Vacuum Pump for Desktop Version

[cj_making_things]

I have a ShopBot Desktop version, and after attending the ShopBot NW Camp last weekend, I've decided to try building a vacuum hold-down solution.

I plan to use:
-24" x 18" x 1" piece of Sintra as my "pod"
-Gasket tape from All Star Adhesives (Products CE_06_25, CR_06_25, or SBC_CE_06_56)

Now I'm trying to decide on a pump. I bought a Two Stage 3 CFM Vacuum Pump from Harbor Freight for $129. But as discussed elsewhere in the forum, there is the "oil mist" issue, which actually IS an issue for me due to the office-like location of my ShopBot. The next alternative I'm considering is the Gast Oil-Less Vacuum Pump offered at Veneer Supplies.

Can anyone post a link to a good pump, or offer comment for an appropriate Desktop vacuum hold-down setup? I'm cutting 1/4" Sintra and HDPE, smallest pieces being around 4" x 4".

Thanks!

http://www.allstaradhesives.com/product_listing.php
http://www.harborfreight.com/two-stage-3-cfm-air-vacuum-pump-66466.html
http://www.veneersupplies.com/products/Excel-1-Continuous-Run-Vacuum-Press-System.html

[meatbal80]

If you are going to use the AC kind of vacuum pump make sure you have check valves, filters and a large reservoir. I use a set of 3 robinair 5 scfm pumps with 2 11gal air tanks (harbor freight) as reservoirs.

Because of how long the pumps run I made a system to choke each pump separate from the rest so that I can refill oil throughout the day. Also made a manifold for the filters where I can pull one at a time out with the system running since they clog fairly fast from stray clips/dust that gets into the system. The amount of vacuum loss caused by a spoil board made it not feasible, unfortunately.

I just recently made an oil coalescing filter that seems to work fairly well. I tapped the exhaust on the pumps and threaded a barb fitting on. Then used a piece of hose to a section of abs pipe which I stuffed (gently) mechanics rags into. I have only used this filter for 1 days’ worth of holding, in that day I added .5 - .75 quarts of oil to the pumps and got back out .35 - .5 quarts from the filter. The rags at the bottom of the stack are completely saturated, I am not sure if they need to be changed out or if they will still filter. If you have the funds you could get a real filter from Solberg, I will be getting one I am saving to afford a very large one so that I can repurpose it for my 7.5hp vane pump when we get it running.

[billp]

Chad,
For the size "pod" you're planning to use the Gast will probably work fine. As mentioned above a check valve , and filter would be well worth the investment, but I don't think the reservoir would be needed initially for the size table you are describing,( you can always add that later if for some reason you can't get the amount of vacuum you need from the rig...).I'd also consider a vacuum switch so that your pump can cycle on/off when needed instead of running all the time ( with Sintra as your product you should get a very good seal, particularly since you are using gasket tape...). Some of the Gasts have a 100% duty cycle anyway.
As mentioned at the NW Camp you should take a peek at the Shopbot web page, under "Support"and look at the "Wiki"for info on vacuum pumps, etc.:
http://shopbotwiki.com/index.php?search=vacuum+pumps&fulltext=Search