Induction brass annealer redux
- Thread starter Gina1
- Start date
G'Day Gina
Up and running. Just a few bugs to iron out. I need a bigger power supply as the even running a 8 turn 1 1/8" id coil at rest its still drawing around 10A. So to get the heat in the neck I have to back the case out quit a bit as I'm only running a 600w supply. So I'm getting a 1000w supply and I have to make up a new coil as I have changed it a few times experimenting with current draw and annealing time.
Also to anneal the shoulder junction the neck gets cooked when I used the original coil.
Update re-did the coil to extact dimensions and dropped the voltage to 42V and got a the amps down to 8.8A. Still going to reduce the turns and reduce the dimensions, maybe even have it tappered down. The standbye current will go up but hopefully with a bigger power supply I'll get more grunt and a bit of current up my sleave.
The reason for a smaller coil or tapper coil is I'll be annealing everything from 303 Brit to 20 PPC.
Up and running. Just a few bugs to iron out. I need a bigger power supply as the even running a 8 turn 1 1/8" id coil at rest its still drawing around 10A. So to get the heat in the neck I have to back the case out quit a bit as I'm only running a 600w supply. So I'm getting a 1000w supply and I have to make up a new coil as I have changed it a few times experimenting with current draw and annealing time.
Also to anneal the shoulder junction the neck gets cooked when I used the original coil.
Update re-did the coil to extact dimensions and dropped the voltage to 42V and got a the amps down to 8.8A. Still going to reduce the turns and reduce the dimensions, maybe even have it tappered down. The standbye current will go up but hopefully with a bigger power supply I'll get more grunt and a bit of current up my sleave.
The reason for a smaller coil or tapper coil is I'll be annealing everything from 303 Brit to 20 PPC.
Last edited:
It took "Hollywood"a bunch of tries, and different size winding to come up with the present coil dimensions. He was mainly going after .308 brass. which works very well for 30-06, 6XC, or 6mm dasher. One of the builders on this thread is thinking about making the coil fixture (fittings and such) interchangeable, for different coil sizes, for cases outside that range.
As I've said before, this is every ones build. There have been some really great innovations on the original GinaErick. Yours could be the next one.
Give your design on the coil a try, and let us know how it works out.
Good luck... Gina
Hi everybody,
First post here and not generally a forum user, so apologies if I have not introduced myself previously, or have broken some unwritten forum etiquette rules.
My internet searches have led me this forum which is fantastic. I had started on my own induction annealer project before I had came upon this thread. As such my project is different, but has a lot of similarities.
I am using a different 1000w heater with a similar coil to here, but the heater has a smaller capacitor bank. It would seem to be 4 0.33uf capacitors (600/1200vdc) arranged in a combined series and parallel config. Problem is that they are getting much hotter than I would like. (seems to be melting the resin potting). This is with a 30-50% duty cycle. Mosfets are running at a satisfactory temp. I'm using 42 volts input and 11.5 amp draw. Approx 6 seconds to over cook a .308
I have the idea of increasing the capacitor bank to be three 0.33uf caps in series, three times, with those three sets then paralleled together. From my limited understanding of the way caps work I think / hope that will help. There are a few people on this thread who obviously know more than I do about this topic.
Hopefully I would like to get to 75% duty cycle and have a respectable cap temp.
Thanks in advance
First post here and not generally a forum user, so apologies if I have not introduced myself previously, or have broken some unwritten forum etiquette rules.
My internet searches have led me this forum which is fantastic. I had started on my own induction annealer project before I had came upon this thread. As such my project is different, but has a lot of similarities.
I am using a different 1000w heater with a similar coil to here, but the heater has a smaller capacitor bank. It would seem to be 4 0.33uf capacitors (600/1200vdc) arranged in a combined series and parallel config. Problem is that they are getting much hotter than I would like. (seems to be melting the resin potting). This is with a 30-50% duty cycle. Mosfets are running at a satisfactory temp. I'm using 42 volts input and 11.5 amp draw. Approx 6 seconds to over cook a .308
I have the idea of increasing the capacitor bank to be three 0.33uf caps in series, three times, with those three sets then paralleled together. From my limited understanding of the way caps work I think / hope that will help. There are a few people on this thread who obviously know more than I do about this topic.
Hopefully I would like to get to 75% duty cycle and have a respectable cap temp.
Thanks in advance
HI Yogi
Glad your on board...Welcome
One site member "GrocMax" somewhere in this thread mentions a heat sink that can be placed on the bottom of the inductor PCB. He said something about a lot of the heat in the capacitors being generated were they are connected into the PCB.
If you check back on his posts, he lists where to purchase this type of heat sink.
Hope this helps... Gina
In this 'tank circuit' application the capacitors create a lot of heat.
