Parallel gripper is a kind of clamp that can hold or move workpieces or parts during the machining progression. As its name shows, the gripper would be opened or closed parallelly that only requires little working space.
They are mainly used to hold and move the parts with a predictable geometry. In other words, parts they can hold and move would be limited by shapes. In general applications, the parallel grippers are used to deal with objects designed with regular shapes like cubes, rectangles, or plates.
These grippers are either driven by air pressure or motors. The biggest advantage of the parallel grippers is that they do not require much working space. However, they are not an ideal choice while the parts they are required to hold and move are designed with round or irregular shapes since they have only two contact points to the objects.
Divided from the driven ways of the parallel grippers, they can be grouped into pneumatic grippers and electric grippers. Each of them contains its own features.
● Pneumatic Parallel Gripper
Pneumatic parallel grippers are controlled by the air pressure from compressed air which would be pumped in and out while working. The force in the gripper would be controlled by the compressed air.
When the pneumatic parallel gripper is required to be closed for holding elements, the compressed air would be pumped into the controlling parts of the gripper to press the pistons and make the two fingers getting closer to hold the parts or workpieces by air pressure.
On the other hand, when the pneumatic parallel gripper is required to release the parts or workpieces it grabs, the compressed air would be released from the control part of the gripper. Once the air pressure gets lower, the strength of the fingers would relax and release the parts or workpieces they grab.
For the purpose of keeping a constant force on the part, the valve can be closed or opened in order to keep the air pressure on the pistons the same.
The advantages of pneumatic parallel grippers are simple working concept and structure. However, these grippers do not contain any solutions to be controlled immediately that would become a disadvantage.
● Electric Parallel Gripper
Electric parallel grippers are driven by electric motors. The choice of the motors can be various, such as servo, steppers, etc.
In most situations, the motor used to drive the electric parallel grippers would be 4-bar linkage structures that can transfer the motion of the motors from rotation to linear.
The motion of the electric parallel grippers is basically controlled by gears. While working, screws or gears would go up and down to make sure the two fingers open and close at the same time which can grab and hold the parts tightly.
Most of the electric parallel grippers contain gear nubs which can stop the motions of the fingers. These nub stops also mark the longest stroke the gripper can reach.
The biggest property of the electric parallel grippers is that their finger motions can be controlled and adjusted by simplified programming methods. Some of the designs can even allow to change the force and speed.
The most common application of the parallel grippers is parallel angular grippers. The two parallel claws they contain would move parallelly to control the claw.
When it is required to hold or move something, the two claws would become closer to grab the parts or components and transfer them to the right places.
Also, the claws can become farther and apply pressure to open the components or parts if it is required to do during the progression.
Like the parallel grippers, the parallel angular grippers can be divided by their powering methods and be categorized into pneumatic and electric versions.
● Pneumatic Angular Grippers
Pneumatic angular grippers are generally less expensive upfront, simpler, lighter, and offer higher gripping forces than the types powered by electricity.
Modern pneumatic angular grippers contain diagnostic features that help maintenance personnel and machine operators identify air pressure loss then the operators can take on next movements as soon as possible.
However, this function would contribute to higher energy costs in pneumatic systems.
● Electric Angular Grippers
Angular grippers designed for powering with electricity would have more strength to deal with large and heavy workpieces but would take more energy to generate the power to do so.
The operating cost of electric angular grippers is less expensive than pneumatic angular grippers.
Nowadays, the major on the market is the pneumatic angular gripper since grippers of this design are considered more reliable. The pneumatic angular gripper offers a wide variety of sizes, much faster actuation times, and ability to produce considerably more force within the same footprint.
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