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Supported inserts cut off instead of breaking off.

Supported inserts cut off instead of breaking off

Here's how a farm-equipment maker harvests savings in parting and grooving operations. New tool with better support does the trick.

When the bulk of your machining operations involves turning short parts out of 20-ft lengths of barstock, much of your machining economics hinge on cutoff operations and parting tools.

Such is the case of Hay & Forage Industries Inc (HFI), Hesston, KS, manufacturer of farm equipment. Their products, used in the field for hay, silage, and forage handling and processing, contain a variety of rotating parts--shafts, spindles, bushings, power takeoffs, etc. At any one time, about 15 different cutoff operations are in process.

In January, 1989, HFI switched over to a new type of parting tool. Now they've standardized on it throughout their operation. Here are the results so far: * A 5-to-1 improvement in machining rate for parting operations. * Incidence of damaged toolholders, once an almost daily occurrence, has dropped to virtually zero. * Run times between insert changes have increased 25 percent on average. This cuts downtime for insert changeover.

The parting tools also are working well for pulley grooving.

Standardizing on new tooling

The switch was to Sandvik Q-Cut indexable-insert parting tools. "We've even seen improvements on the same scale when working on the gummier 1018, 1025, and 1045 steel grades," comments Dennis Dester, HFI senior industrial engineer. A typical case is cutoff of a 3" bushing made of 1045 steel. Previous cycle time for parting was 13 sec. Now it's down to 2.5 sec. Machine settings now are 400 sfm speed and feed rate of 0.008 ipr on radius.

Toolholder breakage

Originally, HFI started searching for a better parting system because of excessive insert breakage and resulting toolholder damage under the old arrangement. The inserts they were using had grooves on both sides, for clamping, and the failures usually took place at the grooves. When the inserts ruptured, the toolholder was fed into the part, damaging the toolholder beyond repair. Such failures happened about once a day.

"The old inserts were supported at two points in the holders--both of them right along the grooves," explains Mr Dester. "Apparently the combination of the grooves, which acted as stress risers, and the presentation angle of the holder, overstressed the structure when dulling began to increase tool pressure and friction."

When HFI switched to the Sandvik Q-Cut system, tool breakage and workholder damage ceased immediately. "We've had only two failures since the changeover, both attributable to `cockpit error' by the operator or setup man," says Mr Dester. Savings in toolholder replacements amounted to better than $1000/month.

Reduction of insert failure and toolholder damage stems from two points about design of the Sandvik Q-Cut parting tool, according to Mr Dester. "First, the insert is supported at three points in the toolholder. Second, there are no point sources of stress, or stress-riser sites, on the insert.

"We also present the cutting edge to the work below the centerline, so any overload would tend to bend rather than compress the toolholder."

Attrition, not new investment

The changeover went smoothly and gradually as HFI gained experience with Q-Cut. "Basically, we did it by replacing the old tooling as the inserts wore out or the toolholders broke. There was no additional tooling investment," he explains. Sandvik field application specialist, Mike Campbell, and territory sales representative, Paul Ingham, helped specify grades and establish machine settings for the new tooling. "I don't think we'd be at 5-to-1 with a 25 percent gain in tool life without their input," adds Mr Dester.

Another thing that sped up the changeover was the availability of standard Q-Cut blades designed to fit Manchester toolholders. "That made Q-Cut immediately compatible with the rest of our tooling on our newer machines," Mr Dester explains.

Do-it-yourself toolholders

Based on the earlier positive experience, Hay & Forage began building their own holders to fit older machines that couldn't use standard tooling. These holders have been designed to use standard Q-Cut blades. Today, about 20 different machines--Barnes and Oliver automatics and turret lathes along with new Mori Seiki CNC turning centers--do their parting with Sandvik Q-Cut tooling. Steels machined include 8620 and 4140, in addition to the grades mentioned earlier.

Grooving experiments successful

In late May, Hay & Forage began experimenting with Q-Cut parting tools for non-cutoff operations--principally grooving of pulleys in cast iron, and generation of relief and oil grooves in rotating parts. "We never even considered this with the old parting tools because of the high breakage we were experiencing in the standard operations. So we can't really compare old and new in grooving," he says.

However, this experiment has been a major success. Machining rates are at least double, and tool life has increased for grooving operations as well. Mr Dester says, "When the same tooling can handle several jobs well, we always come out ahead, and that's precisely what happened. When one tool does more than one job, we cut tooling inventory and simplify ordering and toolsetting."

Updating the Bard

"On a removal-volume basis, parting operations may not amount to much," Mr Dester concludes, "but they can become a troublesome bottleneck unless the tooling cuts fast and trouble free. `Fast and trouble-free' wasn't the case around here--until recently. Now, however, we know something Shakespeare didn't: parting isn't necessarily `such sweet sorrow'."

PHOTO : Sandvik's three-point insert support reduces toolholder damage caused by sudden insert

PHOTO : failure and resulting "plunging changeout."

PHOTO : Speed of parting operations increased by 5 to 1 with switch to Q-Cut parting tools. Here,

PHOTO : operator inspects finished bushing of 4140 steel processes on a Mori Seiki CNC turning

PHOTO : machine in 30 sec.

PHOTO : Bushings and spacers all had two or more operations done by Sandvik Q-Cut parting tools.

PHOTO : Additional operations included machining oil grooves, relief slots, and pulley grooves.

PHOTO : Tool passes for pulley grooving.
COPYRIGHT 1990 Nelson Publishing
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Copyright 1990 Gale, Cengage Learning. All rights reserved.

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Publication:Tooling & Production
Date:Feb 1, 1990
Words:975
Previous Article:Inside a small-parts lathe.
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