Brad Nailer hold down?

[Gary Thomason]

I am considering purchasing a 60" x 120" ShopBot and have been reading what I can find about hold-down of parts. Vacuum sounds great but it is difficult to get a definitive opinion about exactly what sort of system it would take to hold down many small parts. Money is certainly an object, but I am more concerned about it working reliably than about doing it the cheapest possible way (too much risk of frustation). Is there anyone at Shopbot or elsewhere who could be very specific about how to do it? (Of course they would need more information about what I am trying to do.) I have also read about drilling pilot holes for hold-down screws with the shop-bot; is there any way to attach some sort of brad nailer to the ShopBot and let it pin the parts to the underlayer prior to cutting?

[davidallen]

you might want to look at the plastic nails from utility composites (www.raptornails.com) I use their staples for holding rubber liner in wet areas and they work well. I also demo'd their nails at the 'camp' in NJ. with plastic, you don't need to worry so much about placement and, depending on the wood, they blend in OK. the main drawback is you have to buy their guns which are at the high end of reasonable.

some regular guns have a safety latch in the nose. if you hold the trigger and put the nose on a surface, they will fire one nail. you could clamp the trigger and strap the gun to the router then use z moves to actuate the gun. you'll need to work out an offset for the nail but you should be able to adjust the xy zero to compensate. the main problem I see, is removing them after cutting. in my experience, about half will pull through the top piece and remain the table. that could mean a long reach with a pair of pliers to pull them out.

[garbob]

Not nails, but better.

Been there about the vacuum stuff. Everything tht I do is custom, no repeat jobs. After much hunting and gathering of double sided tapes I found a company that has the absolute best stuff for holding just about anything down. I use a cutting surface of particle board with 1/4" round grooves on every inch mark that are about 1/8" deep. If it weren't for this grid cut into the table I wouldn't be able to remove the tape from it. The tape is from Intertape Polymer Group http://www.intertapepolymer.com/ . I hold down pvc, acrylic, mdo, mdf, plywood, signfoam, gatorfoam, styrofoam, etc. I haven't used this particular tape for cutting 6mm thick acrylic letters smaller than 4" high yet, but I believe that it will work. The stuff is amazing. There are two types available with heavy duty tack, namely the 591 and 597. Their web site says that the 591 has less tack, but it is an error that they knew about a few months ago. The price of the 591 paper backed (2" by 36 yards)stuff is under $6.00 USD in case lots. The paper rolls look weird as they are not smooth. I use a parcel packing tape gun, a bit snug on a new roll, but after a few feet it's ok. Get a vinyl sign "squeegee" thing to smooth down the tape.

You'll be impressed AND THEY'LL SEND YOU A FREE SAMPLE BEFORE PURCHASING. Amazing stuff. Time consuming to install, but it removes without a trace and is easy to remove and easier to get the backing off to expose the second surface than the vinyl backed stuff (597).

I hope that you try this, it will solve one of you major headaches, at least for sheet good and wood strips.

Good luck!

Gary

[Ted Hall, ShopBot Tools]

Hi Gary Thomason,

You'll find some good suggestions regarding hold-downs in this thread, and others elsewhere on these forums.

We have no ShopBot party-line on this one. But you are right in being concerned that this issue can be a source of frustration. To the extent that you are talking small parts (say less than 10"sq surface area) holding them down becomes a significant issue. Vacuum gets particularly tricky with small parts.

If you are cutting the same parts over and over, you have the advantage of being able to create a template for the vacuum system. This will make it very efficient, and you will be able to use the shop vac variation rather than the vacuum pump. But even here, as size gets smaller, you will have to do something like adding 'tabs' to the parts to help hold them in place (ShopBot does have a built-in automatic tabbing system that can work well in some situations).

If you are making different parts each run, then for small parts, variations on tape, plastic nails, screws, tabbing, etc ... are probably a good shot. Vacuum with a vacuum pump through a bleeder board works well, but only if the parts are big enough.

