- Fixture Plates are a non-porous, semi-sacrificial surface that sits between your AirWeights vacuum table and your stock. It is meant to be cut into, allowing you to cut completely through your stock and leaving you with finished parts at the end of your program. This method provides the same level of holding force as direct mounting, but with the added benefit of cutting completely through.
- Gasket material is used on the top surface of the Fixture Plate to create sealed vacuum zones that sit within the boundary of your finished part(s). These zones must also account for any internal areas that are cut completely through, such as an internal hole. The basic rule is that there must be a seal anywhere that is completely cut through.
- There are 3 primary approaches to creating vacuum zones on a fixture plate.
Adhesive backed gasket can be recessed in a channel (commonly called in-board gasket), which should be 1/4" wide and .065" to .085" [1.65 to 2.16 mm] deep for the adhesive gasket sold by AirWeights. With the in-board approach, air channels must also be cut into the fixture plate within the gasket boundary to allow air to disperse underneath the material being held.
Adhesive backed gasket can also be used directly on top of the fixture plate (commonly called on-board gasket). Simply use the CNC to trace the outline of your part at a shallow depth, then install the gasket on the interior of that profile and drill a hole in the center. This method is demonstrated in the video below and is great for quick projects and thick stock. In some cases, the stock will float on top of the gasket, allowing complete cut-through capability without cutting into the fixture plate. - Finally, a continuous sheet of gasket material (commonly called cover gasket) can be applied to the entire top surface of the fixture plate. To create the required vacuum zones, an engraving bit is used to cut away the unwanted gasket material and create vacuum zones under each part position. This approach is great for very small and intricate parts that are otherwise very challenging to hold or require secondary processes.
All 3 of these options are valid solutions for fixture plates. - Within the sealed regions, there must also be hole for a vacuum inlet. Place a .400” [10.2 mm] diameter hole so it aligns with a channel in the AirWeights grid underneath, while still being close to centered within the gasket boundary. Smaller holes may be required for very small parts and are acceptable in those cases. Machine the holes last when making your fixture plate and DO NOT CUT THROUGH or pressure will release, your fixture plate may come loose and you may damage your AW by cutting into it. Use a drill, countersink or razor blade from the backside to break through the thin onion skin left at each vacuum inlet location.