Mike Audleman
08-10-2014, 2:57 PM
Oh boy. I may have pooched the screw.
Yesterday, I had a sheet of ply in the bed weighted down (it was slightly warped). I had hit the "Frame" button and the gantry was showing the cut, it was nearly the whole sheet. Unfortunately I had one of the weights too close, and it got a hold of it while framing. It shoved it against one of the z-axis bed screw rods. It knocked the gantry off square, the laser focus tube off kilter and the machine groaned madly and skipped teeth on the right timing belt before I could hit the panic kill button.
So, I spent 4+ hours loosening screws getting the timing belts loose to re-square the gantry. I can only eyeball the tube for vertical as there are not two surfaces that I can put a triangle on to adjust squareness. I held a drafting triangle up to it and got it as close as I know how. Hundreds of 3" squares of paper later, I got all the parallax out and they were square again instead of parallelograms. At least as close as I can measure by eye and drafting triangle. I cut squares from the 4 corners. They all looked and measured perfectly identical. So I went to bed.
This morning, thinking I got it repaired last night. I slapped a sheet in and ran a project only to find out, not so much. Its square and everything but the cut lines have a shadow low and to the left. And even at 100% power and 10mm/s speed it took 4 passes to cut through 3mm plywood and the cuts looked horrible...but only in the lower right corner of the work area. Upper right, straight through at 15mm/s and 75% power, like it used to. The scan etch also looked ok but it was in the upper middle (250mm/s 40% power).
Upon further investigation, it seems I have a beam refraction somewhere, I know not where. The second dot, just from outward guessing, is about 25% of the main beam's power.
I did pulse tests (no gantry movement) at 20%, 50%, 75%, and 100% powers. I briefly hit the pulse button while the gantry was stationary. I moved the workpiece between power changes so the gantry remained in the identical same position between power tests. I then ran it to the lower right and repeated the test with another scrap block.
294614
Full Size (http://www.wolfiesden.com/android/2014-08-10_12-59-11_188.jpg)
The left block was done in the upper left corner of the bed, the right one in the lower right (extremes).
Notice the double dot? It seems more pronounced in the lower right block but its present everywhere. This didn't show up when cutting paper squares last night as the power was very low and the speed was fast the second dot didn't have a chance to scorch the paper.
You can see the shadow effect of the cut on the top of the right block. The masking tape is burned away just below the horizontal cut across the top. Also on the right edge of the left block, same story.
I have checked the mirror alignment (tape over holes and pulsing at extremes) at both the mirror at the gantry and also on the down mirror at the head. The dots on the alignment tape line up darn well and are mostly in the middle of the optic hole. Of course the beam is not in focus at those points so its hard to tell if there is a double dot or not. But it sure looks the same. That points to the focus tube. I think.
Can anyone help me get this corrected? I just don't know where to look or what to look for.
Yesterday, I had a sheet of ply in the bed weighted down (it was slightly warped). I had hit the "Frame" button and the gantry was showing the cut, it was nearly the whole sheet. Unfortunately I had one of the weights too close, and it got a hold of it while framing. It shoved it against one of the z-axis bed screw rods. It knocked the gantry off square, the laser focus tube off kilter and the machine groaned madly and skipped teeth on the right timing belt before I could hit the panic kill button.
So, I spent 4+ hours loosening screws getting the timing belts loose to re-square the gantry. I can only eyeball the tube for vertical as there are not two surfaces that I can put a triangle on to adjust squareness. I held a drafting triangle up to it and got it as close as I know how. Hundreds of 3" squares of paper later, I got all the parallax out and they were square again instead of parallelograms. At least as close as I can measure by eye and drafting triangle. I cut squares from the 4 corners. They all looked and measured perfectly identical. So I went to bed.
This morning, thinking I got it repaired last night. I slapped a sheet in and ran a project only to find out, not so much. Its square and everything but the cut lines have a shadow low and to the left. And even at 100% power and 10mm/s speed it took 4 passes to cut through 3mm plywood and the cuts looked horrible...but only in the lower right corner of the work area. Upper right, straight through at 15mm/s and 75% power, like it used to. The scan etch also looked ok but it was in the upper middle (250mm/s 40% power).
Upon further investigation, it seems I have a beam refraction somewhere, I know not where. The second dot, just from outward guessing, is about 25% of the main beam's power.
I did pulse tests (no gantry movement) at 20%, 50%, 75%, and 100% powers. I briefly hit the pulse button while the gantry was stationary. I moved the workpiece between power changes so the gantry remained in the identical same position between power tests. I then ran it to the lower right and repeated the test with another scrap block.
294614
Full Size (http://www.wolfiesden.com/android/2014-08-10_12-59-11_188.jpg)
The left block was done in the upper left corner of the bed, the right one in the lower right (extremes).
Notice the double dot? It seems more pronounced in the lower right block but its present everywhere. This didn't show up when cutting paper squares last night as the power was very low and the speed was fast the second dot didn't have a chance to scorch the paper.
You can see the shadow effect of the cut on the top of the right block. The masking tape is burned away just below the horizontal cut across the top. Also on the right edge of the left block, same story.
I have checked the mirror alignment (tape over holes and pulsing at extremes) at both the mirror at the gantry and also on the down mirror at the head. The dots on the alignment tape line up darn well and are mostly in the middle of the optic hole. Of course the beam is not in focus at those points so its hard to tell if there is a double dot or not. But it sure looks the same. That points to the focus tube. I think.
Can anyone help me get this corrected? I just don't know where to look or what to look for.