Bridge between different engineering professions
Thermal modelling of camshaft grinding helps design and manufacturing engineers work together to create an optimized camshaft design and manufacturing process. The main focus of manufacturing engineers is productivity, throughput and quality – how to process qualified parts as quickly as possible. The camshaft design engineer must determine the material type and lobe profile based on the camshaft load condition. Metallurgists may also be involved in this process, and he is primarily concerned with residual stresses and the heat generated during the grinding process. With thermal modeling, manufacturing engineers can model new camshaft designs and report to designers and metallurgists on what the model predicts during the grinding process, and whether it can be based on material and design. Accept and so on.
Thermal model making can also be used as a training tool for the camshaft grinding process. For example, before developing such a model making software, it was agreed that processing speed had the greatest impact on lobes burns and cracks, which is why it is usually the first variable to be changed. It has been determined that the machining speed is actually one of the least sensitive parameters compared to the grinding wheel characteristics and the incremental depth of the grinding wheel feed.
This thermal modelling technique can also be used to help identify problems with process variables that have not changed but begin to grind burns or cracks. An example is when a manufacturer accidentally receives a batch of camshafts whose hardness values ​​exceed expectations. Thermal modeling was performed on camshaft lobe that claimed to have hardened to 60 Rc when problems seemed to occur inexplicably. The resulting model showed that no processing problems should occur, so the material hardness test was followed. These tests revealed that the new batch of camshafts had an actual hardness of 65 Rc. Once this is determined, a second thermal model is generated and a new processing speed is obtained for a group of higher hardness camshafts.
Crankshaft crank grinding is another process in which thermal modelling techniques are applied. Thermal model fabrication was also tested in centerless grinding of concentric diameters. As with camshaft grinding, this modeling capability does not completely eliminate the test grinding process, but it does provide an opportunity to greatly reduce the number of trial grindings and develop an optimized lobe grinding process in a more scientific manner.
Term: Definition of camshaft machining
The latest camshaft design has a concave profile on the side of the lobes. These contours are usually machined on a machine with a counter-spindle that uses a smaller wheel than the main spindle for roughing the contour of the wheel. Thermal models are generated for both roughing and secondary finishing/concave contouring operations.
Lift—The total amount of linear motion of the follower in contact with the cam lobe.
Nose—The tip of the camshaft, where the follower lift is at its maximum.
Basecircle—The area where the zero lift is transmitted to the follower on the lobes.
Flank—A generally flat portion of the camshaft that leads to and exits the end of the camshaft. It is in this area that the contact area between the grinding wheel and the lobes is maximized and the grinding machine burn is most likely to occur.
NROC - Abbreviation for negative radius of curvature, which is a concave profile in the side of a crankshaft. The center of the arc is located outside the lobe.
Re-entrant profile - Another name for NROC.
Workspeed—The spin speed of the camshaft during grinding.
Infeed—The amount of linear (incremental) the grinding wheel enters the camshaft lobe per knife.
CBN - Abbreviation for cubic boron nitride, which is the most commonly used abrasive wheel for camshaft grinding.
Turnbroaching—A process of roughing a lobe profile by using a large diameter cutting wheel with a plurality of blades on the circumference to roughly cut the lobe profile before refining.
Greengrinding—The process of grinding a lobe profile from a round bar. The new grinding wheel technology is making this technology a competitor to the transfer process.
Arcofcontact—The contact area between the grinding wheel and the lobe of the camshaft. The contact area is different for the base circle, the side surface, the NROC, and the end portion.
Equivalent Diameter—A value that represents a contact arc that is derived from the diameter of the grinding wheel and the changing machining (lobes) diameter.
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