Non-Contact Dimensional Gauging

Application: Forging Press Die Closure Gauging
The forging press Die Closure Gauge System (DCG) is an automated gauging system which can measure the outside dimension of forged crankshaft journals to determine the degree of die closure immediately after forging. This information can be used to continuously correct the forging parameters (temperature, pressure, etc.) so as to keep all of the product within allowable tolerance. A production file will be created showing the actual dimensions of every crankshaft in a production run for later analysis and certification.

Introduction
The inspection system consists of a large heavy steel frame, with an adjustable "V" block mount on one end, and a camera assembly on the other end. The entire frame has wheels so that it can be moved around, and lowering legs so that it can be fixed in the desired location. The frame is approximately 82 inches long, 62 inches wide and 42 inches high. The camera assembly has a hooded enclosure covering the full width of the frame. An industrial steel control box is mounted on the frame just below the camera assembly. The power requirements are 115VAC at 8 amps.

Inspection Process
When the final pressing is complete, the operator will remove the forging from the press, move it over to the gauge, and place it on the "V” blocks with the parting line horizontal. When it is in the correct position, he will press a button in the manipulator cab to tell the system to begin its inspection. After the system has finished scanning the part, it will display the plus or minus deviations from target dimensions. This is displayed on three nine-inch display panels showing left, center and right journal deviations. The display indicates If one of the readings is outside the allowable tolerance. The time to complete the inspection is 10 to 15 seconds.

If the operator is not satisfied with the inspection readings, he has the option of re-positioning the part and re-inspecting to get a new set of readings. In this case, both sets of readings will be saved in the production data file. Each forging will create a record in the production data file, which contains a sequence number, the date and time of the readings, the three deviation readings and the apparent temperature of the forging at the time it was measured. If the part is re-inspected, a new record will be created with the same sequence number as the first inspection, but with the new measurement data. At the end of the production run, a record will be created showing the number of parts measured and the number which fell outside the allowable tolerance range.

Inspection Technique
The system uses a 2048 pixel line scan camera with a field of view of ten inches to provide a physical resolution of 0.005 inch per pixel. An edge interpolation technique is used to increase the actual measurement resolution to about 0.001 inch. The camera is mounted on a precision transport to scan a forging up to 54 inches long. When the inspection starts it first finds a reference edge on the forging. It then translates to the first journal to take a series of measurements over the designated portion of the journal. A nominal diameter reading for the journal is found, then the system moves to the next journal and the process is repeated. After the inspection is complete the camera returns to the home position.

When a production run is opened production and inspection parameter information is entered into the system. Measurement parameters and inspection location is set-up using a drawing of the part. The part number and parameters are stored in a library for recall later. At the end of the production run all production data is stored in a permanent computer file. A certification part is supplied with the system to periodically check the system. Access to the system is secured by passwords that are set up by a supervisor.