durable vacuum table material


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    Default durable vacuum table material

    Folks,

    I have a 4x8 CNC router that was used in a previous life to do work in plastics. Since rescuing it from an industrial surplus, I've managed to use if for quite a few things, but I'm always having to screw around when it comes to work holding. The machine has a 5/8" thick plate steel top. It originally used retractable pneumatic pins to align and hold work in X/Y and dual rollers to hold work down. The pins (both fixed and moving) protrude through the table and are set up for 39x80 stock and the rollers (along with a few other parts) were missing when I originally got the machine.

    I cleaned up the table and have been using vacuum pucks for most workholding, but the existing table plate is nowhere near flat. It can vary by more than .050 over the entire surface. My thought was to clad it with another material that can be machined flat. Since I have a 10HP becker rotary vane (dry) vacuum pump that I want to integrate for hold down, the question I am now facing is what material to use on top of the steel. Ideally, I would like to bolt it down on a 6 or 8 inch grid with countersunk socket head screws and then machine the topside with a vacuum grid and 6 or 8 ports the will hook up to vacuum plumbing underneath the machine and have zone valves, just like almost every other machine out there.

    I was thinking that .875 thick garolite (black phenolic, grade XX or CE) would make a good choice for a durable cladding material that I can machine the vacuum table grid into and face off to be dead flat. Any recommendations on whether this would be a good choice? I used it for all of my vacuum pucks and they have held up pretty well so far.

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    Phenolic vacuum plates are pretty common. You might also want to consider HDPE or some other similar plastic.



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    I used grade XX garolite to make the current vacuum pucks that I'm using and it works really well. The downside is that I have to make and surface an MDF jig for almost every job in order to get a usable reference plane to work from. This is getting old really fast for jobs that only need surface work done.

    My concern with HDPE and similar plastics would be that they would get beat up pretty badly over time, whereas Garolite is a pretty tough material in that sense.



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    But...phenolic is known to break. HDPE will likely dent and small dents and scratches will be somewhat self-healing.



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    I would highly recommend against HDPE unless you can find some that's specifically designed to be machined. In my experience, the stuff warps like mad after machining - especially if you face it.

    I just made a vacuum table from General Plastics 4540 tooling board and that stuff is magnificent. Not as strong as phenolic but it's a dream to cut. They also make a 4550 board that's 20% more dense.

    I've attached a pic of my vacuum table. My machine is much smaller but this thing is wonderful.

    Goodluck.

    Attached Thumbnails Attached Thumbnails durable vacuum table material-vac-table-jpg  
    -Andy B.
    http://www.birkonium.com CNC for Luthiers and Industry http://banduramaker.blogspot.com


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    Quote Originally Posted by BanduraMaker View Post
    I would highly recommend against HDPE unless you can find some that's specifically designed to be machined. In my experience, the stuff warps like mad after machining - especially if you face it.

    I just made a vacuum table from General Plastics 4540 tooling board and that stuff is magnificent. Not as strong as phenolic but it's a dream to cut. They also make a 4550 board that's 20% more dense.

    I've attached a pic of my vacuum table. My machine is much smaller but this thing is wonderful.

    Goodluck.
    Maybe you missed that he is putting the vacuum table on top of the existing steel table. Or...maybe I missed something.



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    I didn't miss anything. I think that phenolic or the stuff I used would be better because of how much HDPE warps after machining. Just because it's bolted to a steel table doesn't mean it's going to stay flat.

    -Andy B.
    http://www.birkonium.com CNC for Luthiers and Industry http://banduramaker.blogspot.com


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    I ended up ordering .875 garolite plate in 3 36x59 sheets. Not cheap and heavy as hell to ship, but the stuff is fantastically durable and wears about like steel. It isn't as brittle as regular phenolic, so I'm less concerned about having it crack. The real fun is going to be prepping the steel table for it, as I have a few creative thoughts about all of the work holding options I want to have at my disposal.

    My first thought is to lay out a 1.5 or 2" vacuum grid and fasten to the steel table on 6 - 8" centers. The reason for such an aggressive bolt down strategy is because I though about installing threaded inserts into the garolite table between the bolt down locations so that I could then use threaded work locating pins, bolt-down clamps, and any other array of mechanically fixed locating or holding contraptions.

    The good thing is that I can use the existing spindle to prep the steel plate table by doing all of the necessary hole milling and thread milling for the fasteners. It'll be a lengthy program run, but the end result is a table with a super solid attachment, dead perfect grid location, dead perfect locator pin options, and a wear surface that should last a really long time. If it ever needs it, I can resurface it a few times because of the thicker material used.

    Anyone see glaring issues with what I'm planning? I considered a setup like techno uses with a combination of t-slot and vacuum grid strips, but I'm not sure that I like the way that works out, with each vacuum grid only being a 6-8 inches wide and really long. If anyone has a techno and would like to comment, I'd certainly be interested to hear what your experience has been with that layout.

    BanduraMaker, that table is a nice looking piece. I'll have to post a pic of the final table design I put in place for critique.



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    Question Re: durable vacuum table material (Plans?)

    Quote Originally Posted by BanduraMaker View Post
    I would highly recommend against HDPE unless you can find some that's specifically designed to be machined. In my experience, the stuff warps like mad after machining - especially if you face it.

    I just made a vacuum table from General Plastics 4540 tooling board and that stuff is magnificent. Not as strong as phenolic but it's a dream to cut. They also make a 4550 board that's 20% more dense.

    I've attached a pic of my vacuum table. My machine is much smaller but this thing is wonderful.

    Goodluck.
    Great job. Do you have any plans to build this table that you could share?

    Thank you



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    Default Re: durable vacuum table material

    Hello, what thickness do you recommend to make a 48" x 96" vacuum table like that? 1-1/2" is ok?



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