Shop Solutions: Motion Control Cuts Stone And Cost
Cutting large stone slabs into high-end kitchen countertops, reception desktops, and other beautiful interior and exterior fixtures takes tough machinery and a lot of power and control.
The hardest challenge facing the stonecutting industry isn't cutting through solid marble or granite, however; it's doing so with maximum productivity, precision, and efficient use of raw materials. Recently, leading stonecutting tool builder Advanced Industrial Machinery Inc. (AIM; Hickory, NC) redesigned one of its top products, the MasterJetSaw combination cutting saw/waterjet system, to reduce design/build costs and improve stonecutting throughput and productivity.
To realize these design objectives, AIM incorporated a new drive and control system into the MasterJetSaw: the IndraMotion MTX CNC machine control platform, Profibus remote I/O, and the IndraDrive Mi integrated motor and drive system, all from Bosch Rexroth Corp.'s Electric Drives and Controls technology group.
The MasterJetSaw is designed for high-throughput stonecutting for commercial and residential stone surface applications. Combining a rigid, highaccuracy 20-hp (14.9-kW) rotary cutting head, high-speed diamond-tipped blade, and a 50-hp (37-kW) abrasive waterjet cutter into a single unit, the MasterJetSaw allows fabricators to cut accurately and repeatedly in stone up to 4" (101.6-mm) thick. Most cuts are straight, using the 20-hp (14.9-kW) rotary saw. The waterjet is used for radii, sink cut-outs, holes for pipes and fixtures, and other circular or curved cuts.
AIM worked with Livingston & Haven (Charlotte, NC), a distributor of Bosch Rexroth products, to identify the best solution, and chose to upgrade the machine with the Rexroth IndraMotion MTX CNC platform and the IndraDrive Mi integrated servomotor and drive system, for a complete drive and control solution.
Rexroth's IndraDrive Mi combines a servomotor and drive into a single unit, which is about 50% smaller than conventional systems. By mounting the drive electronics on the motor, instead of in a separate control cabinet, it's possible to dramatically reduce machine footprint and component costs.
Using IndraDrive Mi integrated motors and drives allowed AIM to replace a large freestanding enclosure that previously housed all the servo amplifiers, power supplies, contactors, and other components with two smaller, 24 x 24" (610 x 610-mm) cabinets mounted on the machine. This reduced the overall machine footprint considerably and saved costs on the enclosure.
The IndraDrive Mi's cabling design—with a single combination cable containing both power and Sercos communication—also provided savings. The IndraDrive Mi units are connected in a "daisy-chain" sequence with one cable running to each unit, eliminating the need to run separate power and communication cables from each servomotor back to the control cabinet. For AIM, which uses four IndraDrive Mi units on the MasterJetSaw, this reduced the cabling requirement significantly compared to the previous conventional servo setup.
"Reducing the MasterJetSaw's footprint, component cost, and machine build time were all important goals for us," says AIM President Bob Pharr. "The Rexroth IndraDrive Mi was key to meeting all three. By using the IndraDrive Mi, we cut the machine electrical build time in half," says Pharr.
The IndraDrive Mi also improved the MasterJetSaw's operational efficiency. Previously, the machine utilized an incremental encoder feedback system for position feedback, requiring AIM to use over-travel and home limit switches on each axis. Any time stonecutting was interrupted, each axis had to reset back to "zero" to resume cutting. In addition, holes for the limit switches had to be machined into the steel frame and wired back to the control cabinet, increasing labor and material costs.
IndraDrive Mi offers drive-based absolute encoder feedback, eliminating the need to reset the servomotors anytime cutting is stopped, thereby saving time for fabricators needing to fill orders for countertops. In addition, using the absolute encoder feedback allowed AIM to eliminate 12 proximity sensors previously used for over travel and home switches.
The MasterJetSaw has four axes of motion. The cutting heads are mounted on a gantry for X and Y horizontal motion, the Z axis moves the cutting heads vertically in small increments, and the C axis controls the rotary saw blade.
Circular cuts are the most challenging in stonecutting, including rounded edges, oval and circular holes for sinks and fixtures, and curving details on stone surfaces. Rounded cuts require true closedloop control of multi-axis interpolated motion, a capability of the IndraMotion MTX CNC system.
IndraMotion MTX is a high-productivity machine tool CNC that contains all the components—drives, controller, operator software, and a powerful engineering framework—optimized for machine tool automation. It can support up to 64 axes of motion and 12 independent CNC channels, providing the shortest CNC cycle times and minimum PLC program processing times. This helps tool builders achieve high-speed machining and reduce nonproductive setup and changeover times.
The MasterJetSaw uses the MTX platform running on a Rexroth 15" (381-mm) IndraControl VSP model industrial PC. The controller communicates via Sercos III to a Rexroth 70-A IndraDrive unit and Rexroth KCU unit, from which a single cable system runs carrying DC bus, power, control power, and communication to the integrated motor and drive servo axes.
