Hi there. I operate Shapeoko XL and have two problems since the beginning. It seems to appear and disappear in an unpredictable manner (I have not found the cause so far). In the image, you can see both errors. Don’t mind the pocket at the top as it is a hole from the previous attempt and the left sharp damage which was done by me (this was scrap-board).
The first layer is carved incorrectly (see the bottom edge). Often just the beginning of the trajectory is off and then it snaps to the correct path. Every other layer is correct. This replicates onto each copy of the egg in the exact same spot.
When cutting curved objects. Sometimes (meaning project dependent) the machine decides to break the curve and makes some off-movement. You can clearly see it in the upper left “corner”. It is consistent throughout the layers (it followed the wrong path in each layer). Also, it is consistent in each copy of the egg I think (I am not completely sure about this, will test more).
I use Carbide Create and Carbide Motion. As for HW, I have belt axis Z, using Shapeoko BitSetter.
So far I have checked the pulleys on the motors and tightened the screw, also checked the tension of the belts. The gcode is OK. No differences between the first layer and the other ones.
Does anyone have any ideas? I will gladly provide more information if needed. Thank you.
If the machine is mechanically sound (always check per: Machine operating checklist ) then other considerations are:
You have your file set up to cut slots just as narrow as the endmill is wide — this results in near constant 100% tooling engagement which is a difficult cut for the machine to hold — best working practice is to add geometry and cut as a pocket down to tab depth, or the penultimate pass.
Other possible considerations are tooling and feeds and speeds and workholding — check them as well.
do you have one of the two screws properly aligned to the flat on the motor shaft ?
Included in the checklist that Will posted, is checking the V-wheels. If any of them is loose, you can get similar effects to what you have. Check all 12 vwheels, they should be snug against the rail, you should not be able to spin them freely, but jus barely so.
Thank you both for the ideas. Today I’ve spent some time with the machine. Turned out that I forgot I had a crash in some of the latest jobs and really both pulleys on the Y-axis motors were completely loose. I tightened them and check everything else. Re-done squaring the whole assembly and tuned the belts tension as well as V gears. I’ve iteratively tried three samples tuning the cut depth. Thank you for the tabs knowledge, I somehow missed it.
The mistake in the trajectory almost disappeared. It showed itself only in one of the three samples and was almost negligible. However, the first layer problem still shows up despite it is a lot less visible. As seen in the images I suspect that this has also to do something with the Y-axis as the mistake is always top-bottom-wise. However, I have confirmed that it is not consistent speaking of placement on various copies. The two images portray two different copies, one was messed up at the bottom, the other one on the top.
Any other idea for what should I tune more?
Also thanks for the pocketing technique within perimeters, I will use that in the future.
One more question came up during the machine tuning. It is advised by the manual that the belts should have approx. 2’’ overlap at the end. However, at the back end of the Y rail, it is too long because when the carriage goes fully to the back the pulley that ensures the redirection of the belt from the rail to the motor’s pulley has the belt under itself too thick. I’ve noticed this when I was moving with the carriages by hand and at the end, I had to push really hard to get those carriages above the double belt. Is this ok or should this end of the belt be shorter?
OK. I think I finally managed to locate the problem. I have noticed that the first small sample was good and the second was already off. I checked the pulleys again and found out that the screws were loose again. Even without a crash or something bad they just get loose on their own. So I am going to apply a thread locker which I haven’t before. Also, I realized that I am using metric alan keys which are not able to tighten the screws enough probably.
Thank you for your advice. I will confirm my thoughts once I test it.
The hex keys (unfortunately, Allen keys are no longer available since Apex closeted that brand name: https://www.thestate.com/news/business/article126068444.html ) which we provide are pretty good quality, but yes, a good set of Felo or PB Swiss or Beta or other good brand is a great investment. A ratcheting tool is a nice thing (usually bike tools have this option and are reasonable affordable).
Sure. I am sorry. I am not a native English speaker so I’ve got the terms somehow confused. Thanks for the information I have got a metric set that is used in our country (Czech Republic) I will borrow the imperial from work
We haven’t had any machines which use Imperial hardware for a long while — most likely if you need Imperial the fastener is worn or not properly made — contact us at support@carbide3d.com and we’ll work this out.
The hex key/Allen key thing is a personal bugaboo — I regret not having a set of the genuine ones for various reasons (did get a couple in a vintage toolbox I picked up on Craigslist though) — one of these days I’ll pick up the balance of a set on eBay I guess.
One suggestion is to replace the tiny set screws with 10mm long cap screws. The cap screws are easier to tighten and not strip.
If you use thread sealer be sure to use removeable and not permanent. Permanent requires heat to remove possibly destroying your belt, pulley and motor.
OK, time to celebrate. I have located the source of both problems. Very badly spottable. I had the cutting curves just slightly over the cutting area (1-2 mm depending on the front zeroing), therefore the first layer was not bad but actually good. When it reached the top (far back) point, it got stuck for a moment in Y-axis and make all the other cutting offset. Of course this small crash that happened every time I started new cutting was causing the bolts to get loose and then the second problem with skewed movement appeared. The fix is obvious. Look and check the cutting area before
Moreover, thanks to gdon for the suggestions of using cap screws. That is a very good idea and I used it. I have also applied the thread locker (I knew about the removable, I am using blue Loctite). Also thanks for reassurance that the whole machine uses metric parts
I have got a metric set that is used in our country (Czech Republic) I will borrow the imperial from work 