With so many gripper choices available for outfitting pick-and-place automation systems, it can be very confusing to determine which style is the right one for the required application.While choosing the right gripper will result in optimized performance, uptime and operator safety, there are a few questions you need to ask to ensure all operational and design factors are adequately weighed before the decision is made. Let’s take a look at those questions.

What Are the Operating Requirements?

The first decision you need to make is whether to use an electric or pneumatic-driven gripper. So what are the differences?

  • Electric Grippers – generate significantly less operational noise and are well suited for minimizing contaminates into sensitive environments, such as food, pharma and electronic applications. They also provide additional analytical feedback information about their own operating performance or about the part being gripped, such as size and weight. They are easy to install and operate, and connect directly to a control system/PLC with basic standard wiring.
  • Pneumatic (or air-powered) Grippers – the traditional standard. They provide faster actuation speed, a smaller footprint and lower cost, but are noisy and generally limited in providing feedback information to the control system in the format of grip part, open or close status. While the initial cost may be lower, significant hidden costs to be aware of include airlines, filters, fittings, valves, compressor, etc. required for connection to a control system or PLC.

Is The Environment Clean or Contaminated?

The two common classes of operating environments must be considered:

  • Clean Environment – commonly found in medical, pharmaceutical, electronics and food production operations where only very minute amounts of airborne or surface contaminants are allowed. The aim is to keep any grease or contaminant on or in the gripper from being released into the work environment to avoid contaminating the part or process. Look for a gripper that is Clean Room-certified and approved for Clean Room environments.
  • Contaminated Environment – high levels of dirt, debris, oil and grease that are common in automotive, foundry, machining and general industrial applications can adversely affect the internal workings of the gripper and its operation. Here it is critical to protect the gripper from any external contaminants to keep the gripper functioning trouble-free.

Is a Sealed or Shielded Gripper Required? 

Whether operating in a clean or dirty environment, standard or custom-designed shields (or seals) can be used to reliably deflect debris away from the gripper mechanisms in a dirty environment or help keep grease and internal containments from escaping into a clean environment. Shielding may be offered as part of the gripper as standard, optional or as a special request by the end user, who may also add their own shielding as a part of a system integration.

What Are the Key Gripper Specifications? 

When selecting a gripper, considerations for any application should include:

  • Appropriate finger length – noting that excess finger length can cause a gripper to bind.
  • Grip force – too much will damage the part and too little will drop parts.
  • Gripper stroke – too much is wasted operation time and too little will incorrectly grip or release parts. Typically, repeatability is more important than accuracy and becomes a key specification when picking up very small objects or working in a high-precision application where one object is being placed inside another object for assembly.

What Type of Jaw-Support Mechanisms Should I Consider?

The specific application will help to determine which type of gripper jaw-support mechanism to consider. It is important to align the right mechanism to the application to ensure reliable and accurate actuation of the gripper. From an application point of view, common jaw-support mechanisms include:

  • High-Impact Loading Application: Use a plain or wedge-type bearing design identified as a large sliding surface contact bearing.
  • Low-Friction High-Accuracy Applications: Use a line-contact roller-bearing gripper design.
  • Low Air Pressure Precision Applications: Use a point-contact ball bearing design.

What Mode of Power Transmission Is Needed? 

The mode of power transmission refers to the linkage and transfer of power from the internal air piston(s) to the gripper jaws that open and close, producing a grip force. Here are some general guidelines to follow:

  • High Grip Force to Gripper-Size Applications require high grip force, but are constrained by the system’s working space and can require a double-sided wedge gripper design that provides a large surface area for transmitting power to the jaws with the power equally divided between both.
  • Cost-Effective Parallel-Gripper Solutions. A direct drive design uses a pin or rod to direct couple the piston to the jaw. This is your basic gripper design, a simple, cost effective and easy to shield twin-piston design that requires a jaw-synchronizing linkage.
  • Cost-Effective Angular-Gripper Solutions. Many angular grippers use a cam-driven design with direct, synchronized power transmission and bearing-line contact for sending power to the jaws. This has one pivot point per jaw with a minimal number of moving parts. The cam can generate mechanical advantage, resulting in a gripper with high grip force in a relatively small overall package.
  • High-Precision High-Repeatability Applications. The smooth synchronous operation of a rack-and-pinion transmission is very popular for precision applications because it produces minimal wear on the drive components for long durability.

It’s important to consider all options and answer all of the above questions thoroughly in order to determine the right size and type of required for the application.If you have any doubts regarding the suitability for a gripper to an application, it’s best to contact the manufacturer.

DESTACO is the industry’s leading global supplier of high-performance automation, workholding and containment solutions. Our product line is comprised of end effectors, grippers, indexers, manual and power clamps, and remote handling. Contact us today to find out more.