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-   -   Advice On Batch In A Wire Melter (http://talk.craftweb.com/showthread.php?t=2093)

David Paterson 12-02-2003 03:57 PM

Advice On Batch In A Wire Melter
 
I recently built a small electric pot furnace using Kanthal A1. It is about 3 cubic feet on the inside and the pot holds about 100 lbs of glass. So far, I have charged preheated cullet only, and it gives very nice glass.

Up to this point I have used (and still have) an invested pot furnace.

The unit works perfectly, so far. It draws about 4.5 to 5 KW at 2000 F and around 6 KW at 2150.

The elements are around the sides in grooves in insulating firebrick. They are not protected in any way, so I have to be carefull charging.

I would like to melt Spruce Pine, or perhaps another batch, and would like to hear recomendations from anybody melting batch in a similer unit.

Thanks

Ben Rosenfield 12-03-2003 07:09 AM

Hi David,

You're several steps ahead of me; however, your setup sounds a lot like what I'd like to do. I hope to melt the same amount in an electric, using A1 elements. Perhaps I could e-mail you some time and get some insight into your design?

I wish I could give you feedback from personal experience, but all I can do at this point is link you to threads that may help.

http://talk.craftweb.com/showthread....&threadid=2065

You might also want to check out http://www.kurtwalrath.com/largeglassstudio/furnace.htm

David Paterson 12-03-2003 10:40 AM

I am very busy right now with Christmas orders. However once the rush is over, I intend to post pictures and a detailed description of my unit.

Pete VanderLaan 12-03-2003 10:44 AM

For both of you, please keep this discussion going so that other people can read what you post. There well may be observations from others that will help you both as well. It's the purpose of the board. :dog:

Ben Rosenfield 12-03-2003 11:26 AM

No sweat. It'd be my pleasure.

And thanks in advance, David.

Richard Huntrods 12-03-2003 11:27 AM

David,

I've posted about this elsewhere on the board, but this is a good topic.

I recently finished building a small studio (10' by 14') with a 40lb electric wire furnace. The furnace was built according to the plans from Mark Lauckner (Mayne Island Glass). This furnace design is very small (1 cu ft heating chamber, 25" cube outside dimensions).

I too melted cullet, but had a disaster on my first melt, so the furnace is down for repair (details on http://www.huntrods.com under the glassblowing link).

I'm going to melt Spruce Pine batch once the furnace is repaired. There's a lot of people here in Calgary melting Spruce Pine (about 1/2. The rest are using "Seattle Batch"), so there's plenty of expertise locally - although they use gas furnaces.

So - I'm using a very similar setup (but smaller), so once I'm up and running we should compare notes.

Cheers,

-Richard

Steve Stadelman 12-03-2003 12:50 PM

The whole secret to these melters is low wattage on the elements and solid state controls. Use S.C.R.s or S.S.R.s to power them and keep cullet or batch especially off of the elements.

My 80lb wire job has over 14 months on one set of elements. I have used only cullet and not gone over 2150f because I hate rebuilds. I am using a current limiting S.C.R. and preheat my cullet so it doesn't pop much.

Richard Huntrods 12-03-2003 01:03 PM

Steve,

Just out of curiousity, how do you preheat your cullet? To what temperature?

-Richard

Randy Kaltenbach 12-03-2003 02:44 PM

Element duty cycle?
 
Quote:

Originally posted by steve stadelman
The whole secret to these melters is low wattage on the elements and solid state controls. Use S.C.R.s or S.S.R.s to power them and keep cullet or batch especially off of the elements.

I have a question about that. What is a reasonable duty cycle for those elements? i.e. is it better to have them continuously cycle on and off quickly (like every second or two) or is it better to let them run for a minute or so? :confused:

Steve Stadelman 12-03-2003 03:04 PM

I have an answer, the best element life comes with very short (less than a second) switching.

An S.S.R. that swithes every second will not cycle the element temperatures up and down like a mercury relay, so the elements run at a more constant temp and do not get so "shocked".

A burst fired variable time base S.C.R. is your first choice, S.S.R. second, Phase angle S.C.R. third, mechanical or merc relay fourth. The first three give good performance.

Steve Stadelman 12-03-2003 03:19 PM

Quote:

Originally posted by Richard Huntrods
Steve,

Just out of curiousity, how do you preheat your cullet? To what temperature?

-Richard

I think I got it from David Williams to preheat in some stainless tubes to 950f in a tiny kiln I got at a garage sale. Sometimes when I don't pay attention I preheat to almost 1200.

