Abrasive technology offers bite

In years gone by, no toolroom was complete without the presence of a surface grinder. But today's applications are incredibly varied. A case in point is demonstrated by MHV Products of Ashford, Middlesex, which recently had to grind plate-type components intended for machines that punch centre holes in CDs. Measuring around 50 mm thick, 700 mm long and 300 mm wide, the plates were too big to grind using the company's existing surface grinder. The initial solution involved outsourcing the surface grinding operation, but this resulted in turnaround times of anything up to three weeks. The alternative was to invest in a surface grinder with a larger table, although, with only a limited demand for surface grinding, Kevin Hibbert, director and owner of MHV Products, opted for a manual machine. An XYZ 1224 from XYZ Machine Tools fitted the bill, especially as it has a footprint of just 3,550 by 2,550 mm and is supplied as standard with a permanent or electromagnetic chuck, dust extraction and flood coolant, as well as power rise and fall to the wheelhead. Image: An XYZ manual surface grinder was MHV's choice Another recent application called for new surface grinding technology at Constant Precision of Bedford. Here, Constant's milling-based method of producing blades and anvils used in the printing industry for automatically creasing and folding paper and card seemed doomed to failure, due to difficulties in maintaining the tolerances demanded by the high speed machine and because of a projected increase in production output. Ultimately, it was the application team from C Dugard that suggested a switch from milling to grinding. Following trials on a Chevalier Smart B-1224-II surface grinding machine, the new method more than halved the original processing time for the two ranges of parts required and ensured a high level of quality. After further discussions with C Dugard, a single fixture was devised for the Chevalier machine to produce one part at a time that, once proven, led to the application of a double fixture that would enable two blades or anvils to be ground simultaneously, using a paired grinding wheel. Image: Constant Precision moved from milling to grinding, with C Dugard's help EXTENDED RANGE Arguably the name most associated with surface grinding, in historical terms, is Jones & Shipman – there aren't many manufacturing engineers unfamiliar with the almost legendary '540' model. Today, however, Jones & Shipman is a specialist in the design and manufacture of many different types of grinding machine, and now also represents the Spanish-built Doimak range of CNC cylindrical grinders, ballscrew and nut grinders, thread grinders, gear grinders and hob-sharpening machines. The machines have the capacity to handle workpieces up to 1,000 mm in diameter and up to 6 m in length. Most are modular in design and so can be tailored to suit requirements. Gear grinding is, of course, a specialist field and another supplier of this type of machine is also enjoying current UK success. When faced with the need to find a high quality gear grinder to help the company keep pace with growing global demand for its products, directors Nigel Parker and Andrew Jubb at DePe Gear Co considered many options. However, following a period of in-depth research and demonstrations, a Hoefler Rapid 800 was purchased via UK agent, Micronz. "The volume of work now being produced by our new Hoefler machine means that, in one day, it is able to get through the same amount of work that previously took our older machines a week to complete," says Mr Parker. "In fact, we have been able to sell four of our older machines." Unsurprisingly, universal cylindrical grinding machines remain popular across a host of industry sectors. Many established models, such as the S33 from Studer, are only occasionally subject to enhancements, although the latest such modification, the introduction of a new grinding head with two motor spindles, promises to bring a number of important advantages. Now, three grinding wheels ensure that workpieces can be machined even more individually and quickly, in a single set-up. Furthermore, the S33 is now available with CNC control and an integrated PC, thus enabling the use of the new Studerwin operator interface. In terms of newly conceived vertical grinding machines, Danobat is introducing its VG series for grinding medium to heavy parts, such as transmission gears and aircraft engine stators, explains the company. The machine is equipped with two independent slides: on the longitudinal slide is mounted the rotary table with the C-axis and the vertical slide, to which either a grinding spindle or B-axis is fitted. The rotary table is assembled on a hydrostatic bearing that enables radial tolerances of under 2 micron to be achieved, with its vibration absorption properties guaranteeing a surface finish under 0.3 Ra. Image: Danobot's machine employs hydrostatics to support dimensional accuracy and high surface finish With many modern applications demanding increasingly complex component shapes, profile grinding is a more frequent requirement. Here, an important new development has been announced by Blohm Jung (JRA Bennet), which, with its GEOID software, offers contour fault compensation in dressing tools. GEOID ensures the topography of the cutting edge of the dressing tool can be determined with accuracy. Correction values calculated are fed directly into the dressing program and create an optimised contour on the grinding wheel. The result is an increased service life for the dressing tool, reduced costs of tools and improved contour accuracy. Other innovative technology that can improve form includes electroplated diamond dressing blocks from Engis. These can provide a simple and efficient way to turn a standard grinder with reciprocating table, such as a surface grinder, tool and cutter grinder, or optical form grinder, into an automatic form grinder, when combined with power down-feed. Electrogrip diamond dressing blocks are used to dress specific forms into aluminium oxide and silicon carbide grinding wheels. They are said to be simple to use and can be held magnetically or mechanically on the machine table, or mounted within a part holding fixture. The advantages of the Engis Electrogrip diamond plated blocks include simplified set-up, long tool life and the elimination of costly wheel truing attachments, as well as providing added machine versatility. Box Item 5-axis tool grinding Peterborough-based Marlor Tooling has installed another Walter CNC tool grinder – this time a 5-axis Helitronic Vision, supplied by Koerber Schleifring UK. Capable of processing rotary HSS and carbide tools from 3 to 320 mm in diameter and up to 370 mm in length for length/contour grinding and 300 mm in length for length/face grinding, the machine delivers shorter cycle times and consistent surface finishes of 0.1 Ra. Marlor's Walter plant list now includes four Helitronic Powers (two equipped with a 40-tool Disc Loader for unmanned/lights-out machining), one Power Production (also equipped with a 40-tool Disc Loader) and the new Vision. For tool inspection, there is a Helicheck Basic. First published in Machinery, November 2009