Sprune Remover

Craig Machinery Retrofits Tormach’s Personal Mill for 24/7 Automation

Craig Machinery & Design has a reputation for solving problems in the world of plastics reproduction. The company devises a full assembly line of workstations to maximize the efficiency of its client’s manufacturing. Recently, Craig Machinery successfully adopted a new CNC technology to fill a common gap in plastics automation.

The gap in this case involves the problem of sprue. “We were getting requests from companies to de-gate plastics,” says company owner Craig Rabeneck. “In other words, when a product comes off the mold often times there’s a sprue that has to be cut off. In this particular case, the company had a sprue that had to be machined off.”

Sprue is waste plastic material created during the injection molding process. The most recognizable example of sprue would be in a kid’s model airplane. Out of the box, the small plastic parts come on a single wiry maze of plastic. The propellers or landing gears have to be cut off the connective tabs. For many kinds of consumer products, this network of plastic sprue needs to be cleanly cut before the components are assembled and packaged.

Rabeneck’s client, a plastics fabricator making clothes-washer parts for a major appliance manufacturer, had been trimming its components with a small CNC router system. “Small desktop-sized routers are typically used for this job, but they don’t hold up when doing large volumes,” explains Rabeneck. The customer’s injection molding press ran 24-hours, seven days a week. Hobby shop routers are very inexpensively constructed, according to Rabeneck, leading the motors to quickly burn out under constant wear.

For a solution, Craig Machinery turned to an innovative new product released only about a year ago. Tormach built a mill to fill different gap – the one in the CNC market itself. In the past, buyers had a choice between two extremes: either a $100,000+ industrial-sized CNC mill used for high-speed manufacturing, or tiny “hobby” CNC machines which were inexpensive, but severely lacking in power and rigidity.

The Tormach PCNC 1100 was especially designed as an entry level mill. At 1500 lbs it’s small enough to operate on single phase current and move about with a pallet jack, but stiff enough to tackle the toughest materials. Operating on industry standard codes, the machine is easy to operate, and at only $6800, the new Tormach mill makes entry into automated manufacturing easier than ever before.

“Long term cost of ownership is a big part of affordability. In order to create an affordable machine we realized early on that the machine needed to be user serviceable. We made the control system simple and robust so there is no need to depend on expensive field service. Most anyone who can use a voltmeter can service the mill,” says Greg Jackson, CEO of Tormach and developer of the design. “It turns out that the same attributes that make it user-serviceable also make it easy for integrators to modify the machine to meet their own needs. By applying concepts of open architecture design, using a configurable control program and standard electrical components, we’re finding the mill has attracted interest from custom automation integrators.”

Rabeneck is one of the creative integrators, building on the platform that Tormach has created. “We took the Tormach mill and modified it for production use.” Craig Machinery dedicated two machines, one for each of the washing machine parts that needed de-gating. “You hit the palm button, and it will always cut the same pattern that's CNC programmed.”

Setting the desired 3-axis cutting paths to was only the start of the automation: Rabeneck fitted the mill with all the hardware controls native to a factory environment. “We added the fixture, the auto-clamping, the start button, and a vacuum system to remove the chips.” Further modifications, like a light curtain, were installed to ensure operator safety.

“We put in a PLC [Programmable Logic Controller], which monitors the stop button, sends the signals to clamp the part, vacuum, and control the spindle head. After the machine performs the 3D CNC work, the computer gives the controller a signal that the work is done. A light on the front of the electrical box then indicates to the operator that it’s ok to put his hand back in there and remove the material,” Rabeneck explains. “We also upgraded the servo drive on the spindle head, so whenever a hand breaks the light curtain the servo motions and the spindle comes to a quick stop.”

Craig Machinery tuned the he customized Tormach workstation down to only a 20-second cycle to remove all the sprue from the sheet of plastic washer components. “The Tormach is more of a beefy animal for what we were doing. We’re taking advantage of the heavy cast base, the quick lubricating system, the robust motor, and obviously the automatic 3 axis CNC. We’ve just upgraded the mill to be more of a production machine with the extra operator safety features.”

“Although our design wasn’t intended for mass-manufacturing, we’re certainly pleased to see the Tormach PCNC 1100 able to take over some of the peripheral tasks on the factory floor,’ comments Jackson. “Manufacturers can now achieve reliable CNC automation at only a fraction of the capital investment.”

Craig Machinery is preparing more customizations, as Rabeneck sees potential applications for the affordable CNC mill in other areas of injection molding industry. “The PCNC model was a nice easy package to set up,” he says. “Pricewise, we were able to buy that machine, do the modifications, and end up saving the customer some money.”

About Craig Machinery and Design, Inc.

Since 1977, Craig Machinery & Design, Inc. has designed and built automation machinery for the plastics industry. With the experience to handle automation needs from small ultrasonic welding fixtures to large multi-headed rotary index table systems, Craig Machinery can set up production system from start to finish.. The company also specializes in electrical controls, including control wiring and panel layout design, as well as PLC and touch-screen programming. To see a catalog of equipment available and for a list of custom services, please visit: www.craigmachinery.com.