What Is Pneumatic Gripper: 9 Answers You Should Know

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The subject of discussion: Pneumatic Gripper and its features

What is a Gripper?

A gripper is a motion mechanism that mimics human gestures, such as the fingertips. A gripper is a tool that keeps an item in place so that it can be moved about. It is capable of holding and releasing an entity when performing an operation. The “jaws” of the gripper are advanced custom tooling used to grip the target.

What is the difference between internal grippers and external grippers?

Grippers can execute two different types of actions:

  • External: This is the most often used way of keeping artefacts since it is the most straightforward and has the most minimal stroke length. When the gripper jaws close, the gripper’s closing force locks the target in place.
  • Internal: The object geometry or the need to reach the object’s exterior can necessitate holding the thing from the middle in some applications. The gripper’s opening power would own the object in this situation.

What is Pneumatic Gripper?

Pneumatic Gripper Definition

A pneumatic gripper is a type of pneumatic actuator that uses either parallel or angular motion of surfaces to grip an object, often known as “tooling jaws or fingers.” The gripper may be utilized as part of a “pick and place” mechanism that allows a product to be picked up and positioned somewhere else during the engineering design-process when combined with other pneumatic, mechanical, or hydraulic components.

The pneumatically operated gripper is the most often used gripper; it is essentially a cylinder that runs on compressed air. When air is provided, the gripper jaws close on an object and tightly grasp it while any action is done, and the gripper releases the thing when the air direction is shifted. Typical applications include changing the direction of an object or moving it, as in a pick and place operation.

How does a Pneumatic Gripper work? | Pneumatic Gripper Design

Grippers are usually available in two jaw configurations: angular and parallel. The expression parallel denotes that the jaws’ grasping surfaces remain parallel throughout the gripper’s movement.

A primary linkage or toggle device attached to a piston rod, that is connected to one of the gripper’s jaw, is the simplest of the angular designs and other jaw is connected to an opposite linkage. The fundamental angular grasping mechanism is made up of these two opposing jaws. With the correct tooling and construction, this sort of gripper can provide a lot of force in an angulous situation.

The force is equal to the applied pressure to the piston as well as the length of the coupling or toggle and the dimension of tooling connected to the jaw, which is usually an introductory lever. One of the drawbacks of this linear type of gripper jaw motion is that it can only grip a small number of parts due to the lack of advanced tooling.

A third or even fourth, the jaw may be added to this angular gripper to define a central gripping axis or area. The parallel pneumatic gripper is another design or model of the pneumatic gripper that uses one of many various styles of mechanisms to transform piston or rod motion to parallel jaw travel.

Aluminium bodies with different surface treatments are used in the design of most commercially available pneumatic grippers where additional wear characteristics are provided and there corrosion resistance, wash-down provision are required, may include stain-less steels or engineered-plastic materials.

Pneumatic grippers come in various sizes, with grip forces ranging from a few ounces to several hundred pounds. The capacity to bear a particular load is not always directly proportional to gripper force growth. The actuator’s ability to survive moments mirrored back into the gripper’s jaws from forces produced during motion must also be considered. Most gripper manufacturers now provide sizing assistance in the form of technical sizing manuals, sizing applications, or both.

Pneumatic Gripper Mechanism

Various methods may be used, such as:

  1. A direct lateral coupling of two pistons that guides opposing jaws going in opposite directions.
  2. A mechanism in which opposing jaws are powered by a piston rod part that rides on the jaws’ cam surface.
  3. A rack driven by pistons drives a pinion, which drives opposing jaws through a scotch yoke cam system.
  4. A complex process in which the piston parts drives a scroll mechanism analogous to a lathe chucking system.

Both of these parallel systems could be built with three or more jaws to grip circular or unusually shaped sections. Parallel gripper forces are equal to applied friction, much as angular grippers. Parallel gripper can need de-rating factors dependent on the length of tooling attaches to the jaw due to inherent friction inside their jaw mechanisms.

Gripper Force

Grippers have a force level that is measured in pounds per square inch of air resistance. The air pressure influences the gripper’s force; for example, if the air pressure is increased by 20%, the gripper’s force is increased by 20% (up to the gripper maximum air pressure rating). This also tolerates the option of using an air-regulator to decrease the gripper power.

Image4

Where:

  • F = Gripping force of a single finger (N).
  • m= Mass of the workpiece (kg).
  • g = Gravitational acceleration (9.81 m/sec²).
  • a = Acceleration from dynamic movement (m/sec2).
  • n = Number of fingers (n=2 for two-finger gripper; n=3 for three finger gripper).
  • μ = Co-efficient of friction.
  • S = Safety factor.