Ben Rosenfield 12-03-2003 04:19 PM

Quote:

Originally posted by steve stadelman
The whole secret to these melters is low wattage on the elements and solid state controls. Use S.C.R.s or S.S.R.s to power them and keep cullet or batch especially off of the elements.

My 80lb wire job has over 14 months on one set of elements. I have used only cullet and not gone over 2150f because I hate rebuilds. I am using a current limiting S.C.R. and preheat my cullet so it doesn't pop much.

This type of information really inspires me. I know we talked on the phone about me trying to go moly, but damn, if I can get decent life out of wire elements at 2200 F with batch, I'm happy. Not to mention, I would not have the thing running all day, every day. So I think this is a great starting point. I can go moly when my chandeliers are hanging over the canals of Venice ... err ... the muddy creek up the road. Hehe.

Steve Stadelman 12-03-2003 04:43 PM

There are tradeoffs, you can get started cheap with A-1 wire, but you will be wondering when it is going to fail. A moly system costs more to build but it will have far more reliability and consistently make better glass because you can melt hotter. You are just stringing a wire melter along melting batch. It will crap out, right when you don't want it to.

But like I already said, you can get going on a shoestring.

Randy Kaltenbach 12-03-2003 04:43 PM

Quote:

Originally posted by steve stadelman
I have an answer, the best element life comes with very short (less than a second) switching.

An S.S.R. that swithes every second will not cycle the element temperatures up and down like a mercury relay, so the elements run at a more constant temp and do not get so "shocked".

A burst fired variable time base S.C.R. is your first choice, S.S.R. second, Phase angle S.C.R. third, mechanical or merc relay fourth. The first three give good performance.

OK, so short cycles = minimal temp variation of the elements = longer life.

Honestly, this is one reason I love glasswork so much more than many other artforms. I'm both an artsie and a techie at heart (done my time as a professional engineer). Gotta love it! :D

Pete VanderLaan 12-03-2003 05:01 PM

you're absolutely sure it's not because you have latent masochistic tendencies? :dog:

Richard Huntrods 12-03-2003 05:40 PM

Geez - you molly minders just won't quit, will you? I get less flack from the gas melters. :D

Sometimes wire is the ONLY way to go.

1. Wire is boatloads of money cheaper to build. Also way simpler (no huge transformers and all that other stuff)
2. Wire furnaces take up way less space than molly rigs. For very small shops, a wire furnace may be all that will fit.
3. For the "weekend warrior" glassblower, I cannot see any scenario short of winning a lottery where Molly would make more sense than wire.

Besides, <cough><cough> This is a "wire furnace" thread. We don't got no molly religion here! :D

Cheers,

-R

Pete VanderLaan 12-03-2003 06:04 PM

moly furnaces don't take up any extra space and the SCR is not big either. My transformer is outside.

Wire is way cheaper up front, but not in the long run. I can replace an element hot if I have to, try that at home!

Also, I won't have to replace elements often at all. I do tighten things though.

If you are going wire, pay attention to Thumb. He really has this worked out.

I would agree that wire is more approachable than moly but unless you can limit the current, you are in for some long evenings. Use the SCR.

Remember I run both types electric and Gas. I like both and they are very different. :dog:

Jay Holden 12-03-2003 06:24 PM

- you molly minders just won't quit, will you? I get less flack from the gas melters.. We don't got no molly religion here!


Forgive them Steve, God of Molly, For they know not what they do.

Steve Stadelman 12-03-2003 06:30 PM

Quote:

Originally posted by Richard Huntrods
Geez - you molly minders just won't quit, will you? I get less flack from the gas melters. :D

.

Besides, <cough><cough> This is a "wire furnace" thread. We don't got no molly religion here! :D

Cheers,

-R

I'm not trying to give anyone flack bub, I'm just a one trick pony so this is what I yak about.;)

Michael Stevens 12-03-2003 09:06 PM

wire and batch ?
 
I thought we just did this gig. if its wire use cullet hands down.

David Paterson 12-03-2003 10:53 PM

The reason I started this thread was to get feedback from anyone melting batch in a wire furnace.

So far, I have yet to get a serious response and would still like to hear from anyone melting batch.

In regards to the moly debate, there are a few issues I would comment on.

The inside of my furnace is about 19" across and 15" deep, and I have a 16" diameter pot in it. Seems to be a pretty efficient use of space, and the pot is evenly heated on all sides. Could you do this with moly, or would you need a much larger interior space for the same size crucible to get even heating?

