15 Questions To Ask Before Designing an Induction Coil
15 Questions To Ask Before Designing an Induction Coil
Designing a new induction coil? Here are 15 questions to ask to ensure the coil meets all the requirements to do the job.
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This Technical Tuesday feature was written by John Gadus, Design & Sales specialist at Induction Tooling, Inc., and was first published in Heat Treat Today's May Induction Heating print edition.
The scope of information available when designing a new inductor can vary greatly. The tooling designer must understand how the customer will process the parts to achieve the desired heat treat specification. Captive heat treating typically involves dedicated high-volume automated systems that heat treat the same part for the life of the production run. Commercial heat treating can be high or low volume with relatively simple setups that provide flexibility to adapt multiple part geometries very quickly. The induction machine design regarding the material handling system, locator tooling, and cooling and quenching capabilities are all important details that need to be provided for any new inductor design.
When beginning a new project, especially for a new customer, basic background information is always helpful. This initial consultation provides insight when presenting follow-up questions to help familiarize new customers with the correct terminology.
1. Have you had any prior induction experience?
2. Have you processed similar parts previously?
Prior to quoting a new job, the very first thing a potential customer should provide for review is a 'green' part print and heat treat specification. If there are any questions or clarifications needed, this is the time to confirm with the customer the exact heat treat requirements to provide feedback for realistic expectations. The part material and the machined condition of the part prior to heat treating are key to avoid design complications from misquoting.
For new applications, often prototype or mock-up parts are used during development to prove out the heat treating process. This works well for very complicated or expensive parts. Extra care should be taken to maintain identical part geometries between prototypes and actual production parts to keep an apples-to-apples comparison.
Viable questions to ask would be:
3. What is the part material?
4. What is the hardness specification?
5. What are the heat treat pattern minimum and maximum limits for depth and breakout?
6. What are the 'green' dimensions of the part prior to heat treating?
7. Will the part have extra stock for finish machining or grinding?
Specific details and information about the induction machine are very important as well. The machine design sets the stage for the style or type of inductor and determines how the part will be presented to the coil for heat treating. Locators often affect the temperature profile when placed in close proximity to heating zones. This can be used as an advantage especially when anticipating possible overheat conditions due to sharp corners or a thin wall. Detailed drawings of the locators and the material handling system along with close-up photos (or if practical, a visit to the customer's facility) go a long way to avoid awkward tooling setups and machine clearance issues.
Here are a few induction machine questions whose specific answers will aid in the design process:
8. What is the generator frequency and power?
9. Single-shot or scanning?
10. What is the output contact design?
11. Is there an existing bus bar or quick-change clamping adapter?
12. What is the workpiece centerline?
13. What are the locator/material handling details?
Additional follow-up questions to narrow down the specific inductor features will help finalize the design. Cooling is the life blood of any inductor and will have a large impact on cycle life. The part material and heat treat specification will often dictate the quench design to provide optimal hardening results.
Because of the importance of cooling and quenching, the last two questions we must ask are:
14. How many cooling lines (supply & return) and type of quick-disconnect fittings?
15. How many quench supply lines and type of quick-disconnect fittings?
Most induction projects are unique but all share similar design characteristics. Depending on the machine builder or OEM manufacturer, dedicated equipment or custom-built systems can vary greatly even when processing the same or similar parts. Well defined and detailed answers to this list of important questions will provide the tooling designer with the information needed to provide the best inductor design possible to achieve the desired heat treat specification.
About the Author: John Gadus is a Design & Sales specialist at Induction Tooling, Inc. with over 25 years of inductor design experience mentored under the guidance of president/CEO Bill Stuehr and VP of Engineering David Lynch. John has honed his induction knowledge and tooling design techniques working closely with customers to meet project requirements across a wide range of induction heating applications, from initial design concepts to customer support at installation. John is co-author of several design patents and has recently taken the lead to explore additive manufacturing solutions for new innovative inductor designs.
Contact John Gadus:
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Questions about induction heating
Questions about induction heating
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Thread starter
Metallus
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Start date
Aug 17, -
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Tags
- Graphite Heating Induction Induction heating
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In summary, the conversation discusses the basics of induction heating and how it works. The process involves passing alternating current through a hollow coil of copper, generating a magnetic field that heats a conductive material placed inside the coil. The discussion also touches on the use of a cooling fluid to keep the coil cool and the effect of the insulator between the coil and the heated material. The conversation also explores the safety concerns of putting a hand or finger into a powered coil and the role of frequency in induction heating. There are also hobbyist sites and videos available for those interested in making their own induction heaters.
Metallus
Hi there,
I'm a material chemist, currently working on ceramics. I know the very basics of physics, but I have many doubts about electromagnetism.
