Been searching for a little more info on squaring my HDM. I’ve seen several mentions of “squared it up manually.” but nothing explaining exactly how that was done. Also references to “soft crashing” the machine into the endplates, and turning the ballscrews by hand.
This was vague… wmoyWinston
“For the level of precision that’s reasonable to expect in a $4-figure machine…”
Not sure what level Winston was referring to. I was expecting something around ±0.001" (0.025mm) out of the box, and hoping I could maybe dial it in a little tighter.
So, the steps are 0.0004", ballscrew pitch is 5mm per turn, and from this test I need to move one of the Y axis screws about -.006", or about 11°. This is 0.009" off corner to corner on a 5" square
When I initialize the machine, it seems to move to the back right corner until it “crashes” into the ends of the slides. I don’t see where contact is being made. Is the “Thunk” I hear just the steppers abruptly stopping?
If I can manage to turn the Y axis ballscrew exactly 11°, will it be off again the next time I initialize?
What is the “proper” way to adjust the squareness so it will be repeatable? (assuming I don’t lose any steps.)
There is allot of questions here but I’m not sure of the overall objective? Typically I would be running a circle square test in a material like delrin or aluminium not MDF. I would not be measuring the corners.
The HDM uses a 10mm pitch ball screw not 5mm
To talk about 0.025mm accuracy and tolerances we need feeds/speeds and if you have any cutter comp. What end mills are you using and have they been measured i.e. is a 1/4 is it 6.35 or 6.32 etc.
0.025mm accuracy out of the box is very high, what parts are you looking to make which need a 25 micron tolerance? What measuring tools are you using too?
Thanks Luke. The overall objective would be to get the X axis as square to the Y axis as is practically possible. To me, that would be significantly better than 0.006" over 5 inches.
Ah, I measured the distance between each thread, I should have noticed it was a double-helix.
so to move one axis 0.006", I need to turn that ballscrew about 5.5°
I did try to manually turn the ball screw by hand. It takes a good amount of torque, then it jumps what felt like 5-10°.
Not sure why feeds & speeds matter for a squareness test, unless you’re considering runout / deflection on the tool. I used the library S&F for the 1/4" #205 tool, 18000 rpm, 60ipm.
The finish on the cuts was very clean, and the corners pretty sharp. Yes, I’ll use a piece of aluminum or something a bit more rigid to finish dialing it in. This is a piece of composite flooring, which is quite a bit denser than typical mdf.
also not sure why nominal vs actual diameter is an issue. If it’s off, it would be off in both directions.
And is does appear to be a smidge off, since the inverse sin of 45° at 5" would be 7.071, and both my measurements came in under that value.
I am, of course open to suggestions on better testing methods. I assume the circle/square method you mention is cutting 4 circles in a square array? then measuring the diagonal distances???
And this method could also be used to fine tune the steps per distance settings, but in my mind that was the next logical step after getting it squared.
It’s a diamond, stacked on a circle, stacked on a square. I worked up a file at:
The big thing is, you need a measuring tool which has 10 times greater precision/accuracy than you are trying to adjust to when calibrating.
The screws on the HDM should be very accurate/precise for most purposes — usually tool deflection and issues of feeds and speeds are the culprits for things not cutting as expected.
Hopefully a test cut in a suitable material will yield a result you find acceptable.
That said, the folks who are working to the highest degree of accuracy on our machines seem to leave a defined roughing clearance when making an initial cut, measure things, then adjust the file and finish the cut w/ a finishing pass which brings things to their final dimension.
What are you measuring on the diamond, circle, square to determine the machines XY squareness?
The square across the flats? (on a 45° angle). The circle at an estimated 45° angle?
You seem to be focusing on the method to measure how far the squareness is off, but no mention of how to reliably adjust the squareness once I have a measurement?
Again, I’m ONLY looking at the XY squareness right now. I’m already pretty comfortable with tramming the Z axis, and the perpendicularity of the spindle to the Z axis. I haven’t checked or adjusted the linear accuracy, but I understand the process.
OK, checked this one. The circular boss is 0.002" off measuring at 45° and -45°
The outside profile is off 0.006" measuring corner to corner, so a bit off of 45°
This is a bit smaller than my previous test piece which measured 0.009" off on corner to corner measurements. So my results are consistent.
Although my math was off. If I’m 0.006" off over 5", and the Y ball screws are 34" apart, Then I need to move one of my Y axes 0.041". Still assuming the solution is to independently move one of the Y axes, rather than make an adjustment to the structure of the machine.
The “crash“ on homing you mentioned has been discussed here quite a bit. It’s been determined to be related to an abrupt stop of the large mass of the gantry. Several of us have adjusted our acceleration to a more modest value to reduce this.
As already mentioned you’re not going to get an accurate measurement down to .025 mm with vernier calipers especially in MDF… that said the parts i make are acrylic and slip fit into pockets and i find them to be very accurate. Measuring with my Mitutoyo vernier calipers (see above note) i get a variance of ~.01mm to the target consistently. You could always attempt to further calibrate your steps per mm but i find that to be a endless rabbit hole with diminishing returns unless you’ve got some precision measurement tools. If the consistency is there you can also make adjustments in CAM. My HDM has been consistent in accuracy and precision from day one. Welcome to the club!
Good to know. Thanks. I’ve also adjusted my max speed & acceleration, as the changing of momentum was rocking my 300 lb table something fierce
I haven’t tested the repeatability of the homing sequence, but I will.
Dial calipers, HDF (composite flooring) & aluminum. I’m pretty confident my measurement is really close. I’ll borrow a large set of micrometers to finish dialing it in.
My HDM has been really consistent too. The problem is it’s not square, and I’m still not sure how to make it square. How do I change one of the Y axes by a precision amount (either fractions of a degree, or by a specific number of steps?) Can it be done? If I rotate the ballscrew by hand it “snaps” into place once I apply enough pressure to move it. I didn’t measure how much it moved, but it feels like a lot more than I’m looking for. I guess I’ll just have to start taking things apart if no one knows the answer. I was hoping I wasn’t the first person to do this, and could learn from someone else’s follies.
Not really, you are chasing high tolerances and unless you own some very specific metrology equipment you won’t be able to provide accurate measurements for analysis.
Ok, to adjust the square of the machine you might need to remove the hybrid table.
On the left and right side of each Y axis there are 4 turned hold down posts. If you loosen each of these one rotation you would be able to re-align the axis.
Yes, sir. Thank you !!! That is the answer to my question.
My bad if I didn’t word the question correctly in the first place. Or perhaps I got carried away with extra info.
Makes perfect sense now that I see it. Although I’m still curious about the “lost steps” issues I’ve seen mentioned here, and what happens if the 2 Y axes get out of sync?? Or is that highly unlikely on this machine?
I have a couple other things to get in line before making this adjustment. The first being making my table that the machine sits on perfectly flat. I have the machine shimmed up now.
Do I need to worry about moving the Y axes left & right once those hold down posts are loose? They are aligned very well right now & I’d hate to change that.
