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not sure about this 2 stage vacuum pump.
Types of Pumps
What type of pump do you need? There are really three main types of "pumps" commonly available, oil filled rotary vane pumps, diaphragm pumps, and vacuum generators. Each work differently and produce different levels of vacuum. The closer you can get to 100% vacuum, the more air you can remove from your material. The more air you remove, the more resin you get back in and the better your material will be stabilized! Here is a quick run down of the three common types.
Oil Filled Rotary Vane Pump
Brands include JB Eliminator, Robinair, Harbor Freight, Jeny, and many other generic imports
Produces the best vacuum for the money (99.9%)
Does not require any additional equipment
Built to run extended periods of time as required for stabilizing
Requires oil and fairly frequent oil changes
Can produce an oil mist when using cheap pumps or on a system that has a vacuum leak
Brands include Gast, Thomas, and most lab or hospital surplus pumps
Produce a medium vacuum, typically no better than 83.5%
Does not use oil
Does not give off any oil mist no matter how bad of a leak you have and is best used for vacuum chucking
Does not require any additional equipment
Brands include Harbor Freight, Hold Fast, and others
Requires an air compressor to create vacuum through a venturi
Produces a 93.6% vacuum if you have a large enough compressor
Noisy with an air hiss the entire time
Transfers all the wear to your more expensive air compressor
Can freeze up in humid conditions
Vacuum level fluctuates as the compressor kicks in and out if you do not have a large capacity tank
The very best choice for stabilizing and the only type I can recommend is the oil filled rotary vane pump. These pumps are the type used by HVAC technicians and produce the best vacuum for the money which will help you achieve the best results. Since I only recommend oil filled rotary vane pumps, that is all that I will focus on for the remainder of this article.
Single Stage Vs. Two Stage
When shopping for a pump you will see a number of specifications. Some are relevant for stabilizing and some are not! Typically, the first thing mentioned is the number of stages, either single stage or two stage. Two stage pumps basically have two rotors and two sets of vanes. The first stage generates a medium vacuum and the second stage processes the exhaust of the first stage to create a better vacuum. As a result, two stage pumps can produce a deeper vacuum than single stage pumps. However, the typical vacuum chamber, hoses, and fittings can not take advantage of that deeper vacuum! When you get to real deep vacuum, almost everything becomes porous. A typical vacuum chamber and hoses will be doing good to produce a 700-800 micron vacuum (more about microns later but lower is better). A typical single stage pump is capable of creating a 75 micron vacuum where a two stage pump can typically create a 25 micron vacuum. However, if your chamber and hoses leak to the point that they can only get to 700-800 microns, the difference between a 75 micron single stage and 25 micron two stage pump is moot! All else being equal, save your money and buy a single stage!
CFM (Cubic Feet per Minute)
The next specification you will see is the CFM rating. This is how many cubic feet per minute of free air the pump will move. This measurement is made at the pump with nothing attached and drops off significantly as vacuum is created. The question always come up about how many CFM you need. For stabilizing, CFM is irrelevant. Once you get a vacuum chamber down to deep vacuum, maintaining that vacuum requires virtually no CFM. Even when pulling the system down to deep vacuum, CFM plays no part since the typical fittings and vacuum hoses used on a stabilizing system only allow around 1 CFM of air flow. So, even if you have a 10 CFM pump, it is only going to be operating at 1 CFM anyways!