I’m not sure what is going on here. I’ve been working on this prototype for a coaster I’m making for a while now. The toolpaths in question have been used with success and I thought I was just tweaking final design stuff before moving to production. During one of my prototype cuts my x-axis belt broke (the steel fibers snapped and the belt started stretching. This is probably my fault as I’ve been probing the limits of DOC with my machine and probably caused the belt to wear quickly. I’ve backed of DOC and found a happy medium for my material and have been super happy with accuracy and speed.
Anyway, so I replaced my X-axis belt today and went to work. For reference, I am using Fusion 360 for my design and CAM work. This job involves two-sided machining, and the first side (essentially a large pocket with a ridge around the edge) went beautifully. I flipped the workpiece and set the machine working on that side. The first couple of pockets went well…everything was symmetrical and centered with the other side. The next operation involved a tool change to my #102 1/8" end-mill and an adaptive pocket along with a couple of grooves (using a 2D pocket tool path). Upon completion of this operation I noticed the grooves (which are circular) did not line up with the outer border of the initial pocket and the pocket cut with the adaptive toolpath didn’t line up either. I measured with my caliper and found the grooves and the pocket are misaligned along the X by about .005". Thinking I screwed something up in the CAM, I re-selected all geometry and regenerated my .nc file. Ran the job again. Same result. The only thing I’ve changed is the X-axis belt. Could that be causing this? I don’t see how the belt could be the issue because my initial operation is perfect (including the entire first side). I’m at a loss and quite frustrated…I really shouldn’t have shared with a friend that I thought I would be ready to buy production materials at the end of the week. LOL.
I checked it. Sure enough, loose set screw on the x axis pulley. Can’t test tonight (time to go be with family) but I am wondering if this has been developing for a while and is what caused the degradation I saw in DOC capability. I was thinking it was stretch in the belts, but now I wonder. Going to take a bigger bite in my toolpaths now and see what happens.
I’ll test it tomorrow morning and see if it fixed the issue. Tonight is movie night with the family. Thanks @Julien!
That was it…loose set screw on X pulley. I increased my depth of cut again and all is well there too! Thanks @Julien!
BTW…how often do you all check things like set screws? I check belt tension regularly, and have trammed my router and squared the machine…but I didn’t think set screws on the pulleys would loosen this (relatively) quickly. I’ve had the machine for a few months now.
if they do get loose for any reason like it happened to you, use locktite and if they are positioned correctly (one screw against the shaft’s flat) and tight, they should not go loose again anytime soon (or ever)
you can also consider replacing them with M3 socket head cap screws, for easier tightening (there are a few threads on those if you search the forum)
I have some M3 socket heads here in the shop (R/C airplane guy…lots of screws like that laying around) and I thought about replacing the set screws but wondered if it was not recommended for some reason. Thanks!
Longer M3 will give a lot more thread area in the pulley for the screw and threadlock to bite on than the rather too short set-screws they come with. I just used 15mm M3 set screws as that’s what I had to hand.
With the socket head M3 be careful not to over-torque them with the bigger allen key, remember they’re only threaded M3 in a fairly soft pulley.