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Project: My voice coil winder
- Thread starter R!f@@
- Start date
I just caught up with this thread and am sorry for the late comment. If getting your glue to stick to kapton is still a problem, you might consider modifying/etching the kapton surface. There are a variety of things you might try. Some plastics will etch with high-frequency electric discharge or even a soft flame. The flame trick is not to melt it, but to attack (e.g., oxidize or functionalize) the surface molecules with free radicals in the flame. You will not even see a change, but glues, particularly the cyanoacrylics and epoxies, will stick better. However, kapton is an imide, and an even easier etch maybe something as simple as a quick treatment with lye (NaOH) or KOH.
http://www3.interscience.wiley.com/journal/104539666/abstract?CRETRY=1&SRETRY=0
http://www.freepatentsonline.com/4857143.html
Are you still having a problem getting your coils removed from the winding bobbin?
John
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Both... indeed.Job security.
Its a very good skill to be able to build the tools you need. And at the speed you are doing it in, impressive.
You must have a good reputation around (fe)Male'
No John.... I can remove the coil quite easily now.
Thanks anyway
U know john those fancy chemicals is greek to me. As I did not do too well in my chemistry subject.
Any name that I could be familiar, or may be anything I can buy from dispensaries will be A OK.
What kind of chemicals do I need to make the kapton stick to epoxies.
The link you gave shows cookie errors.
Thanks anyway
U know john those fancy chemicals is greek to me. As I did not do too well in my chemistry subject.
Any name that I could be familiar, or may be anything I can buy from dispensaries will be A OK.
What kind of chemicals do I need to make the kapton stick to epoxies.
The link you gave shows cookie errors.
That Wiley link is temperamental. I don't know how to fix it. My attempt to get a good link is one reason for the edit. Only an abstract is presented when the link works, so it probably won't be much help. Basically, the authors showed that kapton surfaces can be etched with strong alkali solutions.
Common household lye is sodium hydroxide (NaOH). Potassium hydroxide (KOH) is used in making soaps. It is sometimes called potash and can be extracted from wood ashes. Both are common, ancient chemicals and are class representatives for strong alkali. Either might work, but if you have a choice, try the KOH. Potassium salts are often a little more soluble in organic solvents. Now, I know you are not dissolving it in anything organic, but you do need for the strong alkaline solution to "wet" the surface of the kapton. If you can get methyl alcohol ("wood alcohol"), add some to the lye/KOH solution and it will help the wetting. I have never tried to modify kapton. I have modified Teflon to make a bondable surface (before you could buy solutions to do that), as well as polypropylene, and nylon. The chemistry of those polymers is different, and different reagents must be used, but the principle is the same.
The flame treatment may work for you too. That way, there are no chemicals that you have to name. Just use a non-sooty propane or butane flame. Move it over the surface fairly fast so as not to melt the plastic. Test on a small piece to see if it helps first.
John
I gave the flame treatment a try, the first one is done. I'll let it dry overnight. if OK I can begin assembling the first woofer
I did a couple of ones to test the glue. A resin I bought off Ebay to seal the Police flasher circuit that I did for cycles.
That glue is a two chemical one that drys to a solid. Another with fiber, Araldite epoxy and dunlop.
Every glue holds the winding and is like metal ring. But the only thing that held & prevent the kapton from coming off a higher degree was the first one. Luckily I have plenty of it
S I used it with the flame treatment. It's left to dry out. So tomorrow I'll know.
The winding ended up at 7.7Ω. Quite good for a guessed length of the coil.
The originals were way below that.
I did a couple of ones to test the glue. A resin I bought off Ebay to seal the Police flasher circuit that I did for cycles.
That glue is a two chemical one that drys to a solid. Another with fiber, Araldite epoxy and dunlop.
Every glue holds the winding and is like metal ring. But the only thing that held & prevent the kapton from coming off a higher degree was the first one. Luckily I have plenty of it
S I used it with the flame treatment. It's left to dry out. So tomorrow I'll know.
The winding ended up at 7.7Ω. Quite good for a guessed length of the coil.
The originals were way below that.
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That depends on the type of music actually.
Programmed and music, heavy metal, all these put's different amount of power to the woofers.
The most important thing is avoid clipping, as clipping will provide a higher RMS current, which is more like a high DCV to the woofer. Prolonged clipping will eventually burn out the coils.
Even if the amp has twice the rating of the speaker, you won't damage any of them if you a careful with the volume setting. Avoiding amp clipping and distortion is the only way to prevent speaker damage.
The coil can withstand temp of the coil insulation and kapton. I'll say both have the same rating approx, which is no more than 100 degrees C
Programmed and music, heavy metal, all these put's different amount of power to the woofers.
The most important thing is avoid clipping, as clipping will provide a higher RMS current, which is more like a high DCV to the woofer. Prolonged clipping will eventually burn out the coils.
