| ts 9 photos | I noticed recently that the machine cannot hold zero. I zeroed the ABS X and Y of the DRO after locating the corner of the vise with edge finder and after using the machine for a while, I located the corner again and found that the drift in the position of the vise corner along the Y axis can be as much as 0.03 mm while that in the X axis is less on average. This is kind of puzzling for me because the round-vertical-column design of the machine should have more problem in holding the zero along the X axis ( head can swing left and right due to play in the tiny vertical rail ) but in reality the Y axis is having more problem. At the beginning the drift seems to be kind of random but I finally found the cause today - it is due to thermal expansion of the head. For some reasons, the head can get quite hot during operation and thermal expansion causes the head to extend outward hence the drift along the Y axis. After the machine is allowed to cool down, the original zero position is found to be restored. This is just a 300 lb bench mill so high precision is not expected. I am just wondering if the same happens to bigger machines and how people deal with it. |
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