Being able to deliver true CNC control and having the engineering expertise to make the MTX platform work for the MasterJetSaw were absolutely essential, says Pharr.
"A lot of companies claim they can do controls, but all they can really do is point-to-point process control. Process control and interpolated motion of multiple axes are two totally different things." he says. "Rexroth proved they could cut a radius at high speed, with a high degree of accuracy, and then match that cut with a different tool or a different size, with the highest levels of throughput."
A critical method for getting the most material from each slab is called "nesting." This involves cutting as many different countertops, facings, and other finished products as possible out of one rectangular 6 x 10' (1.8 x 3 m) or 7 x 12' (2 x 3.6-m) slab. It's akin to cutting out the pieces of a jigsaw puzzle.
In the past, tool operators had to leave 3" (76 mm) of space between each piece to be cut, to make sure cuts for one piece didn't end up cutting into another countertop. The MTX precisely controls the movement of the circular saw and waterjet to make sure each piece is cut properly with minimal waste and much greater accuracy. As a result, operators can space parts with much tighter tolerances, cutting more pieces from each slab.
"The parts are accurate to within 0.004–0.005" [0.10–0.13 mm], far more accurate than what's been done in the past," said Pharr. "Because the original cut is more accurate, it speeds up the finishing process."
Pharr adds he was particularly impressed with Rexroth's technical expertise, especially in the area of CNC controllers and complex, multiaxis interpolated motion. "I had a lot of detailed questions about crucial issues such as masses, accelerations, damping, and inertia ratios," says Pharr. "Everyone I dealt with there knows what it takes to make a true CNC platform work—and that made all the difference," he concludes.
Cam Grinding Makes Bikes Go Faster
S&S Cycle (La Crosse, WI) is an enterprise that began in 1958 with founder George Smith's quintessentially American desire "to make all bikes go faster."
Today, S&S Cycle is an internationally known supplier to the performance motorcycle market. It supplies everything from custom air intakes to complete race-winning engines for American v-twin enthusiasts in North America, Europe, Asia, and Australia.
You'll find S&S performance products anywhere in the world where American v-twin-powered bikes are ridden, and that's quite literally everywhere in the world," explains Tim O'Toole, manufacturing engineer. "We supply everything from individual components to complete street-performance and NHRA Pro-Stock Motorcycle racing engines."
By way of bona fides, S&S Cycle's 160-ci Pro Stock engine powered the motorcycle that won the NHRA Pro-Stock Motorcycle championship this year, and the Pro-Stock engine also has won championships in Australia and Europe. S&S Cycle engines can be seen on many bikes from customizers such as West Coast Choppers, Orange County Choppers, Big Bear Choppers, Zero Engineering, Big Dog Motorcycles, and Arlen Ness, among others.
Quality components manufactured to tight tolerances can double the horsepower of a near-stock displacement engine. With the exception of pistons and valves, all the major components of an S&S engine, including camshafts, cylinders, flywheels, connecting rods, heads, and crankcases, are manufactured inhouse at S&S Cycle.
O'Toole explains: "Heads and other components will generally fit a stock engine. Displacement can be changed by replacing the crankshaft assembly or cylinders, and camshafts, carburetors, and fuel injection components can also be upgraded, so that an owner can build a moderately high-performance engine one part at a time."
If the bike owner wants really big power out of a late-model bike, a complete Hot Set Up Kit that includes a new crankshaft, rods, pistons, cylinders, heads, and cam(s) can be added to produce what is essentially a brand new non-stock engine.
When most bike owners get past simple modifications like changing air intakes, they begin the process of a serious horsepower upgrade by installing a new camshaft. "Camshafts are usually one of the first upgrades someone does to their American v-twin engine," says Paul Turgasen, S&S production programmer. "They represent a healthy business for us, outside of their use in our own engines."
To improve its competitive position in the cam market, S&S decided to bring cam production completely in-house by acquiring a cam grinder. "We wanted to get into the camshaft manufacturing business, so we did some investigation into the various machines that are available, and kept getting the same answer. People would either ask us if we had a Landis cam grinder, or tell us that we needed one," O'Toole says.
"Because this was our first experience with cam grinding, we wanted to be involved in the whole process and wanted something built here in the US, not something pieced together from a global basket of components and then adapted to our needs," O'Toole explains. "We also wanted to be able to talk to the people building the machine, and have first-hand contact throughout the process."
S&S ordered a 3L CNC cam and crank grinder from Cinetic Landis Corp. (Hagerstown, MD). The Landis 3L is designed for production cam grinding and is widely used in the automotive industry. The machine features hydrostatic ways and spindle bearings, and linear motor technology.
