Job Shop Automates Presetting With DNC

Stan Brunell is a manufacturing engineer at Chandler Evans (a division of Coltec Industries), located in West Hartford, Connecticut. The challenge he faced, like many job shop engineers, was to somehow reduce total production costs.

The driver for this initiative was competition. His shop was losing business to outside vendors that could underbid Chandler Evans for work.

This story is about how the shop went from on-line, manual tool presetting and loading of NC programs to automating tool presetting and integrating it with a DNC system for part programs. What they ended up with was a system in which offsets are automatically posted and sent along with the part program, effectively automating two major areas of lost setup time. The results have been impressive.

Looking For Savings

Step one for Mr. Brunell was to begin analyzing his production costs looking for areas where savings could be made. In an aerospace manufacturing facility such as Chandler Evans, orders tend to be high mix with low volume. Mr. Brunell determined that a significant portion of production costs were related to setup times.

After reviewing all setup procedures, Mr. Brunell discovered two areas ripe for potential savings. Both had to do with transferring off-line processes that were traditionally done at the machine tool. The idea was to increase machine utilization thereby lowering manufacturing costs.

For example, a significant amount of setup time involved operators using a machine control to physically touch-off and measure each tool. On some jobs as many as 50 tools may be used. They were setting tools on-line with an average time per tool of more than a minute, including the time needed to enter the offset in the machine control.

Another potential area of great setup savings was the time that operators spent finding and using the paper tape for loading NC programs into the machine controls.

The obvious alternative to setting tools on the machine was an off-line tool presetter. Mr. Brunell knew that a typical tool presetter eliminated the need to touch-off tools at the machine controls. But he also realized that while measuring tools off-line was an improvement, if operators still needed to manually enter the tool offsets into the machine controls, then much of the time saved would be lost.

He determined that what they needed was a tool presetter with software that had the ability to automatically communicate directly with the machine controls. That called for a DNC package, which the shop did not have.

To facilitate communication between the tool presetter and the machine tool and to eliminate delays associated with paper tape, Mr. Brunell recommended Chandler Evans purchase a fully automated DNC system.

This would, on paper at least, solve both of the identified setup bottlenecks. He selected a system from CNC Engineering, Inc. (formerly CNC Innovations, Inc., Enfield, Connecticut) because it could not only link an off-line programming system to the machine control, but also had the ability to link directly to the tool preset database.

The Hardware

Chandler Evans purchased a Microset tool presetter from Tooling Systems Division, DeVlieg-Bullard (Frankenmuth, Michigan). The unit was equipped with software that allows Chandler Evans to capture, store and transfer tool measurement and offset data.

According to Bill Lovejoy, application specialist for TSD, the unit Chandler Evans selected is an optical presetter that uses 20-to-1 magnification projection. The presetter measures lengths up to 24.6 inches and diameters up to 21.6 inches. The toolholding spindle is a No. 50 CAT taper. Reducing sleeves allow Chandler Evans to measure No. 40 and No. 45 CAT tapers as needed.

In operation, an operator places a tool in the presetter spindle. A cross hair on the optical projector is positioned on the tool. The operator presses a "measure tool" soft key to transfer the digital readout (DRO) length and diameter measurements to the presetter software. At this point, tool offsets are computed and stored. It's done automatically, so input errors are virtually eliminated.

The captured tool offsets are stored on a file server for access by the DNC system. It's a quick and automatic process, about ten seconds, that reduces the potential for error.

Moreover, with the tool presetter, operators no longer stand idle while machine controls are in production. Instead, they measure tools for the next job off-line. Having tools measured off-line also allows the machine tool to remain in production for longer periods of time.

Doing DNC

"When DNC first came on the scene, it was primarily a method to replace tape readers as a way to load NC programs into a machine tool control," says Jim Smith, president of CNC Innovations. "DNC has now evolved into a system for centralized NC program file management with program revision tracking and fully automated distribution to the machine controls. An important part of a modern DNC system is its ability to allow users to build and use data relationships between part programs and other shop data such as tooling information, part drawings and production documentation."

In the case of Chandler Evans, automating tool presetting alone, without the ability to connect the tool offset data to the correct part program, wouldn't gain much setup time savings. It would be an island of automation in a sea of manual data input. Without a complementary part program DNC connection, operators would be required to manually verify that the tooling kit and part program belonged together.

