Applications
Applying Fluxtrol to Induction Coils
Fluxtrol concentrator manufacturing and application technique plays a very important role in successful performance of induction coils. With respect to Fluxtrol concentrator application – magnetic, thermal and mechanical aspects must be considered. Additionally, the electrical strength of our concentrator must be considered or insulation provided.
This section is intended to provide methods for safety, handling and machining FLUXTROL® & FERROTRON® concentrator materials when applying the product to induction coils.
Our materials may be machined using various methods (drilling, milling, turning, grinding, etc.). It is not necessary to use cooling or lubricating fluids.
General Rules: Use sharp carbide tools (i.e., TiCn coated equivalent) with a high spindle speed (>6000 rpm) and slow feed rate (i.e., rate of > 20.0). Remember to adjust spindle speed and surface feed rate as needed to prevent chipping. Multiple passes are preferred versus heavy depths of cuts due to the nature of Fluxtrol materials. Make pilot holes when drilling large bores. Drill material on strong support (wooden or plastic block) to avoid chipping.
Our flux concentrator products are soft magnetic composites consisting of metal powders and dielectric binders compacted at high pressures with subsequent thermal treatment. The metal powder may be a source of combustion.
Caution: The primary source of combustion is friction. Red hot chips or “sparks” may be thrown off, fall or drop into the collection tray of a lathe, inside a bandsaw or near the grinding wheel dust. If these sparks land on accumulated machining dust or debris, they could cause a smoldering fire. If left unattended, a fire could result. Coolant is not suggested, in that it impedes the cutting process and is not necessary, if precautions are observed.
- Clean all collection (or “catch”) trays before machining Fluxtrol & Ferrotron concentrators, removing any remnant debris or oils.
- Cut at high spindle speed and slow feed rate as in cutting stainless steels.
- Never use vacuum cleaner type dust collectors to catch falling dust or debris. Instead, use an approved dust collector over the machining operation. This is best for removing all airborne particles.
- Inspect by spreading dust and/or debris for accidental combustion during and after machining operations. Use water and wet rags to extinguish any glowing/smoldering areas. DO NOT INHALE SMOKE OR FUMES.
Read the hazardous material section of our soft magnetic materials Material Data and Safety Sheets.
Our Fluxtrol materials are strong in compression, less strength in tension or bending loads. They may be machined to any shape, drilled for coolant or mechanical attachments.
Threads may be cut directly in material for fastening, but helicoils are recommended for heavy mechanical applications.
Best Fluxtrol material performance may be realized when sufficient care is administered to prepare Flux Concentrator material (magnetic flux controller) and Induction Heating Coil in the area of attachment/interface as described below:
Fluxtrol Flux Concentrator – Clean all surfaces that are to be in intimate contact with Induction Heating Coil by removing any paint. Lightly sand with “medium” to “medium–fine” emery paper (80–180 grit) to give adhesive a good “gripping” surface. Remove any accumulated dust by wiping with a clean dry cloth or with an organic solvent (such as acetone).
Induction Heating Coil – Clean all surfaces that are to be in intimate contact with Fluxtrol Flux Concentrator by removing any machining fluids/oils or residual quenchant. This may include sandblasting the copper surface and then wiping it with an organic solvent (such as acetone). Lightly sand with “medium” to “medium–fine” emery paper (80–180 grit) to give epoxy adhesive a good “gripping” surface. Remove any accumulated dust by wiping with a clean dry cloth.
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The above figure is provided as a surface preparation procedure concept only. For assistance related to this technique, please contact Fluxtrol customer service department.
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There are two main methods for attaching Fluxtrol Flux Concentrators to the Induction Coil:
Adhesive Bonding Mechanical Attachment
For both attachment methods, flux concentrator material performance is advanced when it is in the best possible thermal contact with the induction coil. This can be achieved through the use of a uniform and thin layer of a thermally conductive “medium” in–between the contact surfaces.
Adhesive Bonding is the most common method of attaching Fluxtrol flux concentrator product to an induction heating coil.