How does induction heating exactly work? I understand that you use a hollow coil of copper with a cooling fluid circulating inside, through which you pass alternate current at high frequency. This generates a (oscillating?) magnetic field that points towards the center of the coil (according to right hand rule). If you put an object inside, called susceptor, it gets heated.
1) Why does this happen? What happens exactly at a microscopic level in the susceptor to justify the generation of heat? I always imagine alternating two magnets on a rod of iron and I can't fathom how this would heat it.
2) Does this work with any object or just metals/graphite and why? What would happen if I put, eg, my hand inside an induction coil powered to heat graphite at C? What if I put an insulator?
3) I am amazed that the coil can heat graphite to C without melting, considering that copper melts at C. Yes, there is a cooling fluid circulating, but considering the graphite die is usually 1cm away from the coil, that seems really insane cooling. Or am I underestimating the effect of the insulator between the coil and the graphite die?
Thanks
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The material being heated needs to be conductive, the changing magnetic field creates eddy-currents in the material and the current creates the heat. Your thinking is correct about the magnets and a piece of Iron, but it needs to be a changing Magnetic field. - Example, if you look at the core of a transformer, it is assembled of laminated (insulated) steel plates, to reduce these currents in the core.
The coil does not need coolant flowing in it to make the effect work, it is only to keep the coil cool. To generate the strong magnetic field, the coil needs a lot of current.
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Metallus
I understood that the coolant was for the joule effect, but if the material that is being heated is very close to the coil and it reaches °C, isn't there the possibility of the coil "softening" with just the radiation from that body? °C at 1 cm distance seem quite a lot to dissipate.
Also, if the material needs only be conductive, I assume I could safely put my finger inside a powered coil (granted I don't directly touch the coil and get shocked). Is that right or I'll still get "warmed"?
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Metallus said:
@Metallus
Test that with a hot dog before inserting your finger.
Metallus
Not planning of actually doing it :D, don't worry. I would be more scared of accidentally touching the coil and getting electrocuted, beside the fact that the coil itself heats up on its own. Just curious about what the effects would be on a human.jim hardy said:
@Metallus
Test that with a hot dog before inserting your finger.
Not planning of actually doing it :D, don't worry. I would be more scared of accidentally touching the coil and getting electrocuted, beside the fact that the coil itself heats up on its own. Just curious about what the effects would be on a human.
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Metallus said:
Induction 'induces' current in the material to be heated. That current generates heat by simple I2 X Resistance of the material in the magnetic field.
It needn't be high frequency but it's way more practical to use it .
That's because rate of change of flux is what 'induces' and you well know that dsin(ωt) = ωcos(ωt) . So raising ω let's you use smaller transformer and wire.There are plenty of hobbyist sites making induction heaters. Modern "Inverter" microwave oven power supplies are a popular power source, they rewind the high frequency SMPS power supply transformer to give low voltage high current. Youtube will show you fun hobbyist videos.
Induction 'induces' current in the material to be heated. That current generates heat by simple IX Rof the material in the magnetic field.It needn't be high frequency but it's way more practical to use it .That's becauseof flux is what 'induces' and you well know thatsin(ωt) = ωcos(ωt) . So raising ω let's you use smaller transformer and wire.There are plenty of hobbyist sites making induction heaters. Modern "Inverter" microwave oven power supplies are a popular power source, they rewind the high frequency SMPS power supply transformer to give low voltage high current. Youtube will show you fun hobbyist videos.
Related to Questions about induction heating
1. What is induction heating?
Induction heating is a method of heating an electrically conductive material by using an alternating magnetic field. This is achieved by placing the material in an induction coil, which generates the magnetic field. As the material is heated, its electrical resistance increases, causing it to produce heat.
2. How does induction heating work?
Induction heating works by using the principle of electromagnetic induction. When an alternating current is passed through an induction coil, it generates a changing magnetic field. This magnetic field then induces an electrical current in the material placed in the coil, causing it to heat up.
3. What are the advantages of induction heating?
Induction heating has several advantages, including high energy efficiency, fast heating speeds, and precise temperature control. It also allows for localized heating, making it ideal for heating specific areas of a material. Induction heating is also a clean and environmentally friendly method of heating, as it does not produce any harmful emissions.
4. What materials can be heated using induction heating?
Induction heating can be used to heat a wide range of electrically conductive materials, including metals such as iron, steel, copper, and aluminum. It can also be used for non-metallic materials like graphite and some plastics, as long as they have a conductive coating.
5. What are the common applications of induction heating?
Induction heating is commonly used in various industries, including automotive, aerospace, and manufacturing. It is often used for heating and melting metals in foundries and for heat treatment processes such as annealing, hardening, and tempering. It is also used for brazing, soldering, and bonding in the electronics industry.
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