to for future questions by PP owners.

 

Picked up a pair of "General" brand digi calipers at Home Depot tonight to calibrate my machine. The new USBcnc settings file Mark posted was extremely close to what I measured! Right now my Y measures 1.9975 when I tell it to go 2 in. Woot! If I'm reading my decimal places right that's only 25 thousandths of an inch off, right? That's pretty accurate

I still need to get some harder material, or like you mentioned glue a piece of balsa to the end of a sheet of foam, to calibrate my X and adjust backlash. I cut some circles out today and, like everyone has mentioned, the large ones look fine but the 1" circles are a bit off. Actually you can barely see it the flat spot but it's there! I thought the digi calipers would ruin the fun of the machine for me, but I just couldn't resist. But in fact it was the other way around, I'm amazed at the "repeatability" of the machine so far

- Jeff