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X-ray system cuts inspection time for Precision Castparts.

The power and exposure quality of their new x-ray system is providing PCC with quicker and more detailed views of its cast parts.

Dee Morgan Precision Castparts Corp. Portland, Oregon

Precision Castparts Corp. (PCC), Portland, Oregon, has reduced the time needed to make radiographic exposures of its investment castings. The efficiency improvement has helped the company better serve its aerospace and military hardware customers, who depend on PCC castings as key components for jet engines and other equipment.

PCC uses a Varian Linatron|R~ 200A x-ray system to obtain quality radiographs. The system provides the x-ray power and energy necessary to quickly inspect superalloy castings over a wide thickness range, up to a foot thick. In addition, a remote-controlled transfer system developed at PCC allows faster loading and unloading, saving time.

Before using the new system, PCC found it difficult to meet customers' deadlines. Now, with a more streamlined x-ray process, PCC is better able to give customers what they want, when they need it.

Varied Customer Base

PCC, with sales of $538 million in 1991, produces castings for aerospace, land-based turbines and medical implants for customers in the U.S. and Europe including Pratt and Whitney, General Electric and Rolls Royce.

PCC's Large Structurals Business Operation, with 1400 employees, makes castings that have wall thicknesses as thin as 0.060 in. At the same time, LSBO has produced castings weighing as much as 1400 lb with thicknesses up to 12 in. Some castings have a diameter exceeding 75 in.

The castings, which are made of nickel-based alloys, must withstand temperatures up to 1200F in jet engine and other critical applications.

Before shipping castings to customers, PCC ensures that they meet quality standards defined by the company and the customer. Castings are inspected to detect internal defects such as porosity, inclusions and shrinkage.

Before it bought the new machine, PCC LSBO used exclusively two older radiographic systems for high-energy radiography inspections. But as the volume of its business increased and the thickness and complexity of the castings grew, PCC searched for alternatives.

At the top of PCC's need list was a powerful, flexible system that could quickly penetrate a wide range of casting thicknesses. The old machines took hours to penetrate certain castings, causing delays in inspection and delivery.

PCC also wanted automated equipment where castings could be maneuvered quickly into place and radiographed with little manual effort. This would help speed the process and make it easier on employees.

Finally, the company needed a consistent, ready supply of spare parts for its x-ray equipment. Previously, PCC was forced to purchase additional old units and cannibalize them because replacement parts for the old machines were no longer manufactured.

Measuring Up

Based on these needs, PCC selected two of the new x-ray systems. The first system (purchased in 1982) is used in the Small Structurals Operation, while the second one (bought in 1985) is used by LSBO.

PCC still uses the older machines for castings less than 2-in. thick. But for thicker castings--and for jobs needing faster exposure time--the new systems are used.

A key benefit of the innovative unit is increased power. The unit generates up to a 2000 kV beam with a wavelength that is substantially shorter than that of the previous machine.

As a result, castings, especially those with thick walls, can be radiographed in 10-15 minutes. This is a big improvement over the two hours or more required previously.

The new machine's smaller focal spot also yields images with substantially better definition than previous images. The contrast and resolution achieved with this system are noticeably better than with other machines. This makes it easier to spot indications or problem areas.

In addition, inspection information is gathered and recorded on a computer, which then can be accessed and analyzed by PCC engineers. Radiographs are used not only to judge the quality of final parts, but to critique and improve the manufacturing process as well.

While this system improves the quality and speed of the exposure, PCC has taken the process a step further. After purchasing the unit, the company designed and manufactured a system that remotely maneuvers castings into position.

With other systems, castings must be physically moved so that they can be exposed correctly. This system allows operators to manipulate castings remotely and to monitor the results with a video camera.

Automating the Process

PCC radiographs diffuser cases for major jet engine manufacturers. The project clearly illustrates the operation of the new radiographic system and the remote casting loading mechanism.

First, an employee secures the casting to a fixture on one of four tables. The table, equipped with rollers, is moved by remote control onto an elevator that lowers the casting into the underground bay.

Once in the bay, the table is maneuvered via remote control. A video camera in the bay helps guide casting movements and a laser light emanating from the unit indicates where the x-ray beam will hit the casting, allowing the operator to position it precisely.

While the remote casting loading mechanism takes a while to learn, once technicians are up to speed, this is much quicker than the manual method. It's also easier on operators' backs than having to physically move the castings.

The films and attached penetrometers (image quality indicators) are loaded above ground and then lowered into position in the bay. Both the film cassettes and radiograph are stationary; only the castings move to gain the correct position for exposures.

The combination of the new x-ray unit and the remote part loading mechanism has helped PCC cut exposure times in half compared with the time previously needed for the thicker areas on diffuser cases.
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Title Annotation:Quality in the '90s; Varian-Linatron 200A x-ray system used to inspect castings
Author:Morgan, Dee
Publication:Modern Casting
Article Type:Cover Story
Date:May 1, 1992
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