First off, I love my new X-Carve. This thing is great. This post is mostly a record of what I have done trying to get the cuts to perform better and closer to +/- 0.005 tolerances.
Now, I’m having trouble getting cuts that are within the spec’d tolerances. Most of my cuts are +/- 15 thousandths. I honestly shouldn’t complain, for the price of the machine thats not really that bad. But I know it can do better.
Cutting a 1"sq leaves me with a finished cut between 0.47" - 0.485". This is with either a pocket cut or a profile cut. This is in either MDF or Acrylic with the appropriate IPM and DOC settings and the Dewalt on 1. I’ve tried various IPM and DOC settings to see if that effects the cuts due to bit deflection but i doesn’t seem to.
Measuring a 0.125" bit with the caliper gives me around 0.115-0.117 which is to be expected. Using Phil’s method of measuring the bit (to account for bit deflection, etc.) by measuring the cut yields a measurement closer to 0.122-0.125.
So here is where is gets a little weird.
- Using 0.115 bit diameter 0.5"x1" part cuts to 0.435"x 0.985" +/- 0.01
- Using 0.122 bit diameter 0.5"x1" part cuts to 0.435"x 0.985" +/- 0.01
- Using 0.126 bit diameter 0.5"x1" part cuts to 0.485"x 0.99" +/- 0.01
- Using 0.127 bit diameter 0.5"x1" part cuts to 0.63"x 1.113" +/- 0.01 (why does this slight variation cause the part to go bigger)
The bits I’m trying are the Inventables Single Flute Upcut 0.125" bit. I’ve tried two bits and both produce the same results.
The pertinent deets about the machine.
- 1000mm X-Carve with X-Controller
- New wide maker slide on x-axis
- Steppers have the pulleys crimped on
- Limit switches on all 3 axis
- Standard collet on Dewalt 611
- All cuts are being sent through Easel.
Mechanical things I’ve done/checked:
- X,Y,Z steps are all calibrated using 600mm rule
- All V-Wheels are 2 finger tight and clean and free of debris
- All MakerSlide rails cleaned and free of debris
- Belt tension = 4.5 lb. at 1"in at centers on Y axis belts
- Belt tension = 3.5 lb. at 1"in at center on X axis belts
- Z Axis checked for square along X and Y axis. (off but within acceptable tolerances)
- Homemade dust boot based modified from Phil’s design attached to dust collector
Sorry this is so long.
I know I need to check the squareness of the entire machine. Circles come out slightly off and this is the only thing I have yet to do. I’m going to remove the wasteboard and loosen the angle brackets, clamp on my 4 machinist squares and retighten.
The other thing I need to try is using UGS to send the G-code and check dimensions.
The big question. Am I on the right path to getting this thing within 0.005 +/- tolerances?
Any comments would be greatly appreciated.
Hey @PhilJohnson, thanks so much for the quick replies.
I have your Bit Size Calculator on hand, totally forgot to give that a go. I’ll try that this afternoon.
As for the calipers, I to though maybe I had dropped them one to many times they were off but I pulled out my feeler gauges and my 123 blocks and they measure spot on.
One thing I just noticed this morning over coffee and puzzled looks at the calibration cut I made last night, the circles seem to be slightly narrower on the X axis. I’ll verify with calipers but this would lead me to believe that I’m missing steps?
I did not adjust the pots not the X-Controller as they we set to their spec and the pulleys are the permanently mounted kind. My belts are tight within spec as well.
I guess the next step is to tear down and square everything up, Loctite all the threads, and see if that get it all in-line.
Hey @RobertCanning, I’m not sure what you mean but they are lost forever? At this point I’m just chewing through cheap 1/2" MDF cutting squares and circles to dial it in. No cuts that I need to recover.
I have performed the steps calibration a few times on all 3 axis using a 600mm rule so I think those are pretty dialed in.
My understanding is that if the machine is out of square, your cuts are out of square.
I’m going to try using USG and @PhilJohnson’s Bit Size Calculator this afternoon before the teardown. I also plan on adding Y axis stiffening supports as soon as the post-assembly nuts arrive from Inventables.
@RobertCanning, I know it’s totally weird. Each of those cuts is a separate cut with a separate homing. Something’s using Last Home Postion and sometimes re-homing for each cut.
@PhilJohnson, yeah I’ve don’t that and used your calc to reset the $ for all three axis. I even cut a sharp point in the end of the paper clip to measure half mm values and used 600mm travel as the calculation. I did this progressively, so measure-adjust-measure-adjust for each axis.
I’m baffled and will try a few more things tonight and double check all the things you all have suggested.
Another perspective. Not right, not wrong, just different. How important is tolerance to what you plan to carve? If you’re grinding out mail box signs, that’s one thing. Or, as my son-in-law said, he wanted a wooden wrist watch. I use a micrometer to measure the paper thickness for my Z height setting. Over kill, but that’s the tool I have.
Hey @Phileoka, I totally agree. Set your expectations based of the end use of the part being made. Generally, the things I plan on cutting are not dimension critical. 30 thous is acceptable when you cutting large format media support brackets. 30 thou is not ok when your cutting a caliper bracket to covert your drum brake vintage motorcycle to disc. Then again, do I want to trust my life to a $1,500 machine and my ability to not make a stupid math error! Yes. Yes I do because I am an idiot and life is far too short.
With Phil’s Bit Size Calc. I’m able to get much closer to where I would like, at least on the y axis cuts. My circles are still not coming out circular.
Before Phil’s calc a 1"d circle (outside outline) circle cuts 0.967"x 0.992" (x,y - .MDF 0.125Bit, 80IPM, 8PR, 0.0625DOC DW1)
After Phils’s calc, same file, re-home & zero, it cuts 0.981"x 0.998" (x,y - .MDF 0.137Bit, 80IPM, 8PR, 0.0625DOC DW1)
Phil’s calculation gave me a bit size to enter for the Inventables 1 Flute 1/8" upcut as 0.137"
It would seem that I’m loosing dimension (steps?) along the x axis.
Could my wheels be too tight? When I read that they should be able to just be turned with two fingers, does that mean, I need to really try to turn them or they should turn freely when griped with two fingers?
I hooked up my fish scale to the probe mount hole on my X carriage and it takes about 4.25 lbs of force to move the carriage with the machine turned off. Does this seem about right?