Larger spaces cost more to heat. What would the KW draw be on a moly furnace that would evenly heat a 16" diameter crucible to melt about 100 lbs of glass? Mine idles at 2000F at about 4.5 KW.

Since I am using variable transformers, I believe I have the system that is easiest of all on wire elements. I set an exact output voltage, and the furnace stabilizes at a certain temperature.

It seems to me that 8 monthes to a year on a set of elements is pretty good. I wound my own elements out of 13 guage A1 for about $15.00 each on a bench lathe. They take about 15 minutes each. Cant do that with moly, so what do they cost? Nothing lasts forever. Right now my wire furnace is a secondary furnace, so I intend to shut it down at least a few times per year anyway, and will replace the elements at some point as regular maintenance for the grand total of $60.00.

It seems to me that there is a continual search for "The Best" in technology, when in fact the best is sometimes the simplest.

Steve Stadelman 12-04-2003 12:13 AM

The size of pot you are talking about would use 4 12" moly's hanging from the crown down, they probably (but not always) should be above the potline, They cost $150.00 each.

The K.W. draw would be 10 (roughly) and the unit would run off of a 50 amp 240 volt breaker.

Yes the variable transformer approach is the best you can do. Yes since this is a secondary unit you can get away with shutting it down whenever you want and yes there are alot of ways to skin a cat.

You CAN melt batch in a wire melter but it will reduce the life of the elements, since you know how to make your own, and can do so cheaply, you are in a really good spot.

Most folks who start this line of queationing are talking about this being their ONLY melter and want to know how it should be done with no knowledge of watt loading, power supplies, or cooking times or temperatures for cullet or batch.

That is O.K. and since we seldom know where a person is in their knowledge base it is really easy to throw out lots of answears and opinions.

All that said, do anything that you can to keep batch and it's dust off of the elements, check out Kurt Walrath's setup, and where is Parker Stafford anyway?

If you keep the temp as low as possible to both fine out the batch in a reasonable time, and keep the elements alive you will do O.K.

I have heard of folks fining out Spruce as low as 2200f your results may vary, and that will take alot of time, I don't know how much.

I have never said that moly is the only way to go, it is not the cure-all to everything and I was just as fascinated as anyone else to hear Hugh Jenkins talk about recuperation. Again, there are alot of ways to skin a cat, but I firmly believe that for the investment, my way is very, very good in the long run.

Richard Huntrods 12-04-2003 02:00 AM

Quote:

Originally posted by David Paterson
The reason I started this thread was to get feedback from anyone melting batch in a wire furnace.

So far, I have yet to get a serious response and would still like to hear from anyone melting batch.

...


Actually, you got three good responses right off the bat.

-R

Ben Rosenfield 12-04-2003 07:50 AM

Would using quartz-encased elements help guard against damage caused by batch? Or would this introduce other issues -- aside from increased cost?

Dave Bross 12-04-2003 09:13 AM

I'm melting home mixed batch in a wire melter.

The critical thing there is probably the mesh size of the silica. Tom uses 325 mesh in spruce pine and so do I.

See the "virgin batch" thread here about a page back for the particulars.

I'm melting in a 15# furnace that pulls around 10 amps.

Based on Mark Lauckners design it's one 14 gauge 21 ohm element running on 220. A new element from Duralite all wound up and ready to stretch and install is $40. I've been having some crucible failures (see crucible failure threads here)so I don't yet have a handle on how long it will go. I use cheap assay pots for most things and Pete pots for some things that warrant it. The assay pots cost $20 including freight so if an element goes no big loss. If I was to upsize I would still use the assay pots, just more of them. The largest available is around 15 pounds. I don't use a lot of glass, I'm into smaler things, preferably hollow.

More questions? let me know

Pete VanderLaan 12-04-2003 09:15 AM

Quote:

Originally posted by Richard Huntrods


Actually, you got three good responses right off the bat.

-R

I agree with Richard, you got plenty of valuable response, mostly qualifying that load limiting is the way to go doing this stuff and then it works. As I said, I run both and electric is slower and weirder, but it comes out fine. In the good old days, which weren't all that good, we simply went out and tried it and had no one to talk to at all. The first wire furnace I ever saw was in 1970. It's nothing new.
:dog:

Dave Bross 12-04-2003 10:18 AM

Forgot one detail in my post. I'm using an SSR and a digital controller set up to fire it at one second intervals.

