I finished my CNC router build a few months ago and decided to make a vacuum bed for it. I made it a hybrid type with T slots and 6 vacuum zones. At the time I was building it I didn't know what I was going to use for a vacuum source. Others had used a shop vac and I had that available so my plan was to use that, learn about it's capabilities and decide what I truly needed for vacuum. I had never used vacuum hold down before and I quickly learned that I really liked it. There's nothing easier than throwing a sheet of material on the router bed and flipping a switch to anchor it flat! And not having to use tabs and avoid clamps. Fantastic!

The shop vac worked fine for larger parts but not the small stuff. I needed a source that pulled deep and had decent CFM for flow. The shop vac info I found indicated they flowed around 77 cfm and only pulled a couple psi vacuum. I quickly realized that a capable, used vacuum pump was going to run at least two to five thousand dollars (eBay). Way over my budget. After a lot of looking at various vacuum solutions, I figured out a way to do it that wouldn't break the bank and should out perform a 5hp Becker unit by a substantial amount. It's a combination of two pumps: a Roots vacuum pump paired with a common rotary vane vacuum pump. The roots pump is high flow and is called a roughing pump. It doesn't pull a deep vacuum but flows really fast and is used for evacuation of large volumes rapidly. The roughing pump feeds a rotary vane pump, called a backing pump in this configuration. The backing pump doesn't flow very fast but pulls a very deep vacuum. This is a video of this type of setup: https://youtu.be/tdOKjr4Jylk

The roughing pump generally increases the performance of the backing pump by a factor of 7 to 10x.

So after a lot of browsing on eBay I found a roots pump in great shape and within driving distance. The backing pump is just a common rotary vane pump available in all different sizes and capabilities. I found an oiless version that flows at 22cfm and pulls vacuum to 28" Mercury. I've got it put on a stand and wired up. Still need to do some piping but here's some pics. I'll update this thread as I get it running.

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