Sensors

To detect and manage the working location of the fingers, sensors may be mounted alongside pneumatic grippers. The pneumatic grippers may be equipped with proximity sensors or control switches. They can be placed into the body’s grooves, as seen in the diagram below. These sensors can sense whether the fingers are open or closed.

Selection Criteria

  1. Gripping force: The formula in this article should be used to measure the powerful gripping force.
  2. Workpiece weight: During the process, the grasping force must withstand the workpiece’s weight.
  3. Air pressure: Air friction should be taken into account because it substantially impacts gripping power and affects gripper sizing.
  4. Workpiece configuration: The shape of the workpiece can decide whether two or three finger grippers should be used. 2 finger grippers are very popular and can be used on a wide range of items. Round or cylindrical shapes may be gripped with three fingers.
  5. Grip type: Depending on the workpiece, the gripper can have an external or internal grip.
  6. Environment: Pneumatic grippers should be chosen according to the operating environment it might not be suitable for hazardous situations.

What is the main characteristic of Pneumatic Grippers?

The majority of pneumatic grippers are designed to be double-acting. Compressed air may be used to both open and close them. Internal and external clamping is also possible with this function. In the event that the air resistance is missing, the double acting grippers will provide a spring assist mechanism to hold the workpiece.

Pneumatic Gripper Diagram

Pneumatic Gripper
Image Source: “Parallel pneumatic gripper” by myerspictures is licensed under CC BY-NC-SA 2.0

Pneumatic Gripper Types

The 2 jaw parallel and 2 jaw angular gripper models are the most common pneumatic gripper styles. Parallel grippers are the most common grippers since they open and close parallel to the object they would be carrying. They’re the easiest to work with and can accommodate for dimensional differences. Angular grippers need more room when they tilt the jaws away from the object in a radial fashion. Three jaw and toggle type grippers are also available for more precise handling needs.

Apart from that, pneumatic grippers can be classified according to the action of the gripping fingers, the gripping mechanism, and the settings. The following are some of the most common:

Pneumatic 2 Finger and 3 Finger Grippers

The most popular grippers are pneumatic two-finger grippers. The fingers can be placed in two different places. The fingertips open and close in a synchronised motion against the gripper’s central axis. 3 finger grippers are ideal for handling circular surfaces because they have a firmer grip than 2 finger grippers. The fingers can be placed in three different places. The gripper’s fingers open and close in the direction of the gripper’s central axis. In contrast to two-finger grippers, three fingers have more protection and precise centring.

Single Acting Pneumatic Gripper | Double Acting Pneumatic Gripper

Single acting or double acting pneumatic grippers are available. A spring is used in the single-acting pneumatic grippers to aid push in one direction. The majority of pneumatic grippers are intended to be double-acting. Compressed air may be used to both open and close them. Internal and external clamping is also possible with this function. In the event that the air resistance is missing, the double acting grippers will provide a spring assist mechanism to hold the workpiece.

Pneumatic Magnetic Gripper

Handling ferromagnetic materials is possible with magnetic grippers. Permanent magnets are installed in the grippers’ cores. The magnet can be used to accommodate a range of object sizes depending on its weight. It’s worth noting, though, that permanent magnets lose their magnetic properties at higher temperatures (above 150°C).

Based on the shape of Fingers

The pneumatic gripper’s fingers grasp with stiffness in most cases. However, these fingers may be crafted in a variety of ways to minimise the size and gripping power required for the application. The encompassing and retention form improves grip stability while lowering the force necessary. The illustration below depicts several typical finger shapes.

Based on Repeatability

The gripper’s repeatability is an indicator of its ability to attain optimum location precision. Depending on the number of digits and the speed of action, pneumatic grippers may have varying levels of repeatability. As a result, the repeatability must be calculated depending on the application’s accuracy necessities.

Applications of Pneumatic Gripper

The following companies often use pneumatic grippers:

  1. Robotics
  2. Manufacturing of medical devices
  3. Biotech and pharmaceutical industries
  4. Injection moulding and plastic moulding
  5. Processing in the lab
  6. Automated systems

Pneumatic Gripper Advantages

Although the parallel gripper can be marginally more expensive than an equivalent angular design, others consider it to be superior to the angular type because it can also be used to grip an enormous range of component sizes without adjusting the attached tooling.

The ability to function as dual acting cylinders is another advantage of both angular and parallel pneumatic grippers. As a result, they can be used to grip either the part’s exterior or internal properties. Single-acting models with a spring return are also possible. Another variation uses springs to help with gripping actuation, allowing for much more force capability in a smaller space.

The below are some of the specific benefits of pneumatic grippers:

  1. Lightweight
  2. Budget-friendly
  3. Powerful grasping force
  4. Ability to grip a wide range of workpiece configurations
  5. Gripping power that can be adjusted

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