Synchronous carrier takes tools and parts for a ride, along with the operator, in an automotive assembly line. (Photo courtesy of R.P. Gatta Inc.)

Computer-aided-design (CAD) has become an essential tool for machinery builders, even small ones, for designing various machine elements including PT drive components. Many of their customers are driving the use of CAD — demanding not only that suppliers furnish CAD drawings, but, that these drawings are compatible with the customer’s CAD system. Usually, the supplier that doesn’t comply becomes a nonsupplier!

Machines for car makers

The automated equipment in large manufacturing and assembly plants often originates at small, specialized design firms. Take R.P. Gatta Inc., machinery supplier for the automobile manufacturing giants. Located in Twinsburg, Ohio, this company designs and assembles equipment primarily for automotive assembly lines.

Three designers crank out the machine drawings on IBM-compatible personal computers (PCs) with 286, 386, or 486 microprocessors. The company bought three PCs, each one faster and with more memory than the last. The newest model sports a 120-MB hard drive and a 486 microprocessor that operates at 50 MHz.

Limitations of the older 286 machine, which is only 3 years old, are already evident — it slows down as a drawing grows because of the file space required. To speed things up, the designer divides a large drawing into several smaller drawings that take up less space. The newer PCs are more productive because of higher speeds and larger memory.

Mouse-operated tablets are used to speed the selection of macros — miniprograms that perform special functions — rather than going through a series of menus.

The company uses CADKEY design software from Cadkey Inc., Windsor, Conn. This program offers 3D design, drafting, and solid modeling capabilities.

Though 80% of their machines are custom designed, says Raymond P. Gatta, owner, some require only small modifications from a previous design. Thus, a big advantage of CAD is the ease in making design changes. Also, it is easier to perform multiple iterations, thereby achieving a better final design.

A valuable asset for large, complex drawings is the ability to enlarge part of a CAD drawing on screen to view details. Another useful feature is the automatic insertion of dimensions when the user selects the dimension lines.

Though it is difficult to quantify the benefits of CAD, Mr. Gatta estimates that it increases design productivity about 10% compared to traditional drafting methods. For detail drawing, time savings are likely to be greater, perhaps 25 to 30%. The biggest savings come with pneumatic system drawings because many standard components, such as valves, can be automatically generated on a drawing after being imported from a manufacturer’s catalog disk.

Electrical systems also have many standard components and symbols that can be generated from disk libraries. Further, machine subassemblies, such as a motor-gearbox combination, can be drawn once and saved, then duplicated in multiple locations.

An intricate circuit-board layout produced by J. Nelson Graphics Inc.

Thorns among roses. CAD isn’t without drawbacks, though. One is the need to translate drawing files into a format compatible with the customer’s CAD system. This requires, for example, that a designer translate a CADKEY file, using a generic translator program such as DXF or IGES, to an AutoCAD file before sending it on disk to the customer. This translating step, which typically takes several minutes per drawing, becomes a tedious process when large numbers of drawings are involved.

Also, when software is upgraded, it takes up to a day to incorporate the upgrade and get back in operation.

CAD training begins with a two-day introductory session conducted by a local hardware and software supplier. But the key, says Ray Gatta, is to learn by using the system. The designers recognize that CAD helps the company remain competitive, thereby building job security. Therefore, they have been very receptive to learning the system. Generally, it takes the designers only about 1 mo to become reasonably proficient in CAD.

Stuck on cars

Much of the equipment designed by Gatta is used on automotive assembly lines. For example, three different machines are used in applying side molding strips to cars. These machines latch on to the production line so they move at the same speed. The first machine cleans the car body to provide a good adhesive surface. The second applies the side moldings to within 60.5 mm, using a pneumatic drive. A third machine rolls down the strip to ensure that it firmly adheres to the car body. Then, the machines are repositioned for the next car by a rack-and-pinion assembly driven by an air-motor.

Another machine, called a synchronous carrier, holds parts and tools needed by the production-line operator. Sometimes, it carries the operator as well. The carrier keeps pace with the production line so the parts and tools are readily available when the operator needs them. At the end of a cycle, a chain drive returns the carrier to its original position. Some carriers are electric-motor driven and PLC-controlled. Others use air motors and air logic controls.

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