Find new ways to put your CNC to work

The bane of small shops has always been scheduling. We work in waves. We’re either too busy or too slow. Adding CNC capabilities often helps ease part of the problem as production can be increased to smooth out the busy months. But those slow times still show up, often in winter months, and now it’s not just the crew that are idle: there’s also an expensive CNC router just sitting there, not paying its rent.

Well, that machine could actually hold an opportunity to explore some interesting options. It doesn’t just mill parts from plywood: it can also do a lot of other things. For example, ShopBot sells a pen bit ($39.95), made by WidgetWorks Unlimited, that converts a CNC router into a plotter. It will draw designs and logos or print large-scale parts to scale so visual checks can be made before any cuts are plowed into expensive material. It will also label parts so they can be oriented properly during assembly. The pen can locate screw holes, drawer slides and other hardware in-house. It can even be used to deliver instructions for RTA casework, where a client is doing that task onsite.

And, in slow times, plotting can be used to do work unrelated to cabinetmaking. The ability to both print and cut in fine detail allows a woodshop to get quite creative. It could, for example, partner up with retailers to create kits such as knockdown dinosaurs and simple model airplanes for museums or gift shops or perhaps wine racks for vineyards. Plotters can work with wood, paper, cardboard, plastics and foam, plus a host of other flat, ink-receptive materials. That opens up a number of creative possibilities and new customers can probably be found in local sign shops, advertising specialty suppliers and other image-related businesses.

Replacing the cutter with a drag knife bit ($149.99 from ShopBot) lets a woodshop think about expanding into the sign market. A drag knife can create adhesive-backed vinyl, paper, cardboard and thin-plastics cutouts. When married to the right software, it can be used to create vehicle graphics, professional-quality signs, banners, magnets or parts from thin plastics. The bit, also made by WidgetWorks, holds a carbide knife that swivels as the router drags it around the design and it can cut through vinyl without cutting through its wax paper backing.

For cabinet shops and furniture builders that work with sheet metals, a CNC can also do engraving. ShopBot offers a diamond drag bit that will engrave plastic, metal, glass and stone. That opens the possibility of doing sub work for local trophy and plaque suppliers or even adding brass engraving and wood plaque making to the shop’s furniture and casework capabilities.

From coast to coast

All across the continent, innovative small shops are branching out from casework by adding specialty tooling to CNC routers. It lets them enter whole new market sectors and keep their crews — and their CNC — fully employed year-round.

CNCROi.com is a fabrication and engraving shop in Saint Catharines Thorold, Ontario. The founder, Jonathon Cantin, is a published author, model designer and professional CNC machine operator who has been passionate about the industry for more than two decades. His company offers standard laser and router services, but also uses special CNC tooling to do imaginative things such as create custom Corian cutting boards, commercial jigs, cake toppers, name badges, stamps and seals, wood and plastic models, and trade-show tabletop displays.

JW Machine of Orlando, Fla., is using its CNC tooling capabilities to engrave serial numbers, bar codes and brands on wood, acrylic, plastic, aluminum, stainless steel and other materials for customers as varied as the U.S. Department of Defense and Cadillac. And in West Jordan, Utah, the staff at S&S Manufacturing can do all the big jobs, but also use the shop’s CNC tools to make everything from custom aluminum coasters to trailer hitch covers.

Tooling know-how

If your woodshop is as busy as it needs to be and the CNC is fully occupied making casework parts, then your biggest concern is probably getting the most from existing tools. What’s going to last longest, hold a great edge, cut cleanest and deliver consistent and vibration-free results?

It doesn’t take long to discover that there are literally hundreds of tungsten-carbide grades out there with no true industrywide rules. A “C” grade from one supplier isn’t always the same thing as the same grade from another. How can a woodshop spec what it needs if there are no uniform standards? One can ask a supplier to deliver a certain grade of carbide in an insert or cutter, but there’s no guarantee that the edge will be as fine or as enduring as another one — even from the same warehouse — that has the exact same grading. That’s because some tool suppliers shop around.

“Tungsten carbide from two different manufacturers may have identical designation, but vary widely in almost every imaginable way, including performance,” says Tom Walz of Carbide Processors in Tacoma, Wash.

CNC tooling edges are a delicate dance between hardness and brittleness and that’s an issue for woodshops where consistency is important. Dialing up the best formula has been an ongoing challenge since tungsten was discovered back in 1781, so if you find a supplier you like, don’t be in a hurry to change when somebody else offers a slightly lower price. The two tools might look alike and be described alike, but might not perform alike.

Once a tool supplier has been selected, there are some attributes to consider when placing orders. In most cases a shorter tool (and that includes both the exposed shaft and the cutter) is a better choice in terms of both tensile/shear strength and deflection. It also puts less strain on the machine because the work takes place closer to the spindle. If all the cuts being made are in 5/8” stock, there’s usually no need for a 2” long blade. The farther the tip of a tool has to extend from the chuck, the more likely it will deflect slightly. It’s the principle of the lever: if you add a “handle” that elongates the bit, then there is more pressure at the base.

The same concept governs how cutters are housed in the collet. Bottoming out (seating the shaft all the way in) can cause vibration problems, but so can setting a cutter with too little of the shaft enclosed and solidly gripped by the collet. A “loose” tool can definitely lead to deflection problems.

Length can obviously be constricted, but width probably shouldn’t be. Depending on the parts being milled and the radii of inside corners that need to be milled, a thicker tool (that is, one with a larger diameter) can often be a better choice. There are subtle forces at work here: more metal usually means a little less heat as there’s a better sink and it almost always means more strength and resistance to deflection. However, there is a point of diminishing returns: a larger cutter is doing more work, so it will generate more resistance. Slowing down the speed of travel could be an option.

Take a look at travel direction, too. In complex parts, there are often quite a few short climb cuts and these backing-up maneuvers can leave one edge of the cut a bit ragged, and even show burn residue. That’s because the cutters are essentially spinning backward here. Up-cut and down-spiral bits might help and plotting the path can have an effect. If your dust collection isn’t all it should be, reworking paths can also cause the bit to work harder as it has to plow through the same material twice.

Speaking of dust and CNC tooling, the AirPro from Techniks is a handy little device that removes virtually all of the dust from nested cutting operations. It just replaces the collet nut and the waste is ventilated directly into the CNC’s dust collection hood. There’s a video at www.techniksusa.com.

This article originally appeared in the April 2016 issue.