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/show.cgi?tpc=27&post=67351#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]

3642

3643

3644

3645
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

[gwerner]

Hey Kevin.

Schmalz is capable of making any size plate you need, you supply the phenolic table and Powerstick and send them your measurements. They can make them to order. Regarding our BT48, if we had larger nested sheet good parts, I think it would have made sense to consider a fixed table machine instead. But that is not what we needed. Besides, there are other resources available if you need the parts. Find another Botter who can cut what you need. If you are into the sheet goods production line, you need a fixed machine. The buddy was designed for portability and a smaller footprint when not in use. I would suppose potentially you get into all sorts of engineering issues with more weight and a longer stick as you mentioned, not so much so with the Alpha. Of course you would loose the storability with a big table unless it was removed all the time. Begs the question, why? If you need a fixed table, then that is what you should use. We have an 8 ft. powerstick as well, but rarely cut anything larger than 42 x 42. If we need to, we change tables for specialized work, but those situations are rare.
So far, it works well for us. We are getting a solid hold down.

[cesout]

I made a t-slot table first off and put a pin fence along the xy 0 axes and that works well for some stuff. I concluded that a vacuum hold down was needed for other stuff. I've got a BT48 and I piped through my t-slot table so I can place and remove the plenum when needed. No glue was used on the plumbing but I sanded it to make it not stick. I used wood for the plenum to test it out and it works great. I'm sure there may be some small leaks but even with the losses it still works exceedingly well. I've got a sheet of PVC coming so I'll remake the plenum and see how that works. I use extended pins on the fence in a few places for panel registration/placement. I've got two shop vac units hooked up and I'm amazed at how well it works. It looks like there should be a supercharger or some velocity stacks somewhere. Just my two cents worth.

Oh, you can get regen vacuum blowers from www.centralvacuumstores.com (http://www.centralvacuumstores.com) for about $1500 or so. Three phase.


3646

[dana_swift]

Charles- that looks great!

Update: My new vacuum hold down system had it's first test today..

It is built along the general idea of the Brady system, but is designed to be easily removed and replaced with the conventional spoilboard which I use to mount dedicated vacuum fixtures. Nothing goes through the aluminum slab.

I am using a Bekker KVT3-100 pump (5hp), and before sealing all the trupan bleederboard edges I am getting just over 20" Hg vacuum pressure at the pump. With the trupan "open", I get 6" Hg, to "close" the trupan I just put wax paper over the top surface.

The pump has a regulator on it to prevent operating beyond 27" Hg, so my usable vacuum will be close to that, at least 10psi.

I'm looking forward to getting the system sealed and getting all that vacuum! It will replace some of my dedicated fixtures.

I will post pictures when I have it all sealed up. And ready for "prime time"..

D

[beacon14]

Charles, nice table. That's the first full-sized Buddy vacuum table I've seen. Looks like you have all the power of a fixed-table vac setup on a smaller surface - there should be no holding you back.

Dana - photos please.

[Brady Watson]

Good stuff, guys!

FYI - my version of the BT vacuum table is also easily removeable and replaced with a conventional spoilboard for jobs that require screw hold-down, clamps etc. What's nice about the BT tools is that a single vacuum like a Fein on such a small area, really makes for a nice system...I can't imagine how that 5HP Becker must be! Make sure there aren't any small animals wandering around it or they might get sucked in


-B

[dana_swift]

Here are some shots of my new BT-32 vacuum system:

The base, two layers of 3/4" HDPE machined inside to provide a series of 0.5 x 1 vacuum channels to distribute the vacuum from the manifold to the upper levels. When running the manifold will be to the rear, it is shown to the front.


3647

The vacuum ports from the top of the HDPE to the vacuum distribution channels between the two HDPE sheets. Also the support "pucks" hold up the trupan. I intend to run over 10psi so I provided a lot of support for the trupan. Also note the 1/4x20 bolt that holds the base on the aluminum slab.


3648

The vacuum "inlet" manifold, this is also 3/4" HDPE.


3649

The hole top right (out by itself), is to hold a 1/2" dowel to pin the trupan to the vacuum base. That allows the router to cut through the dowel safely instead of using metal hardware.


3650

Here is the trupan with the dowel still sticking up above the surface.. a mallot drives it so it fits tight in the trupan, and loose in the HDPE. That keeps the Trupan registered relative to the base. Note the handles so the whole thing can be easily picked up and removed.


3651

The three 3/4" ID garden hoses. These are the heavy duty industrial strength type, I discovered by experiment they don't collapse under 30" Hg vacuum. Even if they get kinked, they straighten out and go back to round while under vacuum. Low price, and easy to get.


3652

Hope that gives a good idea of what it looks like, and how it got built.

I am getting over 20" Hg running and I have not finished sealing the Trupan edges yet! It is a high performance table, after using it a few weeks I will have a better understanding of what its capabilities are. And will post an update.

D

[Brady Watson]

Very nicely done, Dana. Thanks for posting pics.

-B

[Gary Campbell]

Dana!
Good job man! Nice design... very nice execution. Can I use a "franken" word here?

Gary

[beacon14]

Wow - outstanding.

[kevin_morin]

Dana, would you mind giving a brief description of how you mounted the vac table- if I read the post right you've bolted/cap screwed the HDPE halves to an aluminum sheet?

Does that mean you have one of the Buddies that has an aluminum table instead of the ply/Powerstick arrangement? If that is true do these models have the rack gear for the X motor drive mounted to the aluminum sheet/plate?

I'm in the process of mounting a few fixtures to the power stick and wondered if anyone has come up with a 'quick mount' that would slide in and out of some locking mechanism so the table/jig/fixture can mount to the power stick without using the weld-back nuts in the aluminum slots as this takes so long to install and remove?

Dana, thanks for posting the fine photos of your very well thought out, and nicely built, vac table fixture.

cheers,
Kevin Morin