Length of Vacuum Lines for CNC Vacuum Hold-Downs

If the pipe is wide-diameter and has few bends, long vacuum lines have little effect on the total vacuum achieved. July 6, 2006

Question
I’m in the process of laying out the locations of our equipment in a new building and was curious how far could I place the vacuum pump from the router without seeing a loss of holding power. Our Weeke flat table router came from the factory with about a 12' hose. Does anyone pipe 50' or is that going to decrease my holding power?

Forum Responses
(CNC Forum)
From contributor M:
We encountered this same scenario over a year ago. We contacted the pump manufacturer and asked them for assistance, they we were able to tell us how far away we could place the pump. This was based on the size of the pump we were purchasing, and the size of the line the machine needed. I am assuming that whoever is supplying you with the pump or the pump manufacturer should be able to do the same for you.



From contributor J:
The pump on our Weeke is 40ft from the machine - we have a long piece of 4" ABS pipe between the machine and pump. As long as there is no leak or collapse of the pipe the only difference distance makes is the total time required to achieve full vacuum.

From contributor D:
I had an occasion to install 2 Becker 250 CMH pumps 120' from the machine they were servicing. Becker made recommendations regarding the diameter of pipe we used and calculated the pressure drop we would see, based on the friction from the pipe fittings the effect of the critical ratio of the diameter of pipe etc. Long story short, we experienced a 1" drop in vacuum. It did not seem to affect our part holding badly. I would suggest that you consider pipe diameter carefully and minimize the elbows etc. For example a 4" 90 degree elbow has an equivalent length of 11" straight pipe.


From contributor R:

If your piping is large enough and sturdy enough, it basically creates an additional vacuum reservoir. Our pump is several hundred feet from the machine, and piped with 8" PVC. It would be a good idea to check with the pump manufacturer as to specifics, but I think that if your pump is big enough, you can put it out in a shed where it will be isolated from the shop. Think about re-cycling some of the heat from the pump into the shop during the winter, because they seem to generate a lot and allow for cooling it in the summer.