Advanced Design and Production Keeps On Truckin'

T he Kress Corporation is a producer of material handling equipment for steel mills, copper smelters and strip mines. For years, the company has produced heavy duty, off-road vehicles that stand two stories high and resemble giant-sized Tonka toys. In its first year of operation, the company manufactured the first slag pot carrier for steel mills, with a 550 cubic foot capacity. Since then, the company has introduced a unitized 150-ton capacity coal hauler; a 200-ton capacity "U" frame and "straddle" type steel slab carrier with tongs, and the first elevating pallet carriers.

Gulliver-sized tools and machinery lend improvement to Brobdingngian -sized trucks

One key move that kept Kress ahead in engineering development was a decision to adopt CAD technology when it was still a fairly new concept in 1986. At that time the company installed two ICEM Technologies DDN (Design Drafting Numerical Control) CAD terminals and linked them to a mainframe computer. During the last ten years, as Kress expanded its business, the number and sophistication of its CAD systems also grew. Today, the company has a total of 41 ICEM DDN seats running on an SGI work-station network.

One of the company's major accomplishments attests to the role CAD has played in Kress' continuing leadership. The company produced the world's largest truck, a 300-ton capacity coal carrier designed entirely with the ICEM DDN system. This single unit hauler can travel at 45 miles-per-hour, and make extremely tight 180 degree turns (only five feet wider than the overall length of the truck). The truck features nitrogen-charged shock absorbers six times softer than the tires, and offers an excellent payload to weight ratio of 2.29 to 1.

The ICEM DDN package is a 3D CAD/CAM system covering all applications, from 2D design and drafting to complex surface and solid modeling, in an open systems architecture. ICEM DDN's modular structure allows engineers to select those parts of the program actually required for their work. A built-in database allows simultaneous access to all data. ICEM DDN is an interactive system, offering a common foundation for the entire product development cycle -- from the first conceptual design through detailing and documentation to the preparation of NC manufacturing data.

The company's engineering sales staff uses the CAD system to build conceptual designs as they work with customers. These proposal drawings are passed on to the client's engineering department and are used as a launching point. Completed designs then move to the manufacturing department for NC-driven torchcut plate tool paths, lathes and mills. The technical publications department also uses ICEM DDN engineering drawings for the production of service manuals and parts books.

As one would expect, however, the greatest concentration of ICEM DDN seats are found in the engineering department, where a staff of 50, working in two shifts, uses 30 of the company's 41 ICEM DDN licenses. The CAD Manager at Kress, Earl Grotts, says that Kress engineers use ICEM DDN to perform engineering analysis, and mass and section property calculations, early in the conceptual design phase -- important tools when designing high capacity vehicles. Fit-up and interference checking can also be performed during the design phase. "Performing these functions at the beginning of the design process, rather than later in the build process, allows changes to be made while cost and impact are still minimal," says Grotts.

"ICEM DDN also allows us to design to tighter tolerances and that helps us deal with one of our greatest challenges: to maximize safety factors by distributing weight most efficiently," explains Grotts. To help optimize a design from this perspective, an ICEM DDN GPL module is used to calculate weight during the design process, and the calculations are indicated on each drawing.

Edward "Ted" Kress, founder and president of the Kress Corporation, also believes in the advantages of CAD. He uses ICEM DDN himself and is impressed with how easy it is to try out design ideas. "I can change a new design over and over. We also use surface shading to make very effective color pictures for sales presentations of our new concepts."

The result of sharing ICEM DDN information across Kress departments is a savings of enormous amounts of time by cutting down on duplicated efforts. In addition, many errors are eliminated that would normally creep into documents or instructions when they are recreated or rekeyed.

Large Hauler in JIT Production

At the John Deere plant in Davenport, IA, two Cincinnati Milacron machining centers handle production of most of the large chassis parts for the five models in the 4-wheel drive loader line. Arranged in a single flexible machining cell, the two units together output 10,000 to 11,000 tons of parts per year. The machines -- a TC-Bar Horizontal CNC Machining Center with dual rotary worktables, a live spindle and 9 CNC-controlled axes; and a Magnum 800 CNC Horizontal Machining Center with a six-pallet Automated Workchanger -- each require just one worker per shift to run operations.

Like most companies today, manufacturing data fed to the machines comes from UNIX-based computers over a centralized data bus. Engineers can make edits on the shop floor directly at the machines, and two-way communications capability over the bus allows those edits to be sent back to the original files.

The TC-Bar unit produces the loader's engine frame, which carries the engine, transmission, cab and rear axle. The basic frame that is fixtured to the two 360,000-position tables is just a raw weldment, often weighing as much as 6,000 lbs. Once fixtured, the operator presses "cycle start," a probe tells the Acramatic controller which frame is on the pallet, and the machine does the rest. The two-table setup allows continuous machining and, if the need were to arise, the unit could likely run 24 hours a day, seven days a week, without interruption.

The Magnum machine handles somewhat smaller pieces weighing 20 to 800 lbs., which includes mounting parts, linkages and axle support components. Because these are key components to producing the remainder of the loader chassis, the Magnum's carousel workchanger is in constant motion. Six off-line pallet stations allow changes in a matter of seconds -- automatic pallet transfer on and off the Z-axis occurs at 1000 ipm. Once the transfer is complete, a quick 180-degree spin on the rotary workchanger brings a new pallet of parts into position for shuttle onto the pallet-forward Z-axis. Again, a probe informs the Acramatic 950 controller assigned to the Magnum what pallet is loaded, and the controller does the rest.

An automated tooling system in the cell constantly monitors horsepower and analyzes it through torque control software. Called AcraSense, each machine's spindle load is tracked, with changes to feedrates handled in-process. This reduces broken tooling while optimizing metal removal and tool life. If there is a disparity between measured cutting torque and programmed values, the software adjusts the cut for such conditions such as air gaps, workpiece hardness, hole break-through, cross and blind holes, and chip buildup. Should the tool break or wear excessively, AcraSense initiates a feed hold or, when so programmed, a tool replacement in the case of redundant tooling.

For more information, contact:

Kress Corp., 227 W. Illinois St., Brimfield, IL 61517. 309-446-3395. Circle 431.

ICEM Technologies, 4201 Lexington Ave., North, Arden Hills, MN 55126-6198. 651-415-4327. Circle 432.

Deere & Company, One John Deere Place, Moline, IL 61265-8098. 309-765-8000.
Circle 433.

Cincinnati Milacron, 4701 Marburg Ave., Cincinnati, OH 45209. 513-841-8280.
Circle 434.

Originally published in the November  1998 issue of designfax.
Please Note: some pictures or diagrams are only available through the printed media.