I’ve been cutting metal parts for a couple months now, and the machine has been doing really good. There’s some lines on the side of parts from each cut depth, but that’s because it hadn’t been trammed, and I was using a table that wasn’t perfectly flat. It was 2 layers of mdf on top of a 2x4 frame.
However, cuts started to get a bit sloppy here recently. Some holes weren’t lining up, but others would during the same job. Since some spots wouldn’t line up correctly, and others would, I assume the zero was fine, it isn’t missing steps or anything like that. It may have just been a glitch in the gcode, or maybe an error in my tool paths.
But then it started to get weird. Because the table I had been using wasn’t rock solid, when the z axis would dive into the metal for it’s first cut, the table would flex, and the end mill would walk around a bit before cutting in. I could actually see the end mill flexing when it’d do that. So I lowered plunge rate which seemed to help. But then I noticed that the tool is flexing even when cutting going around a corner. If I’d make a contour cut, followed by a contour chamfer, the chamfer wouldn’t always line up with the previous cut. It just all seemed to be getting more and more sloppy. Same speeds and feeds as previous jobs, just kind of deteriorating accuracy.
Due to the sloppiness associated with a ‘soft’ table, I ordered a solid metal frame with a rubberwood top, and threw a layer of mdf over it. In the process, I completely tore down the machine, cleaned it, and put it all back together.
I haven’t yet attempted cutting metal with it since getting it out back together. I’m waiting for some parts to arrive for my partial enclosure to keep the chips contained. But while moving the axis manually with the power turned off, I’m noticing some issues I hadn’t noticed before. Bare in mind, this may be me being paranoid because I’m worried there’s an issue beyond just the soft table, but I figured I’d describe what I’m hearing and feeling and see if anyone here might know what it is, or if it’s normal.
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When pushing the gantry back (y axis movement), I feel a bit of a thumping as it travels back. I’m assuming thats the screws since the ends of the screws are able to shift around a bit. Maybe the screws are bent and the thumping is them shifting around in their end pieces. Since the rails look solid, I wouldn’t think that’d be an issue though.
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Also in the Y axis, if I push it quickly I feel a bit of a skip, or maybe stumble is the best way to describe it. Almost like a gear with missing teeth. But if I push it slowly, it feels smooth.
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The x axis has a bit of that thumping as well, though it feels a bit different than the way the y axis does.
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With the machine turned on, when I jog the machine in the y axis, the thumping I was feeling while manually pushing the ganty, makes kind of a knocking sound that I can feel in the hybrid table if I place my hand in it.
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If I grab the spindle at the top and bottom with both hands, and apply force to pitch the z axis forward and back, it feels like there is a slight bit of movement. It may just be the hybrid table flexing since I can see the front corner moving up when I do that, but I’m worried it may have an issue with the gantry mounting points (they are screwed down tight though), or maybe the left and right Y axis assembly where it connects to the rails. Or maybe that’s just normal.
I just re-applied the oil provided with the machine to all of the rails and to the screws. I fully cleaned it when I tore it down to build the new table, but before that it was pretty thoroughly covered in aluminum chips, so I’m worried some chips got into the bearings or something. I would vacuum it down after each job. But I use wd40 for cutting fluid, so some of the chips stick to the rails and screws that I didn’t get removed before the next job.
As I’m sure you can tell, I’m a bit paranoid about every little sound I hear, because I don’t remember it making those sounds before. It may have and I just didn’t notice, but it’s like there’s something that just doesn’t feel right, but I can’t put my finger on what.
A few of the things I’ve done that could have caused damage:
A. A cardboard box got jammed behind the left y axis and cause the stepped motors to Chuck a few times before I hit the e stop. That happens the first day I got it, and it worked fine after, so I’m assuming there wasn’t damage.
B. While cutting a 3mm aluminum plate, a round part broke free from its tabs and spun around the end mill in an oscillating motion since the part wasn’t centered on the end mill when it broke free. It made a pretty loud vibrating noise as it spun around. I hit the e stop after about 2-3 seconds or so amd it plunged into the spoil board. I’m not sure if that would have damaged the spindle or not. It seems to be working fine, and feels solid when applying force to the end mill by hand.
C. Due to the table not being strong enough, each plunge into metal was flexing the whole machine since the table beneath was able to flex rather than the holding the hybrid table solid. I’m wondering if that may have bent something or caused some other sort of issue.
Any help or thoughts would be appreciated. Again, I may just be paranoid about nothing. And I haven’t even tried cutting metal since I don’t have the machine enclosed at the moment. But I may go ahead and just do a quick test tomorrow to see how it does on a small part. I’ll update this regardless of it goes good or bad.