The thermal transfer of heat from the capacitors has two paths- convection to air, or heat conduction thru the wire leads into the PCB, mostly into the relatively large copper ground plane of the PCB. In most of the prebuilt induction boards the capacitors have plastic covers, which reduces convective air cooling.
Using glue on or stick on heat sinks on the bottom of the induction board PCB helps tremendously. There are a large variety of these heat sinks available in many sizes.
Also the capacitor total value plus the coil inductance sets the resonant frequency. How deep in the workpiece the heat gets is a function of frequency and workpiece material.
Low frequencies are used for iron and steel for deep heating, higher frequencies are used for tubing.
For brass tubing the ideal frequency seems to be in the 90K-120K Hz range. With the 1 1/8" OD 8 turn 1/8" tubing coil on the 1000w induction board listed on page one I measured ~110 KHz.
For anyone contemplating building one, highly recommend spending the time and reading thru all 28 pages of this thread, there is a lot of good info and experience buried in this thread.
The thermal transfer of heat from the capacitors has two paths- convection to air, or heat conduction thru the wire leads into the PCB, mostly into the relatively large copper ground plane of the PCB. In most of the prebuilt induction boards the capacitors have plastic covers, which reduces convective air cooling.
Using glue on or stick on heat sinks on the bottom of the induction board PCB helps tremendously. There are a large variety of these heat sinks available in many sizes.
Also the capacitor total value plus the coil inductance sets the resonant frequency. How deep in the workpiece the heat gets is a function of frequency and workpiece material.
Low frequencies are used for iron and steel for deep heating, higher frequencies are used for tubing.
For brass tubing the ideal frequency seems to be in the 90K-120K Hz range. With the 1 1/8" OD 8 turn 1/8" tubing coil on the 1000w induction board listed on page one I measured ~110 KHz.
For anyone contemplating building one, highly recommend spending the time and reading thru all 28 pages of this thread, there is a lot of good info and experience buried in this thread.
Last edited:
potato, potatoe.............
Sorry
never paid that much attention to coil size (just winding number) with the current limiting in place. In fact made several left hand thread coil winding tools for 1/8" OD tubing out of plastic in several different diameters on the lathe, produces a very tight, evenly spaced straight coil even from 1/2-3/4 hard pure 101 copper tubing, if anyone wants to borrow a winding tool PM me. You can make up several coils and send it on to the next person. Takes about 3-4 ft of tubing per coil.
Have a really tight radius bending tool (RC fuel line) for 1/8" too.
If you want to make really tight radius bends, fill the tubing with cerrosafe or similar low melt alloy first, bend, then melt it out. Kinking this small ID tubing can really restrict coolant flow.
Sorry
never paid that much attention to coil size (just winding number) with the current limiting in place. In fact made several left hand thread coil winding tools for 1/8" OD tubing out of plastic in several different diameters on the lathe, produces a very tight, evenly spaced straight coil even from 1/2-3/4 hard pure 101 copper tubing, if anyone wants to borrow a winding tool PM me. You can make up several coils and send it on to the next person. Takes about 3-4 ft of tubing per coil. Have a really tight radius bending tool (RC fuel line) for 1/8" too.
If you want to make really tight radius bends, fill the tubing with cerrosafe or similar low melt alloy first, bend, then melt it out. Kinking this small ID tubing can really restrict coolant flow.
GrocMax,
do have tested with cerrosafe?
Is there no risk that it will remain inside the tube?
My first coil 4mm OD was kinking when I tried to bend the connection to the PCB.
In the meantime I've also tried the proposed 3mm OD (1/8") tube filled with fine sand.
It was a nightmare to get the sand out of the coil... it seems to be ok but it is not optimal.
- Mike
do have tested with cerrosafe?
Is there no risk that it will remain inside the tube?
My first coil 4mm OD was kinking when I tried to bend the connection to the PCB.
In the meantime I've also tried the proposed 3mm OD (1/8") tube filled with fine sand.
It was a nightmare to get the sand out of the coil... it seems to be ok but it is not optimal.
- Mike
If you don't have or want to buy a hunk of cerrobend or cerrosafe-
Mini tube benders can be found at a hobby store that deals in models and radio controlled planes/cars, like this one-
https://dubro.com/products/tubing-bender
I had good success using the above bender on 1/2 hard 101 alloy 1/8" diameter .032" wall copper tube. Have not tried .014" wall tube, that may need filling or annealing or both to keep wrinkles and kinks from occurring. I'm not a fan of coil spring benders.
