Protable Vacuum Tables?

[kevin_morin]

The Buddy is intended for those who might need to tuck the Bot in the corner of the shop when not in use, or to do a large variety of smaller jobs.

Because the table isn't fixed, vacuum hold down systems seem to move a few 0.001's" each time we take that hold down on and off the power stick deck. [this Buddy has no aluminum table component]

We've resurfaced the spoil board a few times but still seem to get some twist, warp, cup or bow every time this fixture is reinstalled.

Has anyone considered making a egg crate/pigeon hole hollow plenum, one with 1-1/2" of depth? My thinking is to build a fixture that was rigid by itself not relying on ply and MDF sandwiches. Instead, of making the plenum form sheet goods what about framing a glued up 2" [deep] hollow of 1-1/2" x 1/4" slats notched to a 1-1/2" gird inside a sheet of 1/2" bottom and trupan or mdf top?

My goal is to have a 'quick change' from one hold down system to another that would retain the surface closer to flat - but not depend on the Bot's table for structure.

I'm cutting plastic labels for industrial control panels and the lettering is turning out thicker and thinner due to irregularities in our current version; copied in miniature from the larger fixed table plenums shown on the Forum.

If anyone cuts labels with a Buddy model 'Bot, I'd sure appreciate learning about their hold down system.

cheers,
Kevin Morin

[dana_swift]

Hi Kevin.. I have the aluminum slab version of a BT-32 and am looking to switch to Brady's general hold down for the "standard table". However I also have two powersticks and have the same problem you do.

I have been considering a design for an HDPE plenum on the powersticks with trupan on top of that for a bleeder. Because the main vacuum line has to flex as the table moves my thinking is to have it "side feed" the Plenum instead of "bottom feed" like most gantry systems use. I have already tested standard 3/4" industrial duty garden hose and found it will not collapse under 29"hg vacuum. So that is how I intend to get vacuum from the main pump up to the plenum.

I intend to have TWO garden hoses feeding each side of the plenum so there will be less restriction to the air flow.

My thinking is to make a two garden hose version for the 4' powerstick, then depending on how well that works possibly use more for the 8' powerstick. It should be a sight to see, but it looks like it might be as simple of a solution as I have been able to come up with.

Now to get it built, and the acid test!

D

[kevin_morin]

Dana,
There is some room under the Power Stick bed/deck/table for a bottom pipe but I have a side connected plastic pipe to a 2'x 2' table now and it 'works' OK.

The idea to build a torsion box or honeycomb vacuum plenum was to get rigidity from that part so it can be placed, used, removed, stored, and replaced again, as the jobs change. While removed and stored I'm hoping for dimensional stability- how will you address this issue in your HDPE plenum?

I've use PVC or ABS piping so far, then made a connection to vacuum cleaners using a short flex hose to the vac's chassis. I have only used the hose in the 24" X direction of the table's movement with the short Power Stick.

I'm not even ready to try more than mechanical holds on the 8' power stick.

Do you think the garden hose will give the volume flow needed?

Speaking of Buddies' design, has anyone removed the power stick side rollers and clamped the ends of some boards to dovetail in that area?

I was thinking that I could make an open frame using the 4' power stick as one side, add an outside rail, like a smaller center extrusion, that had two V grooved rollers exactly like the four that guide the power stick. This open frame table might hold a clamp or Power Stick mounted "vise" with the ends of the box sides, inside the table cutout but under the Buddies' cutting area?

I've looked at all the articles here and don't find anyone with reference to this approach, but I thought it might be worth asking?

The cutout in my table is about 9" x18" or so (I can't recall the numbers) with the 9" leg under the Y gantry, the 18" in the X dimension- so if the open power stick frame clamped a bundle of boards end up they could be pretty wide and still run a dovetail bit through them with full control?

If the boards were oriented so their dovetails cuts were along the X axis, then the Y would just position the spindle/router. By using a straight cutter in a few passes to make the bulk rectangular cut passes and switching to the dovetail cutter for a final pass, I think the Buddie (with the table cutouts) could become a drawer or box maker, what do you think?

just an idea, I'd sure like to hear how your removable plenum works out.

Thanks for your thoughts,

cheers,
Kevin Morin

[dana_swift]

Kevin- I have been resisting the idea of putting things under the powerstick/table because on my bot the support rollers are down there and likely to snag the vacuum hose. It may be a great place, so if you try it and it works out for you let me know.. I may make a future hold-down that works that way.

When I need a rigid table I work with the 24" aluminum slab (ALS) table that came with my first generation buddy. I don't expect the same precision from the powersticks that I am accustomed to getting from the ALS.

HDPE and trupan (or MDF) will not be as rigid as you are looking for, but it will be good enough for my purposes.

As to garden hose flow.. the hose(s) are 3/4", so a single hose won't do it, I will have to have a minimum of 2. Its one of those times when an experiment is worth a thousand expert opinions. I will just try it. Also will be happy to post the results!

I have looked at the buddy and a "micro stick" as a perfect solution for dovetailing. The stick travel only needs to be about 2 inches to make dovetails. The trick will be getting my table stepper motor drive out of the middle of the table area. That will require changing EVERY table installation, and the clearance channels in the support rollers. Probably not going to happen for a while, its not a priority project by any means.

D

[erik_f]

I'm using the 1x3" aluminum tubing that Brady used on his Buddy vacuum system. I only had my Gen I powerstick for a short time, but with the tubing bolted into the right set of pre tapped holes in the aluminum table, the tubing would work with the guide block installed as long as you took the middle roller out of the guide block. I would think this would be a good way to do for the powerstick set up also. Just a thought.

[dana_swift]

Erik - could you take some photos and post them?

D

[erik_f]

http://www.talkshopbot.com/forum/sho...7351#POST67351

This is a post from Brady. Mine is a little different, but I used his idea for the aluminum tubing. I will try and take pics of the location on mine...but I'm pretty sure its the same as his. I used two tubes under the table on either side of the stepper.

[erik_f]

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Sorry about the mess...I've always been amazed at how people are able to always keep their shop spotless. I am in the middle of a move right now and things are a little crazy. I used existing tapped holes in the aluminum slab and ran the aluminum the under the entire table. You could use a shorter piece if you wanted to drill and tap another hole in the table. I also tapped the aluminum tube, but have decided if and when I need to take them off to drill a hole through both sides of the tube and get longer bolts and hold the tube to the table with a nut. I found it harder than it needed to be to tread the bolt through the table and get the thread started on the tubing while getting the tubing nice and tight against the bottom of the table. The hole in the tubing is 2" as well as the hole through the table. I made all the holes using the bot except for the bolt holes in the tubing.

[gwerner]

Kevin.

We came up with a solution that is working nicely for us on our BT48.

Check out our buddy hold down in the resource columns here.

It is very modular in that you can quickly setup the hold down where you need it on the table.

http://www.shopbottools.com/web_columns.htm

Greg

[kevin_morin]

Thanks Greg, I'll look into this thoroughly, it looks like a good solution and seems to be all I'd need in this size table.

I suppose those folks could apply one to the longer power stick as long as the travel was slowed to take into account the potentially heavier mass?

Kevin Morin