Even if the amp has twice the rating of the speaker, you won't damage any of them if you a careful with the volume setting. Avoiding amp clipping and distortion is the only way to prevent speaker damage.
The coil can withstand temp of the coil insulation and kapton. I'll say both have the same rating approx, which is no more than 100 degrees C
Yeah. That was what happened to the glue I used before.
Since I moved I have left almost everything. Thinking that I could get 'em fresh.
But before I did not use kapton, the woofer has some kind of aluminum and it adheres well. I started using kapton once I got a source to get 'em and did not think of the sticking problem.
The epoxy I have is heat resistant. So I don't think it would come off
Since I moved I have left almost everything. Thinking that I could get 'em fresh.
But before I did not use kapton, the woofer has some kind of aluminum and it adheres well. I started using kapton once I got a source to get 'em and did not think of the sticking problem.
The epoxy I have is heat resistant. So I don't think it would come off
Well, It's been raining since I started this winding thing and no sunshine.
I have to find another way to dry the glue. I was in the kitchen when I say the microwave, thought putting the coils in it but it might boil it, next thing I found was a better, mom's rice cooker. So I put all the coils in it and heated it for around 10 minutes when mom came in kicked me out of the kitchen.
Well . the glue are dried and the kapton seems to hold.
Next is to check if the epoxy will hold at extreme operating temp. Like john suggested.
Besides I would not want to go thru all the trouble again
So next idea was to heat up the coil to test it for temp performance.
Applied voltage to the coil with the temp meter connected and below are the results.
The coil was heated to the temperature shown and something started to boil.
The kapton came off, nothing else seems to be damaged.
So I tested if the epoxy I used at the coils held and to my surprises it did, coil is still intact.
Here is the coil heated at a temp of atleast above 200°C.
So the copper insulation and epoxy and the kapton can withstand the temperature at woofer operation.
But the bad news is nothing seems to hold the winding to the kapton.
Well...back to square one
How do you think varnish that is used to seal transformers will do?
I have to find another way to dry the glue. I was in the kitchen when I say the microwave, thought putting the coils in it but it might boil it, next thing I found was a better, mom's rice cooker. So I put all the coils in it and heated it for around 10 minutes when mom came in kicked me out of the kitchen
.Well . the glue are dried and the kapton seems to hold.
Next is to check if the epoxy will hold at extreme operating temp. Like john suggested.
Besides I would not want to go thru all the trouble again
So next idea was to heat up the coil to test it for temp performance.
Applied voltage to the coil with the temp meter connected and below are the results.
The coil was heated to the temperature shown and something started to boil.
The kapton came off, nothing else seems to be damaged.
So I tested if the epoxy I used at the coils held and to my surprises it did, coil is still intact.
Here is the coil heated at a temp of atleast above 200°C.
So the copper insulation and epoxy and the kapton can withstand the temperature at woofer operation.
But the bad news is nothing seems to hold the winding to the kapton.
Well...back to square one
How do you think varnish that is used to seal transformers will do?
Don't use Kapton for insulation. You'll be sorry.
The Navy banned it's use in any Navy/Marine aircraft back in 1985, after a series of mysterious crashes that were finally determined to be caused by Kapton failure, then flashovers, and in-flight fires.
Kapton has a very high voltage insulation rating for it's thickness, is very strong and lightweight - all very attractive for use in aviation. However, just a slight scuff in the surface weakens the material quite a bit; and once Kapton gets nicked, it tends to return to it's "as made" state (it has a "memory") which usually means unravelling from whatever it's been wrapped around.
Also, if there happens to be a flash-over, the Kapton will carbon track, which makes the next flash-over much more likely to occur.
Lacquer is a much better material. You might also look for spray-on conformal coating.
The Navy banned it's use in any Navy/Marine aircraft back in 1985, after a series of mysterious crashes that were finally determined to be caused by Kapton failure, then flashovers, and in-flight fires.
Kapton has a very high voltage insulation rating for it's thickness, is very strong and lightweight - all very attractive for use in aviation. However, just a slight scuff in the surface weakens the material quite a bit; and once Kapton gets nicked, it tends to return to it's "as made" state (it has a "memory") which usually means unravelling from whatever it's been wrapped around.
Also, if there happens to be a flash-over, the Kapton will carbon track, which makes the next flash-over much more likely to occur.
Lacquer is a much better material. You might also look for spray-on conformal coating.
The failures of kapton in avionics are legend, as SgtWookie mentions.
However, for low voltages and high temperature, it is still good. Lacquer doesn't have as high a temp rating as kapton. Nylon and Teflon are other options. Teflon can be "glued," but I suspect that is not where you want to go. What other types of plastics in very thin sheets do you have available? Do you even need a form? That is, is the kapton even needed, once the coil is formed? Will simple "fish" paper work?
