G.H. Tool & Mold

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Auto Castings Fuel Shop’s High-Performance Machining The lighter automobiles become, the heavier the workload gets at G. H. Tool & Mold. The Washington, Mo., business specializes in aluminum die cast molds, serving practically all the major automakers. And as those companies continue to reduce the weight of cars in efforts to lower emissions and conserve fuel, they do so by incorporating more die cast components as opposed to stamped ones. Automotive work makes up over 90 percent of G. H. Tool & Mold’s output, and in the past, the 150-person shop produced molds mostly for housing-type parts for power transfer components, valve bodies, alternators and others. But over the past couple of years, the shop has manufactured an equal number of molds for structural and suspension components as well. The design-to-order company produces complete die cast molds and replacement parts for existing molds in the field. Job lot sizes are between one and 10 parts, most of which are made from a superior grade tool steel. Part machining cycle times vary anywhere from 30 minutes to eight hours, and tolerances typically run between +/- 0.0005 to 0.002”. Service parts for molds usually takes five weeks to finish, while a complete mold is done in as little as 10 weeks. To fulfill increased demand from its automotive customers, G. H. Tool & Mold relies heavily on Mikron high-speed milling machines along with a recently acquired Mikron highperformance 5-axis milling machine, all from GF Machining Solutions (formerly GF AgieCharmilles) and acquired through distributor Hartwig Inc. in St. Louis. These systems deliver the speed, accuracy and surface finish capability the shop needs to produce its high-quality precision molds in the shortest amount of time possible. G.H. Tool & Mold has three Mikron HSM (high-speed machining) 800 milling machines that sport 36,000-rpm spindles and two HSM 500s with 42,000-rpm spindles. With these 3-axis machines, the shop takes quick, light cuts using small diameter cutters at high feedrates to shorten overall part cycle times. The newer 5-axis machine is a Mikron HPM (high-performance machining) 800U-HD (High Dynamics) with a 20,000- rpm spindle, 60-tool storage capacity and more power for aggressive cuts – in both roughing and finishing operations. The machine’s High Dynamics technology delivers 1G machine acceleration rates, and the machine rapid traverses at 1,771.7 ipm in the X and Y axes and at 1,378 ipm in Z. The HPM 800U-HD’s Step-Tec HSK A63 in-line spindle generates 63.7 ft-lbs of torque at 4,450 rpm for high metal removal rates, while also providing the fast spindle speeds necessary for producing superior part surface finishes. It incorporates oil-lubricated ceramic hybrid bearings and is vector-controlled, enabling thread cutting without the use of a compensating chuck. According to Danny Straatmann, programming manager at G. H. Tool & Mold, the shop does practically all of its really critical machining on the Mikrons. They are the shop’s “fast movers,” he said, for lighter smaller components and for both soft and hard machining – typically around 46-48 Rc. Their speed, along with accuracy and rigidity, result in far better surface finishes, and hard machining capability allows G. H. Tool & Mold to mill parts to finished size from hardened materials, thus reducing the amount of die-sinking electrical discharge machining time required. The Mikron machines get their extraordinary rigidity from a special base material, yet they require no foundation. GF Machining Solutions constructs its monobloc (single-casting) machine bases from polymer granite that possesses extremely high vibration-dampening properties, providing strength and rigidity essential for high-speed, high-performance machining. Single-casting constructions of the Mikron machines also ensure machining accuracy and better thermal stability for excellent workpiece surface quality and minimal tool wear. Additionally, GF Machining Solutions outfits the machines
Whenever possible, the shop uses modular-type fixturing and workholding systems from System 3R on its Mikron machines. The modular systems make it possible to easily move parts from one machine to another. In addition to speed and rigidity, Straatmann pointed out that ease of programming and control functionality are other key benefits of the Mikron. For example, the shop’s HPM 800U-HD features GF Machining Solutions’ Smart Machine functions. These include spindle vibration control, crash protection and monitoring. Smart Machine functions detect any imbalance in cutting tools, including instances where an operator improperly balances a tool for high-speed machining. An unbalanced tool can damage the machine’s spindle as well as ruin parts that have undergone several valuable processing hours. with absolute optical linear glass scales on the X, Y and Z axes that operate with a measuring step of 0.02 µm to guarantee unmatched positioning precision. For its first foray into 5-axis machining, G. H. Tool & Mold acquired two larger sized machines that achieved 5-axis capability through spindle movement. These head/head-configured machines, according to Straatmann, were fine for long narrow parts, but fell short when it came to smaller more intricate work. “Often, with the two original machines, we’d have to reposition parts to access certain features needing to be machined,” explained Straatmann. “Plus, the spindle heads on these machines – because they provide the 5-axis movement – are really big, which lessens their agility and reach capability. Our HPM 800U-HD, on the other hand, achieves simultaneous 5-axis motion through its tilt/rotary table. This configuration moves the part around the spindle as opposed to moving the spindle around the part. And because there is much less mass to move around, the Mikron is an extremely faster and much more accurate machine.” The shop can also run shorter tooling on the Mikron – due to its rotary/tilt table configuration – and thus easily access deep, intricate part cavities. Plus, the table eliminates any issues associated with long tooling overhangs. The function basically monitors G acceleration and shops, such as G. H. Tool & Mold, can set a specific level between 1 and 12 Gs. So, if the spindle reaches the specified force level, the machine will automatically stop the process or initiate a tool change to a properly balanced tool. Besides fast spindle and axis speeds, a special tool changer on the HPM 800U-HD also contributes to shorter part cycle times at G. H. Tool & Mold. The changer is designed/mounted at an angle, which places it closer to the spindle at one end. Instead of the tool magazine being straight along the side of the machine, it angles inside closer to the spindle. This shortens the distance the spindle must travel for a tool change, resulting in faster tool changes and reduced non-cut times. Plus, the changer’s door will only close if tools are the proper length. So if a tool is longer than the machine can accommodate, the tool magazine door will not close. Advanced machine designs and features, such as those on the Mikron machines, enable G. H. Tool & Mold to further shorten its die cast mold turnaround times and remain a go-to shop for major automakers. And according to Straatmann, continuously implementing new ways to boost efficiency and productivity are essential for keeping pace with the surging automotive industry. As a result, G.H. Tool & Mold was able to transition many of its smaller intricate parts from the older 5-axis machines to the Mikron. And for many of those parts, the HPM 800U-HD not only improved surface finish quality, but also slashed average machining cycle times by half. “We did look at other brands of machines, but cost-effectiveness and machine performance, along with service and support from both GF Machining Solutions and Hartwig, convinced us to stay with Mikron. Every part run on our older 5-axis machines has undergone evaluation, and we now run many of them on the HPM 800U-HD. If it fits within the machine travels, we run it on that machine.”
Page 1: Success Story: G.H. Tool & Mold EDM

G.H. Tool & Mold

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