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Cut Quality From Various Cutting Tools - Part 3 - Jig Saws & Waterjets

Apr 26th 2021

In the second to last post in this series we review two items that couldn't be farther part in their nature. One is most likely in your garage, one is most definitely not (unless you have a really awesome garage).

Jig Saws

Although primarily used best in wood cutting applications jig saws are also an option for cutting fabricated laminates. Challenges with Jig saw on a composite application are that they are prone to cause edge damage on laminates due to a back and forth motion while cutting. A rotary cutting tool has a higher surface area in which the cutting surface can dissipate heat as the smaller surface area of a jig saw blade does not. This lack of surface causes the cutting blades to heat at a faster rate. This heat is transferred to the laminate and can cause edge delamination. Without the use of special composite cutting blades or use of metal cutting blades, a jig saw will not cut a composite effectively. Even with carbide grit blades made for cutting composites, service of a jig saw is still mostly limited to flat sheets. When using a jig saw, it is advised to cut well beyond the desired final edge of the part and sand down the laminate to the desired cut line. Use of a 60-80 grit diamond or carbide abrasive blade will yield the best results when choosing to cut with a jig saw. In addition, a jig saw equipped with a vacuum attached to it or close by will help control dust.

Body saws, or saws-alls are very similar to Jig saws. A simple back and forth motion of a blade contacts the part. It shares the same advantages and disadvantages as the jig saw although more complex parts can be cut from a body saw as it is not fixed such that as a jig saw is. The blades instead come out of the tool parallel instead of perpendicular to the tool's surface.

Waterjet

A waterjet cut provides a cut from a finely adjusted abrasive line of water with additives to aid in the cutting process. A waterjet is known to minimize time for secondary finishing and allow a high variation in the different thicknesses it can cut through. Rather than friction cutting, a water jet abrasive cut mitigates opportunities for delamination. Programming allows for tight dimensional tolerancing throughout cuts at hard angles and can lower costs associated with trim tools. A waterjet will usually produce a smoother finish than that of rotary tools as its surface speed is much higher. Waterjets are commonly used to cut ~95% of a laminate's dimensional criteria. However, machining processes such as countersinking, drilling, and surface milling are outside of the waterjet's scope.

Pierce through delamination issues can occur when initially cutting a "window" or larger hole out of a given laminate. In order to eliminate this problem, a "starter" or pilot hole should be mechanically drilled before making the cut through. Afterword, the waterjet can be placed into the pilot area for cutting to resume. Upfront costs associated with buying and commissioning a waterjet will be at least $5000 for a desktop version but can go up to more than $200k on more advanced 5-axis machining models.