Indexable inset mill cuts tool steel much faster

Uprated CAM software and an indexable insert end mill are machining tool steel guides for rubber extrusion lines five times faster than multiple pass milling techniques used before.

At Cooper-Standard Automotive in Maesteg, Mid Glamorgan, UK, where they manufacture weather seals for car doors, tool steel guides for the companys rubber extrusion lines are being machined five times faster using uprated computer-aided manufacturing (CAM) software and an indexable insert end mill with integral 40-taper from NCMT, called the BIG Daishowa Fullcut Mill.

Around 60 guides per year have to be machined to replace worn and damaged components.

The D2 tool steel parts were previously machined from solid billets using area clearance (Z-level) roughing in multiple step-downs from top to bottom, using a 15mm diameter bull nose mill with round carbide inserts to ramp in and take successive 0.5mm cuts.

The roughing cycle took four hours for the larger guides, partly owing to the toughness of D2 and partly because it was necessary to stop the spindle of the vertical machining centre every 20 minutes to turn or change the insert.

Following an upgrade to version 6 of Depocam software from NC Graphics, which includes core roughing routines and dynamic feed-rate control, Cooper-Standard Automotive is able to bring a 32mm diameter FullCut mill in horizontally from the side and, by stepping down in 3mm increments in Z and feeding in to full depth, rough out the billet in 40 minutes by interpolation in the X and Y axes.

(The cycle would be even faster if the 11mm length of the carbide insert were to be used, but it is not possible in this case as the method of clamping the component is not sufficiently rigid.) Die development engineer, Nigel Francisco, is however experimenting with raising the current machining parameters ? 800 rev/min spindle speed : 300 mm/min feed ? by around 25 percent, which will reduce the machining time further.

Waterline finish milling with a torroid cutter to remove the steps left by the FullCut roughing cycle takes a further 10 minutes, bringing total machining time to 50 minutes, which is a five-fold saving compared with the previous method of producing the guides.

A further benefit is the longevity of the FullCut Mill?s three twin-edge carbide inserts, which rough three complete guides before they need replacing.

Commented Francisco, ?We also use the FullCut Mill for other jobs in D2 steel, such as gapping rolls for special purpose machinery, and there is at least a two-fold improvement in cycle time and better insert life in all cases compared with the square shoulder, indexable insert end mills and the solid carbide cutting cutters we were using.

We also do some FullCut milling of mild steel and the tool literally eats it.? The cutter?s effective metal removal can be put down to the sharpness of the edge, made possible by high positive rake angles in both the radial and axial directions, leading to low resistance cutting, quiet operation and accuracy of cut.

Eccentric relief is adopted for the first time in an indexable insert mill, improving toughness of the cutting edge without sacrificing its sharpness.

Spiral chip pockets are incorporated to achieve high rigidity and through-holes for semi-dry cutting or coolant improve insert life.

FullCut Mills are available in the diameter range 12 to 50mm with straight shanks or integral taper (CAPTO C6 and C5, HSK, BBT, and DIN).

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