Erection Levelling and Aligning

Erection Levelling and Aligning

Erection Levelling and Aligning - The accuracy of any machine tool depends to a great extent upon the accuracy to which leveling is done. At the time of preparing the foundation its surface will have been levelled off and. after the few days necessary to harden the concrete have elapsed, the machine tool may be placed in position for leveling and aligning.

Method of Holding Down Machine Tool Bed on Foundation

Machine tools are installed on foundations with the aid of leveling pads, wedges and shoes with the machine being held down by means of foundation bolts and its base being grouted with cement mortar; without foundation bolts but with grouting; and without foundation bolts and grouting but with the use of either leveling wedges or elastic rubber and metal supports.

The machine tool bed is secured on the foundation by means of ­ foundation anchor bolts, which are placed into special pockets in the foundation. The foundation bolt is threaded through each of the holding down holes in the base and allowed to remain loose with a nut on the end to retain it from falling.

It is practically impossible to install the machine with suffici­ent accuracy directly on the foundation since the top surface usually varies from the horizontal by at least 0.25 or 0.5 mm per 1000 mm. Therefore, the machine tool is levelled on the foundation by using.

Steel wedges about 50 to 75 mm long, 25 mm wide and 3 to 4.5 mm thick, tapering to nothing. If the base is a complete rectangle one of these should be driven in at each comer and one at suitable points, whilst machines such as lathes, standing on two cabinet legs, should have one at each comer of the legs.

Arrangement of Wedges for Levelling Machine Tools

The Machine tool is levelled by driving in such wedges as are necessary to cause the required correction, always ensuring that all wedges are tight.

The machine tool is levelled by means of an accurate spirit level (0.03-0.05 mm per meter) placed on the table in both, transverse and longitudinal directions. Deviations are compensated by carefully driving the wedges.

After the machine has been levelled, the nut, of the foundation bolts ate evenly tightened under constant check by means of the spirit level. Do not use excessive force while tightening the foundation bolts. Watch the spirit level. The machine tool is then left to settle down for a day or two. After this time a further check for level should be made and if this is acceptable the machine may be grouted in.