Creep feed grinding is a kind of strong grinding, also known as creep grinding. The workpiece can be ground to the required size and shape accuracy after one or several strokes. Slow feed grinding is suitable for grinding surfaces and grooves of high hardness and toughness materials, such as heat-resistant alloy steel, stainless steel, high speed steel, etc.  

Differences between creep grinding and conventional surface grinding

Compared to the common surface grinding, creep-feed grinding adopt a heavier grinding depth combined with a slow traverse rate, generally with a profiled grinding wheel to generate a given geometric form at a material removal rate that is much higher than than that of the finishing passage generally known for grinding.

Creep feed grinding process:

1. Large grinding depth. Long contact arc between grinding wheel and workpiece, high metal cutting rate. Rough grinding and fine grinding are completed in one process, and the production efficiency is 3-5 times higher than that of ordinary grinding.

2. Small grinding wheel wear. Because the feed rate is very low, the grinding chip thickness is thin, the grinding force borne by a single abrasive particle is small, and the abrasive particle is not easy to wear and break off. Secondly, the reciprocating stroke of the table is less, the feed is slow, and the impact between the grinding wheel and the workpiece is less, which reduces the impact between the grinding wheel and the workpiece edge, so that the grinding wheel can maintain the accuracy in a long time.

3. Because the grinding force of single abrasive is small, the grinding precision is high and the surface roughness is low. At the same time, the machining accuracy is stable because of the good retention of the grinding wheel profile. In addition, the contact arc length can attenuate grinding vibration, reduce chatter, reduce surface corrugation and surface stress of workpiece, and it is not easy to produce grinding cracks.

4. Good economic benefits. Because of the large cutting depth, grinding is almost not affected by the workpiece surface defects, such as oxide skin, white layer of castings, etc., can be directly the blank of investment casting or precision forging grinding into shape, reduce machining procedures, reduce the blank processing allowance and working hours, shorten the production cycle, reduce the production cost.

5. High equipment cost. Creep feed grinding machine must increase the power and rigidity of grinding machine, with slow feed and speed change system, grinding wheel automatic dressing and automatic compensation devices and strong cooling system, so the structure of grinding machine is complex, high precision requirements, equipment cost is much higher than ordinary grinding machine.

6. Large contact surface increases the grinding heat, and the length of contact arc makes it difficult for grinding fluid to enter the grinding zone, and the workpiece surface is easy to burn, so it should be equipped with a strong cooling system.

Requirements for machine tools for creep feed grinding

1. grinding power: slow feed grinding is efficient grinding, mostly used for shape grinding, so the wheel drive motor is required to have a large enough power, generally more than 18kw.

2. Table feed movement: when the table slowly feeds, it is required to be stable without crawling when the feed speed is 20mm/min. Generally do not use hydraulic transmission, and use mechanical transmission. At present, most screw pairs or ball screw pairs are used to ensure that the machine tool has a higher transmission stiffness. There should also be stepless speed regulation and fast return mechanism.

3. The stiffness of the machine tool: the stiffness of the process system is one of the reasons for the workpie ce processing error. Slow feed grinding requires high dynamic and static stiffness of machine tools. In order to improve the static stiffness of the system, it can be used on the front and rear bed, column and drag plate and other main components of the double-walled structure; Increase the spindle diameter; The vertical guide rail of grinding head and the side guide surface of the column drag plate moving horizontally adopt the pre-loaded roller guide structure to eliminate the gap between the guide rail and improve the contact stiffness.

4.Spindle system accuracy: due to the creep feed grinding spindle power is large, but also forming grinding, so the spindle rigidity is required to be good, do not allow axial or radial movement.

5. Cooling and washing: creep feed grinding has two special problems: one is the thin and long grinding chips, easy to plug and adhere to the surface of the grinding wheel. Second, single abrasive bear small grinding force, grinding wheel self-sharpness is poor, easy to make the workpiece surface burn. Therefore, it is required to strengthen the cooling and washing effect of grinding fluid.

---EDITOR: Doris Hu

---POST: Doris Hu