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END USER: Tech NH Inc., (603) 424-4404, www.technh.com. CHALLENGE: Reduce polishing time when producing hardened steel molds. SOLUTION: Long-reach, small-diameter endmills for hard milling. SOLUTION PROVIDERS: Harvey Tool Co. LLC, (800) 645-5609, www.harveytool.com; Industrial Tool Supply, (888) 200-8887, www.itslowell.com.
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Courtesy of Tech NH
Tech NH applies small-diameter, long-reach endmills from Harvey Tool, such as this 0.047 "-dia., 2-flute, AlTiN-coated one, to hard mill many mold features that were previously EDMed.
Tech NH Inc., Merrimack, N.H., provides molding services including engineering and manufacturing molds and injection molding parts. The shop performs prototype and custom work, as well as production runs from a few thousand to several million pieces.
The molds Tech NH produces often are complex and require fine surface finishes. Achieving those finishes typically required up to 50 hours of polishing time after EDMing. To mill graphite EDM electrodes, Wayne Burgett, toolroom manager, had been applying PVD-amorphous-diamond-coated miniature endmills from Harvey Tool Co. LLC, Rowley, Mass. Seeking to maximize tool life in the abrasive material, Burgett wondered whether Harvey Tool could coat the tools with CVD diamond, estimating that the thicker coating could extend tool life eight to 10 times.
Tim Stimson, sales representative for distributor Industrial Tool Supply, Lowell, Mass., brought Harvey Tool representatives to Tech NH.
In addition to confirming the availability of CVD-coated tools for machining graphite, the Harvey Tool personnel “wanted to look at my other processes,” Burgett said. “They just happened to come in when we were producing a twin- cavity mold made of 48- to 53-HRC 420 stainless. The required finish was almost a mirror.”
Harvey Tool was able to provide small-diameter, long-reach endmills that enabled Tech NH to hard mill many mold features that were previously EDMed. Hard milling imparted a finer surface finish than EDMing, enabling Tech NH to achieve the mirror-like finish with only 5 to 6 hours of polishing instead of the 40 to 50 hours necessary when EDMing was more extensive. (Tech NH still EDMs some small features that a milling tool can’t access.) In addition, Burgett said, “We are saving time on electrode design, graphite milling, EDMing and programming.”
To mill complex mold contours, Tech NH uses small-diameter cutters with stub-length flutes. “I don’t need long flutes, I just need reach,” Burgett said, “because everything we are doing is 3-D and has draft angles. Plus, the stubby cutters are more rigid. On the ⅛"-dia. tool, I might go up to a 1⅞" or 2" length, and I use quite a few 0.010"-dia. ball mills with a ⅛" reach.”
According to Burgett, a major advantage of using Harvey tools is immediate availability of what otherwise would be specials requiring long lead times. Marcus Ralston, Harvey Tool vice president of sales and business development, said, “Shops ordinarily have to order these tools as specials, pay an additional cost for lower quantities and wait a long time. We take that same product and make it a standard-stock inventoried item, and we can have it to the shop the next day.”
According to Ralston, the endmills for hard milling from Harvey Tool feature proprietary geometries and an advanced AlTiN coating.
Depending on the complexity of the part, Tech NH can move from an initial quote for a job to a finished mold in 4 to 8 weeks, Burgett noted. In addition to quick delivery of “standard special” tools from Harvey Tool, he credits the rapid turnaround to “all the other new technology. Last year we got a new F3 vertical machining center from Makino.” Most important, he said, is the skill and commitment of Tech NH employees.
Related Glossary Terms
- 3-D
3-D
Way of displaying real-world objects in a natural way by showing depth, height and width. This system uses the X, Y and Z axes.
- abrasive
abrasive
Substance used for grinding, honing, lapping, superfinishing and polishing. Examples include garnet, emery, corundum, silicon carbide, cubic boron nitride and diamond in various grit sizes.
- chemical vapor deposition ( CVD)
chemical vapor deposition ( CVD)
High-temperature (1,000° C or higher), atmosphere-controlled process in which a chemical reaction is induced for the purpose of depositing a coating 2µm to 12µm thick on a tool’s surface. See coated tools; PVD, physical vapor deposition.
- electrical-discharge machining ( EDM)
electrical-discharge machining ( EDM)
Process that vaporizes conductive materials by controlled application of pulsed electrical current that flows between a workpiece and electrode (tool) in a dielectric fluid. Permits machining shapes to tight accuracies without the internal stresses conventional machining often generates. Useful in diemaking.
- flutes
flutes
Grooves and spaces in the body of a tool that permit chip removal from, and cutting-fluid application to, the point of cut.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- machining center
machining center
CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.
- milling
milling
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- milling machine ( mill)
milling machine ( mill)
Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.
- polishing
polishing
Abrasive process that improves surface finish and blends contours. Abrasive particles attached to a flexible backing abrade the workpiece.
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