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Schedule taking too long

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Mary Lou
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Schedule taking too long

Postby Mary Lou » Sun Jun 17, 2012 2:52 pm

Is it likely the cause of a schedule taking 2 hours longer than it should to reach anneal point could be a worn element? I have a new element to install but have been procrastinating since I'm getting ready for a solo show and hoped the present one would last until all the work was finished. Figured if anything was going to go wrong it would be when I tried to install a new element.

Bert Weiss
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Re: Schedule taking too long

Postby Bert Weiss » Sun Jun 17, 2012 5:55 pm

If the 2 hours was spent getting up to temperature, an element could be defective, or dead. It totally depends on your setup. On mine, 2 out of 3 elements will not get me up to 1400.

If the extra time was getting down to anneal, there could be a programming or controller problem, which is adding power when it shouldn't be.
Bert

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Mary Lou
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Re: Schedule taking too long

Postby Mary Lou » Mon Jun 18, 2012 12:53 am

Hi Bert, Not sure when it happened, I know before I went to bed I looked at the controller and it seemed on schedule, then I checked the kiln this morning at 11:30 a.m. and it was just starting to anneal, which surprised me. I started the program at 7:30 p.m. the night before. The total run time was 22 hours 03 minutes.
My schedule was
100 1050 45
75 1250 30
400 1500 10
9999 900 3.0
100 800 0
180 700 off

Not sure if I needed the bubble squeeze but the powder was thick in some areas.

I was slumping a 9mm, sys 96 blank, onto a bas relief carved in 3 layers of fibre paper coated with layers of powder. which is why I went to 1500 to fuse the blank to the powder. I was using top and side elements. The top element is 6 years old, sags in a couple of spots even though I've used epoxy to keep it in the channels. I know I need to eventually replace the element but I've been reluctant.

Bert Weiss
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Re: Schedule taking too long

Postby Bert Weiss » Mon Jun 18, 2012 2:13 am

Program the controller to make the kiln heat up quickly, then look at the elements. They should both be glowing bright red.
Bert



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Stephen Richard
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Re: Schedule taking too long

Postby Stephen Richard » Mon Jun 18, 2012 4:06 am

Mary Lou wrote:Hi Bert, Not sure when it happened, I know before I went to bed I looked at the controller and it seemed on schedule, then I checked the kiln this morning at 11:30 a.m. and it was just starting to anneal, which surprised me. I started the program at 7:30 p.m. the night before. The total run time was 22 hours 03 minutes.
My schedule was
100 1050 45 =ca 11'15"
75 1250 30 =ca 3' 10"
400 1500 10 = ca 45"
total of ca 15 hours 10. 19:30 plus 15:10 hours =10:40 am so I don't think you have a big problem.

9999 900 3.0
100 800 0
180 700 off

Not sure if I needed the bubble squeeze but the powder was thick in some areas.

I was slumping a 9mm, sys 96 blank, onto a bas relief carved in 3 layers of fibre paper coated with layers of powder. which is why I went to 1500 to fuse the blank to the powder. I was using top and side elements. The top element is 6 years old, sags in a couple of spots even though I've used epoxy to keep it in the channels. I know I need to eventually replace the element but I've been reluctant.
Steve Richard
You can view my Blog at: http://verrier-glass.blogspot.com/

Mary Lou
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Re: Schedule taking too long

Postby Mary Lou » Mon Jun 18, 2012 8:19 am

Bert, I will do that test to see if the elements glow. Thanks

Stephen, The kiln was at 78 when I started and I think it took 2.5 hours to finish the bubble squeeze, so that adds a variance of about 2 hours to what I calculated. Should I not be concerned?

