CNC VACUUM JIGS
and how to use and make them
This is an example of an in-house made vacuum jig.
It was designed to hold down 10 pieces of solid timber
for machining circles. Five pieces per board.
An Overview
I did my trade prior to CNC Routers when Overhead Routers were very popular. So this is where I learnt about making and designing vacuum jigs. At the time, if pumps were not standard on a router it was always available as an option extra. As a side not, while Overhead Routers have taken aback seat, I think they are now under rated and are still a very versatile machine.
The Basics
CNC Vacuum Jigs are an awesome way to hold your workpiece down while routing. We are not taking about the vacuum table normally associated with a flatbed or even a pod and rail machine. No, we are talking jigs that can hold even the smaller piece down. Either one or multiple. I hear you saying, “why not use a pod system?’ The answer is “home made” vacuum jigs are much more versatile and way cheaper. You just need some scrap plywood and some ⌀6mm round insertion rubber. In Australia available from Clark Rubber.
The Vacuum Pump
There are two way to achieve the end result. One is by using a vacuum pump which you can purchase online or from a specialty store. There are two types. The cheaper ones available on eBay Etc. utilise oil and work fine but just probably won’t last a long time. The other type are carbon vein which will pull a greater vacuum but cost a lot more. In either case if you are only doing one or two parts at a time you don’t need anything too powerful. In my experience 2.5CFM to 3CFM per minute works fine. Certainly nothing like the power of a vacuum pump on a flat bed.
How To
The first method is if you do not have a vacuum bed or want to save a bit of electricity by not running you power hungry built in vac pump.
- Build a box with four side and a top. Open at the bottom to allow a small diameter air hose to come up under the pattern. The pattern then sits on top of the box and you mechanically fasten the box to the CNC table. this method is also handy when you are machining limited number of a small piece.
- Method two involves using you machine’s built in vac pump (if you have one). Configure it using the insertion rubber to hold down your pattern as if it were any other piece of flat material. As in the above photo, once you start your pump the air is drawn down through the center holes in the pattern allowing the timber sitting on top to be held down on the rubber. Note the “bow” shaped trenches machined in the pattern. The shape is not important but having them is very. They are there to allow the air to flow freely down the center hole from all parts of the jig . The last thing you want is the workpieced blocking the center hole. If this happens the job will let go and damage to the cutter can occur
Hopefully you will gain some insite from this information and it will translate to faster change over and therefore production times. If you have any questions please drop me a line.
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