For intermittent creep grinding the calculation is simple. Continuous dressing requires more calculation steps, but in any case grinding costs can be controlled by predicting the service life of the grinding wheel. #base
Creep creep grinding is a form of precision grinding that has proven to be a huge advancement in modern grinding technology. It has great potential to improve productivity and dimensional accuracy compared to traditional surface grinding. Creep-feed grinding is characterized by high removal rates, typically exceeding 0.030 inches or 2 millimeters per pass. The purpose of this article is to demonstrate the calculation of the service life of grinding wheels during creep feed grinding. Calculating grinding wheel life is critical to predicting grinding wheel usage and abrasive costs associated with the grinding process. To calculate grinding wheel life, it is necessary to understand the dressing method used. There are two types of dressing methods used in creep feed grinding processes:
1. Intermittent dressing, in which the mold is periodically inserted or moved into the grinding wheel using an overhead or tabletop diamond dresser. The volume of the bandage is programmable in inches or millimeters.
2. Continuous trimming is beneficial in mass production of materials that are difficult to process or grind. Continuous dressing allows the grinding wheel to remain sharp while maintaining its complex shape. Slow continuous dressing grinding uses a top diamond dressing roller to provide continuous plunge dressing during the grinding cycle. The dressing amount is programmed in inches or millimeters per revolution of the grinding wheel.
NCD creep feed wheel life is equal to the amount of abrasive available divided by the amount of dressing per part. Below are some representative process data illustrating calculations for creep feed grinding with NCD:
Wheel life in CD creep feed grinding is equal to the amount of abrasive available divided by the amount of wheel wear per grinding cycle. Here’s how to calculate grinding wheel wear per grinding cycle:
Most slow feed machines are equipped with variable speed motors to ensure that the grinding wheel speed, measured in surface feet per minute (ft/min), remains constant throughout the life of the grinding wheel. A constant speed is necessary to ensure optimal service life of the grinding wheel. Decreasing SFPM will result in fewer cutting edges being used per unit grinding time, resulting in higher loads on each particle. This leads to increased grain looseness, which leads to premature wheel failure. As the wheel gets smaller, the SFPM remains constant, so the number of revolutions per minute (RPM) will increase. The ruling roller feeds the grinding wheel to a certain depth with each revolution. Therefore, the amount of dressing increases as the grinding wheel becomes smaller. Therefore, to calculate the average service life of a wheel, consider the rotation speed at half the wheel diameter:
Wheel diameter (DH) at half-life (inches) = starting diameter. – ((initial diameter – minimum diameter) / 2)
In slow CD grinding, as soon as the grinding wheel begins to move, the diamond roller begins to dress the grinding wheel. Therefore, the feed length of the grinding wheel (often called the grinding wheel stroke) is taken into account when calculating the dressing amount per cycle. As wheels get smaller, the clearance needed to prevent collisions between the wheel and parts decreases. Most machines take this into account automatically. As the grinding wheel gets smaller, its starting position is closer to the workpiece, which means the grinding wheel stroke decreases. Therefore, the diameter of the half-life wheel is used to calculate the average wheel life.
To calculate the half-chord length under the full contact arc, we need to know the depth of cut (DOC) of the workpiece and the radius of the grinding wheel (r).
We can calculate the feed length (L) using basic geometric formulas derived from the Pythagorean theorem using DOC, grinding wheel radius and half chord length at full arc of contact. See picture:
Grinding wheel wear per grinding cycle = continuous dressing volume per wheel revolution (CD) × rpm × grinding wheel stroke/table speed
This article describes how to determine grinding wheel life in creep feed grinding operations. Calculating grinding wheel life is critical to predicting grinding wheel usage and abrasive costs associated with the grinding process. To calculate grinding wheel life, it is necessary to understand the dressing method used. Wheel life is calculated by dividing the available abrasive by the wear rate of the wheel. Calculating grinding wheel wear during continuous creep feed grinding is very difficult. The amount of dressing per revolution of the grinding wheel is programmable. The number of grinding wheel revolutions per cycle depends on the wheel diameter, wheel speed (feet per minute), grinding length, depth of cut, and table speed.
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Post time: Nov-01-2023