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Cut Quality From Various Cutting Tools - Part 4 -Wet vs. Dry Cutting & Sanding/Finalizing Cut

May 3rd 2021

In the last installment of this series we focus on Wet vs Dry Cutting and then finishing off your composite parts.

Wet vs. Dry Cutting

When given the option, wet cutting of a laminate offers the advantage of keeping a laminate’s surface cool during cut. In industry today, CNC routers use coolants to aid when cutting through laminates during machining. Keeping the laminates surface cool makes all the difference when cutting larger and thicker laminates. Water is generally used as a coolant and will also aid in keeping dust away from the cutting surface and surrounding areas in which people may be exposed to inhalation hazards. Although other coolants may be used, water is generally an industry choice due to other coolants’ possibility of introducing contaminants to the part, especially in secondary bonding processes. Coolants with any rust inhibitor should not be used as they will degrade Carbon Fiber.

There are challenges to wet cutting a composite, such as an efficient means of supplying water to the surface of the laminate. “Spraying” water onto the surface while cutting is neither efficient nor safe. To overcome this obstacle, wet blade cutting kits are available as an addition to most grinders or right-angle sanders. Some minimal modifications may have to be made to existing rotary tools. However, this will ensure the most efficient cut and prolong the life of cutting blades.

Sanding & Finalizing Cuts

After utilizing the cutting blade to get a near net cut, wet sand the laminate edges with a fine grit sandpaper or light abrasive pad to achieve final part dimensions. Wet sanding can be performed by hand or with a right-angle grinder /pencil grinder attached with circular sanding disk or other media such as “scotch brite” red, gray, or white. Grit size may vary slightly per user, but for part quality ~600 grit is a good starting point. Use of a hand block sander in a back and forth motion will aid in this process when detail is needed for tighter dimensional tolerances. Wet sanding edges will keep heat away from the laminate edge to prevent possible delamination of cured edges and mitigate dulling of blades / bits. Larger “sanding wheels” may also be used as needed but are stationary and are limited by mobility for use.

Scotch Brite Bits

Circular scotch brite bits can be used with right angle grinders / sanders to sand away small areas during finish sanding. These bits are commonly screwed into the end of right-angle grinders. Scotch brite pads come in assorted grit and diameter sizes. Some are made for high abrasive content (usually red in color) and others that are less abrasive and can be used when only needing to touch up given areas or provide differing surface finishes for prep on laminate surfaces (usually green / white / grey in color).