Abstract: Machine tools are improved capacity remarkably during the 20th century. Improving the precision of machine tools are related with precision of products and accurate processing is always associated with the subject of interest. There are a lot of the elements that determine the precision of the machine, as guides, motors, structure, control, etc. In this paper we focused on the phenomenon that vertical movement system has worse precision than horizontal movement system even they were made up with same components. The vertical movement system needs to be studied differently from the horizontal movement system to develop its precision. The vertical movement system has load on its transfer direction and it makes the movement system weak in precision than the horizontal one. Some machines have mechanical counter balance, hydraulic or pneumatic counter balance to compensate the weight of the machine head. And there is several type of compensating the weight. It can push the machine head and also can use chain or wire lope to transfer the compensating force from counter balance to machine head. According to the type of compensating, there could be error from friction, pressure error of hydraulic or pressure control error. Also according to what to use for transferring the compensating force, transfer error of compensating force could be occur.
Abstract: This paper describes a method to measure and
compensate a 4 axes ultra-precision machine tool that generates micro
patterns on the large surfaces. The grooving machine is usually used
for making a micro mold for many electrical parts such as a light guide
plate for LCD and fuel cells. The ultra precision machine tool has three
linear axes and one rotational table. Shaping is usually used to
generate micro patterns. In the case of 50 μm pitch and 25 μm height
pyramid pattern machining with a 90° wedge angle bite, one of linear
axis is used for long stroke motion for high cutting speed and other
linear axis are used for feeding. The triangular patterns can be
generated with many times of long stroke of one axis. Then 90°
rotation of work piece is needed to make pyramid patterns with
superposition of machined two triangular patterns.
To make a two dimensional positioning error, straightness of two
axes in out of plane, squareness between the each axis are important.
Positioning errors, straightness and squarness were measured by laser
interferometer system. Those were compensated and confirmed by
ISO230-6. One of difficult problem to measure the error motions is
squareness or parallelism of axis between the rotational table and
linear axis. It was investigated by simultaneous moving of rotary table
and XY axes. This compensation method is introduced in this paper.