[gerald_d]

We have had a ShopBot for a year and we also had all these concerns about holding down the work in the beginning. Even purchased 2 different types of vacuum pump and had them ready to install in case a job came along for which vacuum clamping was essential. Well, that job hasn't come along yet!

There has almost always been a way to simply use two G-clamps and cut. BUT, the big trick is to know WHERE to start cutting.

An example is a recent job where we had to get 14 pizza platters, each nearly 18" diam, out of a 8'x4' sheet of marine ply. What we did was to draw the full sheet in a CAD program, and then started placing the platters (plus a 1/4" cut allowance) furthest away from the (0,0) corner. This left about a 6" wide strip along the left edge of the board (running in the y-direction).

Two G-clamps were placed, one at about (0,0) and the other at about (0,48) ie. the leftmost 2 corners. We knew from our CAD drawing that the cutter wouldn't come nearer than about 5" from the clamps (quite safe) and a strong, long off-cut would remain between the clamps for a strong anchor point.

Using a downward spiral cutter, to push the board gently down, we started to cut the first platter - the one furthest from the clamps. This is critical; it is like slicing bread - you must start furthest away from your holding hand so that the slices fall off one by one. Logical ain't it, and easy to remember.

But, the big trick is that for each individual platter (component) you must start the first plunge nearest to the clamps. In this example the cut is started at about the 9 o'clock position of each platter. The reason is that you want the platter to be attached to the firm clamp side during the last few seconds of the cut. And that really is all there is to it!

Just think your cutting sequence through carefully as if you are slicing off bread slices and remember that each part must be firmly attached to the anchor side until the last moment.

Okay, we have made a basic vacuum system, but we never rely on it for the clamping force. Our vacuum system is only to flatten down warped boards. Two G-clamps do all the holding-in-position work.

Using this starting-furthest-away method, you can keep track of half-used boards in the CAD system. It is very quick to throw a board down at the (0,0) point, put on 2 clamps and start cutting.

In the beginning we were concentrating too hard to start the cutting at (0,0) and destroying our reference points and clamp strength in the process. Rather start far away and work back to (0,0)

[gerald_d]

Hey, the formatting is working!

[Mayo]

I use a lot of double sided carpet tape, available from Home Depot. It's made by Manco, and it's called Indoor/Outdoor Carpet Tape. 2"x75 feet costs 7.94 plus tax.

It holds so well that you sometimes have to remove your cut parts slowly with a putty knife or flat chisel.

I think they may have recently changed their formulation for this tape because the liner in between the two sticky sides is now different and it's also 1.8" instead of a full 2".

[gerald_d]

Some guys have asked me for a sketch of what I tried to describe above:


5336

blue lines are jog lines, reds are the platters

[bobsjoinery@nireland.com]

Just in case any one is interested. I do a lot of repetitive work and instead of drilling pilot holes every time, I screw up from underneath the table into the new sheet. This way the screws are in the right position evry time already. A small washer stops the screw sinking in with repetitive use. I let the screws hang when not in use. For a different programme I have another set of screws. All screws are labelled by writing a shortened programme name on the base board close to each screw. I also made my table a foot higher than normal to allow room for a pallet of sheets and space above it to manoever an electric screwdriver.

[raptor1saro@hotmail.com]

I am in the Sales Department for Utility Composites, Inc. / RAPTOR Nail Division. We manufacture and distribute the polymer nails recommended above by David Allen. We also have polymer staples, brads, headless pins and clamps. Please contact me if you would like any information. I would be glad to help.
Thank you, Saro Helpinstill 800-460-6933

[raptor1saro@hotmail.com]

I am in the Sales Department for Utility Composites, Inc. / RAPTOR Nail Division in Round Rock, Texas. We manufacture and distribute the polymer nails recommended above by David Allen. We also have polymer staples, brads, headless pins and clamps. Please contact me if you would like any information. I would be glad to help.
Thank you, Saro Helpinstill
800-460-6933 or 512-255-8525

[Ronnie Smith]

I found some Vacuum Clamps that work great and do not cost alot. I found them on Ebay. They sell them regularly. I use them on the CNC and for doing cabinet work. Just go to Ebay and do a search for Vacuum Clamps.