Tool upgrades boost lightweight auto parts production

Lighter automobiles are creating heavier workloads at G.H. Tool & Mold. The Washington, Mo., business specializes in aluminum die-cast molds, serving practically all the major automakers. As companies reduce vehicle weights to lower emissions and conserve fuel, die-cast components are becoming popular alternatives to stamped ones.

Automotive work makes up more than 90% of G.H. Tool & Mold’s output – historically, housings for power-transfer components, valve bodies, and alternators. But more recently, the 150-person shop has manufactured an equal number of molds for structural and suspension components.

The design-to-order company produces complete die-cast molds and replacement parts for existing molds. Job sizes are between one and 10 parts, most made from a superior-grade tool steel. Cycle times range from 30 minutes to 8 hours, and tolerances typically run between ± 0.0005" to 0.002". Mold service parts usually take five weeks. A complete mold can be done in 10 weeks.

To fulfill increased automotive demand, G.H. Tool & Mold relies heavily on Mikron high-speed milling machines along with a recently acquired Mikron high-performance 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 for its high-quality precision molds.

G.H. Tool & Mold has three Mikron HSM (high-speed machining) 800 milling machines that sport 36,000rpm spindles and two HSM 500s with 42,000rpm spindles. The shop uses these 3-axis machines to take quick, light cuts using small-diameter cutters at high feed rates, shortening part cycle times.

Danny Straatmann, programming manager at G.H. Tool & Mold, says the shop does practically all of its critical machining on the Mikrons. They are fast movers for lighter, smaller components and for both soft and hard machining – typically around 46Rc to 48Rc. Their speed, accuracy, and rigidity result in better surface finishes. Hard machining capabilities allow machinists to mill parts to finished size from hardened materials, reducing die-sinking electrical discharge machining time.

Special base materials that require no foundation give the Mikron machines their rigidity. GF Machining Solutions constructs monobloc bases from polymer granite with high vibration dampening, providing strength and rigidity for high-speed, high-performance machining.

Monobloc bases enable machining accuracy and better thermal stability, ensuring workpiece surface quality and minimal tool wear. The machines are outfitted with absolute optical linear glass scales on the X, Y, and Z axes that operate with a measuring step of 0.02µm to guarantee positioning precision.

For its first foray into 5-axis machining, G.H. Tool & Mold acquired two larger machines that achieved 5-axis capability through spindle movement. Straatmann says these machines were fine for long narrow parts but not for more intricate work.

“With the two original machines, we’d have to reposition parts to access certain features needing to be machined,” Straatmann explains. Large spindle heads lessened the machines’ agility and reach capability. But the HPM 800U-HD, “achieves simultaneous 5-axis motion through its tilt/rotary table.”

Moving parts around the spindle instead of moving the spindle around the part, reduces mass, making the Mikron faster and more accurate, Straatmann says.

The rotary/tilt table configuration lets the shop run shorter tooling on the Mikron, giving easy access to deep, intricate part cavities. Plus, the table eliminates tooling overhang issues. G.H. Tool & Mold was able to transition many of its intricate parts from the older 5-axis machines to the Mikron, improving surface finish quality and slashing cycle times in half.

In addition to speed and rigidity, Straatmann says the Mikron offers ease of programming and control functionality. The shop’s HPM 800U-HD features GF Machining Solutions’ Smart Machine functions – spindle vibration control, crash protection, and monitoring.

Smart Machine functions detect imbalances in cutting tools, such as an operator improperly balancing a tool for high-speed machining. Unbalanced tools can damage spindles and ruin parts. The technology monitors g acceleration, allowing shops to set a level between 1g and 12g. If the spindle reaches the specified force level, the machine will stop the process or initiate a tool change to a properly balanced tool.

Advanced machine designs and features enable G.H. Tool & Mold to further shorten its die-cast mold turnaround times and remain a go-to shop for major automakers. Straatmann says continuously boosting efficiency and productivity are essential for keeping pace with the surging automotive industry.

G.H. Tool & Mold
www.ghtool.com

GF Machining Solutions
www.gfms.com

IMTS 2014 booth #S-8754