Indexable Drill Saves Setup And Cycle Time

Manufacturing Engineering, May 2006

Rapid growth and a large number of orders are a good thing, but only if the contract manufacturer can meet the demands placed on its machining capability.

Harrison CNC Machine Co. (Sherman, TX) is a company that has experienced rapid growth in diverse industries in addition to projects for its core mining and medical industry customers.

The rapid growth and variety of customers made it difficult to keep up with the large number of orders being received. While welcoming the new business, Harrison CNC needed to improve its machining processes in order to keep up with the demand for its services.

Harrison CNC was founded in 2002 by Sam Harrison, who had 25 years experience in manufacturing. For 20 of those years, Harrison had been involved with CNC machining. With only five employees and four machines, it became imperative for Harrison to become as efficient as possible.

On one particular project, Harrison needed to drill eight holes in a 1 " (25.4-mm) thick flange. Each of the holes was 0.625" (15.88 mm) in diam and required being machined holding 0.004" (0.10-mm) tolerance. In addition, chipping the material had to be avoided when breaking through the hole. The goals for this project were to produce these parts in one minute or less per part, and to be able to produce 10,000 pieces per year with one machine.

The first tool tested on this project was an HSS drill. This tool produced one part in 3 min and had a setup time of 10 min to change and recalibrate. The tool operated at 80 fpm (24.4 m/min) while taking a cut of 0.005" (0.13-mm) per revolution. Operating with these parameters, the life of this drill was 30 holes, or five parts. A disadvantage, however, was that the feed rate had to be slowed down as the drill broke through the hole in order to avoid chipping the work piece. Also, the HSS drill was unable to hold the exact tolerance needed on this project.

The second tooling option tested was the Chamdrill Jet from Iscar Metals Inc. (Arlington, TX). This drill offers many advantages over the more traditional HSS drills. The Chamdrill Jet is an evolution of the original Chamdrill replaceable-tip drilling system. This system features a solid steel shank with a replaceable solid carbide drilling head. This makes it possible to quickly and easily replace a worn drilling head without the need to touch off and recalibrate the drill. The time saved in the setup of the Chamdrill leads to savings throughout the machining process.

The Chamdrill Jet system offers many of the same advantages as the Chamdrill, in addition to two internal coolant holes that extend through the drill body and out through the cutting edges. This feature allows coolant to be delivered directly to the cutting zone where it is needed most.

In addition, there are four standard drillhead geometries available, each designed specifically for optimal performance on specific types of material. The four types of drill-head geometries are:

* IDP-Features a honed cutting edge for use on carbon and alloy steel (ISO P).

* IDM-Features a T-land on the cutting edge for use on stainless steel and high temperature alloys (ISO M).

* IDK-Features a honed cutting edge and two peripheral chamfers for use on cast iron (ISO K).

* IDN-Features a sharp cutting edge and polished flutes for use on aluminum (ISO N).

For Harrison's particular project, the IDK-type drilling head was selected and is used. Its specific design for cast iron makes it well suited to drilling the gray and ductile cast iron flanges on this project.

With this tooling in place, Harrison CNC was able to operate at 450 fpm (137 m/min) taking 0.012" (0.30 mm/rev). Under these machining conditions, the Chamdrill Jet had a cycle time of 30 sec per part and a setup time of approximately 3 min. The quick-change design of the Chamdrill Jet made it possible to reduce the setup time from the HSS drilling system by 7 min. In addition, the specially designed IDK drilling head geometry and internal coolant helped to reduce the cycle time from 3 min down to 30 sec.

Even with the increased speeds and feeds, the Chamdrill Jet had a tool life of 15,000 holes or 2500 parts. This is a 500× increase from the tool life of 30 holes, or 5 parts with the previous tools. Furthermore, the Chamdrill Jet did not need to be slowed as it broke through the hole. It could be operated using the same parameters throughout the entire cut without chipping the material as it broke through, while also achieving the required tolerance.

The Chamdrill Jet enabled Harrison CNC to meet its goals of a cycle time of 1 min or less per part with the ability to produce 10,000 parts per year with one machine.* Circle 263