In a job shop environment, keeping track of the latest revision to a workpiece and making sure that revision is being run on the machine is a constant battle. Using a centralized database is a big step toward eliminating some of the error potential from running the wrong revision.

That's what DNC brings to the operation. Using the same centralized data collection source for the program and tooling kits is how Chandler Evans has obtained the setup reductions they needed to compete.

How Does It Work?

The combined DNC and tool presetting system used by Chandler Evans is linked to a common file server via a local area network (LAN). This file server is also used to store NC programs created by the CAD/CAM programming area. By using a common file server, the software running on each DNC host computer has access to the tool data created by the presetter software and the NC programs created by the CAD/CAM department. Three separate DNC hosts serve three different departments within Chandler Evans with each having access to the common information.

The process starts with NC programs created in the CAD/CAM area. From a separate terminal, a DNC librarian moves these programs to the "active program area" on the file server making these programs available to the machine controls through the DNC system.

Meanwhile at the presetter, tools are measured and kitted for each specific job. The tool data, including offsets, is loaded into the file server. Tool kits are given job specific identifiers relating them to the program.

During setup, operators make a simple "remote request" directly from their machine control to the DNC system. The DNC system automatically retrieves the correct NC program and the most recent offsets for the tools associated with that job (part/operation) and transmits these files directly to the CNC controls.

To ensure that the operators are receiving only the latest NC program versions, the DNC system is configured to obtain NC programs only from a specified set of program sub-directories. These program sub-directories are under the control of the DNC librarian and are continuously updated.

To ensure that the operators are using only the most recent tool measurements, the tool preset software contains a warning "flag" for each tool. This flag is "set" when a specific tool's offsets are transmitted to a machine control and "cleared" only when that particular tool is re-measured.

Unexpected Benefits

Operators are pleased with the system. The combined package of program and tool offset data makes their job easier and less hazardous. They no longer need to climb in and out of the machine enclosures to touch-off tools. This has reduced the risks of slipping on coolant, getting caught on the chip auger, having coolant drip on them, and more.

With the combined package, Mr. Brunell experienced some unexpected benefits. Prior to using the tool presetter, operators experienced up to 15 percent breakage of carbide tools during touch-off. With the off-line tool presetter, there is no breakage.

The optical presetter also allows Mr. Brunell to measure critical gage points on tools that could not be adequately measured with physical touch-off at the tool tip. For example, with the presetter, operators can optically "see" and measure the chamfer edge on a center drill.

With this critical dimension, operators no longer have to find the proper drilling depth by repeatedly making and measuring trial cuts. This is resulting in significant time savings and a reduction in scrap and rework. The setup time for a typical job with 50 tools has been reduced from 13.38 hours to 8.38 hours.

Shop-Wide Use

After reviewing Mr. Brunell's proposal of the system for his department, Chandler Evans decided to implement the DNC system in the NC departments throughout the shop. Three host computer DNC systems and the optical tool presetter computer were connected to a common Novell file server. By connecting everything to a common file server, all departments can share both the tool offset information and NC program files.

By combining DNC with a tool presetter, Mr. Brunell experienced a significant reduction in setup times, eliminated the chance for manual data entry errors, and increased worker satisfaction. In one case, the completion time for a particular part has been reduced from 44 hours to 18 hours.

Mr. Brunell determined that Chandler Evans' investment for the combined DNC and tool presetting systems had a payback of less than one year. With this investment, the company lowered its total production costs, and, more importantly, is starting to win back contracts that had previously gone to outside vendors.

According to Mr. Brunell, "Our tool presetter and DNC software has allowed my department to stay competitive. It has reduced setup time, along with scrap and rework. It has enabled us to constantly maintain depths and chamfer diameters. The combination has allowed us to be very flexible in how we touch-off a tool, and allowed us more tolerance on our form tools."

Continuous Improvement

Mr. Brunell is now upgrading his host computers to accommodate Focal Point DNC for Windows and Toolset Manager for Windows. With these upgrades, operators will be able to take advantage of additional features like the viewing of tool and part drawings, more flexible NC file administration, and user definable formulas for tool offsets.

Jumping into computerized manufacturing has been beneficial to Chandler Evans. Their original goals of trying to reduce setup have been realized. Delivery times for parts are down, and scrap and rework are down. With reduced setup, throughput and machine utilization is up.