Can I build an oversize table for a regular PRS 96x48?

[EricSchimel]

Hey all, I've got a PRS 96x48 with a pretty worn out table.

I've got 4 Lighthouse motors bolted to the bottom with a standard plenum design.

I want to build a new table and I am not sure how to proceed..

What I want is a table that is larger than 48x96. It looks like I can go up to 59" wide and well over 96 if I want. I realize the machine can't cut in these areas, but I want to be able to screw down some nice removable stops for when I put large sheets on. I also want to have a place for the tool to zero itself to the table if possible. (outside of the cutting area)

Has anyone ever built an oversize table? The only way I can think to do it is with piecing together 4x8 sheets to make it larger and I think with the plenum I might run into problems with leakage...

As far as the lighthouse motors go, they all function, but my table has lots of leaks on the side so I don't get very much suction. I never use the vacuum at all because of it. With a new table is it worth re-installing these the way they are?

I know the real answer is likely to go with a better vacuum setup. I like Gary's boxes, and I'd really like a regenerative blower, but for now I'd like to work with what I have.

Thanks for any help!

[myxpykalix]

My table is for a PRT Alpha 5'x10' and i have an indexer bay. I can do up to 8' long by 12" wide columns and that is why i made my table this wide and long.
I can leave a sheet of plywood on the table and do a column in my bay without having to change any setups. Unfortunately when i'm not doing anything on the indexer the bay tends to collect clamps and tools, material ,ect.
I have a vacumn table but i rarely use it but this setup allows me to clamp stuff down easily.

I realize the machine can't cut in these areas, Actually it can. If you had 20' long rails you could cut 20' . I think i can cut as close as 4"(?) on either side.

[Brady Watson]

If you make the table larger than the nominal 48x96, you are going to shoot yourself in the foot later on down the line. First, you will not be able to clamp things around the perimeter, which is important for properly laminating the support board to the plenum layer - as well as for times when you cannot use vacuum & you need to use clamps.

Some people have made the support board go from table side to table side with an MDF 'island' in the middle that the tool can reach. This keeps chips off the floor, but eliminates the use of clamps & chips can build up on the top surface & blow in your face.

Most who index longer sheets do so with an outboard table and/or roller supports.

In terms of vacuum, you absolutely have to track down the leakage or you will be doomed to failure. If your motors are bolted up to the support board, there absolutely needs to be a gasket between the motor and table of some sort. After this, you have to turn on the motors listen and feel for leaks, then plug them up. The edges of each board need to be sealed as well since a 3/4 X 48 X 96 perimeter area equates to a 15x15" area of leakage. The system should have some type of vacuum gauge - otherwise you will have no clue what the system is capable of or actually doing when you turn it on.

I would copy what others have done with their table and not reinvent the wheel if you want your vacuum to be useful.

Please post pics of what you have because they tell the tale of what you have going on. One can only imagine what you have there.

-B

[EricSchimel]

I totally get about the leakage. As you'll see in the pictures my table has massive cracks in it which is certainly why my vacuum system barely works.

The table looks to be made of regular plywood, not MDF. Even not cracked on the edge I'd think that it would be porus and leak air?

You make good points about the clamps, I didn't even think about not being able to clamp it when building it. 3 pieces of plywood sandwhiched together is going to be awfully heavy to move without a forklift! My orignal plan was to mount some T track along the long edges a bit outside of the cutting area, which is why I was thinking of larger plywood at first. Maybe I can make a regular (48x96") sized table and then make some "table sides" that have my track on them. I could install them after, and remove them if they get in the way...

As far as these lighthouse motors go.. They are so loud. I think I want to mount them in a box and plumb them in with PVC. Even working they make so much noise that I really hate using them.

Here's my ShopBot table: https://goo.gl/photos/Nc7kWyw98HJoRkYR9