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Thread: 4'x8' vacuum table build questions

  1. #133
    Community Moderator ger21's Avatar
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    Default Re: 4'x8' vacuum table build questions

    I cannot remember the stepover but the feed & speed was 50 ipm at 12000 rpm it just seemed to take forever.
    Try 175-250ipm @ 18,000, or even faster at 24,000 rpm.

    It's hard to make money on 3D work, unless you are charging a lot.

    Yes, I'd take full depth passes, removing 1/16"-1/8".

    Gerry

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    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  2. #134
    Community Moderator ger21's Avatar
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    Default Re: 4'x8' vacuum table build questions

    having a buddy surface them on his 20" plainer.
    Planers don't make boards flat, they make one side parallel to the other.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  3. #135
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    Default Re: 4'x8' vacuum table build questions

    Quote Originally Posted by ger21 View Post
    Planers don't make boards flat, they make one side parallel to the other.
    +1 to Gerry's comment.

    A planer's presssure will mechanically flatten a non-flat board as it passes through. The board will also rock as it passes through, which will defeat what you are trying to do. Once the board through the planer, it springs back and returns back to it previous non-flat condition, or in the case of rocking, the planer just follows the defect. That said, you can flatten a board with a planer, but doing so adds a layer of complexity (and time) to the process. You start by constructing a flat, rigid substructure at least a little longer than the board you want to flatten. I'll call it a carrier. Then you put the board on the carrier and shim the board from underneath where it fails to make contact with the carrier. You need to immobilize the the board you are flattening. Hot melt glue works well. You run the assembly through the planer until the top side is flattened. Once the top is flattened, you remove the board from the carrier and plane the other side.

    I've done this when I have a board that is wider than my 8" jointer, but is a lot of extra work.
    Fortunately, I rarely run boards wider than 8". Having a jointer with a wider capacity is a big plus.

    If you decide to shop for a jointer, remember that the longer the bed length the better. You pay more for a long bed, but it gives better results, especially when jointing longer boards. Also, a spiral index cutter is better than knives. Of course, you pay a premium for them.

    Setting knives in a jointer is a fussy business, if done correctly. I use a dial indicator, which sets them more accurately than any other method I've found. The spiral cutters use carbide insert that index to the cutter. The inserts have four sides, so they give a lot of life. One advantage is that there is no setting involved. Just rotate the insert and you are back in business. Another advantage comes when you nick a cutter (and you will). Just rotate the nicked insert and you're done. If you nick a blade (you will likely nick all of the knives), you have to offset the nicks, or resharpen them to remove the nicks, and reset them. Maddening when you are in the middle of a project. I haven't converted my jointer to a spiral cutter yet, so I keep 2 extra sets of knives on hand so work doesn't stop. Just some things to keep in mind.

    On thing to consider when using the CNC to flatten boards. You probably won't be able to use your vacuum to hold the board down, and wouldn't want to. The vacuum won't hold if there are gaps, and if you got it to hold, you would have the same problem as running through a planer without a carrier. You would need an alternate hold down method. I haven't given it a lot of thought, but I suppose you would use blocking to keep the board from moving around and a downcut bit to discourage lifting. You may be able to use a surfacing cutter, but I'm not sure whether they are upcut, downcut, or just neutral. The ones with carbide inserts are probably neutral, but I'm not sure. Obviously, you wouldn't want a holddown that was on top of the surface, unless you want to face in multiple toolpaths. Multiple toolpaths would allow you to move the holddowns around. Again, a jointer would be much faster.

    Gary




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    Default Re: 4'x8' vacuum table build questions

    Thank you Gerry & Gary, I agree that a jointer would be faster but I think for now I'm going to try to use the CNC until work demand gets high enough that I can justify it. I've been putting out a lot of money & not really making any back yet.

    I've got a couple ideas on how to hold down pieces but that is for when I'm messing with 1.5" - 2" air dried slabs & not .75" thick kiln dried wood. Are you using hot glue to hold the material to your spoil board or do you have a board on top of your spoil board?

    Thanks again
    Gary



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    Default Re: 4'x8' vacuum table build questions

    Quote Originally Posted by Gary-Wiant View Post
    Thank you Gerry & Gary, I agree that a jointer would be faster but I think for now I'm going to try to use the CNC until work demand gets high enough that I can justify it. I've been putting out a lot of money & not really making any back yet.

    I've got a couple ideas on how to hold down pieces but that is for when I'm messing with 1.5" - 2" air dried slabs & not .75" thick kiln dried wood. Are you using hot glue to hold the material to your spoil board or do you have a board on top of your spoil board?

    Thanks again
    Gary

    Sorry, if I gave you the wrong impression, Gary. I haven't used a CNC for planing or jointing. I have both a jointer and planer and have never needed to. The hot melt glue thing was for holding a board on a carrier to put through a planer. Having said that, if I were to use the CNC, I would probably use the same general technique. Instead of making a box as a carrier, I would fasten a piece of sheet goods to the spoilboard and then shim and hot glue as with the technique I discussed for using a planer. I have always used t-track in my spoilboard, so holding down the sheet goods is fast, easy and secure. Only you know whether you trust your vacuum system enough to hold the sheet goods. If you do, you will need to leave the vacuum running while you do the setup. You wouldn't want things getting moved about while you mount the board for planing. I would be reluctant to try to do the mounting work on my bench, for fear that a single thickness carrier might flex when being moved around and weaken or loosen the glue holding things together. Also, I'm not sure the hot melt is a strong enough connection to resist the CNC cutting forces. I'd want to experiment with some cheap stuff to check it out and work out a technique.

    Gary




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    Default Re: 4'x8' vacuum table build questions

    Gary,

    I forgot about a holding technique that might appeal to you (getting old's a b***h). I've used it and can attest that it works very well. It wouldn't do you much good when facing the first side of a board, since you wouldn't have a flat surface. However, it would work great on the second side and when jointing. Here's a how to YouTube video:



    Gary





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    Default Re: 4'x8' vacuum table build questions

    Gary, Thank you, Yes I've seen that video or one like it explaining the process. Now that I ordered the compact router & a couple flush trim bits I'm not real concerned with holding down the regular kiln dried stuff my concern is figuring out a way to hold down the rough cut air dried lumber. I'm going to work on / with the router tomorrow. I'm going to wire & install an led light ring on my spindle & see if I can figure out what caused my one vacuum motor to stop working



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