The lack of temp swings with the tighter control is supposed to prolong element life 400 times in the case of an SSR and up to 4000 times with SCR control. I'm sure these numbers were achieved somewhere more element friendly than the glass environment but you get the idea.

The best electrical heating stuff I've seen on the web is at Watlow's site and you have to search around for it because they keep moving it. It's called The Watlow Educational Series and has THE BEST explanations of all things resistance heating and control with pros and cons and simplified explanations.

David Paterson 12-04-2003 11:33 AM

I didnt mean to insult anybody over their responses. I was hoping someone had melted batch for a year in a well designed wire melter and had some insight on element life.

To further the moly debate a little, consider this:

My furnace consists of less than 90 insulating firebrick, 3'' X 4.5" X 9" each, a few bags of insulating castable for the floor, and a few boxes of fibre blanket. Total cost was not a lot more than the $600.00 for 4 moly elements, and that doesnt include the expensive transformers that moly needs.

My furnace draws about 5 KW at 2150F, apparently half of a small moly furnace. The trick is that I have no crown, reducing the interior space to be heated by about 50%. The lid is made of 3" thick IFB mortered together in an angle iron frame, with 1" of fibre on top. The lid rolls back and forth on angle iron channels. I intend to automate it using an air cylinder.

Perhaps you can see where I am going with this: For a similer construction and operating cost, you could run two wire furnaces for the price of one moly furnace. I am not sure at that point that there is any advantage to moly at all. In fact the reverse would seem to be true.

Randy Kaltenbach 12-04-2003 11:37 AM

Quote:

Originally posted by Dave Bross
...
The best electrical heating stuff I've seen on the web is at Watlow's site and you have to search around for it because they keep moving it. It's called The Watlow Educational Series and has THE BEST explanations of all things resistance heating and control with pros and cons and simplified explanations.

I found this stuff at http://www.watlow.com/literature/prodtechinfo/index.cfm

Just select "Information Type": Training and Education and you can pick any of the 7 PDF file books.

Steve Stadelman 12-04-2003 11:51 AM

Quote:

Originally posted by David Paterson

To further the moly debate a little, consider this:
Perhaps you can see where I am going with this: For a similer construction and operating cost, you could run two wire furnaces for the price of one moly furnace. I am not sure at that point that there is any advantage to moly at all. In fact the reverse would seem to be true.

I don't consider it a debate at all, it's a choice. The first one of these that I built is now over six years old, costs less than $250.00 monthly to run at $.065 KWH and has the origional elements.

The only maintenance it has had is to replace pots.

For short term use or projects etc, I would heartily reccomend a wire melter, I am using one right now because I didn't have the power or money available to build the big moly that is under construction right now, I am looking at the next ten years, and using really good castables, great electronics, high quality componants. When this thing is up and running, I want to blow glass out of it and I know it will make the best quality I can have because it will reach the temps I need every day and it will not have to be torn down until the pot change.

Can you blow lots of glass out of a wire melter? HELL YES! Parker Stafford and Sam Davisson do it all the time, and they know thier maintenance schedules religiously and stick to all the little tricks to make it work.

Ben Rosenfield 12-04-2003 12:07 PM

Quote:

Originally posted by David Paterson
For a similer construction and operating cost, you could run two wire furnaces for the price of one moly furnace. I am not sure at that point that there is any advantage to moly at all. In fact the reverse would seem to be true.
According to the temperature ranges Pete listed in the Building Shop Stuff thread (http://talk.craftweb.com/showthread....&threadid=2065) about melting SP batch, a good melt is 2250, which is about 86.5% of the Kanthal A1's operating maximum. He also cites approx. 2350 to finish the reaction, which is about 88% of the 2552 F max for A1.

And with all the good information here about SCR, SSR, etc., I don't see any reason for a beginner such as myself to go beyond this type of setup. I think this is the most bang for the buck at this point. At the same time, I do see the value in the molybdenum technology, particularly for large melters, or situations for lots of color pots. The setup at http://www.mountainglassworks.com/Studio.html is nice.

Mark Wilson 12-04-2003 12:38 PM

i have a wire melter, although i melt cullet and not batch. i installed a spare element, that is normally not energized. when an element burns out, i use a volt ohm meter to determine the bad element, and then use the spare element to keep the furnace up until the crucible is empty, then i shut down for service. yes the spare element does age because it is hot, but it does not age anywhere near as fast as a powered element does. this way, i have a way to deal with a burnt element, and save the crucible and the blowing time.

