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I am looking into making a vacuum hold down for my router now and have run across these motors.
https://www.ebay.com/itm/Vacuum-Moto...a40I:rk:2:pf:0
Its the same ones that I see recommended from here a lot, just cheaper.
https://www.centralvacuummotor.com/shopbot.htm
Just wanted to pass this along to anyone still on the fence. I played with using a shop vac and it gave me the fever to go for it with these motors.
How big of an area will one pump handle?
What is your work flow using them?
We do a lot of smaller stuff and from what I have read smaller parts don’t work the best on vacuum tables.
I should have added that I havent got them yet. I am still in the planning of my system, thats just the motors I see recommended for the DIY vacuum guys. I am looking to use them for cabinet parts at the moment. There are several threads on the shopbot forum on a "Brady Vac" system where a spoilboard is bolted to the machine and left solid, then "plenums" are made to different sizes as needed and layed grid side down over the vacuum holes to allow for smaller custom parts to be held with more concentrated force. And if the need for screwing or clamping an odd piece is needed then it can be done to the underlying spoilboard without using the vacuum hold down system.Quote:
Originally Posted by PapaLima
I have 3 of the motors linked on a 5’x10’ table but I have a 4th motor I want to add for better performance. And yes, smaller pieces are harder to deal with but I either close unused zones and/or use foam or spare wood to cover unused space.Quote:
Originally Posted by PapaLima
Some also put T-track in between zones so you can have the best of both worlds.
Interesting Link on the subject of vacuums and why those measurement claims of vacuum motor venders as above are posting do not ring true.
http://solarmfg.com/wp-content/uploa...g-Vacuum-9.pdf
Hi wmgeogre,
that is an interesting article but note that it predominantly talks about vacuum in the range 10-4Torr to say 5 Torr as is appropriate
for vacuum furnaces for brazing and melting. To put that in perspective that means a vacuum of (1- 5/760)x 100=99.99% or better!
If atmospheric pressure is 14.7 psi then the same vacuum used to hold a part in place would exert 14.7lb of holding force per square inch
of the part.
Quite frankly the vacuum apparatus described in this article and the instrumentation to measure and control it are far removed from the reality
of vacuum hold down as to be totally off subject, however interesting.
The pumps linked to are centrifugal pumps not dissimilar to that you would find in a household vacuum cleaner and would not be expected to
produce a vacuum of better than 200 Torr, or 73% of theoretical perfect vacumm. The holding force it would exert on a part would be 10.8lb per sq inch.
Certainly somewhat less than the furnace vacuum but still very adequate for hold down purposes and at a small, very small fraction of the
price for the pump required to achieve 10-4 Torr.
I use vacuum for moulding model areoplane parts. The wing cores are made of low density polystyrene foam and fiberglass skins are held in contact
with the core by putting it in a vacuum bag. If the vacuum is much greater than 1 psi gauge, ie 13.7 psi absolute or only 7% theoretical vacuum it crushes
the polystyrene core and stuffs it up. The essential point is that you don't require high vacuums to exert very substantial holding forces, and can easily crush soft
materials. The vacuum pump I use is actually the old refrigerant compressor from the local butchers shop, they were throwing it out. It can at best produce
a vacuum of about 100 Torr but is much MUCH greater than I require.
For vacuum hold down purposes it actually the vacuum 'leaks' that determine the pumps effectiveness. Depending on the size and shape of the part only a fraction
of the vacuum holes will be covered by the part. Those uncovered holes admit air which in turn raises the pressure and therefore reduces the holding force.
Centrifugal pumps are very good at pumping LARGE volumes of air while still maintaining vacuums of several hundred Torr and makes them very suitable
or hold down purposes.
I want a vacuum pump for vacuum drying of fibreglass composite boats (for repairs). To have water vaporize at room temp requires a vacuum of about 10-2 Torr.
That can be done with a two stage rotary vane pump commonly used by refrigeration techs for pumping down refrigeration systems prior to charging with refrigerant.
A small cheap Chinese made pump of say 140 cu ft/hr is about $400, a quality European made pump more like $1500 and still only 2.5 m3/hr. As good as
these pumps are they are poor choices for vacuum hold down because they pump so little volume even if they can reach really good ultimate vacuums.
In short the sort of pumps that are required to achieve the vacuums that the article is concerned with are tens if not 100s times the cost of these centrifugal pumps.
Its a bit like saying both that little Toyota Corrolla over there and that Mercedes Formular One are both cars and should be comparable....they are not.
The 'Real Deal' for vacuum holding and many other industrial purposes like degassing and resin infusion are done by Liquid Ring Pumps. It has a rotating
scroll and the tips of the scroll are sealed with a liquid, usually water, that rotates with the scroll. They tend to be big, reasonably expensive with hunking great
three phase induction motors to power them up. They can get to about 10 Torr and can easily be 200m3/hr or more, but cost thousands even second hand.
Craig
In the industrial router world, the standard for vacuum pumps are rotary vane, in the 10HP to 40HP range.Quote:
The 'Real Deal' for vacuum holding and many other industrial purposes like degassing and resin infusion are done by Liquid Ring Pumps
Thanks for posting.... but I am pretty much versed on deep vacuums as I used them when doing deep vacuum evacuation of refrigeration systems. I was posting to enlighten others on those measurement claims of the eBay listings. Just wanted to point out, that here on planet Earth anyway when you are pulling a deep vacuum the max pressure forcing the material to the table is 14.7 psia. (Pressure per Square Inch Absolute) .
What's not true about them? They pull a maximum vacuum of ~140" H2O, which is about 10"Hg, which gives you about 5psi of holding power (best case scenario)Quote:
Originally Posted by wmgeorge
Gerry you just pointed out what those ads do not tell you. Here is a really good Link that explains it > https://www.cnccookbook.com/router-v...table-cnc-diy/
It doesn’t really matter, for those of us that don’t want to spend rotary vane type money, these vacuums have worked for many, many people including myself. I have a 5x10 CNCRP machine with 3 vacuum motors of the type linked in the first post and it works well though not in all situations. I plan to add a 4th (already have it) when I have time but the 3 motors work well for our normal production work. I expect we’ll upgrade to a bigger CNC and vacuum motor at some point but things are working very well currently.
Hi Aerojunkie
I started building a vacuum system for my router. I plan on changing my top from MDF to an aluminium extrusion that is made specifically for our local fast ferry builder for light vehicle decking.
The extrusion is similar to the planks painters us but they lock together, with the ends capped and slots milled into the top and a thin MDF spoil board on top.
The top will have sections to turn on and off with poly valve as used on irrigation.
These are the only photos I had on hand, hopefully you can imagine how it will be when all together.
p.s. The pvc fittings have extension on them which join both motor suction ports together then will be plumbed to valve manifold.
Attachment 408860
Attachment 408862
Attachment 408864
Attachment 408866
Attachment 408868
Attachment 408870
Here is my home brew setup-works great for sheet goods, small items in <10 square inches still need some additional holding.
It works well enough that I’d do it again in a heartbeat. ymmv
Cheers
Sean
https://www.cnczone.com/forums/attac...d=409314&stc=1
I got my vacuum motors from amazon. An 117123 Ametek 3 Stage Vacuum Motor, it is 240 volt but I do get 1500 air watts. $140 each
I have installed in San Paulo a water system for my business. It is a difficult system, I needed to install separadores água e óleo e bombas industriais. You need to find a right company which will help you with that because if the installation is bad then in future time you will have problems. So my idea is that if you are not sure that you can install something, then better will be to ask a help of professionals, maybe it will be expensive but it will be cheaper than in future to lose money because you have installed it incorrectly.