Haas machining centres have been available with full fourth axis options since the release of the very first one way back in 1987 and throughout all of these 23 years the fourth axis has been programmable as a ‘full’ fourth axis – that is simultaneous rotary motion with a range of +/-99999.999 degrees.
This last piece of information is important because it gives the total range around a central 0 degree position, in other words programming the fourth axis to move 720 degrees (A720.) means just that – two complete revolutions away from the zero position (A0.).
Why is this important? – Well it’s because when commanding a return to A0. users are sometimes surprised to see the rotary table perform two complete revolutions in the opposite direction to get back to what is perceived as the ‘same’ position, but as we have discussed above A0. is not the same as A720. in respect of the distance travelled.
However through customer feedback Haas introduced the function Quick Rotary G28 under Setting 108 which provided the ability for the rotary axis to take the shortest route when being commanded to return to reference position using G28 A0. this will directly affect the user cycle time and thus bottom line profitability.
Turning this setting ON will return the rotary unit back to zero using the shortest distance.
For example if the rotary unit is at 10° and a zero return is commanded, the rotary table will rotate 350° if this setting is OFF. If the setting is ON the table will rotate -10°.
In order to use Setting 108, the parameter bit CIRC. WRAP. (10) must be set to 1 on parameter 43 for the A axis and Parameter 151 for the B-axis. If param–eter bit(s) are not set to 1 the control will ignore setting 108.