Get A Grip & Learn How To Choose The Right Gripper

Despite the significant role they have in successful automation systems, grippers are often overlooked.
If you’re aiming to achieve optimized performance, uptime, and improved production there are several factors you need to keep in mind when selecting grippers for your operations, including operating requirements, operating environment, tasks performed, gripper styles, source of power, and safety features.
In this article, we will examine each one of them so that you can make a well-informed decision. 

What are the operating requirements? 

Before deciding what grippers to purchase, consider your facility’s operations to determine whether pneumatic or electric grippers are the best solutions for your needs. 

Pneumatic (or air) grippers 

Currently, more than 95% of grippers are pneumatically powered and they have remained the standard for many years.
They are smaller, faster, and noisier than electric grippers. Even though their initial cost is significantly lower, there are hidden costs associated with air grippers. They also provide limited feedback to control systems and can compromise air quality.
One of their main defining features is their gripping force.

Electric grippers 

Electric grippers are relatively new when compared to their pneumatically powered counterparts.
Their initial cost is much higher but their installation process is easier. Also, they deliver lower maintenance costs than traditional air grippers. This type of gripper is more environmentally friendly and quieter than air grippers and minimizes contamination in sensitive environments. 

How is your operating environment? 

To ensure the effectiveness of your grippers, you need to choose the right ones for your operating conditions. Generally speaking, there are two main classifications of operating environments that require particular attention: clean and contaminated.

Clean Environments

Clean environments are common in pharmaceutical, medical, and food-production verticals. These industries allow for minimal contamination and your focus should be on keeping anything on or in the gripper from contaminating the environment.
To prevent bacteria buildup and oxidation in clean environments, you should also consider specific gripper coatings such as hard-coat anodizing, stainless steel, and nickel-plating. 
Also, if your application requires a clean environment, electric grippers may be the safer choice as they eliminate the potential for air leaks.

Contaminated Environments 

When working in contaminated environments, your focus should be on keeping the grippers protected. It is common to find debris, oil, dirt, and grease in general industrial applications that, along with high temperatures, can ruin and affect the performance of your grippers.
Your contaminated environment preventative maintenance program should include grease fittings, purge ports, and low-pressure air.
Note that shielding can increase reliability in both contaminated and clean environments.

What tasks will the grippers be performing?

Pneumatic grippers are used for three basic tasks:

1. To grip, hold, and move a component while it’s being transferred, for example when a box is moved from a conveyor into a container;
2. To grip and hold a part while other work is being done, such as holding a box while a label gets applied to it;
3. To put the part in the correct position to prepare it for the following task, such as turning a box so that its label can be applied.

As previously mentioned, air grippers don’t allow for precise control but allow for high force. Therefore, if you are looking for a solution for high-speed applications maneuvering light to moderate loads or for precision assembly tasks, you should consider electric grippers. 

What are the different gripper styles?

A gripper consists of three main parts: the body (which includes the means of power transmission), the fingers, and the jaws. Typically, grippers can have two or three jaws and can be created with parallel and angular styles.
Parallel grippers are typically used to handle a variety of little parts with a predictable geometry. They have a simple, cost-effective design that makes them easy to program as you are dealing with one axis of motion. 
Angular grippers are typically used to grip off-centered objects or to create a wider opening thanks to their angular stroke. That’s why they are often used in applications where limited space is available. If you need a solution for holding oddly shaped, large workpieces, angular grippers are hard to beat. 

What’s the preferred source of power? 

The term “Power Transmission Mode” refers to the way power is linked and transmitted to the gripper jaws to allow them to open and close. What do your grippers get power from: air or electricity?

Air-powered grippers 

Pneumatic grippers use pressure from a compressed air system to supply the power required open and close the gripper’s jaws. Most factories already have access to an air supply, which simplifies the use of pneumatic grippers. Also, it’s easy to translate the power of a piston into gripping force since air grippers have no gears or motors.

Electric-powered grippers 

Electricity is the other major option when looking for a source of power for grippers. Simply put, electric-powered grippers control their tooling fingers by using an electric motor. Because they connect directly to a control system, electric grippers are easy to install and they save on maintenance, power, and operating costs. 

What safety features should you keep in mind?

There are a couple of situations where you should think about safety when dealing with grippers: when a power failure happens and when considering gripper finger design.

1. If a power failure happens, the gripper fingers design should prevent dropping the part handled. In order to ensure this happens, pay attention to what materials are used for both gripper fingers and the surface of the part. 

Additionally, you could add external fail-safe valves to the ports to ensure a secure grip force. Rod locks should also be considered for grippers that allow for them since they automatically clamp on the jaws when air pressure is lost. 

1. Safety should always be prioritized, even when considering gripper finger design.

There are three types of gripper finger design and gripping methods to consider:
Friction: it’s the most common method (to avoid when handling greasy or oily components). If air pressure is lost, the component will drop.
Cradled: if the air pressure is lost,  the part might drop as the gripper fingers may “cam open” due to gravity.
Encapsulated: it’s the most secure method and if power is lost, the part will not drop.
Also, if you’re handling fragile components, consider placing urethane pads on the gripper fingers in order to increase the gripping friction without dispensing unnecessary force that could damage the components.
If you want to avoid grip marks, use soft materials for grippers such as plastics or nylon instead of steel and aluminum. 

Conclusion 

Yes, there is a lot to keep in mind when choosing the right gripper for your operations. 

• Learn the differences between pneumatic grippers and electric grippers.
• Consider what type of work environment you have: clean or contaminated.
• Think about what tasks you need the grippers to perform.
• Consider all the different gripper styles.
• Understand what your preferred source of power is.
• Think about safety features when it comes to gripper finger design and power failure.

Choosing the right gripper for your applications can be overwhelming. Reach out today with any questions you may have by Contacting Us.