HIGH-ACCURACY GRINDER SETS THE STANDARDS AT PROTOTYPE-ONLY FACILITY.
Ford's prototype-only facility, Engine Manufacturing Development Operations (EMDO), holds extremely close tolerances on test parts using a Gardner G750 double-disc grinder that is nearly identical to the carmaker's production-floor grinders.
Ford's Engine Manufacturing Development Operations (EMDO) site smoothes the road to production for the company's most dependable and widely used engines. At this facility in Allen Park, Mich., engineers develop only prototypes. But just as important, they conduct the accompanying product and manufacturing process testing that would otherwise interfere with day-to-day operations at a mass-production plant.
Parts and processes are tested as well as tooling. Evaluating grinding wheels, for example, determines if they will crack or fracture during production, how many dresses to expect from each wheel, what types of materials the wheels can be used on, and so forth — all the variables of that particular tool.
In one case, EMDO employed a Gardner G750 double-disc grinder from Landis Gardner of Waynesboro, Pa., to determine roughing and finishing operations for stepped connecting rods. The thickness of such a rod is different at the crank and pin ends, as opposed to co-planar rods in which the thickness is uniform.
Prototype connecting rods are first forged from powdered metal prior to grinding for the required flatness and parallelism. To produce the stepped-down, pin-end thickness, EMDO finish grinds the whole rod to the larger thickness of the crank end and then refixtures the rod, holding it from the crank end, to finish grind the smaller thickness of the pin end. The pin end is essentially unsupported at this point, but testing at EMDO proved that high-quality stepped rods could be reliably produced using this method.
Each rod is then checked for flatness and parallelism using a 0.0001-in.graduating indicator on a granite surface plate. All new engines must pass stringent government certifications, so EMDO must make the parts as accurately as possible. According to Ford, this is one reason EMDO chose the G750 for its connecting rod grinding.
Another is that Gardner manufactures both double-disc grinders and grinding wheels, and EMDO says this contributes to holding the extremely tight tolerances for prototype applications.
With an added reciprocating fixture, EMDO's G750 holds size within 0.000050 in. This machine is similar, if not identical, to those found on a Ford production floor. However, EMDO's grinder has the custom, reciprocating-type fixturing necessary to accommodate special prototype parts.
With this setup, the servomotor-driven, paddle-type fixture moves parts between the grinding disc faces. EMDO operators load the test rods one at a time because of the lower part volumes. However, conventional connecting rod production uses rotary-carrier fixturing with a 42-in.-diameter grinding wheel. For the prototype operations, EMDO mounts smaller, 30-in.-diameter disc wheels. In addition, the grinder's reciprocating fixture has a built-in nest with inter-changeable inserts to accommodate different test parts.
EMDO's G750 features three servo axes, one on each wheel head, and one on the paddle. Operators change the in-and-out movement of the paddle with Gardner's Lektrifeed III control unit, which also controls all changes in grind lines and feedrates. The Lektrifeed system features an open architectural design, and, for the EMDO application, changes parts over in 15 min or less. Also, sensors throughout the grinding machine alert operators to potential problems. If one is detected, the operator cannot cycle the machine again until the problem is defined and the fault is cleared.
Once part sizes are perfected, EMDO test drives the process. Ford instructs the facility to use a make-like-production standard in all phases of its operations — the parts it produces, the processes it implements, and the procedures it follows. Facility personnel realize that these elements may very well become part of a mass production operation. And as such, they need to be not only optimized, but near perfect. They typically produce volumes of about 3 to 500 parts per run, as compared to production-plant levels of 7 to 800 parts per hour. EMDO's comprehensive research also addresses questions concerning costs to produce the part and whether or not the benefits outweigh the costs.
Ford Motor Co., headquartered in Dearborn, Mich., recognized the need for a prototype-only facility nearly two decades ago, and EMDO has been instrumental in testing design and manufacturing feasibility ever since. Today, EMDO produces engine prototypes for not only Ford, but also for Jaguar and Mazda — from popular V-6 and V-8 models to powerful V-10 and V-12 power plants.
Validating machine accuracy
When precision components have roundness specifications of 0.000025 in. or less, shops need an extremely capable measuring machine to check them. That's why Landis Gardner recently invested in a new roundness and geometry measuring machine for its product assurance lab. The new machine, a Mahr Formtester MFK6, is a 7-axis computer-controlled gage that accurately measures roundness and other part attributes to within 0.000004 in.
According to Aron Brall, vice president of quality at Landis Gardner, the roundness and geometry gage measures critical components for grinding machines that the company builds. It also validates production grinders for customers by checking high-precision ground parts.
Considered a critical machine component, most of Landis Gardner's precision grinding spindles are checked on the Mahr machine. These parts fall within 0.000015 in. of perfect roundness, and checking them with conventional methods is virtually impossible, says Brall.
Since installing the sophisticated measuring machine, which is the only one of its type in North America, Landis Gardner engineers have worked with Mahr to develop new measuring techniques for extremely difficult-to-measure parts. One such customer application, says Brall, couldn't have been done without the high-tech Mahr measuring machine.
The customer's part was designed to be eccentric by only 0.0015 in. from perfect roundness with a tolerance of 0.0001 in. "Our ability to first grind the part to such close tolerances and then measure the part accurately helped convince the customer that the Landis 1SE CNC production grinder was the right machine for the job," comments Brall.