From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Article on the use of X-ray photography for the quality control and inspection of metal castings.
| Identifier | ExFiles\Box 143\3\ scan0191 | |
| Date | 25th April 1940 guessed | |
| 15 X-ray photographs reveal the innermost secrets of metal parts to the expert eye of the metallurgist. Here a negative of aluminum castings is being carefully scrutinized. parts are frequently photographed on the same negative. Every negative has a number and each part radiographed also has its number. The negative numbers are of lead. The part numbers are pressed into the metal with a pneumatic tool invented for the task. Negative files are maintained so that the record of any individual part can be found instantly. The X-ray photograph shows the inspector, a trained metallurgist, everything he needs to know about any internal imperfections that might impair the strength and efficiency of a part. He examines the negatives for evidence of shrinkage, porosity, cracks, foreign matter, or other faults. The five X-ray machines used at the Lockheed plant include two portable outfits which permit the use of radiography for the examination of assemblies in the completed plane as a final, vital check. The 180,000-volt machine installed at the Lockheed plant was made by Triplett and Barton for X-ray photographs of aluminum castings. They made another machine, of 220,000-volt capacity, to examine light weldings, large aluminum and small steel parts. The 300,000-volt machine, built to their specifications by General Electric, is used for radiographs of heavy bronze and steel castings. Each stationary machine is set up in its own room, the walls of which are lined with three thicknesses of lead sheeting. Safety doors, which are operated electrically, prevent the entrance of an operator while the X-ray exposure is being made. A main switch starts the circuit. Then a button, which operates through a time relay, turns on the power in the X-ray tube, closes the doors, and turns on the circuit for the exposure. The exposure time is pre-set. At the end of the period, everything is turned off automatically and the doors of the chamber open. A lead-topped table carries the negative. The parts to be X-rayed are placed on a cardboard and set down on the negative. A plumb-bob is used to center the parts under the X-ray tube. The average exposure is about 60 seconds. Experiment and calculation have given Triplett and Barton a table of exposure times for different parts and different metals. Variations in voltage produce changes in contrast. At least two exposures are made of all parts—one for the thick side, one for the thin side. It has been necessary, in certain cases, to take as many as 48 exposures from as many different angles. Every angle of a part must be X-rayed to insure conformity and coverage of all angles. Even minor parts are given exposures for their different dimensions. Triplett and Barton began their X-raying for the aviation industry with one machine. That was expensive. The use of five machines, in addition to increas- (Continued on page 88) [Image Caption 1] The parts which are to be X-ray photographed are placed on the film which is in a paper envelope. The X-ray machine is shown above the head of the worker. [Image Caption 2] Before each part is X-ray photographed it is given a record number which is then pressed into it with a special machine. | ||