The Selection And Design Of Manipulator Grasping Method

The Selection And Design Of Manipulator Grasping Method

1. Hydraulic clamping and grabbing

The hydraulic system (combination of hydraulic station, hydraulic cylinder, special fixture, etc.) generates gripping force to grasp the parts. Its characteristics are that the grasping force is large, the lifting process is reliable, the control is accurate, and the action is sensitive. However, the hydraulic system has a disadvantage The problem of leakage of hydraulic oil will occur. Due to the influence of environment and time, the rubber seals in hydraulic valves and hydraulic cylinders will age and qualitatively change, which will lead to hydraulic oil leakage and pressure loss. The maintenance cost is relatively high.

Because the hydraulic clamping force is very large, when using this grasping method, you must fully consider the quality and structural rigidity of the grasped parts, and fully calculate the grasping force of the hydraulic manipulator to avoid excessive grasping force. Large causes deformation and damage of parts. At the same time, in the selection of solenoid valves and the design of hydraulic control principles, the safety of the grasping process must be fully considered. For example, how to deal with hydraulic leakage, whether there is corresponding self-locking Mechanism to prevent the parts from falling, is there a safe passage in the trajectory of the manipulator, etc.?

2. Pneumatic clamping and grabbing

The combination of pneumatic systems (air compressors, solenoid valves, cylinders, special fixtures, etc.) generates corresponding clamping force to grasp parts. Its characteristics are simple structure, relatively small output force, rapid clamping response, and maintenance The cost is low, but the pneumatic clamping also has certain defects. Because of the compressibility of air, the stability of its working speed is poor. In the process of air compression, it is easy to produce dust, water and other magazines, which leads to the damage of pneumatic components. The frequency of damage and replacement is too high, and the reliability is greatly compromised. The use of the air pipe is extremely vulnerable to environmental influences, which can cause aging, cracking and cause air source leakage. And because of the small clamping force, its application occasions It is also subject to certain limitations.

Our article mainly shares two pneumatic clamping methods, which are also two common clamping methods for pneumatic clamping.

The clamping force and clamping stroke of this pneumatic finger are relatively small, which is suitable for the grasping of some small parts. It is widely used in many assembly and processing automatic lines. When selecting, you must pay attention to the maximum pressure and The choice of stroke must meet your design requirements. At the same time, because the claws of this part are too short, we need to make corresponding designs according to the shape and characteristics of the clamped parts during use, and we must also fully consider them. Rigidity requirements and wear resistance requirements, because the operation of the automatic line is a large number of repetitive processes, so for the design of the clamping jaws, we suggest that the contact parts should be quenched or alloyed, which can greatly improve the resistance of the clamping jaws. Degree of grinding. 

At the same time, the selected locking screws should also try to choose high-strength screws, such as 12.9 screws. Because the fixed screws of this kind are relatively small, the screws of general strength are easy to break and slip teeth. In fact, the treatment of these details It is the most reliable guarantee for the stability of an automatic line.
For the use of vacuum suction cups, we must fully consider the quality of the parts to be grasped and the surface finish, because only a relatively good surface finish can form vacuum suction smoothly and provide reliable gripping and suction force. 

We must also consider various Exposure to solvents will affect the corrosion and aging of vacuum chucks. For example, we usually use vacuum chucks on automatic processing lines. Most processing coolants have a certain corrosive effect, especially for plastic products, so it is easy to cause the aging of vacuum chucks. 

At this time, we need to make some special requirements and consultations with the vacuum suction cup supplier on the vacuum suction cup material. When necessary, we can ask the other party to provide corresponding samples for trial and then finalize the shape.

In addition, pay special attention to the cleanliness and sanitation of the vacuum generator, because after the air is compressed, the dust in the air will also be compressed. After mixing with the water and oil mist in the compressed air, it will form sludge, which will block the vacuum. 

The final result is that the suction force of the suction cup is extremely reduced, and the workpiece cannot be grasped normally. In this case, we can replace the vacuum generator or disassemble the original vacuum generator for cleaning.

3. Electromagnet grabbing

The parts are grasped by the electromagnetic system. The application of this electromagnetic system has certain limitations. For example, it can only grasp some specific parts that the electromagnet can absorb. In many cases, it may not be used, for example, you want to grasp. 

For a plastic product, stubbornly this kind of gripping method is not appropriate. The electromagnet’s gripping method is stable and reliable, the adsorption force is extremely strong, and the structure is very simple and clear, but it also has certain negative effects, for example, it will be magnetized and captured. Parts, there are certain structural requirements, there are certain hidden safety hazards when the power is suddenly cut off, and the maintenance cost and threshold are relatively high.

There are two options for this electromagnetic grabbing method:

• 1) Energized with magnetism. Under normal circumstances, this kind of electromagnet is non-magnetic. Only when it is energized, it will produce corresponding magnetism, and the magnetism will generate adsorption force. After the power is turned off, the magnetism disappears and attracts. The force also disappears. Of course, if the electromagnet is large, the magnetism will not disappear instantly, and there will be a certain remanence phenomenon. Therefore, when choosing this kind of grasping method, you must consider the magnitude of the remanence and the time for complete demagnetization. . And for many electromagnets, the energization time cannot be too long, because too long energization time will cause the electromagnet to heat up, and the continuous heating will easily cause the aging and damage of the electromagnet.
• 2) The magnet is energized and demagnetized. Under normal circumstances, this kind of magnet is magnetic. When it is energized, the magnetism will disappear and the adsorption force will also disappear. However, this method of grabbing usually has a corresponding effect on the surrounding parts. Requirement, because a magnetic force can be transmitted through space, it may be attracted to other things during the grasping process of parts, so full attention should be paid when designing.

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Link to this article：The Selection And Design Of Manipulator Grasping Method

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