Table Flatness

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Dave Burtchell
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Table Flatness

Postby Dave Burtchell » Mon, Oct 31 2005, 9:54PM

Hi,

Can't seem to clear up this problem.
The bit's not cutting into the wasteboard as deep on the end of the table with the tool bar. In order to get a .002-.003 thru cut on that end, it has to cut .010-.015 in the middle of the table. It's not always consistant so I'm even more confused. I flycut the spoilboard and both sides of the wasteboard. Something's moving somewhere but I can't find it.

???
Dave

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Brian Shannon
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Postby Brian Shannon » Mon, Oct 31 2005, 11:07PM

Dave,

I had the same problem and saw the same on the router that Thermwood had at Las Vegas. I was only running a 3/4\" spoilboard. I then added a 1/4\" wasteboard on top of that and my through cut looks even now. I can't explain it unless maybe the wasteboard seals the rest of the table better. The guys that I bought my router from used to cover the area(with plastic) of the spoilboard that was not being cut by the flycutter. This helped hold down the spoilboard more like it would be with a sheet of mt'l on it.

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Postby Paul Ford » Mon, Oct 31 2005, 11:36PM

Hi Dave,
We had that problem for a little while and then I painted all of the edges and faces of the spoil board which were not in use as Brian just described. I also painted the edges of the wasteboard to stop us from loosing vacum pressure through there and everything seems to be working fine with it now.

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Postby Nick M Singer » Mon, Oct 31 2005, 11:51PM

One important contributing factor is weather. I have noticed massive deviation (warp) depending on weather conditions. Supawood (MDF) is very adsorbant of moisture and there is not much that can be done about it

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Same problem !

Postby DanFecteau » Tue, Nov 01 2005, 10:16AM

We always had this problem,I always wonder why it does'nt cut at the same depth everywhere on the table,sometimes it's ok but most of the time it is'nt, it's very annoying, we have a 5' x 10' table, we don't use full table very often so if it's really the cause of our problem, it won't be solve....

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Jason Susnjara
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Postby Jason Susnjara » Tue, Nov 01 2005, 10:43AM

Hi,

I have also seen different thickness within the same sheet of wasteboard. You can try to flycut the wasteboard but you can only do that a couple of times before the wasteboard starts to bow. Check to make sure that the wasteboard is the same thickness on all four corners.

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Postby Forrest Chapman » Tue, Nov 01 2005, 12:57PM

Hi All,

Are you cutting plywood when this occures? Plywood is usually where we have this problem because the ply never sits completely flat allowing the wasteboard to float up under the material. If your waste board cups up on the edge then flip it when you flycut, don't worry about the grooves in the under surface it doesn't make much difference. If you can write a program in cad to flycut from the outside spiraling in this has the best affect. In the program include the spoilboard+ a set wasteboard thickness line so that whatever setting you have is the actual thickness you end up with (hence no calibrating ever again). We have a 5X12 table and two cutter diameters one 5\" and a 2\" so we've written a few programs.

Forrest

PS. I'll get an example of the program for anyone who wants but please don't use it without altering it for your machine.

Dave Burtchell
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Postby Dave Burtchell » Tue, Nov 01 2005, 5:05PM

Thanks for your input.
Glad (sad) to see it's not just my problem.
I do use a .25\" waste board. I do seal the edges of the spoil board. I do have a problem with weather conditions. Humid here. I flycut the spoil board and both sides of the waste board and immediately have problems with uneven cut thru. Haven't had any problem with waste board warping. I think the trick is to cut both sides. I use up both sides before surfacing again. Remove 10 thou per side. Useful for me down to about 1/8\" thick. That's 5-6 times.
There was mention a while ago about not using the table gasket. Has anyone removed it yet? Make any difference?
Forrest, I'd like to see your program. I wrote my own g-code and have that annoying calibration problem. Never thought to do it in cad and adjust the thickness. COOL!
I'm going to pay closer attention to this problem and see what I can come up with. I'll report back later.

Dave

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Postby Jeff Norris » Tue, Nov 01 2005, 5:29PM

i screw my spoilboard down with nylon screws, this way i can keep pretty consistant tolorences with or without vacuum,

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Bill Rutherford
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Postby Bill Rutherford » Wed, Nov 02 2005, 6:14AM

Forrest,
Are you saying you no longer have to manually get daylight for your first tool to set the tool length sensor? If so then I am definetly interested in some more detail on exactly what you are doing. Thanks.

Bill R

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Postby Forrest Chapman » Wed, Nov 02 2005, 9:31AM

Hi Bill,

This is one of the flycut programs that we use on our Thermwood 40. We drew the program in BobcadCam but the Startup Post and end I borrowed from my CV Post.

After the initial daylight set up if you use this program to flycut your spoilboard you can adjust the daylight value by the amount of your flycut.

Example:
Daylight value is 8.50
Set Flycut wasteboard to (-.01) which removes .01 from spoilboard
Add .01 to 8.50 and your new daylight value is 8.51
Reset all tool lengths

You may want to manually check your daylight value.

Forrest

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Bill Rutherford
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Postby Bill Rutherford » Fri, Nov 04 2005, 6:02AM

Forrest,
Thanks. I will give it a try.

Bill

Dave Burtchell
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table gasket

Postby Dave Burtchell » Sun, Nov 13 2005, 2:05PM

Hi,
I took out the table gasket on Friday. After flycutting the wasteboard, I started a job with lots of small parts. I'm getting a fairly even cut thru. A little deeper on the ends now. I need to flycut the spoilboard and see how even I can get the cut thru. I could hear a little air escaping? past the gasket slot, but so far no part movement.

What size vacuum pump are you using on 4x8 tables? Told the boss we should upgrade to 40 hp and he wondered why the salesman thought 18 hp was enough.

Forrest, Thanks for the flycut program. I modified it for our CS40. I cut the perimeter and then call a label ( I don't remember if that's the right term) that cuts back and forth on the X axis with 1 7/8 stepover. I love the \"Set wasteboard to desired thickness \" feature. Works like a charm! I keep the flycutter mounted in the toolbar and can have the board surfaced in just a few minutes. And now that the cut thru is even, I don't have to do it as often.

Thanks for all your input everybody. Keep it coming.
Dave

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Jody Wilmes
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Postby Jody Wilmes » Sun, Nov 13 2005, 2:28PM

I've flycut a spoilboard and cut sheets in the morning. By the afternoon I was cutting (etching) deeper towards the center of the spoilbord than on the ends. Since I was in a high humidity area, I believe that the spoilboard was swelling in the center because the vacuum ports for the table (located somewhat center) pulled most of the humidity through the center of the spoilboard. Placing a wasteboard on top reduced the amount of swelling but did not get rid of it. Like I said though, there was a lot of humidity in that shop.
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Forrest Chapman
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Postby Forrest Chapman » Sun, Nov 13 2005, 3:25PM

Dave,

I think 18HP is fine for a 4x8 we have a 40HP for a 5x12 with 2 ports. I don't see where the benafit of removing the gasket is. Our gasket is mashed flat anyway.

I'm glad that the flycut program works for you however I did notice that its not the spiral in program that works best so I'll repost sometime first of week. You've gotta love the instant wasteboard thickness though. Hope Thermwood picks this up and uses it.

Jody,

There is no doubt that humidity has a big affect on the wasteboard. We notice more problems in the spring and fall when were not running the air or heat. Usually a flycut every morning takes care of these issues.


See Ya,

Forrest


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