Vacuum hold-down on Magnum Phoenix GS router?

[jeffmorris]

The Magnum Phoenix GS Router came with a vacuum hold-down system that uses an air compressor. The table has a grid for gaskets. There is only one hole in the center of the table. I tested the vacuum hold-down and I don't get enough vacuum. I need to use spoilboards if I have to cut out parts. From reading messages on this forum, I found out that some people have problems with vacuum hold-down systems. What if I make spoilboards the same size as the table and clamp them at the front edge? The router is inside a cabinet so I can't use clamps at the back edge. The plastic "glass" is attached to the cabinet using some kind of gaskets and may be glued to the cabinet. If the "glass" is glued to the cabinet, how do I remove the "glass" from the cabinet and put hinges on the "glass"?

[ger21]

Vacuums that run from a compressor use a venturi. These create high vacuum, but very low flow rates. In order to work well, all leaks in the system need to be eliminated.

Typically, when using a spoilboard, you'd use a high flow vacuum pump, which typically has lower vacuum. The reason is that vacuum will suck right through mdf, and wood as well to a lesser extent. The high flow rates allow parts to be sucked down to the spoilboard by the vacuum sucking through the spoilboard.

With your low flow system, all the vacuum would be lost through the edges and exposed surfaces of the spoilboard.

The best option for that type of system would be to make dedicated vacuum pods from a non porous material, like acrylic. If it has a grid routed in it, gaskets can be configured to fit your parts. With a very good leak proof seal, a pod system can get tremendous holding power. Keep in mind, though, that holding power is proportional to part size. The bigger the part, the more power you'll have. Small parts can be extremely difficult, if not impossible to hold with vacuum.

See the following links for the type of fixtures that you should use with your system.
Vacuum Clamping (Vacuum Hold-Down Jig)
How to Build a Vacuum Clamping Matrix

[jeffmorris]

On my CNC router that I built about two years ago, I used T-Track and hold-down clamps. If I use HDPE sheets as spoilboards, how do I attach the pieces of wood or plywood to the sheets? Double-sided tape may ruin router bits.

[sutton450r]

I have never used a forum before and this is the only one i found on vacuum tables. My Question is...If I am cutting cabinet parts out of a sheet of plywood, how does the table maintain vacuum if Im cutting all the way through the plywood? Is there some trick that Im not finding?

[jeffmorris]

I built a new tabletop with T-Tracks that fits over the original tabletop so that I don't need vacuum hold-down. If you're going to cut parts out of plywood, you need another sheet of plywood as spoilboard. If possible, clamp the plywood to the table.

[ger21]

I have never used a forum before and this is the only one i found on vacuum tables. My Question is...If I am cutting cabinet parts out of a sheet of plywood, how does the table maintain vacuum if Im cutting all the way through the plywood? Is there some trick that Im not finding?

Usually, vacuum is drawn through an MDF spoilboard. There are no seals between the plywood and spoilboard, so there is constant vacuum on the entire sheet.
Be aware, though, that each time you make a cut through the plywood, you create a space for vacuum to leak, so the total vacuum slowly decreases while you're cutting.
You need a very large pump to use this method, typically at least 7HP. Some ShopBot users use 4 smaller pumps.
On the 5x12 router we have at work, we use 2 25HP vacuum pumps.

[sutton450r]

Was not aware that a pump could pull vacuum through an mdf board, thanks for the reply