How to Select an Electromagnetic Gripper
Selection of an electromagnetic gripper involves matching of the magnetic performance of the gripper to the workpiece, robot, environment and automated process.
1.Determine the material of the workpiece.
First of all, it is necessary to establish whether the material is ferromagnetic. Only mild steel and other iron-based materials will work but aluminum, copper, brass, plastic and some stainless steels may not attract sufficiently. Thus, the material composition should be checked before selection.
2. Measure dimensions and weight of the workpiece.
Establish the maximum and minimum weight, length, width, thickness and shape of the workpiece. The nominal maximum rating should not be taken into account when selecting the gripper.
3. Examine the contact surface.
Flat, smooth and clean steel provides better magnetic coupling than curved, rough, painted, coated, rusty or uneven surface. Gaps in the surface considerably reduce the effective holding force.
4. Take into consideration the thickness of the material.
Thin steel may not be as good magnetically as thick steel. Check the manufacturer’s holding force data for the actual work piece thickness.
5. Define robot payload requirements.
The robot should carry the gripper, workpiece, mounting hardware, cabling and other tooling. Make sure that the total load is within the robot’s rated payload and moment limits.
6. Determine the proper electrical parameters.
Check the voltage, current, control signals, switching frequency, duty cycle, power consumption. Electrical compatibility of the gripper and controller should be checked.
7. Consider the safety.
Think about power-loss behavior, backup systems, sensors, mechanical retention, emergency-stop performance and other safety controls needed in case of dropping a load that can cause injury or equipment damage.
8. Analyze the environment.
Heat, dust, oil, moisture, vibration, impact and contamination in case of welding, machining, foundry or outdoor operation.
9. Evaluate the mounting options.
Examine the bolt pattern, mounting dimensions, cable routing, orientation and clearance around the gripping surface.
10. Workpiece real test.
Test the gripper with real workpieces under real operation conditions before using it in production process. That is the best way to check holding force, cycle time, release behavior and reliability of the gripper.
Tips to Avoid Common Mistakes in Electromagnet Gripper Design
Not all materials are magnetic.
Don’t select the gripper based on the weight of the workpiece.
Think about the air gap caused by paint, rust, dirt, coatings or uneven surfaces.
Consider the minimum workpiece thickness, not the maximum thickness.
Don’t base everything on the ideal lab conditions.
Check robot payload and moment limits.
Before installing the controller, check voltage and current requirements.
Think about the heat produced during high duty cycles.
Use proper cable protection and strain relief.
Think about the consequences of the power outage.
If workpiece detection is needed, consider installing appropriate sensors.
Allow sufficient clearance for pickup and release.
Test the gripper with actual production materials.
Check holding force at the actual working position.
Consider vibration and acceleration when a robot moves.
Keep magnetic contact surfaces clean and in good condition.
Don’t forget about safety and emergency-stop requirements.
Start high-speed production only after confirming the duty cycle of the gripper.
Document installation, inspection and maintenance requirements
