Vacuum bagging is a commonly used technique in composites, and for good reason. When done correctly, your part will have a nice, uniformly distributed compression about the surface of the layup. This in turn helps to minimize any voids (e.g. bubbles and wrinkles) in the buildup of layers. Also, when used with a porous substrate made of peel-ply and breather-cloth as we'll see, it assists in having the optimal ratio of resin to reinforcement (e.g fiberglass, or carbon fiber, or Kevlar) by squeezing out the excess.
The project is quite simple for illustrative purposes. I'm making a small container from a mold of a nice tea container lid. I'll go over the steps to make this part, but the vacuum bagging phase is what this topic is about, so we'll be delving into that a bit more thoroughly.
First, a few suppliers that I've had quite good success with:
Fibreglast dot com - Lots of supplies for the intrepid.
Aerospace Composite Products - They also had the check valve and bag attachment and 1/4" neoprene tubing used in DrCrash's vacuum tool, and very personable customer service.
Tap Plastics While they don't have much for vacuum bagging, it's still a worth while source to mention with all their instructional material and from my experience, good staff.
USPlastics Is also well known supplier.
Both TapPlastics and Fiberglast have some very good instructional material that is invaluable for someone learning about new techniques.
Step 1: Ingredients
Check Valve Only allows air to pass one way in the vacuum line. The one available at ACP appears to be for an aquarium (brand name tetra), but it works okay.
1/4" neoprene tubing Acts as the vacuum line.
Tubing clamp holds the air out of the line once the vacuum has been set
Bag Connector securely attaches the hose to the bag.
ACP has all the parts that I used to make the pump.
For the bag:
Bagging Plastic The stuff I'm using is made of stretchy and resilient plastic, and it comes in 60" wide rolls, that you can purchase by the yard from the suppliers that I mention.
Bagging tape is a ribbon of pliable and sticky material that's coiled up on itself such that one side is covered with removable wax paper. You could probably use window caulking, too.
Peel-Ply is a plastic fabric that wont stick to your layup but allows resin to seep through.
Breather Cloth Is a high-loft material placed on the outside of the Peel Ply to absorb the resin and allow the vacuum to be passed uniformly over the surface of the layup.
Knife or Scissors The bagging material is kind of hard to cut; I've found a good rotary cutter works best.
Masking Tape Holds the peelply and breather cloth together when wrapping the layup. Also good for holding down the vacuum bag plastic when making the bag
Straight edge for measuring and will help hold the bag down when sealing the edges.
Cutting mat also handy. I got this one made by Fiskars, but I found that the rotary cutter can slice through the top layer :(