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CAD/CAM transforms mold and die shop.

CAD/CAM transforms mold and die shop

In 1982, Cleveland Mold & Die Inc (CMD), a 28-person job shop in Cleveland, OH, embraced the concept of CNC machining. Since 1983, the company has increased the number of completed projects monthly by 240 percent, at the same time maintaining quality standards expected by its customers.

That same year, CMD required a job lead-time of six weeks, on average. Today lead-times are down to one week.

When the company began using CNC machining centers and EDMs, a typical NC part program took several weeks to write, and consisted of nearly a quarter-million ASCII code characters. Now that same program can be written in a matter of hours, with fewer than 1000 macro characters.

Furthermore, the company's mold and die quality, scheduling, and delivery performance have all improved substantially over 1982-83 levels.

What brought about this rapid, dramatic transformation? Company executives attribute gains largely to adoption of CNC, CAD/CAM, and DNC. Another major boost has come from the company's development of its own macro language for NC programming. Through these measures, CMD has quickly propelled itself to the leading edge of computer-aided moldmaking and diemaking.

First CNC in '83

The company was founded in 1945 by Alois Weissmann, an immigrant from Germany. Now owned and headed by Rosemarie Evans, his daughter, CMD occupies a 14,000-sq-ft facility on Cleveland's southwest side. Products include a wide variety of custom tooling for magnesium, aluminum, and zinc die-casting, plus tooling for plastic injection molding, including transfer and compression molds.

Serving the moldmaking and die-casting industry across the US with complete, in-house design and build capabilities, CMD machines molds and dies from a range of steels. These include H-13, Viscount 44, beryllium, copper, and stainless.

The company's ventures in electronically-aided metalworking began in early 1983, when they bought their first CNC machine. This is a Model FNC 74 vertical machining center from LeBlond-Makino Machine Tool Co, Cincinnati, OH.

"It seemed appropriate to get into CNC and other computer technology," says Rosemarie Evans. "We saw it as the way of the future for moldmaking and diemaking.

"In addition, we felt a need to complement our machinists' skills, and to take advantage of the increases in quality, speed, and consistency made possible by computer technology."

Since 1983, the company has added five other CNC machines. These include three additional LeBlond-Makino machining centers: A Model MC 65 horizontal, FNC 106 vertical, and FNC 128 vertical. All four machining centers have Fanuc Model 6M or 11M CNC controls.

Later the company purchased two LeBlond-Makino CNC ram-type electrical discharge machines. All told, the company uses about 50 machine tools, including an Easco-Sparcatron ram-type EDM and a variety of manual mills, grinders, drill presses, and other types.

About six years ago, CMD began experimenting with computer-aided NC programming for its CNC machines. "We bought a hand-held computer and wrote some simple programs," relates Tom Evans, manager of manufacturing. "They worked, but their best effect was to arouse interest in the methods and possibilities of computer-aided NC."

Under his direction, CMD began developing a full-fledged, networked CAD/CAM system. They started by installing Anvil 1000 CAD software from MCS Inc, Irvine, CA. This software runs on MS-DOS PCs from Leading Edge Products Inc, Canton, MA.

Later, CMD added three other Leading Edge PCs to run Anvil 1000, and a System P, Model G CAD/CAM computer system from General Numeric Corp, Elk Grove Village, IL. CMD uses this system for an occasional 3-D CAD modeling project.

The PCs are linked on a DNC network that joins engineering and programming offices with the CNC machining and EDM departments. Hosting this DNC network is a Tandy 1000 PC from Tandy Corp, Ft Worth, TX. This PC runs PC-DNC software from Suburban Machinery, Willoughby, OH.

Other units installed on the CAD/CAM and DNC network include digitizing tablets for CAD, two plotters, a text printer, and a multiport controller. In all, the company has invested only $35,000 for hardware and software in this extensive, networked system.

Typical procedures

CMD receives most specs for molds and dies on paper or mylar drawings. Some arrive on a fax machine, while a few customers mail or carry in CAD files on floppy disks.

For some projects, the company starts from a model or prototype of the diecast or molded end-product. A machine operator installs a mechanical probe on one of the vertical machining centers, and picks off measurement data. These are combined to create a CAD database for the product. Through mirror imaging, female representations are generated for mold or die components.

After giving a quote and having it accepted, CMD decides which components should be made on manual machines and which on CNC. Also part of this phase is determining what carbon electrodes will be required, and which of these need to be made on CNC equipment.

