Figure 1: Quick Change Chuck

Figure 2: “Smart” Junction Box

Figure 3: Framework

Figure 4a & 4b: Spring Loaded Vacuum Cup Assembly and Gripper Finger Assembly

Figure 5: Rotary, Slide Table, and Parallel Cylinders

Figure 6a and 6b: Sprue Plier Assembly and Sprue Plier with Sensor Assembly

Figure 7: Sprue Cutter Assembly

Figure 8: Locator Pin Assembly and Photoelectric Sensor Assembly

Modular End-of-Arm Tooling for Your Robot

By John M. Westbeld, Design Manager >SAS< Automation, LLC

Reprinted with permission by Techologia Del Plastico, a publication of B2Bportales. July/August 2002.

The success of any robotics pick-and-place application depends on how consistently its end-of-arm tooling (EOAT) secures, manipulates, and releases the parts and runner system. To build an EOAT that suits your application and assure its success you need a flexible system of modular components. Modular components are preferred in most cases because they are adjustable, lightweight, and often-time less expensive. 

The basis for any modular system of EOAT components is how it interfaces with the robot. Quick Change Chucks can be mounted directly to the robot and can facilitate quick EOAT changes (see figure 1). The mating dovetail plate to the chuck is on the EOAT and it quickly slides into the chuck and locks and locates into place. The EOAT has quick disconnect fittings that plug into the chuck for your air and vacuum lines. Also, a "smart" junction box is used for the electrical interface with the robot (see figure 2). It has LED's to assist troubleshooting and the inputs/outputs can be sinking (NPN), sourcing (PNP), or dry contact.

The EOAT framework consists of lightweight aluminum extrusion and connectors that mount directly to the dovetail plate (see figure 3). From this framework you can mount the components used to secure or manipulate the part.

Securing the parts can be achieved by vacuum or some mechanical means (see figures 4a and 4b).

Vacuum cups are often the preferred method to secure the parts (if they lend themselves to the application). They are the least expensive option and most of the time they secure parts best. The other most common method to secure the parts is by means of a mechanical gripper finger or parallel cylinder. These are used in situations when vacuum cups can't be used due to part contour or texture. Some parts need to be manipulated to remove them from the core, to get them out of the press, or to interface with dunnage or a fixture at part release. To do this the modular component system must integrate various types of pneumatic cylinders to perform desired motions (see figure 5). Rotary cylinders, slide table cylinders, and parallel cylinders are just a few of the cylinders you have at your disposal to manipulate the part.

As well as securing the part you may have to secure the runner system as well. Runner systems can vary so it's a good idea to have the sprue pliers adjustable (see figure 6a and 6b). As well, your sprue plier can have a sensor in the jaw for sprue/runner presence. With the sensor in the jaw the size or integrity of the hot material is not an issue. It will sense the sprue/runner regardless.

Runner systems may also need to be degated from the part. It is desirable to do this with the EOAT whenever possible to eliminate a downstream operation. Sprue cutters can be incorporated into the EOAT to cut various styles of gates (see figure 7).

Other modular components that are useful in securing parts are locator pins and photoelectric sensors (see figure 8). The locator pins can be used to guide the part while its ejected and to support the part. Photoelectric sensors verify part or runner presence or can be used to detect obstacles.

A modular component system for EOAT needs to be lightweight so the total weight of the EOAT will not exceed the operating payload of the robot. Lighter EOAT also extends the performance and life of the robot as well. By using lightweight aluminum framework and components you don't have to sacrifice strength for weight reduction. Clamps can be made of injection molded plastic composites to reduce weight also. The success of any EOAT application depends on how well the components perform their specified tasks and how well the EOAT and robot work together. A modular system designed specifically for plastic injection molding will insure the greatest possibility for success.

John Westbeld is Design Manager for SAS Automation. He can be reached at 937/372-5255.

Reprinted with permission by Techologia Del Plastico, a publication of B2Bportales. July/August 2002.