Lumber vs Plywood – table build

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This topic contains 8 replies, has 4 voices, and was last updated by  Bill 1 month, 1 week ago.

Viewing 9 posts - 1 through 9 (of 9 total)
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  • #66560

    Kelly D
    Participant

    I was at Home Depot pricing out the lumber for my table plans and after looking at the options wondered why I don’t just build it up like a cabinet maker would using 3/4″ plywood? If I laminate the ply for the structural bits like the leg sections and the cross pieces under the table top wouldn’t that be a super strong and quite likely cleaner looking build? To make things even better most of the cuts can be done right at HD on their $10,000 panel saw nice and square. I know a few of the guys there and we can make the cuts bang on.

    I’m just not a structural engineer so I don’t know what’s stronger – two-by lumber or laminated ply. Although I have my own hunches (ply).

    And let’s throw this in the mix while I’m here…..I opened up Sketchup to whip up this little doodle and thought “Ugh – I’m going to use Cinema4D instead because I’m so much faster with that software”. While putting the attached together I wondered why I couldn’t use Cinema4D for my 3d needs as far as the MPCNC goes (for milling and the eventual 3d printer capability that’s surely going to follow)? I am a very strong Illustrator user so I’m sure any simple cut-out stuff can be done there. Cinema gives me a myriad of export options including DXF. Is that what I need? I know I’m getting ahead of myself here so forgive me the daydreaming. Lots to learn I know. Ultimately I want to be milling stuff like the Pegasus carve I saw but imagine all the cut-out scraps of 3/4 ply this table setup would give me to practice with! ; )

    #66563

    Ryan
    Keymaster

    Yeah that table should work, and look great.

     

    Any software should work. Whatever you know best should be easy to adapt, if it is needed.

    #66626

    Jeffeb3
    Participant

    The requirements for the MPCNC table are much less than a normal workbench. That design should be very strong.

    I used to have some workbench boxes that were basically a 4 piece frame for each side, made from 3/4″ ply, 3″ wide, joined with pocket screws.

    Each side was then combined with a solid top and bottom piece to make a box. They were really strong.

    I took them apart because they were just so big and rigid that they took up too much space.

    So one 24″x24″x36″ box would be:
    Top, bottom: 24″x24″ qty 2
    Vert. Stiles: 3″x34.5″ qty 8
    Horiz. Rails: 3″x18″ qty 8

    You could definitely get that feom sheet of plywood. If you made them 2.75″, I bet you could fit a much larger table. Then you’ll also need like 50 screws…

    #66642

    Kelly D
    Participant

    I laugh (quietly to myself) at the irony in the fact that if I had a running MPCNC I could put it to great use making a super skookum table. Hahaha

    Soon I’ll be making all kinds of everything!

    #66643

    Jeffeb3
    Participant

    I hope you share it all. I love working vicariously.

    #66648

    Kelly D
    Participant

    Quick question (planning the ply cuts). The top is going to be two thicknesses of 3/4 ply which I’ll cut through so the hydraulic lift can lift the ice up into the mill. Can I go 1 1/2” below the feet of the mill therefore using the mill itself to cut the hole for me when the time comes? Does that make sense? I guess what I’m asking is, is zero Z depth the table surface or could I get negative Z and cut down right through the table top to cut the stepped hole I’ll need?

    #66654

    Jeffeb3
    Participant

    The short answer is yes, but the length of the Z has a big impact on the rigidity. After you cut 1.5″ more than the base, you’ll want to shorten it up by that 2″. Or, you could shrink the legs to make it reach and then somehow make it grow again to your final height.

    #66657

    Kelly D
    Participant

    I had been giving some thought to pass through holes under the feet and then using longer tubes but with the hydraulic lift underneath it seemed redundant. And still does. Is it safe to plan the zero Z depth to be the tool collet? Or should I plan it to accommodate an 1” or 1 1/2” cutter thereby stiffening the z axis that little bit more? I’ll still be using the big old bit for the ice so now I’m referring specifically to table surface level work. If the collet is absolute zero then I can squeak the insert cutout by virtue of the cutter length. But really…..I also have a jigsaw…..I could just make the cuts.

    I really appreciate all this guidance too by the way. I tend to be an over thinker before I move to doer mode. I think that’s why I was so drawn to the chainsaw…..there’s not a lot of time for thinking. You gotta keep up with the saw! Now if I could devise a tool mount for an eight pound chainsaw and add a fourth and fifth axis to rotate  and pivot like a robot arm I’d REALLY be in business. Hahaha

    #66663

    Bill
    Participant

    Zero Z is typically set to have the tip of your bit at the top surface of the piece you are going to be working on. You actually want your system to support moving a half inch or more up from Z zero so you can move around without cutting (that’s your clearance plane). Leg length then determines how much below zero you can move. Typically that’s set to match your longest working bit, maybe a couple of inches for wood. You’ve got a really long bit IIRC so you’ll want to plane on being able to move that much down. If you have, for instance, a 125mm cutting depth on your bit and a 25mm clearance plane you want a total Z height of 150mm, or about 6″. Set your ice so it’s top surface is a inch below the bit tip with Z raised all the way, then move the carriage to your lower left corner of the ice block, spin the Z axis down to where the bit just touches and power everything up. You should be good to go then because that will be your 0, 0, 0 for that run.

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