The discriminating principle of abrasive belt wear resistance and replacement abrasive belt

One: belt durability

Durability is the amount of time a tool can be used effectively. For abrasive belt grinding, the durability of the abrasive belt refers to the time for the abrasive belt to grind under certain grinding conditions (such as material removal rate, grinding force, grinding temperature, etc.), usually in seconds (or Hours) to represent, in practical applications, it is also represented by the cumulative grinding amount, that is, the total amount of material (mm3) ground by the entire abrasive belt or the cumulative number of workpieces processed. Although this method is not strict enough, it is simple and easy to apply, and can roughly reflect the actual situation of the durability of the abrasive belt.

The durability of the abrasive belt is different from the durability of the grinding wheel. The latter refers to the processing time between two dressings, while the former usually cannot be dressed, and an abrasive belt has been used until it can no longer be used. Therefore, the durability of the abrasive belt is much longer than that of the grinding wheel only from this point of view, generally 4~10h. Its durability is shorter for heavy-duty grinding and longer for light-duty grinding. The worst belt may only use 10~30,min, and the best belt can be used for several days, which depends on the specific processing conditions.

Two: The principle of judgment for replacing the abrasive belt

Judging whether the use of the abrasive belt polishing machine has expired is mainly based on its wear condition. When it enters the end of wear, the service life of the abrasive belt will end, indicating that a new abrasive belt needs to be replaced. Whether the wear has entered the final stage is mainly reflected by the following parameters:

1) When the material removal rate or grinding efficiency drops to the specified resin, it can be considered that the service life of the abrasive belt has expired for this grinding (given grinding amount and other conditions).

2) Grinding force. When the grinding force exceeds a certain value during the grinding process, it can also be used as a sign of the expiration of the service life of the abrasive belt.

3) Grinding temperature. During the grinding process, if the grinding temperature is better than the specified standard, it can also be considered that the service life of the abrasive belt has expired. In practical applications, the most direct way to determine whether the temperature exceeds the standard is to observe whether there is burns on the surface of the workpiece.

The above judgment is only from one aspect of grinding performance. In actual production, production cost is also a very important factor, because replacing the abrasive belt too early means increased tool consumption, too late, the grinding efficiency is too low, the labor cost increases, and the cost increases. Therefore, to determine whether the abrasive belt should be replaced, the two must be combined, and the goal is to minimize the cost per piece. Statistics show that: through the analysis of the average cost of a single product, when the abrasive belt grinding is carried out at a higher production rate, although the abrasive belt life will be shortened, this is different from obtaining a longer service life for each abrasive belt. And love is more economical than using lower efficiency. For a belt with high initial grinding efficiency, its economical life may be only 1/3 of its life when ground at low efficiency. Of course, it would also make machining more economical to replace the blunts in turn and use them for finer machining, but that's another story.

An easy way to decide when to replace the belt to get a lower cost per piece is to draw a diagram like the one shown, where the cost curve is derived from experimental results. The productivity curve represents the number of parts machined at different times.

Assume that the cost of the abrasive belt is 2 yuan, and the time to replace the abrasive belt is 5 minutes. Accordingly, the labor cost at this time should be included in the processing cost (calculated at the labor price of 6 yuan per hour).

Therefore, in this example, the initial value is 2.5 yuan. With the increase of grinding time, the labor cost is also included in the processing cost. For example, after 1 hour, the processing cost should be 8.5 yuan.

Extend the cost curve (straight line) to the left so that it intersects the cost baseline at point A. To find out the economic processing conditions and the belt replacement time, just draw a tangent from the productivity curve at point A. In this case, the 45min corresponding to the tangent point is the best replacement time. Replacing the belt any time before or after this point will increase the cost.

Another way to determine the timing of belt replacement is to plot the increase in cost versus time and the decrease in material removal rate versus time. The time corresponding to the intersection of the two curves is the time of belt replacement.