Low Cost Automation Tutorial

#023 Locating Pins - How to Use Locating Pins

Category : Locating Technology

December11, 2009

How to use locating pins

Two pins are generally used to position a workpiece on a locating fixture.

One of the pins is round, whereas the other is diamond shapedand oriented as seen in Fig.3. This configuration will allow easier insertion and compensate for small dimensional misalignment when it comes to the distance between the two mounting holes in both plates.

The two pins are of differing heights. The longer pin preliminarily positions a workpiece, and the shorter one provides accurate positioning when the workpiece is inserted onto it (refer to [Fig. 1]).

The end of each pin has a round or conical shape or is chamfered for the purpose of maintaining workability (e.g., ease of insertion) and quality (e.g. prevention of damage) (refer to [Fig. 2]).

If insertions are performed frequently, select a locating pin with a considerably large inserting guide at the end (spherical shape at the end + conical shape).

The taper lead angle is large, 60 degrees or less, for light workpieces and manual operation, but it is frequently between 10 and 30 degrees for large-size workpieces that are difficult to handle, or when an automatic machine is used.

Set the length of the pin locating portion based on the precision of (parallelism between) two parts and operation frequency.This lecture describes the key points of positioning methods using pins.
Examples

	*	Parts that are not parallel to each other: Reduce the length of the locating portion.
	*	When insertions are performed frequently: Increase the length of the locating portion.
	*	For automatic machines: Increase the length of the locating portion, and allow larger clearance so that the contact length of the fitting portion can be reduced (refer to [Fig. 3]).

As both the locating pin and the positioning hole into which it is inserted wear out and deteriorate in precision, adopt a mounting method that allows these parts to be replaced (refer to [Fig. 4]).

Another method positions a workpiece to the sides with two or more pins (refer to [Fig. 5]).

« PREV