Economic removal of feeders from precision castings with the High-Pressure Abrasive Belt Grinding Machine from Reichmann.
Post Date: 08 Jul 2015 Viewed: 372
The high performance abrasive belt grinding machine achieves very high stock removal rates without the use of coolants. The prerequisite for machining with little or no thermal influence and long tool life is the mastery of high pressure abrasive belt technology.
High-pressure abrasive belt grinding is used for all materials which are difficult to machine with traditional methods.
Typical applications are:
• Removal of feeders from precision castings
• Heavy wear parts:
- e.g. Plates for cement mills, teeth for excavator shovels, gas turbine blades
- Parts for medical engineering: e.g. Surgical implants
• Parts for the aerospace industry:
e.g. Turbine blades
• Parts for the automotive industry:
e.g. Wheels for turbochargers, „Container edges“, etc.
High stock removal rates without significant thermal effects require minimal contact time, which is only possible with high-power drives and rigid machine designs. mHeat created by the grinding process can not only damage the workpiece but also significally reduce abrasive belt life.
Low drive power and insufficient machine rigidity, often found in older machines, can prematurely wear abrasive belts. The main reason for reduced abrasive belt life is glazing. The abrasive belt still has a thick mineral coating but it does not cut anymore because the machine does not apply the required contact pressure and does not run at the correct running speed.
So what exactly happens during this process?
Friction and pressure during grinding cause the abrasive grains to heat up. The abrasive mineral does not break up to form new cutting edges. They are melting and going rounded – they glaze. The abrasive grains has lost its cutting ability – the belt is glazed and must be replaced, even when abrasive particles still remain on the belt.
The Reichmann high pressure system overcomes this problem. A powerful drive coupled with a rigid machine design allows high contact pressures to be applied which increases the load on the abrasive mineral. The mineral breaks down in a controlled manner producing new cutting edges which keep the belt sharp until the end of its designed life. The sharp edges cut without producing excessive heat. This process runs continuously until the abrasive minerals are completely worn out. The tool costs are considerably reduced and the grinding process is significally improved, without the risk of adverse thermal effects on the casting.
Grinding without coolant improves environmental aspects, and provides a key criterion for the choice of high pressure abrasive belt grinding. Despite this relatively cool grinding process it is advisable to monitor temperature. For this purpose, Reichmann use heat sensors on which temperature limits can be set. They also reliably detect the end of the grinding belt service life.
Reichmann has achieved a sensational result with the high-pressure belt grinding machine HBM 55/150 in conjunction with a 3M abrasive belt.
The combination of a powerful drive and high machine rigidity has made this result possible. Grinding high-strength Inconel alloys set at a cut of 2 mm per stroke achieved a stock removal rate of 20.000 mm³/s!!!(twenty thousand cubic millimetres per second). The Inconel part did not overheat and the ground area was totally free of cracks.
Grinding the feeders in this way reduces not only the cost of the abrasive belts, but also reduces the cycle time. The low thermal impact on the castings makes managing the process easier and safer.