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Shop cuts time for prototyping.

Shop cuts time for prototyping

Schulze Manufacturing Co (SMC), Burlingame, CA, is a metal stamping and fabricating company serving the state's computer industry. SMC manufactures the metal supporting substructure located just below a computer housing's plastic skin, as well as the compartments that hold 3.5" and 5.25" disk drives. Founded in 1944, the company employs 95 people.

Before CAD/CAM was recently implemented--both at SMC and its client companies--design work involved much time-consuming, manual drafting and dimensioning. The process began when a design engineer at a client company created a 2-D or 3-D part drawing. The client's drafting department then drew detailed blueprints, which were forwarded to SMC. There a flat-pattern drawing of the part was manually produced and dimensioned.

Next, flat-design information was entered manually into SMC's NC programming system. This is CAM-tech III software from Techware, Clearwater, FL. SMC runs the software on a DEC PDP 11/23 + minicomputer from Digital Equipment Corp, Maynard, MA. This system generated an NC tape, which was read by the CNC on a turret punch press from Strippit Inc, Akron, NY.

Besides being slow--creating a prototype assembly could take 10 to 12 weeks or more--the process was vulnerable to errors in drafting and calculations. To speed up the process, SMC turned to CAD/CAM. A decision was made to automate creation of flat patterns, provide CAD tools for drawing fixtures and tooling, and then downlink with CNC equipment.

Compatibility wanted

In choosing a CAD system, SMC looked for a package that was compatible with its customers' varied CAD systems, and with its own NC-programming system. Company engineers also wanted an easy-to-use system with enough memory and power to manipulate 3-D part images.

To perform design tasks, the company chose AutoCAD software from Autodesk Inc, Sausalito, CA. This program was augmented by a FlatPatt program for flat-pattern layout, and a FADD+ program for datum dimensioning. Both supplementary software packages are from ADC Computer Services Inc, North Kansas City, MO.

SMC also selected Sun Microsystems' Sun386i engineering workstation with 8 MB of memory and a 19" color monitor (see photo). The workstation is linked by PC-NFS to an IBM PC/AT-compatible computer with 1 MB memory. PC-NFS is Sun's own networking software, used to facilitate communications between Sun workstations and PCs using MS-DOS.

"We like the Sun386i because of its flexibility in working in both MS-DOS and Unix operating systems, and because it can be linked easily with existing equipment," says Rick Schulze, CAD system manager. The few MS-DOS design program SMC had run on a PC were easily transferred into the Sun.

In addition, Schulze likes Sun's icon-based user environment, and the workstation's power. The Sun 386i supports simultaneous performance of several functions, such as printing, plotting, and editing.

SMC was aided in setting up its CAD system by Avcom Corp, Palo Alto, CA. Avcom is a Sun value-added reseller (VAR).

First projects

One of the first projects SMC tackled with its new Sun/AutoCAD system was creating prototypes for a six-piece computer housing. A design engineer at the client company, a Silicon Valley computer manufacturer, created a 3-D rendering of the housing, using his own AutoCAD system.

Instead of sending the drawing to his drafting department to make the usual blueprints, though, the designer carried the drawing directly to SMC on a floppy disk. Today, SMC clients can send and receive their own drawings over a modem attached to the workstation network.

SMC engineers sent the design file to the CAD/CAM system simply by inserting a disk and calling up the file. Flat patterns were developed using FlatPatt, with an engineer answering screen prompts regarding material type, thickness, and desired bend radii. The software then generated a flat-pattern representation based on this input.

"The flat-pattern process used to be tedious and vulnerable to mistakes," says Rick Schulze. "With our CAD/CAM system, however, I actually look forward to producing flat patterns, because it's so easy and mistake-free."

Dimensioning was carried out in FADD+ software. An engineer first selected a part area with a mouse. Dimension information such as length, width, the thickness--contained implicity in the customer's CAD model--were then revealed on the screen.

Total time for flattening and dimensioning: Just 1.5 weeks, versus the 2 to 3 weeks needed previously. Making changes produced big time-savings, as the CAD system accomplishes this in minutes versus the hours needed to make changes manually.

After manipulating the design information, Schulze suggested to his client that he make part modifications to cut costs. One suggestion was to eliminate a metal hem on one of the parts, thus reducing fabrication time by about 20 percent.

Design information was then downloaded into the NC-programming system. An NC tape was produced, and the turret punch press knocked out 50 prototypes. All this design, programming, and punching activity was done in four weeks, whereas previously it would have taken 10 to 12 weeks.

Make dies, too

After prototypes were created and approved, SMC's CAD/CAM system reduced by 40 percent the time needed to design and make dies for mass-producing the computer housing parts. SMC engineers automatically created multiple copies of the flat pattern, and generated a strip layout of the manufacturing steps.

If a mistake occurred in this lay-out, engineers made a quick correction on the workstation screen. They didn't have to manually redraw entire sections.

SMC engineers design dies with the aid of a CAD-generated library of standard die shapes and punches. This saves time over the old process of creating die designs each time a new product is to be manufactured.

Once a die design is finalized, its information can be fed instantly into an HP 9836C computer from Hewlett-Packard, Cupertino, CA. This computer runs Go Elan NC-programming software from Centech, Glenview, IL. Part programs then go to Model F40 and Robofil 552 CNC electrical discharge machines from Charmilles Technologies Corp, Mt Prospect, IL. The two EDMs are used to cut dies.

"Our CAD/CAM system is helping us keep up with the increasing turnaround times of our customers," says Rich Schulze. "Perhaps just as important, it shows customers that we are on the leading edge of mechanical design and manufacturing."

For information on Sun workstations, write to: Sun Microsystems Inc, 2550 Garcia Ave, Mountain View, CA 94043. Phone (415) 960-1300.

For information on AutoCAD software, write to: Autodesk Inc, 2320 Marinship Way, Sausalito, CA 94965. Phone (415) 331-0356. 2101
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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Publication:Tooling & Production
Date:Sep 1, 1989
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