Lasercutters don’t require hold-down methods for the materials, whereas CNC mills, spinning at tens of thousands of RPMs, do. What about waterjet cutters? There might not be any rotational forces, but there is still tens of thousands of PSI firing straight downwards.
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That’s one thing that occurred to me as I watched this video of a waterjet cutting through a glass sheet. Posted by manufacturer Wardjet, it shows one of their machines cutting a spiral into a sheet of glass, which then allows the remaining material to be pulled into a deep bowl:
Here’s what the cutting action looks like:
So how did they hold the sheet down, and what did they use as a spoilboard?
“It is recommended that a soft yet sturdy sacrificial material such as wood, foam, or drywall be placed between the cutting table and a glass workpiece,” the company writes.
“This will provide an even foundation for the workpiece, prevent damage from contact with the metal cutting table, and reduce frosting on the underside of the glass due to the abrasive reflecting off of the support grates.”
As for the holddown, they only used two clamps at diagonally opposite corners.
“Place a soft buffer material between the workpiece and the clamp to prevent damage,” they recommend.
After your hold-down setup is complete, there’s still plenty of tweaking to be done to the set-up. When cutting glass, you’ve got to keep the jet moving (in the X/Y axes) at such a speed that it does not transmit downward force to too large an area of the glass at once, or you risk shattering the thing. You’ve also got to tweak the abrasive flow, and program your toolpaths so that the head starts moving before the jet and abrasive begin to flow, or again, you’ll risk shattering the workpiece.
There are plenty of details like this, and more, at Wardjet’s tutorial on waterjet glass cutting. And if you manage to master all of these, you’ll have the ability to wield quite the versatile digital fabrication tool. “There aren’t many other machines,” the company justifiably brags, “that allow you to go from slicing through 12 inches of solid titanium to making precision cuts in 1 mm glass sheet without changing any tooling.”