Eight heads are better than one

If you’ve only got two hands, you might dream of being an octopus. If you’re a stone edge/polish machine with one spindle head, and you have to make repeated pass/returns and bit changes over each slab, you may dream about getting six or seven more heads, making the stone get up and move around, and saving loads of time, too.

To help make this dream come true, Park Industries in St. Cloud, Minn., recently spent two years developing its Velocity decorative edge shaper/polisher machine for natural stone and stone-like materials. These usually include granite, marble, limestone, bluestone, and various quartz-and-glue combinations, including Silestone, Cambria, and Zodiac.

The new machine uses a conveyor to present 3x6 or 3x8 ft slabs of granite to a bank of 13 spindles driving one cutting/shaping head and seven polishing heads, which move in and out at 190º around the edge of the slab. These heads are directed by cam profiles and functions in a motion controller to produce six or more different decorative edges. Though there’s unlimited room for adjustment, the machine produces all of the seven to 10 industry-standard convex shapes needed by the countertop market.

“Traditional methods evolved from powered hand-tools that moved around fixed slabs to single-head CNC polishers that also moved around fixed slabs,” says Craig Kurvers, Park’s sales and marketing vice president. “This would take seven, eight, or more separate passes, and would require frequent bit changes to progressively finer tools to reach a polished edge.”

Unfortunately, this process takes a long time, and Park reports its customers no longer have time to wait. “The demand for stone and stone-like products has been growing fast for the last several years,” add Kurvers. “It used to be that only 8% of builders were using it, but now 20-30% of them are doing so. More people are putting countertops and other fixtures in kitchens and baths, but they’re also adding them to bars, showers, staircases, outdoor entertainment centers, BBQ centers, and swimming pools.”

Kurvers says high-volume shaping and polishing has been available in Europe for several years, but now his customers are pushing through 100 kitchens per week, and they need to do it with more efficient production and reduced labor. “This is why the fabricators we sell to have been looking for much higher production rates, and they want to achieve it by increasing automation,” says Kurvers.

     STONE COLD ON THE EDGE

One cutting and eight polishing heads are directed by cam profiles that combine to make them about 10 times faster than traditional edge/polishing methods.

As a result, Park uses Siemens E&A Simotion controllers to create cam profiles for Velocity’s three required motion axes, with communications carried out via Profibus. One axis handles the ball-screw linear actuator on the edging/cutting head. The second manages the bank of spindle heads on their frame, which is pushed pneumatically against each slab. The third cam runs the conveyor. Tim Keough, Siemens’ motion control business developer, says the master cam works with the polish spindles, while the slave cam works with cutting head’s actuator.

Adjustments for stone type, thickness, and desired finish are entered on-screen into Velocity’s programming, where they join directives for conveyor speed, spindle motor selection, hold-down functions, and restart. Once a selected profile is called up, the machine produces a shaped and polished edge in one pass, and the conveyor keeps the machine continuously loaded. Diagnostics and production data are sent to a database, which Park can access to remotely assist its users.    

“The programming also lets Velocity collectively adjust for several variables to achieve the best finish,” adds Kurvers. “The challenge is regulating all these factors at the same time in a way that relatively lower-skilled operators can run it.”

Keough estimates that Velocity’s operation is about four times faster than traditional edge/polishing technologies. “Not only is there a huge time savings, but there’s little or no downtime because the operator just picks the next program change,” he says. “Labor is further minimized because the operator doesn’t have to constantly monitor the machine, but can do some other tasks, too.”