Mini tube benders can be found at a hobby store that deals in models and radio controlled planes/cars, like this one-
https://dubro.com/products/tubing-bender
I had good success using the above bender on 1/2 hard 101 alloy 1/8" diameter .032" wall copper tube. Have not tried .014" wall tube, that may need filling or annealing or both to keep wrinkles and kinks from occurring. I'm not a fan of coil spring benders.
powderbrake
Gold $$ Contributor
Filling with water and freezing, or filling with fine sand also work
I had read through the whole thread quite thoroughly and had seen the references to the heat sinks for the caps, which I am sure would be adequate to drop the temp for what I am currently doing. However, what I am looking to do is increase the duty cycle to approx 75%
(heating for 6 ish seconds, idle for 2 seconds). I had used my rudimentary understanding of circuits to calculate that my proposed cap configuration should still have the same capacitance as before (to maintain the current induction frequency), but dropping the voltage across each cap should hopefully give me the temp reduction I am looking for. I could well be wrong, and my calculations fubar. I'm sort of looking for validation or ridicule I guess.
Yogi-
I'm inferring you made your own tank circuit?
I'm using the cheapie chinesium zvs 1000w induction board listed on the first page, and have stress tested it and the cooling sytem (100% DC) for 5+ minutes straight at 15.7 amps (100% of the current limit for the PS). Four stick on heat sinks on the bottom of the board near the tank cap leads and a good sized fan, fan speed control for the board is based on PCB temp. During this test about 2 minutes in fan will hit full speed for awhile then settle back down but the caps don't get hot, just warm.
Doing cases as fast as can be fed it doesn't even turn the fan past 75% speed. Maybe I got thermally lucky due to the current limiting feature of the PS that drops voltage to maintain the set max current. Once the circuit has started (from 48v) it will keep working fine to very low voltages, this PS will trip a low voltage fault and shut down right around 5v but anything above that its fine.
I'm inferring you made your own tank circuit?
I'm using the cheapie chinesium zvs 1000w induction board listed on the first page, and have stress tested it and the cooling sytem (100% DC) for 5+ minutes straight at 15.7 amps (100% of the current limit for the PS). Four stick on heat sinks on the bottom of the board near the tank cap leads and a good sized fan, fan speed control for the board is based on PCB temp. During this test about 2 minutes in fan will hit full speed for awhile then settle back down but the caps don't get hot, just warm.
Doing cases as fast as can be fed it doesn't even turn the fan past 75% speed. Maybe I got thermally lucky due to the current limiting feature of the PS that drops voltage to maintain the set max current. Once the circuit has started (from 48v) it will keep working fine to very low voltages, this PS will trip a low voltage fault and shut down right around 5v but anything above that its fine.
Ok my update. Changed the inducting coil its a double up design. The ID is 1" with four turns then 3 turns around the outside, gradually going back up the inside coil.
The reason is just a experment to see what would happen. No load current is around 9.2 amps at 46V. When annealing Norma 22-250 brass current went upto around 13.5 - 14 amps. Thus also annealing time dropped a lot. Also my annealing time for S&B 303-25 dropped by nearly 2.5 seconds.
The down side is the 600w power supply is not really designed to handle this, it didn't trip but it would be a matter of time.
I have a 1000w supply coming. Also for a smaller hieght coil is so I can annealing 22 PPC brass, as the original 8 turn single coil was to long. Its also took to long to anneal as well.
Now to hook up water cooling and fibre wrap the coil, with a new power supply we are up and running.
Cheers
Varmtr
The reason is just a experment to see what would happen. No load current is around 9.2 amps at 46V. When annealing Norma 22-250 brass current went upto around 13.5 - 14 amps. Thus also annealing time dropped a lot. Also my annealing time for S&B 303-25 dropped by nearly 2.5 seconds.
The down side is the 600w power supply is not really designed to handle this, it didn't trip but it would be a matter of time.
I have a 1000w supply coming. Also for a smaller hieght coil is so I can annealing 22 PPC brass, as the original 8 turn single coil was to long. Its also took to long to anneal as well.
Now to hook up water cooling and fibre wrap the coil, with a new power supply we are up and running.
Cheers
Varmtr
I'm new to this forum and I'm just getting started into reading this thread so i might have missed an early discussion about the power supply ON/OFF input. Any reason why the remote ON/OFF function on the power supply was not used (pins 13 & 14) versus using a heavy duty relay/contactor to switch on and off the 48VDC? This is an optical isolated input that controls the PWM of the power supply. Does it take to long to power up under an immediate load?
Never went that route. Cost of the relay was low enough, so did not use remote on/off. BUT it may not work. The inductor PCB requires full power on instantly in order to break into oscillation. The relay does that.
If your going to build one. Check out that option, and let us know how it works out.
Gina
If your going to build one. Check out that option, and let us know how it works out.
Gina
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.