Any epoxy adhesive used must have the following characteristics:
- high temperature stability
- electrically non–conductive
- high bond strength
- good thermal conductivity
- low moisture absorption
- chemical resistance
Care should be taken to clean all dirt, oils, greases and mechanically roughen the contact surfaces prior to bonding. A thin layer of epoxy adhesive should be applied to both the Fluxtrol product and induction coil copper contact surfaces and then these two surfaces are to be brought into contact and held together with light pressure. Wipe away the excess glue with a damp cloth and then follow the curing instructions for the respective adhesive.
For common applications (lightly loaded having larger tolerances etc.), we suggest a gap or space in–between Induction Coil copper and Fluxtrol product of 0.008″ – 0.012″ (0.2 mm – 0.3 mm) and use J–B Weld Epoxy Resin Part No. 8265–S & 8265 (from J–B Weld Company).
For severe applications (heavily loaded having high flux density and long duty cycles), we suggest a gap or space in–between Induction Coil copper and Fluxtrol product of and recommend 50–3100 High Thermal K Heat Transfer Epoxy Resin(from www.epoxies.com). ”. A thin epoxy layer of this epoxy type 0.004″ – 0.006″ (0.10 mm – 0.15 mm) may be applied evenly to the induction coil & flux concentrator.
Note: Silicone rubber is a poor thermal conductor and is recommended for use only in lightly loaded inductor coils.
If an E–shaped concentrator is broken into two isolated C–shaped sections, no electrical insulation between the coil tubing, stud and concentrator is necessary (see below figure).
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The above figure is provided as an adhesive bonding application concept only. For assistance related to this technique, please contact Fluxtrol customer service department.
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Mechanical Attachment is another example of how Fluxtrol flux concentrators are attached to an Induction Heating Coil. The purpose for the mechanical fastener is to keep the flux concentrator in a secured position (i.e., in place). A technique may be used where a stud (i.e., screw or bolt made from non–magnetic stainless steel, brass or copper) is brazed to the induction coil coupled with a clearance hole drilled through the Fluxtrol product. Use where possible a thermal medium that is electrically non–conductive and thermally conductive “heat sink paste” (usually silicone based), like those used for mounting transistors in power supplies. Both the Fluxtrol product and Inductor contact surfaces should be coated with a thin and uniform layer prior to fastening. After tightening down the nut on the stud, excess paste should be wiped away with a dry rag. BE careful no to over–tighten the nut, as this may lead to cracking of the Fluxtrol flux concentrator.
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The above figure is provided as a mechanical fastening application concept only. For assistance related to this technique, please contact Fluxtrol customer service department.
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As an alternative to mechanical fastening, mechanical assembly (please see photo below) is a viable option where induction coils are exposed to high intensity manufacturing environments, such as heavy loaded, highly automated and operate 365/24/7.
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Maintenance of Coils with Fluxtrol Concentrators
In many applications Fluxtrol concentrators can work longer than copper
Mechanical damage is one of the main factors causing coil failure and proper preventive measures must be taken.
Visual control of Fluxtrol concentrators:
- Check concentrator integrity, attachment (loose parts, cracks in glue, mechanical damage) and insulation conditions when applicable
- Periodically clean concentrator from metallic chips and scale
- Restore damaged coating when applicable
– Dark surface may be due to smoke and quenchant residue buildup. Gently scratch the surface with knife or other sharp tool. Cleaned surface must have grey metallic color typical for a particular type of material.
– Dark and crumbling surface shows that concentrator material was overheated. Concentrator must be replaced. If the coil lifetime is not sufficient, provide additional cooling or change the coil design.
– In some applications, especially in installations with tube generators, sparking from a concentrator to the part or fixture may occur. If there is a ground protection, the generator turns OFF quickly however there might be small areas on the concentrator damaged by sparking. Remove damaged volumes with a sharp tool and eliminate a factor that caused sparking (too small gap, metal particles etc.). Concentrator can continue to work if damage was small.
