Known for its natural beauty and outdoor recreation, Stevens Point, Wisconsin is home to Pointe Precision, a high-tech machined parts producer. Manufacturing close tolerance, complex parts for the aerospace, paper, fluid power, medical and other industries has enabled Pointe Precision to grow to a $10,000,000 company in its 2 1/2 year history. An employee's average machining experience is seven to ten years.
Pointe Precision has a simple philosophy regarding machine resources: "The more services we can offer the customer under our roof, the more inclined they'll be to do business with us," according to Joe Kinsella, Chief Executive Officer. With the exception of special processes, Pointe Precision possesses many conventional capabilities in-house. Their "one-stop shop" approach is one of the keys to their growth. This philosophy has driven a strong commitment to continuous technological improvements. As with many new companies, due to initial limited capital, Pointe Precision began business with mostly used machines. To keep up with customer demands regarding price, quality and delivery, Pointe Precision has acquired four new machining centers, a new OD grinder, two new two-axis turning centers and a new four-axis turning center, all in the course of just 2 1/2 years. "Our machinists are continuously looking for ways to increase productivity via creative programming and constant interaction with our tooling vendors," says Mr. Kinsella. It is through these partnerships that Pointe Precision feels it can best position itself to provide the kind of service its customers require.
Scot Barton of Machinery and Supplies, an Appleton, Wisconsin-based Greenfield Industries (Augusta, Georgia) cutting tool distributor, introduced a Metal Removal brand 120-27 series high cobalt micrograin solid carbide end mill to increase productivity in Pointe Precision's milling processes. This end mill was developed because of the increasing demand for end mills that will perform at elevated speed ranges inherent in most modern CNC machining centers. The 120-27 is designed to function most efficiently at accelerated speeds, yet is versatile enough to operate at more moderate speeds for use on older machine tools. The design of the 127-20 encompasses several features that enable optimum value in high speed machining of T-6 free machining aluminum. These include: 0.0005 concentricity between cutting diameter and shank; 0.0005 cutter diameter tolerance; and 0.0002 end gash "lip height" variation.
It is a deep two flute, high shear, raised margin design with a 42-degree helix and a long/short gash end, which improves plunging and ramping capabilities.
Pointe Precision used a Metal Removal 120-27 series 1-inch diameter end mill to pocket out a 2 1/2-inch round solid aluminum bar, removing approximately 93 percent of the material. "We used to purchase an aluminum casting to make this close tolerance aerospace part at considerable cost and very long lead time. Now we're able to mill round stock from our existing raw material inventory at extremely high feeds and speeds at lower costs and an almost non-existent scrap rate," says Perry Zorn, Pointe Precision's milling cutting tool coordinator. "The 120-27 end mill has allowed us to do this."
Metal Removal initially recommended using this end mill in this deep pocket application at 8,000 rpm (the machine tool limit) with a feed rate of 128 ipm. Perhaps the most interesting achievement in this application, however, is maintaining a chip load of 0.023 over the 0.008 originally recommended by Metal Removal at 360 ipm.
The predecessor to the 120-27 was Metal Removal's 157 series carbide end mill. This was Pointe Precision's end mill of choice prior to the introduction of the 120-27. In comparing the performance of these two tools, Mr. Zorn has determined that the 120-27 provides a 59 percent savings over the 157 end mill. Mr. Zorn contends, "Even though the 120-27 is a more expensive end mill, the productivity improvements far exceed the additional cost."
The next challenge Pointe Precision faced was to try to make this gain universal throughout the entire shop. A horizontal machining center cell was selected as the next logical area to apply these productivity gains. This cell is home to a family of large high silicon aluminum casting parts. In this case, a 3/4-inch 121-27 extended length end mill was selected. The results were strikingly similar. Over a period of one year, due to accelerated cutting speeds, this cell expects to gain in excess of 900 machine hours. In some applications, the ipm feed rates were greatly increased by 1400 percent over those used to run a general purpose uncoated end mill. The greatest time savings came from the elimination of finish passes. This is possible because of the wiper flat incorporated into the design of the end mill.
The final test of versatility of the 120-27 came in trying to apply the same technology in a live tooling application on a turning center. The results had been so favorable in conventional milling that they wanted to find out if it could work with limited horsepower in a live application. The machine tool in question was a four-axis turning center. The objective again was to replace an aluminum casting with a solid hog-out. They started experimenting with a 3/4-inch Metal Removal 120-27 end mill and found that with the available 3,000 rpm on the live axis, they were able to mill at 50 ipm and do the 2 1/2-inch diameter part in one pass while maintaining a +80 RMS finish. At one point, after many hours of cutting time, the 3/4-inch end mill started to dull. To further test this cutter, Tim Lange, Cutting Tool Coordinator, replaced it with a general purpose two-flute end mill. "I started to plunge at 20 ipm and the general purpose tool really began to scream. Then I entered the profiling sequence and the torque limiter tripped and actually shut the machine down," recalls Mr. Lange. "I was only running at 50 percent of what the 120-27 was cutting at with a 90 percent load when the machine shut down with the standard end mill. I got the 120-27 resharpened in our tool grinding department and was back up in no time."
Pointe Precision believes in working closely with its tooling suppliers to optimize the tool's capabilities. Encouraging machinists to push cutting tools even beyond recommended limits gives them a strong sense of accomplishment and is certainly beneficial to the company as well. The organization continues to learn that there are monumental benefits derived by sharing technological innovations shop-wide. All too often improvements are isolated to the specific machine tool when, in fact, they may be applicable globally. Pointe Precision is committed to flowing technological information throughout the shop. MMS