John
However, for low voltages and high temperature, it is still good. Lacquer doesn't have as high a temp rating as kapton. Nylon and Teflon are other options. Teflon can be "glued," but I suspect that is not where you want to go. What other types of plastics in very thin sheets do you have available? Do you even need a form? That is, is the kapton even needed, once the coil is formed? Will simple "fish" paper work?
John
The thing is kapton is mostly used in general purpose ones. When I say general purpose I mean power rating not more than say 400W Cont.
High powered and dual voice coil plus adjacent aluminum coil (which are flat) wound ones which have typical power rating that can go beyond 800W has a former made of aluminum or something like that, ( for better heat transfer. It's silver colored and pretty thin. I used to have copper wire which can be heat bonded to any material so sticking issue was never a problem and any thing I repaired never came back.
After winding the coil is heated between 100 to 200°C, the coil is coated with something. The original voice coils I bought of ebay for this job is also the same, it past all the test I did tonight with flying colors.
As I said I lost the reel during the move. As in these woofers uses kapton bobbin, I bought kapton reel and the coil wasn't available to my location now. The original winding was toast and the kapton also were melted. I have to go for a complete remake.
As Sgt suggested the kapton may be useless to high voltage but these woofers never go beyond 80V RMS. As they a paralleled the total Voltage will go down and being rated at 300W Cont. V is equal to or most likely less than 48V. Audio being dynamic this is hardly the nominal voltage woofer will see. So I guess kapton will do. Anything else is impossible to get here.
If you guys can forward me to a seller who has these type of material and the glue Sgt suggested I would appreciate it.
The previous try failed and as I checked the kapton gave away unraveling the coil and jamming the voice coil, a second attempt is impossible and will destroy the cone and spiders if I cut it and gluing won't be enuf to hold them during the thumping. I have to get new cones and spiders. Nothing is available here, even the coil, ( I'm using mains rated wire now). I have to get them abroad and it does take a lot of time, and these have been a big fuss to keep them with me as these darn things are not small and have to keep them separate due to the strong magnets.
The Kapton are not used for insulation purpose Sgt, they are to hold the voice coil in the air gap centered to the poles. The kapton provides a higher temp usage as the coil will heat to a level which can boil water. Paper also can be used but not for power rating above 10W or so, as heat will destroy the paper letting loose the coil. The kapton and the glue is responsible to hold the coil in place as the kapton is the one bonded to the spider and the cone. So a bobbin is necessary what ever the material may be.
I have done a pretty intense search to night. I am posting the link so you guys can get an idea of the material mostly used for voice coil building.
The epoxy I used did not soften as the winding it still rock solid, only concern is the kapton lets go of the coil, this is a big no no, since inside the air gap if this happen the two wire end of the coil is the only thing holding the coil from slipping or moving. And this won't last even for song duration as the coil will break due to heavy movement. There goes my 5 star rating down the drain. I was lucky the customer brought them back to me. I am fixing em free of charge but it is taking so long that I too am getting frustrated. Still I won't give up.
John,
I see what I kind of chemical I get tomorrow, I have to write down those fancy words and go around to dispensaries..
Thanks guys for the comment. I truly am thankful that I am a part of this forum, it does help a lot of my problems.
High powered and dual voice coil plus adjacent aluminum coil (which are flat) wound ones which have typical power rating that can go beyond 800W has a former made of aluminum or something like that, ( for better heat transfer. It's silver colored and pretty thin. I used to have copper wire which can be heat bonded to any material so sticking issue was never a problem and any thing I repaired never came back.
After winding the coil is heated between 100 to 200°C, the coil is coated with something. The original voice coils I bought of ebay for this job is also the same, it past all the test I did tonight with flying colors.
As I said I lost the reel during the move. As in these woofers uses kapton bobbin, I bought kapton reel and the coil wasn't available to my location now. The original winding was toast and the kapton also were melted. I have to go for a complete remake.
As Sgt suggested the kapton may be useless to high voltage but these woofers never go beyond 80V RMS. As they a paralleled the total Voltage will go down and being rated at 300W Cont. V is equal to or most likely less than 48V. Audio being dynamic this is hardly the nominal voltage woofer will see. So I guess kapton will do. Anything else is impossible to get here.
If you guys can forward me to a seller who has these type of material and the glue Sgt suggested I would appreciate it.
The previous try failed and as I checked the kapton gave away unraveling the coil and jamming the voice coil, a second attempt is impossible and will destroy the cone and spiders if I cut it and gluing won't be enuf to hold them during the thumping. I have to get new cones and spiders. Nothing is available here, even the coil, ( I'm using mains rated wire now). I have to get them abroad and it does take a lot of time, and these have been a big fuss to keep them with me as these darn things are not small and have to keep them separate due to the strong magnets.
