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END USER: Precision Technologies Inc., (978) 649-8715, www.precision-techno.com. CHALLENGE: Boost feed rate when milling tiny slots. SOLUTION: Variable-helix miniature endmill. SOLUTION PROVIDERS: Harvey Tool Co. LLC, (800) 645-5609, www.harveytool.com.
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Precision Technologies Inc., Tyngsboro, Mass., provides machining and assembly services, as well as engineering consulting assistance to maximize the manufacturability of its customers’ parts. “A lot of times customers come to us if they have a part that nobody else can make correctly,” said Bill Goyer, general manager. “We help them with their problem.”
Precision Technologies continually seeks ways to reduce costs by shortening cycle times. A good example involved a medical component machined from 303 stainless steel. Precision Technologies sought to cut the part’s 90-minute machining time in half.
Courtesy of Harvey Tool
A 3⁄64 "-dia. variable-helix endmill from Harvey Tool enabled Precision Technologies to more than quadruple the feed rate and increase the axial DOC by 2.5 times when milling tiny slots in a stainless steel medical component.
Programmer Frank Rogier said he regularly gets tool application advice from Jim Childs, president of Industrial Tool Supply, Lowell, Mass., a distributor of cutting tools and other machining supplies. “I can show Jim an application and he gives me ideas on what tools to use,” Rogier said.
“All of our guys sell on the value added, technical end,” Childs said, adding that the staff continually receives training in new technologies and performs tool tests.
After reviewing the medical component job, Industrial Tool Supply specified tooling. “We helped them on the drilling, milling and facemilling,” Childs said. In analyzing the job, he said: “My approach was to start with the operation that was the longest, because speeding that up took off the most time. Then we just kept on going. [However] we got to a stumbling point with a tiny little tool.”
The tool was a 3⁄64 "-dia. endmill for creating six 0.0625 "-wide × 0.125 "-deep × 0.300 "-long slots. Precision Technologies was cutting the slots with a standard 3⁄64 "-dia., 4-flute, uncoated endmill run at 10,000 rpm and a 1-ipm feed on a Mori Seiki vertical machining center. “We couldn’t get the speeds and feeds we needed out of it, and the tools would break on us,” Rogier said.
Failure came without warning for the delicate tools. “You wouldn’t hear anything,” Rogier said. “You would go over and look at the part and notice that the slot wasn’t there.”
Childs noted that the standard endmill would snap at 2 ipm. “One ipm was the best that we could get.”
To solve the problem, Childs suggested applying a variable-helix miniature endmill from Harvey Tool Co. LLC, Rowley, Mass. According to Harvey Tool, the variable-helix design reduces chatter and harmonics and permits increased metal-removal rates. Tool geometry is complex; spacing varies between the flutes, and the helix angles change not only from flute to flute, but also along each flute’s length. And to maintain consistent cutting edge relief, the rake angles of each flute also vary. An AlTiN Nano coating provides increased hardness and heat resistance compared to uncoated tools.
Harvey produces the tools in diameters from 1⁄32 " to ¼ ". “We sell a lot of variable-helix tools from different manufacturers,” Childs said. However, such tools under 1⁄8 " in diameter are not that common.
The trials were successful, enabling the feed to be more than quadrupled. “We started the tool from Harvey at 5 ipm,” Childs said. “It was silent.”
In addition, the tool remained intact when the axial DOC was raised from 0.01 " to 0.025 " per pass.
“As far as the run time,” Rogier said, the new tool “probably cut it to a quarter of the time. I don’t think I ever broke a tool.” While tolerances were not particularly tight at ±0.005 ", Rogier said “the tool held the same dimensions all the time. It didn’t vary at all.”
Childs noted that the Harvey tool reduced cycle time for the job by 2 minutes. In total, Precision Technologies reduced the cycle time from 90 minutes to about 45 minutes.
In addition to reducing manufacturing costs, accelerated cycle times help Precision Technologies meet shorter lead times. “On all our orders, lead times aren’t as long as I’d like them to be anymore,” Rogier said, noting that customers are “waiting until they need the parts, and then they want them turned around as fast as possible.”
Related Glossary Terms
- chatter
chatter
Condition of vibration involving the machine, workpiece and cutting tool. Once this condition arises, it is often self-sustaining until the problem is corrected. Chatter can be identified when lines or grooves appear at regular intervals in the workpiece. These lines or grooves are caused by the teeth of the cutter as they vibrate in and out of the workpiece and their spacing depends on the frequency of vibration.
- endmill
endmill
Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.
- facemilling
facemilling
Form of milling that produces a flat surface generally at right angles to the rotating axis of a cutter having teeth or inserts both on its periphery and on its end face.
- feed
feed
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
- 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.
- hardness
hardness
Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.
- inches per minute ( ipm)
inches per minute ( ipm)
Value that refers to how far the workpiece or cutter advances linearly in 1 minute, defined as: ipm = ipt 5 number of effective teeth 5 rpm. Also known as the table feed or machine feed.
- 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.
- rake
rake
Angle of inclination between the face of the cutting tool and the workpiece. If the face of the tool lies in a plane through the axis of the workpiece, the tool is said to have a neutral, or zero, rake. If the inclination of the tool face makes the cutting edge more acute than when the rake angle is zero, the rake is positive. If the inclination of the tool face makes the cutting edge less acute or more blunt than when the rake angle is zero, the rake is negative.
- relief
relief
Space provided behind the cutting edges to prevent rubbing. Sometimes called primary relief. Secondary relief provides additional space behind primary relief. Relief on end teeth is axial relief; relief on side teeth is peripheral relief.
