+p new milling cutter reduces machining cost 60%: replacing a shoulder milling cutter with a new face milling cutter in a roughing operation reduced machining costs by more than 66%.

"A shoulder milling cutter, used by one of our customers for roughing operations, produced unacceptably high radial forces," advises Lothar Grosser, service engineer, Walter USA (Waukesha, WI), supplier of the new cutter. "Even the machine manufacturer made recommendations to change the machining process."

The customer used its existing tool to produce a small 90[degrees] shoulder on one side of the work piece, then decided to machine the entire work piece surface with this shoulder milling cutter. This produced unacceptably high radial forces.

To remedy the situation, Walter recommended its new Xtra-tec F4033 face milling cutter. With its approach angle of 45[degrees], the new cutter diverts the majority of the radial forces in an axial direction, explains Grosser. "The 45[degrees] approach leaves an inclined surface of 45[degrees] on one side of the work piece, which could be easily removed by the shank-type milling cutter used later for finishing," notes Grosser.

Prior to trying the new tool, the operation suffered from vibration and noise. However, the face-milling cutter excelled in machining the alloy steel block very smoothly and without any vibration, according to the service engineer.

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The new cutter is fitted with indexable inserts specially designed for this series. For this application, the WKP35 cutting grade, which is relatively insensitive to temperature fluctuations, and is recommended for wet cutting operations, was applied. The 1.50" diameter milling cutter is fitted with four teeth, and the inserts can be indexed eight times. The original problematic 2.0" diameter shoulder milling cutter featured one additional tooth, but only two cutting edges per insert.

High Velocity

The new F4033 Xtra-tec cutter with a 1.50" diameter and four inserts with eight cutting-edges, performs at approximately 40 ipm (0.04" ipr.). That is three times the feed of the tool the shop was using before. This resulted in machining costs being reduced by more than 60%, Grosser points out.

"The Xtra-tec face milling cutter took less than one-third of the contact time (0.59 min.) taken by the previous cutter (1.98 min.) for a cutting length of 23.6", which was comprised of several steps. The ratio is about the same when it comes to the feed rates, observes Grosser. "The Xtra-tec milling cutter ran at 40 ipm, while the other tool performed at less than one-third of this. This resulted in a similar ratio relating to the machining costs."

Cost Reduction

Because the Walter tool has eight effective cutting edges, it fares much better in terms of reducing material costs, creating a cost savings of 2.5 times. The higher cutting data requires more tool changes, but is of little importance considering the tremendous time saving realized. And, the tool performed even during extended applications

"There is practically no insert breakage or other failure," says the shop's project manager. "We are able to use all eight cutting edges of the insert to its limit."

To further optimize production, other tests were developed using another Walter cutter, the Xtra-tec F4042 shoulder-milling cutter. "The tool provides the same benefits as the face milling cutter, which justifies using this new tooling system in our operations," states the project manager. Walter USA

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RELATED ARTICLE: Roughing 3X Faster

Comparison of F4033 Xtra-tec with the original shoulder milling cutter.

Operation: roughing of high-alloy steel, cutting length: 23.6"

                                 F 4033             Shoulder Milling
                                                    Cutter

Tool size                        D = 1.50", Z = 4"  D = 2.00", Z = 5"

Cutting Edges/Indexable Insert:  8                  2

Period of Engagement:            0.59 min           1.98 min

vc:                              410 fpm            328 fpm

vf:                              40 ipm             12 ipm

n:                               1044/rpm           626/rpm

Savings achieved on more than 70,000 components per year:

* Reduction of machine costs (machine overhead rate = $60/hr.) by accelerating the machining operation: about $104,000.

* Material cost savings: about $32,400.

* Considering the slightly increased tool changes and set-up costs, the Xtra-tec milling cutter ensures a total saving of about $127,200/year.

Taking the processing and tool changing times into account, an additional machine capacity of about 96,300 minutes is created, according to Walter.