"Actually, we initially ordered a Landis LT1 grinder," O'Toole says, "but, at the time, we were seriously considering grinding our own crankshafts as well as camshafts, and the 3L model gave us the ability to do that on longer parts than the LT1. As it turned out, we eventually decided not to bring crankshaft grinding in-house just yet, but the 3L gives us that option for the future."
CBN superabrasive wheels are used to grind both lobes and journals on the 3L machine, which has automatic wheel balancing, an acoustic sensing system, and in-process gaging. Cams are ground from billets of 8620 steel, with journal tolerances of ±0.0003" to 0.0005" (0.008–0.013 mm) and lobe tolerances of ± 0.005" (0.13 mm).
The 3L is equipped with a hydraulically powered diaphragm-type chuck and a set of retractable centers designed by Cinetic Landis to meet S&S Cycle's requirements. Journals are ground with the camshaft between centers, and the part is then chucked for the cam profile-grinding operations.
"Most high-volume applications use separate grinders for journals and lobes," O'Toole says, "but it makes more sense for us to grind both journals and lobes on the same machine."
Cinetic Landis' Tetra 4000 software is used to produce control programs for the camshafts. Turgasen says the software "gives us the ability to smooth out the profiles, generate a work speed and feed program, and also do a thermal analysis of the grinding process. All of those things directly impact quality, and Tetra 4000 lets us control them very precisely."
"We have a fully staffed R&D department," notes Dave Jensen R&D engineer. "We can do complete valve-train analysis, camshaft design, and dyno testing in-house, giving us the ability to validate everything we design."
S&S Cycle's manufacturing operations run on a five-day/two-shift schedule to meet demand for their products. That leaves the 3L grinder available for R&D, new product development, and special projects.
"We also use the Tetra 4000 software in our work," Jensen continues. "It helps us create and evaluate experimental lobe profiles quickly. Then the most promising ones are smoothed with Tetra 4000 before we develop the work speed profile for the 3L. It's really efficient."
"Our future plans include expanding beyond the v-twin market to cover more PowerSports applications including other motorcycles, four-cycle snowmobiles, and ATV's of all kinds," O'Toole says.
Tooling Relieves Hydrant Cost Pressure
Anyone who questions the value of attending trade shows might want to take a lesson from the engineers at Kennedy Valve (KV; Elmira, NY).
Kennedy Valve is a 100-year-old, privately held company, currently owned by the McWayne family. It is one of the largest manufacturers of fire hydrants and water valves in the world, employing 400 workers with sales exceeding $125 million.
While attending IMTS, several years ago, Michael Lombardi, a KV manufacturing engineer, made a stop that changed the company's approach to cost savings, time savings, inventory reduction, and overall profitability.
Lombardi's visit to the booth of Walter USA (Waukesha, WI) inspired him to recommend Walter as a tooling source to Chris Hern, another KV engineer. Hern is responsible for designing fixtures, manufacturing solutions, programming machinery, determining proper tooling selections, and managing continuous improvement.
KV's concerns involved reducing costs and inventory, while increasing output and reducing time training machine operators. Working with Competitive Edge Solutions Inc., a local distributor, KV was able to test different tooling products provided by Walter.
The specific part Kennedy wanted help with was a gate valve made from ductile cast iron. The operation involves rough and finished drilling. The number of parts produced is 150,000 a year.
"We had been using carbide drills exclusively for all of our drilling operations," says Hern. "This process amounted to a considerable expense on our part, since we needed to house 180-plus drills in the shop. We knew we could do better, and Walter showed us how."
The initial concern involved the parts themselves. Hern explains: "Solid carbide needs to be pre-set to determine tool length. That takes a lot of time away from actual operation. It also requires a separate tool to exchange used tools, which translates into even more time for the operator as well as additional dollars. Carbide also requires regrinding and re-coating, which is an off-site process. When you add in shipping costs to send products out for these operations, you are looking at even more money heading out the door."
When Walter came in to test some of its products, the results were immediate and dramatic. Paul Lewis of Walter brought in the Xtra-tec B4013 indexible drill and WXK25 inserts.
The large inventory of drills disappeared. Re-grinding and re-coating costs were eliminated, and tracking the tooling—a major headache for KV employees—was over.
"The Walter drill has only one screw where the insert is attached, so change-outs are a snap," Hern says. "Change-outs can be done right at the work station, enabling even entry-level workers to perform this operation in no time."
Hern refers to this operation as "plug and play" capability. The toolholder does not need to be removed from the machine. Operators simply install the new insert and push a single button. This creates an extremely simple and fast process for operators, because time needed for change-outs is significantly reduced.
"Now, instead of 180 tools, we only need about 16, based upon different sizes required for small or larger holes. Cut time has been increased from 68 to 88 min, a 27% increase in tool life."
