The newly developed MG77-D magnetic gripper with alternating field demagnetization enables the safe magnetic handling of hardened ferromagnetic components without leaving residual magnetism on the part during release.
Preferred application: robot handling and automation applications.
Why is low residual magnetism critical?
In many industrial applications, residual magnetism is a critical influencing factor. Even low magnetic fields can cause particles to adhere to component surfaces. This negatively affects, among other things:
- technical cleanliness
- assembly processes
- coating quality
- eddy current testing
A value below 4–5 Gauss is already considered technologically non-critical in many applications and significantly reduces the risk of process disturbances. However, higher requirements apply to eddy current testing.
How low is the residual magnetism after gripping?
On hardened steel components, the following residual magnetism is typically achieved on the contact surface after handling with standard pole shoes (approximate values):
- 1 to 5 Gauss with largely full-surface contact between the component and the magnetic gripper (e.g. shafts, thick-walled rings, formed parts, forged parts, sheet metal parts)
- 2 to 20 Gauss with partial contact and irregular component geometry (e.g. thin rings, certain gear shapes)
- With application-specific integration using optimized pole shoes, values below 5 Gauss can be achieved in most cases.
- For rolling bearing rollers (material 100Cr6, hardened), application-specific values below 2 Gauss are achievable.
- Unhardened components are generally uncritical.
These values apply to parts that do not exhibit elevated residual magnetism in their initial state or have already been demagnetized.
Conventional magnetic grippers, in comparison, typically leave residual magnetism between 20 and over 100 Gauss, depending on component geometry and material.
The demagnetizing effect of the MG77-D extends beyond the gripping surface and effectively reduces residual magnetization even outside the contact zone. Depending on the component and geometry, the demagnetization effect extends approximately 5 to 50 mm beyond the contact area. Demagnetization can also be used as a standalone function without gripping.
This enables the MG77-D magnetic gripper to support demanding applications across many industrial sectors.
What is the key difference compared to conventional magnetic grippers?
The key difference lies in the functional principle during release.
The MG77-D combines:
- releasing the workpiece
- alternating field demagnetization
into a single process step.
While conventional magnetic grippers simply release the component by switching off the magnetic field, the MG77-D additionally reduces remanence actively through a precisely controlled pulsed alternating field demagnetization using different frequencies.
Advantages of this integration:
- reproducibly low residual magnetism
- in most cases, no additional demagnetization step required (and if required, a simple and cost-efficient demagnetization is sufficient)
- reduced process complexity and resulting cost advantages
- stable downstream processes
What is an electropermanent magnetic gripper?
The MG77-D is based on an electropermanent magnetic system:
- Holding force is generated by a permanent magnet
- Energy is only required for magnetization/demagnetization, i.e., gripping/releasing
- The gripping state is maintained even in the event of a power failure
Characteristics:
- fail-safe (no loss of the workpiece in case of power failure)
- magnetic holding force without continuous power supply (energy-efficient)
- finely adjustable gripping force
Technical data MG77-D
| Magnetic pot diameter | 77mm |
| Max. holding force (flat steel, without safety factor) | approx. 500–1,000N (depending on pole shoes) |
| Pole shoes | Application-specific variants depending on use (interchangeable) |
| Gripping force | Adjustable (approx. 40–100%) |
| Gripping time | 100–300ms (adjustable) |
| Release time (demagnetization) | 700–1,500ms (adjustable) |
| Cycle time | approx. 5–10s (optional air cooling) |
| Required power module | LM14-MG or LM20-MG (230VAC / 16A) |
Conclusion
The MG77-D combines three key characteristics:
- adaptable to a wide range of components through different pole shoe variants
- reliable electropermanent technology
- virtually no magnetic imprint after magnetic gripping on hardened components (unique selling point)
Preferred industries/applications:
- handling of hardened ferromagnetic components
- handling of magnetically sensitive steel semi-finished products
- handling of larger rollers in the rolling bearing industry
The combination of magnetic gripping and integrated alternating field demagnetization during release also enables new applications where magnetic grippers have previously been deliberately avoided.