END USER: SFI, (901) 363-1571, www.sfifab.com.
CHALLENGE: Reduce cycle time when slot milling an A-36 steel part.
SOLUTION: A 4-flute, solid-carbide endmill for roughing and finishing in one pass at full slot width and depth.
SOLUTION PROVIDER: Iscar Metals Inc., (877) BY-ISCAR, www.iscarmetals.com.

A shop's standard, go-to cutting tool is subject to change when a better one comes along. SFI, Memphis, Tenn., realized this when cutting a 382 "-long × 0.25 "-wide × 0.253 "-deep slot in an A-36 steel oil pan. The company, which also has a facility in Conway, Ark., designs, develops, supplies and services medium- to heavy-gauge components for OEMs in the agricultural, construction, industrial, transportation and defense industries.

When slotting the first four prototypes of the oil pan, SFI was applying its then-standard ¼ "-dia., full-radius, 4-flute, solid-carbide endmill. Run on an SNK RB-4VM 5-axis gantry mill with a 6m × 2m table, the machining parameters were a 160-sfm cutting speed, 2,443-rpm spindle speed, 5.86-ipm feed rate, 0.0006-ipt feed per tooth, 0.25 " WOC and 0.05 " DOC. Average thickness for the fragment-type chips was 0.0006 ", the metal-removal rate was 0.07 in.3/min. and each cutter lasted one part, with flank wear being the predominant type of wear.

When run at the full slot depth on the oil pan job, the standard endmill snapped, causing rework, noted Matt Watts, machine shop supervisor. Using trial and error, SFI backed the tool off so it could get through the part, but the cycle time consumed about 6.5 hours. When extrapolated for the proposed 100-piece run for the family of oil pans, total cutting time would have consumed an unacceptable 651.6 hours, according to Watts.

Fortunately, Watts and Greg Archer, SFI programmer, attended a seminar presented by Iscar Metals Inc. at the toolmaker's headquarters in Arlington, Texas. They asked Rex Luxmore, Iscar's sales engineer for western Tennessee, if the FINISHRED solid-carbide endmill they saw demonstrated at the event was suitable for the oil pan application. "I said, 'Hell yeah, that's perfect for it,'" Luxmore recalled.

An Iscar ¼ " solid-carbide FINISHRED endmill reduced cycle time from more than 6.5 hours to 8 minutes when slotting an A-36 steel oil pan at SFI.

SFI then tested an Iscar ¼ "-dia., 4-flute, solid-carbide FINISHRED endmill, the EFSI-E44 250-500C250CF2.5, and another toolmaker's ¼ ", 4-flute, solid-carbide endmill. The Iscar "chatter-free" endmill has two finishing flutes that extend slightly farther than the tool's two roughing flutes, so it simultaneously roughs and finishes a workpiece. "It leaves a beautiful finish," Luxmore said, adding that there's no specified surface finish. "It looked like an easy win for me."

And it was. Although the other tool tested reduced cycle time by more than half, the Iscar endmill reduced it by more than 97 percent. "It was done in 8 minutes," Luxmore said, "and they couldn't believe it."

Luxmore added that the air blowing beside the machine spindle—instead of coolant—is effective for evacuating the comma-shaped chips FINISHRED endmills produce. Coolant usually pushes the chips back down, and air blows them out, he noted.

According to the test results, the Iscar endmill slotted the 382 " length at a 300-sfm cutting speed, 4,580-rpm spindle speed, 36.64-ipm feed rate, 0.002-ipt feed per tooth, 0.25 " WOC and full DOC of 0.253 ". Average chip thickness was 0.002 ", the mrr was 2.32 in.³/min. and each cutter lasted two parts, with flank wear also being the predominant type of wear.

Although the FINISHRED endmill costs nearly 2.5 times as much as the one originally applied, the longer tool life and, more importantly, the vastly enhanced productivity achieved a projected cost reduction of $80,828 per 100-part batch based on a $128 machine cost per hour compared to the full-radius endmill. Looking at the tooling and time cost per part, the Iscar tool reduced costs by 94.5 percent.

SFI is in the early stages of production for the oil pan and expects to have an on-going order of 100 parts per year, according to Watts.

"Once we get into full production, we will more than likely try to push the tool a little harder," he said, noting the machine tool is running close to its maximum spindle speed. "The Iscar tool has become the standard for just about everything we're doing."