Chasing Microns -

Diving under the railway arch on the way - to IMTS Grinding Technology  and entering Gas House Road may conjure up images of Tony Han- cock and East Cheam railway sidings - however, nothing could be further from the truth. The reality is a company that specialises in chasing microns.

Main thrust of this high-tech business is rebuild, retrofitting and the design and build of special purpose machinery. The economic way to do this, according to managing director Charles Thurston, is via PLC's. What you finish up with is a microprocessor-controlled machine complete with solenoid valves and servos; the hydraulics are the same but by using a PLC instead of relays you can change the program.

A recent IMTS development uses a stepper motor/ballscrew arrangement on a single axis infeed system, resulting in 'many of the advantages of CNC at a substantially reduced cost.' This first came about when a customer was having problems trying to hold size on an internal grinder and was considering the retrofit of in-process gauging. IMTS suggested that, because both the workhead and component were moving there could be a vibrational problem - which would not be easily solved by gauging. The IMTS solution, adopted by the customer, was to use a different method to grind the component. The original machine used a simple cam system to provide infeed. IMTS fitted a ballscrew system and small programmable controller. The final system had four infeeds, plus spark-out and an automatic dressing cycle. The delighted customer is now holding 5µ all day long without making any adjustments. He has also decreased cycle times and scrap.

IMTS is currently rebuilding two more cylindrical machines based on a similar philosophy - one for Desoutter and one for Lucas. Later this year Thurston is looking to develop a two-axis PLC controlled machine. The plan is to take a Tschudin base, and add ballscrews to the X and Z axes. This doesn't become a full CNC machine, but rather a low cost option. IMTS is also looking at the feasibility of doing multi outside diameters and radius wheel dressing. 'Problem is', says Thurston, 'if you go for full CNC you go into Category 3 of the CE marking procedures which means a totally enclosed machine. With the PLC or microprocessor, if there isn't any feedback you only need to go to class 2 for CE marking. That means we can produce the machine at much lower cost for the customer'.

With CNC, the main business is retrofitting CNC systems to manual machines or updating existing CNC machines with more modern controls. In most cases, this requires fitting new servos and drives. Thurston's largest customer, Lucas has a lot of work undertaken on machines used in the production of fuel injectors. UK bearing manufacturers RHP, Faffnir, Torrington and SKF are also prominent customers.

Then there is tool grinding. IMTS developed a creepfeed system, which has already been successfully retrofitted to four Tripet surface grinders - others are in the pipeline including a Jones & Shipman machine. IMTS spent a year developing a special valve with a Swiss company, which automatically compensates for pressure and temperature fluctuations during the creepfeed process. This has been a vital element when grinding carbide inserts where it is imperative to maintain constant speed while avoiding burning or chipping of the carbide.

One of the first special purpose machines designed and built by IMTS was a five-axis CNC knife grinder. This had a CNC dresser plus infeed; the wheel is the X axis, the table motion is the Z and a C axis swivels the component about the wheels centre line. When entering relief parameters into the control, the computer automatically corrects the wheel form to produce the required relief when grinding coil-fed machine knive or sawblade blank stock. The machine is based on a 1968 Tschudin cylindrical grinder.

IMTS even designs and builds new machines - one example being a cylindrical grinder complete with glass scales and CNC system, with a resolution of two tenths of a micron, for grinding Lucas fuel injection nozzles. Not bad for a company in Castle View Business Centre - approached via the railway arch into Gas House Road.