Marposs’ New Gage Head Designed for Internal Grinders

The Thruvar from Marposs is a through-the-spindle gage for in-process measurement application on internal grinding machines and was introduced at Eastec. According to the company’s press release, the gage reduces downtime and eliminates the special tools that are sometimes necessary. Using an automatic setup feature, it is possible to reset the gage without operator intervention for a size variation up to 25 mm. Similar gages that use a special tool for manual adjustment of the gage may require about five minutes of changeover. The gage is mounted inside the grinder’s workhead spindle, and it measures workpiece inner diameter as the part is ground. Signals are sent from the gage to the monitor, providing outputs to the grinder control based on real-time measurement of the workpiece size. Outputs are used to control the wheelslide infeed for precise size and finish consistency. Access to the fingers and contact is obtained without removing the gage from the spindle. Finger retraction is pneumatically-controlled, and the retraction distance is selectable in three increments: 92 mm, 6 mm and 10 mm. One set of fingers and contacts covers a 25 mm diameter size range with no downtime for changeover.