Originally Posted by
scudzuki
Backlash is easy to measure. Set a 123 block or similar on the table. Hold an indicator in the spindle (indicol holder, chuck, whatever) oriented to the axis you are testing. Slide the 123 against the indicator and zero . Have someone hold the ballscrew (it can't turn or the results are invalid), then grab the table and try to move it fore and aft. Indicator reading will reflect the total backlash in the system. Not rocket science.
Joe
Joe, that is not entirely true. Backlash is caused by clearance between the nut and screw. Lost motion is caused by axial movement of the screw (the screw is not held rigidly at the fixed end). For every action, there is an equal and opposite reaction. Not only does the screw push against the nut, but the nut also pushes against the screw. If the screw can move, it will.
Checking for backlash this way will produce a sum of backlash + lost motion . Two different problems. The proper way is to eliminate any movement of the screw before checking for backlash.
Diplomacy is the art of saying "Nice doggie" until you can find a rock. - Will Rogers