Steve Stadelman 12-04-2003 12:47 PM

Quote:

Originally posted by Ben Rosenfield


According to the temperature ranges Pete listed in the Building Shop Stuff thread (http://talk.craftweb.com/showthread....&threadid=2065) about melting SP batch, a good melt is 2250, which is about 86.5% of the Kanthal A1's operating maximum. He also cites approx. 2350 to finish the reaction, which is about 88% of the 2552 F max for A1.

And with all the good information here about SCR, SSR, etc., I don't see any reason for a beginner such as myself to go beyond this type of setup. I think this is the most bang for the buck at this point. At the same time, I do see the value in the molybdenum technology, particularly for large melters, or situations for lots of color pots. The setup at http://www.mountainglassworks.com/Studio.html is nice.

Yes it is, I talked Matt through building that (the moly part) a couple years ago.

And yes Ben, you can do this on the cheap and learn alot of stuff along the way. You will learn lots of valuable things about electricity and castables, power supplies and glass types.
I am pulling lots of good ornaments out of my wire melter right now. Once again I want to say that there are TONS of options out there to do your glass with, I am just a proponant of moly.

Watlow has a great website like Dave pointed out and all of thier stuff is also available on cd rom. It gives great demonstrations of WHY different power technologies work like they do.

Richard Huntrods 12-04-2003 01:11 PM

I use a Watlow controller and two digital relays on my wire furnace.

The default settings for the Watlow controller have it powering the elements for a small burst every second or so.

I have both my annealer and furnace running the same controller setups (just different thermocouples), and it works great.

Power consumption is not totally known yet, but I can fire up both and the main 40A breaker does not trip.

My furnace is built according to the Mark Lauckner plans, although I use a different element size and configuration.

The nice thing about Mark's plans is that the element heating chamber is covered - this protects it from the "normal" glass environment.

Just not from spillovers :rolleyes:

I will be melting batch once the furnace is repaired. According to what I've read here (thanks Pete) and what Ben re-iterated just a post or so ago, there's no reason to avoid batch in one of these units.

-Richard

-R

Richard Huntrods 12-04-2003 01:15 PM

David,

One other thing...

While bringing up my furnace for the first time, I emailed a bunch of people with wire furnaces (made using Mark's plans).

Basically, what I found out so far is everyone I contacted has melted cullet only - not batch. However, this seems to reflect convenience and suppliers rather than any inherent problem with batch.

Since I cannot get cullet readily, and all the gas-furnace people in Calgary melt batch (either Seattle Batch or Spruce Pine), I will use batch (Spruce Pine).


-Richard

Ben Rosenfield 12-04-2003 01:22 PM

Quote:

Originally posted by steve stadelman
And yes Ben, you can do this on the cheap and learn alot of stuff along the way. You will learn lots of valuable things about electricity and castables, power supplies and glass types.
That is invaluable at this stage of the game. I don't take this stuff lightly.

Let me thank you again for the help you gave me, and same to everyone else. This type of knowledge base is not as common as it should be. This is a damn fine board.

:toast:

Pete VanderLaan 12-04-2003 03:28 PM

I don't consider it to be a debate unless it's a debate over whether you can afford a Porsche as opposed to a Ford Taurus.
The Taurus will get you there while the Porsche will get you there effortlessly. The Taurus may break down on the freeway on ramp, and while repairable will cause you to curse at the time. Remember those Moly elements cost more, but they have no known life span unless you break it yourself. :dog:

David Paterson 12-04-2003 05:46 PM

If someone gave me a porsche, I would sell it and buy a good PU truck, and use the remainder of the money to upgrade my glass studio. A friend of mine had a Ferrari. It went really fast, but otherwise was big and expensive and not practical in any way.

Jay Holden 12-04-2003 09:00 PM

The setup at http://www.mountainglassworks.com/Studio.html is nice. [/b][/quote]


Man,That setup is sweet. Thanks for sharing it with us.

Rick Sherbert 12-05-2003 04:53 AM

I see a lot of reference to kilowatts here as a basis for what it costs to run these things. Remember that a kilowatt is just a snapshot in time, an intantainous value. When talking about cost of electricty you must use Kw/Time or kilowatt hours (KwH). Steve and Pete are hip to this.

Just because you see something pulling 23 amps (5Kw at 220 volts) when you measure it doesn't mean it does it all the time.
On off on off right?

Then the cost per KwH varies regionally....

$.02

Rick


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