Vacuum pump recommendation?

[kgracey]

Hello there,

We're struggling with choosing a vacuum pump for our CNC router. Although I own a ShopBot, this particular request is for our Haas SR-100 CNC router.

Haas ships the router with a vacuum table and a number of ports, but no pump. They are happy to sell us one for $4K but it requires water (for pump coolant?). We are putting this router in a place where there is no plumbing, but we have any power supply we may need to provide.

Could somebody recommend a pump, hopefully a used one, which would be sizeable enough to match the SR-100's needs?

We're running polycarbonate and occasionally (but not often) plywood.

Thanks a bunch.

[dana_swift]

The best vacuum pump is not a single thing.

It could be a one or two stage "blower" type.

It could be a vacuum cleaner motor or two in series.

It could be a vane pump.

Each of these types have their advantages. How porous is the material you will be cutting? Will you cut through the material? Will you always work from full sheets?

For inexpensive, its hard to beat the vacuum cleaner motors, there are many users who have found that to work well with large sheet cutting.

Compound blower types are good as holes get cut through the material, they can blow a lot of air (100+ CFM) and maintain hold-down pressure (10+ "Hg). To accomplish that they run high horsepower motors 12-15hp. Run costs are higher of course.

Then vane pumps can achieve higher vacuums (25+ "Hg) while having medium-level of CFM (75+) at low pressures. (I personally am using a 5hp vane pump currently.)

Oil based vane pumps can achieve almost perfect vacuums (29+ "Hg) but have low flow (5+ CFM). Formerly I used this type of pump, but couldn't allow anything to cut-through.

Cost is pretty much- what you get is what you pay for. When you get a used pump, how much life is left in the bearings? How long till the motor needs rebuilt? If its a vane pump, how many hours of life until the vanes need replaced?

The cutting forces are the same on any cnc router. The cutting force is determined by the feed rate, the bit and the material. Therefore the hold down requirements are identical.

Good luck-

D

[bleeth]

Ken:

That machine should have a regenerative blower for full sheets. I would look for a minimum of 7.5HP and when I piped it make sure that my pipe was a large enough diameter to have a good volume of air in it (like 2-3").
The "Brady Vac" is a great value priced option but in the long run I think you would be happiest with the regen.

[carlcnc]

Ken
if you need water cooling,you can always setup a radiator,fan and an inexpensive water pump to circulate.
I helped a guy do one for an Ebara system. I think he got his at auto salvage complete with 12v fan.
He had Roots type blower feeding into a rotary vacuum pump. required circ was like 6 litres a minute or about 2 gallons
that Ebara setup provided a lot of flow[over 200cfm,and down to about 26" hg. with 2 5hp motors.

Carl