For interrupted dressing of creep feed grinding, the calculation is simple. Continuous dressing requires more computational steps, but in any case, grinding costs can be controlled by predicting the life of the grinding wheel. #base
Feed grinding is a form of precision grinding that is a significant advance in modern grinding technology. Compared to conventional surface grinding, it has superior potential for increased productivity and dimensional accuracy. Deep groove grinding is characterized by high stock removal, typically in excess of 0.030 inch or 2 mm per pass. The purpose of this article is to demonstrate the calculation of wheel life in creep feed grinding. Calculating wheel life is critical to predicting wheel usage and abrasive costs associated with the grinding process. To calculate wheel life, you need to know which dressing method is being used. There are two types of dressing methods that can be used in creep feed grinding processes:
1. Intermittent dressing, in which the mold is periodically inserted or moved into the grinding wheel using a hanging or tabletop diamond dresser. The trim value is programmed in inches or millimeters.
2. Continuous trimming is beneficial for mass production of hard-to-cut and hard-to-cut materials. Continuous dressing keeps the grinding wheel sharp while maintaining complex shapes. Continuous straightening depth grinding uses elevated diamond dressing rollers to continuously dress at a feed rate during the grinding cycle. The amount of dressing per wheel revolution is programmed in inches or millimeters.
NCD depth feed wheel life is determined by dividing the available abrasive by the number of dressings per part. Below are some representative process data illustrating NCD creep feed grinding calculations:
The service life of a wheel for deep-feed grinding in a circle is determined by the ratio of the available abrasive to the amount of wheel wear in one grinding cycle. Here’s how to calculate wheel wear per grinding cycle:
Most depth feed machines have variable speed motors to ensure that the speed of the grinding wheel (measured in surface feet per minute (sfpm)) remains constant throughout the life of the grinding wheel. A constant sfpm is critical to ensure optimum wheel life. Reducing the number of steps per minute will result in fewer cutting edges being used per unit of grinding time, resulting in a higher load on the particle. This leads to increased grain fragility, which leads to premature failure of the grinding wheel. As the wheel gets smaller, the RPM stays the same, so the number of revolutions per minute (RPM) will increase. With each revolution, the dressing roller is pressed into the grinding wheel to a certain depth. Therefore, the number of edits increases as the grinding wheel gets smaller. So, to calculate the average wheel life, we calculate the RPM as half the wheel diameter:
Wheel diameter (DH) in inches at half wheel life = initial diameter. – ((initial diameter – minimum diameter) / 2)
In circular creep feed grinding, the diamond roller rules the wheel as soon as the wheel begins to move. Therefore, the length of the feed of the circle, commonly referred to as the stroke of the circle, is taken into account when calculating the number of dressings per cycle. As the wheel gets smaller, the amount of clearance needed to prevent the wheel from colliding with the workpiece decreases. Most machines will take this into account automatically. As the wheel gets smaller, the start position of the wheel gets closer to the workpiece, which means the wheel moves less. Thus, the half-life wheel diameter is used to calculate the average wheel life.
To calculate the half-chord length of a full contact arc, we need to know the depth of cut (DOC) of the workpiece and the radius (r) of the grinding wheel.
We can calculate the pitch length (L) using basic geometric formulas derived from the Pythagorean theorem using DOC, wheel radius and full contact arc half-chord length. See picture:
Wheel wear per grinding cycle = continuous dressing (CD) per wheel revolution x rpm x wheel travel/table speed
This article describes how to determine the life of a grinding wheel in creep feed grinding. Calculating wheel life is critical to predicting wheel usage and abrasive costs associated with the grinding process. To calculate wheel life, you need to know which dressing method is being used. Wheel life is calculated by dividing the available abrasive by the wheel wear. Calculating wheel wear in continuous dressing creep feed grinding operations is a complex task. The number of edits per revolution of the grinding wheel is programmable. The number of revolutions a wheel makes in one cycle depends on the wheel diameter, wheel speed (feet per minute), sharpening length, depth of cut and table speed.
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Speed changes the rules. To maximize metal removal rate with a high speed spindle, follow some basic tooling principles and mill at the correct RPM.
Post time: Apr-18-2023