For over 60 years, the MuShield Company of Londonderry, New Hampshire has been designing and producing mumetal magnetic shielding components for multiple industries worldwide.
Such industries include:
- High tech / Electronic
- Medical / Healthcare
- Industrial / Manufacturing
If it concerns building a high permeability magnetic shield for low frequencies and static magnetic shielding applications , we are your trusted source. We will work in conjunction with you and your colleagues to provide feasible, efficient, and cost effective shielding solutions for your unique application need – from development through production.
Contact us today at firstname.lastname@example.org or 603-666-4433
with any mumetal or magnetic shielding questions.
A few short examples of applications
There is a story behind every shielding application. Contracted by NASA to design and build atomic clocks for space exploration, the people at SAO had the opportunity to test Einstein’s Theory of Relativity. Our role was to provide them with some carefully constructed mumetal magnetic shields that are used to maintain the precision of the atomic clocks. Working with minds like this is an honor; as is every opportunity to create a shield design that works.
Our expertise lies in understanding the science of magnetic shielding and providing design and fabrication solutions for a wide range of applications. Typical sources of magnetic interference include:
- Permanent magnets
- Earth’s magnetic field
In operation, a mumetal magnetic shield both absorbs and diverts magnetic flux by providing a path around the sensitive area. In addition, shielding is used to contain the magnetic field generated by a device.
MuShield is fortunate to have several design engineers on staff who bring extensive experience in the field of magnetic shielding to the table. In many cases two design minds are better than one, and we work as a team to develop an end product that works. We’re a small company that tackles big problems for our clients. Our flexibility enables us to build, test, and ship prototypes within reasonable time frames to ensure that you get what you need when you need it.
MuShield works closely with customer design engineers to create a viable shield and then build them according to agreed upon specifications, and test for performance. Simple. Effective. Efficient.
Should you have an existing shield design we’ll will provide cost effective production parts. Along with traditional machining capabilities such as metal forming, hydroforming, spinning, and welding, MuShield has talented machine operators specializing in CAM, precision laser work, and tool making. We are fully equipped for production runs; big and small.
MuShield is an industry leader in the fabrication of high permeability mumetal magnetic shields. Our capabilities include:.
- Convention Sheet Metal Fabrication
- CNC Machining and Turning
- Laser Cutting, Machining and Welding
- Heat Treating
Video highlights how MuShield
works with mumetal
What Is mumetal?
Mumetal is a “soft” ferromagnetic material that does not retain a macroscopic internal field after the removal of an external magnetizing field. Most alloys are permalloys meeting spec ASTM A753 Alloy Type 4 and containing approximately 80% Nickel (Ni), 20% Iron (Fe) and small amounts of Molybdenum (Mo). Mumetal high permeability magnetic shielding material is a non-oriented 80% nickel-iron-molybdenum alloy which offers extremely high initial permeability and maximum permeability with minimum hysteresis loss.
Ferromagnetism originates at the quantum level. Ferromagnetic elements have a lowest energy e- orbital state that aligns the e- spins parallel, thus giving an intrinsic magnetic moment to the atom. The lowest microscopic energy state of an ensemble of atoms is with these magnetic moments aligned to produce a net magnetic field. Since maintaining an external magnetic field would require energy, the lowest macroscopic energy state requires that the atoms divide into domains about 1,000 atoms across and that the magnetic orientation of these domains be randomized.
In the presence of an externally applied magnetic field, the domains magnetically realign to some degree and thus generate their own external field. The primary field continues to exist, but now the net field is the sum (or superposition) of the primary and induced field. The induced field must have an alignment of opposite polarity to the primary field (just like two bar magnets must align North to South and South to North), and the superposition of the two fields results in a lower observed field, and there you have magnetic shielding.
MuShield works closely with customer design engineers to create a viable magnetic shield and then build them according to agreed upon specifications, and test for performance. Simple. Effective. Efficient. We’re a small company that tackles big problems. Our flexibility and talented mix of engineers enables us to build, test, and ship prototypes on time, every time.
Planning and collaboration
We work in conjunction with you and your colleagues to provide feasible, efficient, and cost effective shielding solutions. We’ve had countless opportunities to provide initial design assistance for new products which has enabled our customers to significantly shorten their design cycle. In some cases, a formal contract for this service is appropriate as it is the most cost effective and least time-consuming alternative to magnetic shield design. In other cases, a quick study of the shield design you have created will enable us to guide you as you develop your product for production.
You may find it helpful for us to give you our perspective on a complicated magnetic shield you have designed for production. Our manufacturing experience enables us to look at a part from a production standpoint, and to offer suggestions for improving cost efficiencies.
On occasion, MuShield is asked to visit a customer site for formal consulting on an electromagnetic interference problem. In cases such as these, we are contracted to provide a suggested solution, complete engineering drawings, and create prototypes as necessary.
Hydrogen Heat Treating
Hydrogen Heat Treating
MuShield heat treats mumetal magnetic shields and materials onsite.
With every magnetic shield MuShield manufactures, the goal is to attain the maximum shielding capacity or permeability for that part while maintaining its dimensional and structural integrity. MuShield meets these objectives by heat treating magnetic shields and materials onsite.
Why is heat treatment necessary?
Typical manufacturing methods for magnetic shielding involve:
- Cold working
- Mechanical finishing.
Bending and forming are mechanical operations which can work-harden and/or stress high permeability materials. Welding introduces oxygen to the material, and mechanical finishing and cold working can introduce carbon. Each of these factors contribute to the degradation of a magnetic shield’s ability to perform effectively.
What is permeability?
Imagine a sponge. Some sponges have big holes, some are more tightly structured; each of them absorbs liquid to the point of saturation. Mumetal reacts in much the same way. Depending upon its structure, the material absorbs magnetic interference to a point of saturation. As magnetic interference increases, so too should the permeability of the material.
How does heat treatment increase the permeability of mumetal?
When the magnetic shielding materials that MuShield uses are exposed to extremely high levels of heat (2100ºF for 1-2 hours), the grains of the material grows, increasing the materials ability to absorb magnetic flux. In addition, the hydrogen atmosphere in the heat chamber produces a chemical reaction with the shielding material, removing impurities such as carbon and oxygen, thereby enhancing permeability.
Finally, rapid and controlled cooling of the magnetic shield “freezes” the desired grain of the shield, yielding maximum permeability. MuShield engineers regulate the temperature and the time the parts are in the heat chamber with care as it is critical that the parts maintain their structural and dimensional integrity.
In the case where a hydrogen furnace cannot be used for heat treating mumetal, a vacuum furnace is a suitable replacement.
Does MuShield provide heat treatment services for parts other than their own?
Absolutely. MuShield has a large heat treating capacity and is committed to investing in additional equipment to keep up with the demand for these services. Fast turnaround of heat treated magnetic shields is critical to MuShield customers.
Mumetal is a non-oriented 80% nickel-iron-molybdenum alloy which offers extremely high initial permeability and maximum permeability with minimum hysteresis loss.
Alloys meet military specification MIL-N-14411 and ASTM A753.