The Kapton are not used for insulation purpose Sgt, they are to hold the voice coil in the air gap centered to the poles. The kapton provides a higher temp usage as the coil will heat to a level which can boil water. Paper also can be used but not for power rating above 10W or so, as heat will destroy the paper letting loose the coil. The kapton and the glue is responsible to hold the coil in place as the kapton is the one bonded to the spider and the cone. So a bobbin is necessary what ever the material may be.
I have done a pretty intense search to night. I am posting the link so you guys can get an idea of the material mostly used for voice coil building.
Above second link will show you the materials used as they are mostly polyester material, I donno what kapton is made of, I assume they may be the same thing.
The epoxy I used did not soften as the winding it still rock solid, only concern is the kapton lets go of the coil, this is a big no no, since inside the air gap if this happen the two wire end of the coil is the only thing holding the coil from slipping or moving. And this won't last even for song duration as the coil will break due to heavy movement. There goes my 5 star rating down the drain. I was lucky the customer brought them back to me. I am fixing em free of charge but it is taking so long that I too am getting frustrated. Still I won't give up.
John,
I see what I kind of chemical I get tomorrow, I have to write down those fancy words and go around to dispensaries.
.Thanks guys for the comment. I truly am thankful that I am a part of this forum, it does help a lot of my problems.
If I had my way, woofers rated for more than 10W would be outlawed.
Back to the subject...
Since your epoxy stands up to the temperatures and your kapton won't adhere to the epoxy, have you considered eliminating the kapton and using fiberglass for the bobbin? Get light weight glass cloth. I would use something less than 100 g/m^2. Wet it out with your epoxy. You may need to thin the epoxy a little with alcohol or acetone. Blot it almost dry. Then, wrap two layers on the form. Next, wrap the wire and let it all set up. To make the lightest coils, I would wrap the entire assembly with a release layer, then blotter layer, and a final compression layer. A lot of excess epoxy will be removed without greatly affecting strength.
Getting the epoxy sleeve off the form may be a little difficult. I use a combination of good release agent, compressed air, and brute force. As an alternative, you could make the epoxy sleeve first. Let it set up. Remove it , trim, replace, then wind the coil onto it. Epoxy is good for that purpose in that it stays "green" for quite a while after hardening and subsequent coats will stick. It does not have wax in it like polyester resins do, so you do not need to clean and abrade the surface to get another coat to stick.
You can make very light fiberglass sleeves by methods like I describe here, but there are details of course to learn. If that is a direction you want to go, let us know.
John
Back to the subject...
Since your epoxy stands up to the temperatures and your kapton won't adhere to the epoxy, have you considered eliminating the kapton and using fiberglass for the bobbin? Get light weight glass cloth. I would use something less than 100 g/m^2. Wet it out with your epoxy. You may need to thin the epoxy a little with alcohol or acetone. Blot it almost dry. Then, wrap two layers on the form. Next, wrap the wire and let it all set up. To make the lightest coils, I would wrap the entire assembly with a release layer, then blotter layer, and a final compression layer. A lot of excess epoxy will be removed without greatly affecting strength.
Getting the epoxy sleeve off the form may be a little difficult. I use a combination of good release agent, compressed air, and brute force. As an alternative, you could make the epoxy sleeve first. Let it set up. Remove it , trim, replace, then wind the coil onto it. Epoxy is good for that purpose in that it stays "green" for quite a while after hardening and subsequent coats will stick. It does not have wax in it like polyester resins do, so you do not need to clean and abrade the surface to get another coat to stick.
You can make very light fiberglass sleeves by methods like I describe here, but there are details of course to learn. If that is a direction you want to go, let us know.
John
Hehe .. why? You don't like loud music. My home theater Woofers are at 800W Cont each with dual voice coil and the sub is at 1600W. I can rock the whole block if I want to. That's why every body wants it and yet nobody can make a second one .
Yes About the epoxy.. let me find where I got it.
And it does hold the coil. I had hard time unraveling the bad ones.
I would try anything about now.
But keep in mind that I sometimes don't understand most of the terms used. Well not most of them, just some fancy words, that I don't use during normal communication. Having another mother tongue complicates things. A simpler explanation will be appreciated.
I am good to go what you are going to suggest, I have plenty of epoxy, enuf to make 100 of coils..
So shoot.
.Yes About the epoxy.. let me find where I got it.
And it does hold the coil. I had hard time unraveling the bad ones.
I would try anything about now.
But keep in mind that I sometimes don't understand most of the terms used. Well not most of them, just some fancy words, that I don't use during normal communication. Having another mother tongue complicates things. A simpler explanation will be appreciated.
I am good to go what you are going to suggest, I have plenty of epoxy, enuf to make 100 of coils.
.So shoot.
