Induction coil design and fixtures interaction.

[fastline12]

We are trying to automate the heating of some small copper rods. We have two issues or concerns.

1. It has become complicated to create a simple way to either lift the part or lower the coil around the part for heating so the question has come up of what type of coils can we consider for uniform concentric heating of the end of these parts without too much interaction with the Aluminum automated structures. Something that only passes by the part with the part spinning comes to mind but not sure if that will severely increase heating time.

2. We are not sure, as a rule of thumb, how close a coil can be to other metallic structures with minimal interaction. Assuming a typical 2-3 turn helical coil with an ID of 1", Some of these parts are only 1.25" long and only .500" on the end need heated. The issue is with the conveyor and such, the coil would end up being only .25" or so from the ALuminum guide conveyor.

 

[VEBill]

The fields in and around a coil (solenoid) can, in theory, be modeled and predicted to a high degree of accuracy. Inside the coil is typically significantly higher than outside (think about it conceptually on a per unit volume basis).

I suspect that you would have problems with something that is only .25" away and - importantly - a fixed target.

One option would be to modify the conveyor guide to something non-conductive.

Another idea that you might not have thought of would be to only apply power to the coil when the copper rods are in position. This would reduce the duty cycle of the exposure of the conveyor guide.

Standby for others' input.

 

[fastline12]

Thanks the reply and yes, the design did call for only energizing the work coil once the part was in position. However, since the part is only about .75" long and we need to cook up the top .25" of it, we can just barely get the part into the coil but safe to say the work coil will have to be close to something that is holding or supporting the part.

I am just trying to estimate the power that might stray into the holding fixtures during heating. A little heat will not hurt a thing but I am more concerned with the EMF playing havoc on some other electronics and small motors in the area.

I would like to better estimate the flux that could stray into the fixture but wondering if this is mostly a process of trial and error?

 

[VEBill]

If the induction heating system is itself a commercial product (as opposed to something that you've home-brewed), then the company probably has application engineers. If so, then you should establish contact.

There are quite a few examples on YouTube; perhaps those videos of induction heating would show something. Most examples show the power being quite tightly confined to inside the coil; but you're correct to be cautious.

You would definitely want to move sensitive electronics out of the immediate area, and apply E3 design rules as required.