Manufacturer’s metrology upgrade helps ensure tight-tolerance quality

Situation

Part of the Renk group, Horstman is a manufacturer and global supplier of suspension systems for heavily armored and tracked vehicles. It also produces safety-critical engineering components allied to its core products for the subsea and aerospace industries. These components are up to 1.15 m long by 0.75 m in diameter, made of steel, titanium, and aluminum.

The factory at the company's headquarters in Bath, U.K., was an early adopter of coordinate measurement machines. The company has had a succession of different CMM models over the years, most recently three machines of small, medium, and large capacity.

At Horstman, new designs are being introduced with increasing regularity and to ever-tighter tolerances for hydropneumatic suspensions, electronic and electrohydraulic active vehicle ride management systems, military thermal management systems, and the aerospace and subsea products. That is why the metrology departments were often under pressure and wanted to move quality control technology forward in terms of speed of data acquisition and the accuracy of the data collected, in particular for form measurement.

"As we are involved in the supply of safety-critical, defense-related products, we decided that we needed a second large-capacity measuring machine that could inspect every size of component that we manufacture to provide redundancy in our capabilities if one of the CMMs should break down or require servicing,” said Stephen Ellis, quality manager at the Bath factory.

Resolution

The company chose to install the new LK AlteraM 25.15.12 bridge CMM at its factories in Bath and Sterling Heights, Mich.

"We manufacture some components for our U.S. factory, and they produce others for us, so it was expedient to duplicate the metrology facility in our Sterling Heights plant,” Ellis explained.

The machine, which has a large inspection volume of nominally 2.5 by 1.5 by 1.2 m and is equipped with traditional touch trigger probing and an advanced tactile scanning probe, replaced the smallest of the three previous machines.

The CMM captures dimensions and shapes rapidly, and results are compared with the corresponding CAD model to ascertain fit and finish. Typical measurement cycle times are between 10 minutes and one hour. Features with a total tolerance down to 7 microns need to be inspected, and some parts have reflective surfaces, which is why the manufacturer has not opted for the rapid, high-density point cloud acquisition of laser scanning. It would entail surface preparation, and in Ellis’ opinion, laser sensors do not offer the same level of accuracy and repeatability as tactile probes.

"The contact scanning capability of the new LK CMMs acquires many hundreds of surface points every second, enabling interrogation of form as well as size and position, including of bores 400 mm deep,” said Trevor Prynne, business development director at Horstman.

The latest version of LK's CAMIO 2021 software for programming and reporting has been supplied to the two factories. It also can be retrofitted to other CMMs at both sites in the future to enable interoperability between the different machines. The software features a graphical user interface, single- and multipart loading instructions, program queuing, and advanced error recovery for automated inspection.