There are several reasons that could lead to the damaged blade of an automatic band saw paper cutting machine. Some of the common causes are discussed below.

1. Improper use: The blade of an automatic paper cutting machine is very sharp and should be used with care. Any misuse of the machine could lead to the blade getting damaged. For example, using the machine to cut materials other than paper, using the machine to cut material that is too thick, or applying too much pressure on the blade could result in the blade getting damaged.

2. Improper maintenance: Regular maintenance of an automatic paper cutting machine is necessary to ensure that it functions optimally. Lack of maintenance could lead to the blade getting damaged over time. For example, if the blade is not lubricated regularly, it could become dull and less effective.

3. Material quality: The quality of the paper being cut also plays a significant role in the longevity of the blade. If the paper being cut is of poor quality or contains hard materials such as staples or paper clips, the blade could get damaged faster than usual.

4. Blade quality: The quality of the blade used in the automatic paper cutting machine can also affect its lifespan. If the bade is of low quality or is not compatible with the machine, it could get damaged faster.

5. Machine age: The age of the automatic paper cutting machine could also affect the blade’s lifespan. Old machines may not function as efficiently as newer ones and could cause excess wear and tear on the blade.

In conclusion, there are several reasons that could cause the blade of an automatic paper cutting machine to get damaged. Proper use, maintenance, and material selection are crucial in ensuring the machine and blade last long.