Here's a quick rundown of questions you should ask, and things you should be sure to check out in specifying end-of-arm tooling for your robotic applications.

The success of any robotics pick-and-place operation depends on how consistently its end-of-arm tooling (EOAT) grips, holds, moves and releases parts. In our industry, this often means moving and releasing a part that is heavy or awkward, like a car bumper or a dashboard instrument panel.

In addition, many parts require the gripper to not only remove the part from the mold, but also index and/or rotate it for positioning in a secondary operation, such as assembly or decoration, or into a shipping or packaging container.

So how do you determine what type of EOAT is right for your application? Here are some key questions to ask:

Part Information What is the size, weight and shape of your part? Does it have restricted surfaces that may not be contacted or touched before a clear or colored top coat is applied in a secondary operation, e.g., a Class A finish? What is the position of the part in the mold? Where are the sprues?

The answers to these questions will determine which types of EOAT you'll need: gripper fingers, gripper plates, vacuum cups, actuated vacuum cups, pliers and/or sprue cutters.

Mold Information How big is your mold? How much space is there between the mold halves when it opens? Will EOAT fit between the tie bars? Where is the center of the mold? What is the location of ejector pins and plates!

The answers to these questions will help you ensure that the EOAT fits within the space limitation of the mold and/or the robot's drop-off location. It should line up with the center-line of the mold and the EOAT frame should be as large as the part for maximum adjustability of the gripper components.

Robot What is the load capacity and arm size of your robot? Does it have connections for pneumatics and part sensing or controls? What are the mechanical interface requirements, such as mounting hole sizes and locations? Do you need EOAT/robot quick change? Will the robot move the part or will the EOAT need to move or turn the part? Where will the part be placed?

What to Look for in EOAT

Quick changeability: What features are built in to easily adjust the tool and make quick EOAT changes? A quick-change chuck permanently attached to the side of the robot allows EOAT to be affixed to a dovetail that slides in and out of the chuck. All air connections are made to the chuck via quick-touch connectors (no hand tools are required).

Modular components: Can the required EOAT frame accommodate various types of grippers?

Durability: EOAT should be longlasting and strong, yet lightweight. Make sure the vacuum cup material (e.g., polyurethane) is durable and able to withstand the high temperatures of just-molded parts (>200F).

Light weight: The weight of the EOAT, combined with the part, should not exceed your robot's weight capacity. Choose EOAT that is as light as possible.

Low profile, compact design: The modular parts and components, when assembled, need to fit into or around tight areas in the mold due to constraints in the opening, tie bars or ejection lifters.

Flexibility: Look for tooling components that are fully adjustable for 'onsite' fine tuning and possible modifications.
Reprinted with permission from Plastics Auxiliaries Magazine, September, 1998

Five Steps to Design and Build EOAT
EOAT is designed and built based on the available part surfaces and the available room in mold.

Step 1 -- First a frame is constructed on a dovetail mounting plate (to slide into quick-change chucks, if required) to the size of the part.

Step 2 -- Next, EOAT is built with the necessary clamps, arms and gripping devices. Vacuum cups can be used as suction devices on a part surface. Pliers usually grab the part or sprue, and fingers are used to secure a part. These devices come in a range of sizes and need to be specified for each application. Then if necessary, the sprue cutters, as well as part sensors and controls are added.

Step 3 -- The pneumatic system is then added to provide the vacuum for the vacuum cups and air supply for activation of air slides and cylinders used to flex or shift part. The electrical system is also added to operate the part sensors and controls.

Step 4 & 5 -- The last steps are assembly, testing and documentation. Testing should consist of proper alignment of all gripper components, on a jig or fixture, along with actual vacuum and air testing of the tool with the part to adequately simulate the part being ejected from the mold and secured by the EOAT. Finally, documentation includes drawings, test results and specifications and will be used for replacement and spare parts.

Reprinted with permission from Plastics Auxiliaries Magazine, September, 1998