Multilayer heat-shrink tubing with high mechanical resistance and high thermal coefficient, to fix and protect against centrifugal forces of all types of permanent magnets applied on the rotors of BLDC brushless motors.

After lengthy Research and Development, in constant contact and comparison with the technical departments of our international customers, Politubes is proud to present an innovative high efficiency glass fiber reinforced armor sleeves that enables the manufacturers of brushless motors with permanent magnets to position and secure them effectively, safely and easy to use in automatic industrial productions.

This innovative solution eliminates a series of problems well known to brushless motor manufacturers and relating to loss of performance, complications of assembly processes and higher costs, due to use of traditional permanent magnet attachment systems.

The spiral-wound tube is fitted onto the rotor with the magnets in position and is then instantly heat-shrunk, resulting in:

1. Firm attachment of the magnets to the rotor
2. Protection for the magnets from scratches, abrasions and polluting agents
3. No danger of cracking or damage to the delicate permanent magnets during the assembly process.

The SHRINK FIBER is a multilayer tubular high efficiency solution that includes all the advantages of perfect adhesion even at the edges of the rotor due to the heat-shrink polyester, with the added benefits of extremely high mechanical strength and temperature resistance offered by glass fiber.

As a matter of fact, our solution contains a special composite fiber which exponentially increases the mechanical seal and resistance to temperature compared with simple polyester.

The SHRINK FIBER tubing is inserted on the rotor with the magnets in position and heat shrunk (by using temperatures much lower than Curie point and avoiding any risk of reduction of magnetic flux), obtaining strong adherence, even at high revolution speeds. It is also resistant to the thermal shock produced by the motor in lengthy operation, up to 170°C.

Compared with very expensive metallic rotor sleeves, our high efficiency solution avoids eddy-current losses that reduce motors efficiency and that may cause also overheat of electric machines.

Compared with tubing and wrapping which use epoxy resins, the SHRINK FIBER heat-shrink solution offers greater mechanical resistance and avoids lengthy resin activation times in the oven; this increases dramatically our customers’ motors productivity.

In motors which use Bonded magnets (NdFeB or Ferrite) obtained through compression or injection moulding, the SHRINK FIBER tubing protects the magnetic material against corrosion.

As a matter of fact SHRINK FIBER TUBE is easy to be removed if permanent magnets have to be recycled.

Due to its limited thickness, which ranges between 0.19 – 0.35 mm, the SHRINK FIBER sleeve guarantees the correct magnetic flux of permanent magnets and therefore the best performances of the motor itself.

The system patented by Politubes is simple and efficient and is already an integral part of the production processes of leading companies operating in the electrical motor sector.

The SHRINK FIBER heat-shrink system can be introduced into automatic construction processes and on motor assembly lines, eliminating the critical aspects of traditional tightening systems and the waiting times for adhesives to harden, allowing shorter assembly times and lower electrical motor costs.

Benefits obtained with the Politubes tubing for BLDC brushless motors:

• High mechanical resistance
• High resistance to temperature ( – 70°C – + 170°C)
• Elimination of expensive steel or brass rings their risk to damage permanent magnets during assembly
• Reduction of motor noise
• Protection of magnets and increase in motor lifetime
• Low interference with magnetic flux
• Protection of magnet edges
• Perfect adhesion and protection at the edges of the magnets
• Rapid and easy positioning in automated industrial processes
• Reduced thickness, dimensions and weight
• Elimination of problems involved in use of expensive special adhesives
• Perfect adherence of the tube to the rotor and the magnets
• Easy to be removed if permanent magnets have to be recycled