Hern summarizes the cutting cost savings recognized by Kennedy Valve after the company began using Walter tools for drilling the ductile cast iron gate valve:
Cost per cutting edge was reduced by 36%. The number of components produced per insert increased from 200 to 225. Insert cost per component was reduced by 42%, and annual machining costs were reduced by 13%. In addition, tool change-out costs were reduced. Tool changing time was reduced by two-thirds, and cost per tool change-out was reduced by 66%. Total change-out costs were reduced by 70%.
Because of Xtra-tec's coating on the insert, the new drill and insert increased tool life, which eliminates some tool changes. In addition, the B4013 Xtra-tec drill and WXK25 insert offer a much more stable hold. The screw fit system holds the insert in place more tightly, producing a high-quality, burr-free hole, which, in turn, reduces potential injury to operators working with moving parts.
"We tested similar tools from competitors, but they did not offer the same life of the tool body or the same process reliability. Walter's tooling provides repeatability of surface finish, consistency of holes per insert, better quality of holes produced, and simpler tool changeouts," says Hern.
All of this progress bodes well for the future. Hern explains: "The movement toward different materials such as ductile iron is on-going now, due to its ductile's lighter weight and higher tensile strength. That allows for thinner walls to be made, decreasing weight—and ultimately costs—in terms of material, time, and shipping." Hern also anticipates more global competition in price, which will drive his suppliers to produce even better tooling to meet the demand.
Molding a Press Partnership
Several years ago, production at Stahlin Non-Metallic Enclosures (Belding, MI) on its compression molding presses was running near capacity. The market for its fiberglass composite electrical component enclosures had continued its healthy growth trend.
Stahlin's fiberglass composite enclosures are sold to industrial electrical markets and OEMs that use them for housings for electronic or electrical components. Stahlin, which has been in business for more than 60 years and is owned by Robroy Industries, employs 115. Its plant encompasses 100,000 ft2 (9290-m2) and runs three eight-hour shifts, six days a week, to provide an extensive instock line of non-metallic enclosures and accessories.
The manufacturing plant was originally outfitted with eight compression molding presses designed to mold enclosures. It is equipped with CNC cutting equipment, automated light assembly machines, a compounding facility, and an automatic gasket-dispensing cell. The equipment is used to manufacture all the necessary parts and then assemble them into UL-standards recognized electrical enclosures.
Faced with the continuing prospect of growth, Stahlin's management determined it needed to acquire two new presses to expand molding capacity. "We decided that making the large capital investment for two new presses to address our new capacity needs would help us improve party quality, reduce scrap, and continue to provide customers with high-quality and cost-effective enclosures," explains Jeff Seagle, president.
Equipment must be able to meet long cycle times and operate in a demanding environment. Cycle times are dictated by the thermoset materials, which require long cycle times of 3–4 min for proper curing. The material is then compressed into shape with tools that are heated to 350° F and pressurized.
It isn't uncommon for temperatures to reach 120° F degrees in the plant in summer. Dies and tools are heated to 350° F degrees, and the atmosphere can become dusty and grimy. Parts that are being manufactured weigh 30–40 lb (13.6–18 kg).
After several months of evaluating suppliers, Stahlin selected Greenerd Press and Machine Co. (Nashua, NH) to design and build two compression molding presses. Stahlin felt the presses would meet their requirements, but what won them over was Greenerd's commitment to addressing all of their design concerns from potential oil leaks to tooling up and unloading parts from the press.
The two Greenerd 400-ton hydraulic compression molding presses that Stahlin purchased in 2007 are credited with significantly improving Stahlin's production capabilities and flexibility, principally because of their large tonnage and bed size. These new machines are capable of running 90% of all Stahlin molding tools and are easier to operate.
Greenerd's compression-molding series features their proven 4 Post design, which minimizes deflection and ensures consistent die alignment. It also enables loading of the press from any of four sides, and permits easy integration into production lines or manufacturing cells.
Press controls allow the operator to easily adjust press tonnage ranges for running a wider variety of molds for greater production flexibility and reducing scrap. "Adjusting the press speed is easy compared with manually controlled hydraulic presses that required mechanical adjustment," comments Dean Childs, composites supervisor.
According to Childs, pressing is a delicate balance of speed and control. If you don't press fast enough, the material can start to cure. If you press too fast, the paste runs out to the edge with excess resin, and the fiberglass isn't carried out to the edge of the mold like it should be. Either way, the part is scrap.
"We've gotten much better quality control results with the Greenerd presses and have reduced scrap on those presses by at least 20% over the older manually controlled hydraulic presses we were using," comments Childs.
"The machines have expanded our capacity and have delivered good, reliable performance with no major issues. We're very pleased with Greenerd's support through the acquisition, installation and follow-up processes. We feel we have a true partner," Seagle concludes.
This article was first published in the December 2008 edition of Manufacturing Engineering magazine.