Thursday, June 18, 2020

Productivity Improvement Through Tool and Toolholder Change - Corogrip

Case Study 35 of  Industrial Engineering ONLINE Course


Fermer Precision (Ilion, New York) machines a variety of precision parts from aluminum, cast iron, powdered metal, carbon steel and low-carbon steel for automobiles, firearms, medical products and train brake systems. The company uses a Mori Seiki SV-500 and two OKK KVC 600 vertical machining centers for drilling, reaming and chamfering operations. A typical drilling operation requires drilling nine holes in six workpieces mounted in a single fixture.

The powdered-metal core drills presently used were supposed to last 200 parts per drill, but they were only averaging 120.  Operators were at risk of burning their hands when removing the tooling from the shrink-fit toolholders. If tools with steel shanks were used instead of  solid carbide, the coefficient of expansion of the toolholder and the tool's steel shank are too close to the same and hence there was difficulty in removing the tool.  In most cases, you need to use a mallet and a drive punch to remove the tool. After removal of  the drill, the toolholder still could not be used for another 1.5 hours till it . cools down enough for handling and then retooling. During the reheating and cooling of the shrink-fit toolholder, operators ran the risk of injury. 

The long retooling times are forcing the firm to keep on hand three times the number of toolholders actually needed for drilling. One is cooling, one is working and the third one is ready for the next change. The company was looking for alternatives and  DoAll and Sandvik Coromant (Fair Lawn, New Jersey) team came out with a suggestion.  The solution suggested was a hydromechanical clamping toolholder and a dual-grade drill with high toughness and good wear resistance—Sandvik's Delta C GC1020 drill and the Sandvik CoroGrip toolholder.

The key to the new drill's performance is the sintering of two substrate materials together at the drill tip. The grade at the tool center provides toughness and withstands tension and pressure on the drill point. The grade at the tool periphery provides wear resistance at high surface speed. This combination results in high speeds and feeds without sacrificing edge security. The CoroGrip high precision chuck for high speed machining offers twice the clamping force of shrink-fit chucks and three times that of ordinary hydraulic chucks.

The tooling combination demonstrated dramatically longer tool life. The average number of parts each drill handled increased from 120 to 300. The increase in tool life varied from 50 to 200 percent on tool life in different applications. 

The runout on the CoroGrip is 0.002 mm and is another benefit.

Feeds and speeds on the machines remain unchanged with the new drill and toolholder. A typical operation is drilling several 0.4313-inch diameter holes, 1 ¾ inch deep at 250 sfm in low-carbon steel workpieces.

Fermer technicians were happy with the safe, easy and quick tooling setup with the CoroGrip chucks. The toolholders are fitted with a tool and ready for insertion into the machines in just 15 seconds which is  360 times faster than the setup time required for the shrink-fit toolholders.

Fermer no longer needs to inventory more toolholders. The gloves and mallet are no longer necessary to change drills. During tool setup there are no forces exerted on the clamp or the tool pot, since only shop air is applied to move internal toolholder components.

The design of the CoroGrip toolholder optimizes balance and torque transmission. The combination has increased overall productivity and the quality of our products according to executives of Fermer.


2001 article
https://www.mmsonline.com/articles/retooling-saves-time-and-space

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