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Author Topic: CNC Bed Level?  (Read 2388 times)

AtomicProf

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CNC Bed Level?
« on: February 02, 2013, 11:45:19 PM »
So I made my first cut on the CMC machine (Video to follow).  I think the wooden bed on the machine is warped.  That is I do not think it is equidistant from the router head for all positions on table.


See the photos below.  One photo is from the top of the finished workpiece and the other is from the bottom.  I cut 1/2 plywood.  My cut depth was .55 .  Had I used a cut depth of .60 it still would not have been good enough.  I found the difference at it's thickest to be .108 inches. 


Also, just setting the cut depth DEEPER doesn't solve the problem.  Notice that I cut DADOS into the oval piece.  These were set to be .22 inches deep.  And That is what some measured, but the dados where the piece didn't cut through were shallower.   So the work piece was father from the cutting head at these locations.


I think we should run the 1 inch wide bit across the entire wood surface to smooth is out.  That and a fine sanding will make the bed equidistant from the cut head.
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AtomicProf

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Re: CNC Bed Level?
« Reply #1 on: February 02, 2013, 11:51:37 PM »
A couple more observations.


Jim and I put a couple of straight edges on the bed.  And it did indeed seem to have a low spot in it, where that happened. 


The poor cut through may have been compounded by the fact that I didn't have a solid board under my work piece.  I do think it has more to do with the bed than the support I had used.
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tomlong74

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Re: CNC Bed Level?
« Reply #2 on: February 03, 2013, 08:24:29 PM »
Yes you're correct about the bed, this is a known issue.

AtomicProf

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Re: CNC Bed Level?
« Reply #3 on: February 03, 2013, 11:11:30 PM »
Tom -- Do you think the following is a solution.


1:  Find the low point of the table.
2:  Calibrate the Z axis to to think the Low point is 0.0
3:  Cut over the entire table to a depth of .05 inches?







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PockyBum522

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Re: CNC Bed Level?
« Reply #4 on: February 04, 2013, 09:52:21 AM »
Yes, that would be the solution, but check with Chorca before you do it.

AtomicProf

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Re: CNC Bed Level?
« Reply #5 on: February 04, 2013, 12:43:26 PM »
Chorca -- Lets do this
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tomlong74

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Re: CNC Bed Level?
« Reply #6 on: February 05, 2013, 04:57:56 PM »
Chris has mentioned doing that same mill down.
We should wail till the end stops are in place because of the size of the mill pattern.

P47

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Re: CNC Bed Level?
« Reply #7 on: February 05, 2013, 05:16:56 PM »
I'm going to bring a dial indicator to the lab tonight to mic up the table, and log the results. There might be a few things we can do before having to flycut the surface.

AtomicProf

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Re: CNC Bed Level?
« Reply #8 on: February 06, 2013, 03:46:48 AM »
End Stops meaning Limit switches?  I don't see the point for that.  the 1 inch bit that we have, will keep us from hitting the stops.


I talked With Pat, he does have some good ideas about looking at the flex in the bed, and maybe added vertical support up from the floor. 



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tomlong74

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Re: CNC Bed Level?
« Reply #9 on: February 07, 2013, 01:09:35 AM »
End stops = limit switches yes.
If you've used this machine and the back pullies pop off  :o because of going beyond the end stop you'll know what I'm talking about. Basically the machine self destructs a bit. Kinda scary when you're the only one at the lab. Not that this has ever happened to me, :-X but if it should happen to you I know how to put it back together. 8)

AtomicProf

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Re: CNC Bed Level?
« Reply #10 on: March 20, 2013, 08:05:45 PM »
OK -- here's what I intend to make happen.


A -- Make a mount for the monitor, version 1.00 will have it attached to the cutting bed at about table height.  I know many people want a wall mounted one.  Well that can happen also.  I'm just going to move it and mount it there for now.
B -- Then am going to level the bed. The following are steps I think will work.
  • The bed is larger than what the tool can cut.  So to avoid a step in the front and the back of the bed, the bed will be shortened as follows.
  • Determine how far to the front and the back the planar bit can cut.
  • mark a line along this limit
  • remove the two outer boards - and cut them at the line.
  • Clamp a straight edge to the bed and cut the remaining boards in place with a hand held circular saw.
  • Reinstall the two outer boards.
  • NOW the bed is the size that can be planed to an even plane parallel to the cutter head.
  • Measure the table and find the minimum depth need to cut for the entire table.
  • Cut the top.
  • Clean up the mess.




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