Hi All,
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I need some advice on a couple of niggles I have with my gantry type router:
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First up is two sided machining - I am getting a step of 0.5mm between the two sides in the Y axis, even though I am using an L shaped jig (aligned to within ~0.02mm to the machine), with the part zero in the centre of the block and flipping about the X axis. Stuff I have already tried/checked:
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Checked the G-Code in case there is a reason for the problem (can't see any).
Checked repeatability using my touch probe from a known point on the machine to the jig on the Y axis and its acceptable at <0.05mm or less.
Checked the same with the touch probe between the jaws of my digital callipers - same accuracy.
Run several two sided jobs and its consistent (which I guess is a blessing).
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Here's where things get a little weird: after drawing a blank I decided to have a go at a part and using a simple straight line slotting cut back and forth along the x axis trimmed a 30mm ali block down to the size I need to do the job. I then noticed that whilst the slot was nicely 6mm wide (6mm end mill) the slot looked like it was ~0.25mm further towards Y+ from the Y zero point, which could explain why my two sided jobs are coming out stepped i.e. the job is offset by +0.25mm from zero in the Y on one side and when flipped the other side is the same, which would come out at a ~0.5mm step in the work.
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I thought "hmmm might be backlash?" but its in one direction only and the dimensions of the completed job are accurate enough.
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Hopefully that all made sense and I'm now wondering if I have made a cock-up in MACH3 that is offsetting every job by +0.25mm from zero in the Y axis? I will use a "kludge" for now by offsetting the Y zero by -0.25mm, so the job starts cutting in the right place.
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Second niggle (which has occurred after the first so not necessarily related), which I think I know the answer to anyway:
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My vertical axis seems to have become a little "slack" i.e. I can push the bottom of the Z axis plate in the y axis direction and I have some play (not much, but enough to cause chatter when cutting in the Y axis direction) and it seems to be getting progressively worse.
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I've run round all the bolts on the "carriage/z-axis" and all is tight, so I am suspecting I may have some Y axis bearings going on the fritz, but also another reason maybe that if you look at my machine on my build thread the 120x60mm top gantry beam may have "slipped" down the gantry sides and is causing some slack, but I'm no expert in whether the bearing blocks would allow this and/or whether any slippage would allow play considering there "shouldn't" be any to start with unless the bearings are worn/wearing.
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As usual opinions/advise welcome.
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Cheers
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Chris