Once a CAD drawing of a mold or die component is brought up on the PC screen, an engineer checks for correctness of geometry. "We usually find something to correct," says Tom Evans. "In fact, most drawings we receive are highly inaccurate. If the lines are not geometrically correct, they may create big problems later on.

"It has been difficult to impress on customers the importance of having their designers make drawings line-perfect--that is, geometrically sound. All CAD and NC data originate in the first part print. If there's an error in geometry, it may be carried all the way into the machined part."

After checking and correcting a customer's drawing, an engineer generates a CAD graphics file. Details are checked again, and draft and shrinkage factors, along with dimensions, are added.

As noted previously, CMD does most computer-aided design and drafting in Anvil 1000. A 2.5-D, 8-color, wireframe system, Anvil 1000 runs on MS-DOS PCs. This software produces fully annotated engineering drawings, and allows as many as 1024 layers in any drawing.

About 90 percent of the company's CAD work is done in 2.5-D, but the remaining 10 percent call for 3-D. For this, CMD uses the General Numeric System P. Model G system. This features automatic programming in FAPT language, and conversational input of graphics in Symbolic FAPT. Particularly useful is the system's ability to do automatic 3-D die sculpturing from 2-D sectional curves.

Once a CAD drawing has been plotted out and approved, it is transmitted to another PC for NC programming. A programmer picks out a shape or component to work on, establishes a datum point, and generates cutter paths. This machining program then goes into a customized postprocessor, which automatically produces G and M codes in CMD's own macro language.

After a postprocessed program has been produced and checked, it goes into disk storage until needed. Later, when a machinist is ready to run a part, he calls for the program to be transmitted over the network to his machine's CNC.

The company's DNC network management software, PC-DNC, enables any CNC unit in the shop to receive or send programs through an RS-232 port. When receiving, PC-DNC uses automatic code recognition. Distribution of data takes place through a single 8:1 port controller.

More with less

Early in their experience with CNC, the company saw drawbacks in conventional NC programming. Complex in its contours, a typical mold or die requires long, complicated programs containing hundreds of thousands of characters. Not only do such programs take much time to write, but their length and complexity open many opportunities for errors.

To overcome this shortcoming of conventional NC code, CMD began developing a macro NC code, one that compresses many commands into a few characters. Written in Basic, CMD's macro code leans heavily on the computing power resident in the Fanuc CNC units.

"Macro code wouldn't work without the power in our machine controls," Evans says. "Much of the number-crunching is done at the CNC controls."

The approach to programming at CMD has been to do each job with as little machine code as possible. In one case, for example, a program that would require 241,000 characters in ASCII code can now be written in 848 macro code characters. That's a reduction ratio of 281:1.

CMD's code enables each program to think ahead through all spindle and table moves, and through all tool selections, before machining begins. Feeds and speeds are calculated automatically, but operators can override at any time. Adjustments can be made in feed rate, for instance, in increments from 1 to 200 percent. Programs automatically check to ensure that the proper tools are in the magazine.

"An operator doesn't have to concern himself much with a program," says Evans. "The software and controls do most of the planning and thinking for him. As a result, he can concentrate on part dimensions and machine performance."

Further, use of macro code enables programmers and machinists to prove out new part programs quickly and accurately. The procedure is so dependable, in fact, that machinists need not cut wax models, but go directly into production cutting of steel.

Since the macro code is structured the way a machinist thinks, training machinists to read part programs is relatively easy, Evans says. "We can have a good machinist producing parts in less than a week. What's more, using this code enhances the skills and capabilities of our veteran machinists. In effect, it can turn a machinist into a diemaker.

"Another good result of adopting macro code is that it has pressured us to standardize tool selection, machining procedures, and program commands. With less diversity in these factors, we have reduced errors and confusion. And of course, lead-times are shorter now.

"Perhaps the biggest benefit of using CNC and our new macro language, though, is a capability for longer periods of untended machining," Evans adds. "We can prove out a program quickly and begin cutting a mold or die without having to make a model or prototype."

Right now, Tom Evans won't reveal full details about the macro code. "We've already invested hundreds of hours of time into its development," he explains, "and we intend to package and market the software commercially."

For information about CMD's services, write to: Mrs Rosemarie Evans, President, Cleveland Mold & Die Inc, 5160 W 164th St, Cleveland, OH 44142. Phone (216) 267-8128.
COPYRIGHT 1989 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Cleveland Mold & Die Inc.
Author:Quinlan, Joseph C.
Publication:Tooling & Production
Date:Sep 1, 1989
Words:1709
Previous Article:A guide to upset forging.
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