Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: NormB on March 08, 2010, 10:09:10 AM
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I am not sure what to look for. I am pocket cutting and the rectangle is coming out approximately 1/64 of an inc undersize. This happens even when I cut a round pocket or hole. I have not noticed a problem until I went to fit a clock insert into a hole that was too small. All the other carving seems to be correct but I am not sure I would notice a small error is it were consistant. But when you put 1" peg into a 1" hole that is quite noticeable. actually I made the opening 1/32 larger than the insert for a bit of clearance and it was still tight .... Any ideas what I should check?
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Have you done a test with the circle pocket wizard to make sure its not the code that is wrong?
Is the cutter definitely the correct size that the code is thinking it is?
Hood
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Yes, I checked the tool first it's within 1/2 thou so really close. The code is generated by Vcarve. I get a full circle or rectangle just a bit undersize. It's strange if I were loosing stps I would think the circle would become a elipse etc. I checked to make sure the feed screwes were tight also.
Where is thge circle picket wizard?
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Found the wizard I will have to tryt that and see if the results are the same
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I just had a thought not sure if this is possible, could my 1/4 bit cutting up to 1" deep be flexing?
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It will flex if cutting hard material but not likely by anything near that much,what kind of spindle is it?
Hood
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it is a router motor mounted to a plate guided by V slides and bearings V that ride on the track. Same for the X axis. I am only cutting wood and usually only 1/8 per pass conservative on the material removal to allow the cutter to clear the flutes. I also only run around 50 IPS not fast.
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Router bearings will not be precision but even at that they should still be no where as much out as you are seeing. See what the wizard gives you and we can take it from there.
Hood
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I am planning on that tonight. It might even be the vertical and horizontal tracks with the v rollers sloppy enough for a small movement. 4" above the work surface it would not take much of a movement to move 7 thou and drag behind the gantry.....I will be looking at that tonight too. First make the cut with the wizard see what I get then move from there.
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Hi Norm,
Also might be worth checking the backlash on your axes. Have you done this?
Daniel
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I think I have found at least part of the problem I cut with the wizard a 3" dia meter hole it was about .005 undersize. then I looked at my x and z axis found I could move them slightly with my hand so I think when the router pulled on the bit it lagged behind the motor then when it pushed it still lagged behind the motor creating some of this undercutting. I am trying no wot get them adjusted so they are snug but not tight. These bearings are a bear to adjust. it's a bolt through an eccentric and a hex nut so you have to sort of coordinate the tightening of them so you can achieve a good fit. The wizard helped a lot took any variable of software etc out of the equation//
How can you check backlash on the machine? I have never doe this before.
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Is the play you found along the axes? If so it's backlash. One way to measure backlash is to put a dial indicator aligned with the axis being tested, move the axis towards the dial indicator till it engages and read the value it shows, then program a move (say 1mm long) in the same direction, then program the same move in the opposite direction and read the value. The difference between the two readings is your backlash. Repeat this at several spots along the screw and see how it differs.
Daniel
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I can do that. The movement I saw was grab the router standing in front of the machine and I could move it along the y axis in and out about 1/32 then from side to side along the X axis same thing. I have tightened the bearings a bit removing that slop now I can check for backlash knowing what I am looking for.