Mechanical vs. Electronic Position Monitoring of Your Drawbar Shaft

Authored By: Crystal Van Vleet, Global Marketing Director

By: Harold Goellner, OTT-JAKOB Drawbar Specialist

There are several ways to monitor your drawbar shaft position when rotating your spindle including mechanical position monitoring and electronic position monitoring options. It is important to monitor your drawbar position to prevent rotating your spindle in ‘unclamp position’ or ‘clamped without tool position’, which can cause:

  1. The tool changer to remove the tool from the spindle too early. 
  2. The spindle to start moving before the tool is correctly clamped. 
  3. More frequent maintenance, loss of precision, and misclamping. 
  4. Potential damage to the workpiece and the machine. 
  5. A safety risk to the operator.

Traditional ways of monitoring drawbar shaft position involve more manual work from the operator and can involve inaccurate results. Electronic drawbar shaft position monitoring options guarantee safe clamping and unclamping with accurate results.

Mechanical Options for Drawbar Position Monitoring

There are three types of mechanical options available to monitor the position of your drawbar shaft: 

Thread in Pulling Head/Drawbar Shaft

This option involves position monitoring through three threaded holes in the pulling head. It is a cost-effective, straightforward solution for detecting the position of the tool. The pulling head features threaded holes that you can use to attach a signal ring to. The clamping position is determined by sensors or proximity switches.

 

Thread and Pulling Position Monitoring Device

Signal Ring

In principle, a signal ring is identical to the thread in pulling head/drawbar shaft option. However, a signal ring is supplied with a clamping system that features digital or analog sensors. The sensors are attached directly to the clamping system (e.g. steep taper clamping systems in ES configuration), or they are linked to the drawbar connection (e.g. dual-passage SR rotary unions supplied by OTT-JAKOB).



Signal Ring Position Monitoring Device

Inquiry Via Piston

The inquiry via piston has the signal rind on the end of the spindle in front of the unclamping unit. The unclamping unit has to be fixed-mounted or fitted with extended grippers so the sensor can access the signal ring. Both digital and analog sensors can be used depending on the signal ring. 

Thread and Pulling Position Monitoring Device



Electronic Options for Drawbar Position Monitoring

A built-in electronic Distance Measurement System (DMS) records the exact position of the drawbar shaft, and in turn, the current position of the tool--guaranteeing safe clamping and unclamping for the machine and operator.

The DMS combines analog sensor electronics with a limit switch. It also features a compact design that comprises an inductive sensor and a target ring on the drawbar shaft.

To learn more about the advantages of electronic position monitoring options, read: Why Monitor the Drawbar Shaft in a Spindle?

The mechanical options for position monitoring create more work for the design engineer or operator, which can lead to more errors. For accurate results that do not involve additional mass or complicated installation processes, an electronic option may be the best for your application.

 The distance measurement system is an electronic position monitoring system that guarantees safe clamping and unclamping for the machine and operator.
The distance measurement system is an
electronic position monitoring system that
guarantees safe clamping and unclamping
for the machine and operator.