What are the requirements for the design of gripper for manipulator of injection molding machine?

The design of the picking fixture of the manipulator of injection molding machine directly affects the picking efficiency, product quality and production safety, and needs to meet various requirements, as follows:

First, grab stability and reliability

This is the core requirement of fixture design, to ensure that it will not fall off or damage the product during high-speed operation.

Adapting the product shape: design the contact mode according to the geometric structure of plastic parts (such as curved surface, hole position, boss, etc.), such as:

Vacuum sucker can be used for plane plastic parts (the sealing surface should be flat);

Plastic parts with holes or grooves can be fixed by mechanical clamping claws (by clamping the hole position or edge);

Easily deformable plastic parts need to increase the contact area and disperse the clamping force.

Reasonable clamping force: if the force is too small, it will fall off, and if it is too large, it will crush the product. The clamping force should be calculated according to the hardness and strength of plastic parts (such as PP, ABS, PC, etc.), and dynamically adjusted by pressure sensor if necessary.

Anti-falling design: For special-shaped parts or curved parts, auxiliary positioning structures (such as positioning pins and guide plates) can be added, or the combination of "mechanical clamp+vacuum suction" can be used for double fixation.

Second, it does not damage the product

The surface of plastic parts usually requires no scratch, indentation and deformation, and the design should focus on:

Selection of contact materials: soft materials (such as silica gel, rubber and polyurethane) are preferred for the parts in contact with products to avoid direct contact with hard metals; For high-precision surfaces (such as mirror plastic parts), materials with low friction coefficient (such as Teflon coating) should be used.

Avoid stress concentration: the contact points of jaws or suction cups should be evenly distributed to avoid excessive stress at a single point. For example, long plastic parts need at least two supporting points to prevent bending deformation.

Compatible product status: The plastic parts that have just been demoulded may have residual temperature (60-100℃) or tiny burrs, and the fixture material should be resistant to high temperature (such as silica gel temperature ≥150℃), and the edges should be rounded to avoid product damage caused by scraping burrs.

Third, efficiently adapt to the production rhythm

Fixture should match the cycle of injection molding machine and the running speed of manipulator to reduce non-production time.

Lightweight design: the weight of fixture directly affects the running speed and energy consumption of manipulator, so high-strength lightweight materials (such as aluminum alloy and carbon fiber composite) should be used to reduce the weight on the premise of ensuring strength.

Quick pick and place: the action path of picking should be concise to avoid unnecessary movement. For example, the vacuum response time of suction cup fixture should be ≤0.5 seconds, and the opening and closing time of mechanical gripper should be synchronized with the mold opening time of injection molding machine.

Compatible with multi-specification products: If the production line needs to switch different plastic parts (like multi-cavity products of the same mold or different models), the fixture should be designed as an adjustable structure (such as adjusting the jaw spacing through screws and replacing suction cups of different sizes), and the adjustment time should be ≤5 minutes to reduce the downtime of mold changing.

Fourth, security

It shall conform to industrial safety standards to prevent equipment damage or personal injury.

Anti-collision design: the edge of the fixture needs to be rounded to avoid sharp parts hitting the mold, injection molding machine pull rod or other equipment; Install anti-collision sensors when necessary, and stop the action immediately when triggered.

Overload protection: When the clamping force is abnormal (for example, the product is stuck), the fixture should have overload protection function (for example, mechanical limit block and torque sensor) to prevent the gripper or manipulator motor from being damaged.

Electrical safety: If vacuum system or pneumatic components are used, pressure detection devices (such as vacuum pressure gauge and air pressure sensor) should be set to automatically give an alarm and stop when the pressure is abnormal, so as to avoid the product falling due to insufficient suction.

Five, compact structure and spatial adaptation

The space around the mold of injection molding machine is limited (especially multi-cavity mold or large mold), and the fixture needs to adapt to the operation in narrow space.

Size adaptation: the overall size of the fixture should be smaller than the internal space of the injection molding machine after opening the mold to avoid interference with the mold, pull rod or thimble. Before design, it is necessary to accurately measure the available space (length× width× height) of the mold after opening.

Modular design: the fixture is divided into positioning module, clamping module and driving module (such as air cylinder and vacuum pump) for easy installation, disassembly and maintenance. For example, the suction cup assembly can be replaced through the quick release interface, reducing maintenance time.

Six, durability and convenient maintenance

Wear resistance and corrosion: the fixture should be resistant to oil stain, dust and slight chemical corrosion (such as mold release agent residue) in the workshop environment, the metal parts should be surface treated (such as zinc plating and anodic oxidation), and the moving parts (such as cylinder piston rod and guide rail) should be lubricated regularly.

Maintainability: key components (such as suction cups, sealing rings and cylinders) need to be easily replaced, and spare parts are versatile (such as standard vacuum suction cups and pneumatic connectors) to reduce maintenance costs.

Life requirement: according to the production intensity (for example, running for 20 hours every day), the life of the core components of the fixture (for example, clamping jaws and suction cups) should be ≥ 100,000 times to avoid frequent downtime and replacement.

Seven, adapt to the manipulator and automation system

Compatibility of installation interface: the connecting flange between the fixture and the manipulator shall conform to the standard interface of the manipulator (such as ISO 9409-1), so as to ensure firm installation and high concentricity and avoid shaking during operation.

Signal linkage: the state signal of the fixture (such as "grabbed", "released" and "insufficient vacuum") needs to be linked with the manipulator control system and the PLC of the injection molding machine to realize automatic closed-loop control. For example, after the vacuum chuck detects that the negative pressure reaches the standard, the manipulator will perform the load shifting action.

summary

The design of gripper for manipulator of injection molding machine should balance the four core objectives of "stable grasping, product protection, efficient adaptation, safety and durability". At the same time, it should be customized and optimized according to the characteristics of specific plastic parts (shape, material and precision) and production scenes (batch, rhythm and environment). If necessary, the stress and motion trajectory should be simulated by simulation software (such as SolidWorks and Adams) to avoid problems in advance.