Bert Weiss
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Re: Schedule taking too long

Postby Bert Weiss » Mon Jun 18, 2012 10:35 am

If the elements are intact and working, there is a setting inside the controller that could possibly cause this. I'm sorry, but I forget the details. I just remember that once, using a Bartlett RTC1000 (Ortons are very similar), I did adjust this program setting. It is one of those things, hidden inside, that you never touch. I don't use that kind of controller in my studio, but I have put them on kilns I built for others. If the elements appear to be working properly, I'd telephone the controller manufacturer and ask about the problem, there.
Bert



Bert Weiss Art Glass*

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Susan B
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Re: Schedule taking too long

Postby Susan B » Mon Jun 18, 2012 12:38 pm

I see that kind of problem when my relay needs replacing.
The controller also starts giving messages about low firing rates.

Morganica
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Re: Schedule taking too long

Postby Morganica » Mon Jun 18, 2012 5:51 pm

Are you sure you're not miscalculating? I ran your schedule through my spreadsheet tool and came up pretty close to Stephen's schedule. (Mine's a bit shorter, I think because I was starting from 78F):
schedule.gif

I have you reaching the 900F anneal point around 11AM, give or take some time, which isn't too far off from what you observed. It sounds as if your other firings go much faster--are you sure they're the same schedule as the slowpoke? Obviously I don't know what kiln you're using or how fast it spills heat--in one of my kilns this schedule would run maybe 8 hours longer because it's very, very good at holding in heat.

If it's a relay problem, you'll know soon enough, as Susan said--your controller will start flashing error messages about the heating rate being too slow and then it'll just flat-out fail.

I don't think I'd mess with the kiln until more problems crop up, but if you're on a tight schedule for a show it might not hurt to order replacement elements and relays. Much nicer to have them available than pay overnight shipping charges in an emergency.
Cynthia Morgan
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Mary Lou
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Re: Schedule taking too long

Postby Mary Lou » Mon Jun 18, 2012 8:54 pm

Cynthia, thanks for the spreadsheet check, what a neat idea. My other firings do seem to go faster, but there are variances in the setup and design. I need to do more monitoring and comparing of schedules to like work and making better use of inf. in my notes. My kiln is an Evenheat 23". I Stephen I apologize for thinking my calculations were more in line. Susan, I hope it's not the relay, but I do have spare relays and a new element on hand.

One thing I didn't mention and may have caused the difference is the work is well dammed with kiln furniture and firebrick, it's 11 x 17 and 10mm thick. I don't think I will tinker with anything before everything is finished, Thanks all for the feedback.

Morganica
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Re: Schedule taking too long

Postby Morganica » Mon Jun 18, 2012 9:22 pm

No prob. I set up the spreadsheet several years ago, mostly for casting so I didn't have to keep getting up in the middle of the night to close the vents. The spreadsheet lets me play around with the schedule so that I can pay attention to the kiln at reasonable hours. ;-)
Cynthia Morgan
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http://www.cynthiamorgan.com

"I wrote, therefore I was." (me)

DonnaG
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Re: Schedule taking too long

Postby DonnaG » Fri Jun 22, 2012 11:00 am

Nice spreadsheet. Is it sharable or for sale? =P~
I'm finding that some of my schedules seem to be taking an awfully long time. A friend has the same size kiln (I know --no two kilns are the same but still.....i have the Olympic GF314ETLC) and the same firing schedule takes her 19 hours and takes me 23. I tried Spectrum's slumping schedule and it was a whooping 35 hours before the temp was back down under 100 degrees.

Mary Lou
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Re: Schedule taking too long

Postby Mary Lou » Fri Jun 22, 2012 6:33 pm

Morganica wrote:No prob. I set up the spreadsheet several years ago, mostly for casting so I didn't have to keep getting up in the middle of the night to close the vents. The spreadsheet lets me play around with the schedule so that I can pay attention to the kiln at reasonable hours. ;-)


That's something I'm just starting to work on. It's nice not having to get up in the middle of the night to monitor the progress of unusual runs. Thanks again. The project in discussion turned out fine.
Last edited by Mary Lou on Fri Jun 22, 2012 10:36 pm, edited 2 times in total.

Morganica
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Re: Schedule taking too long

Postby Morganica » Fri Jun 22, 2012 7:43 pm

DonnaG wrote:Nice spreadsheet. Is it sharable or for sale? =P~
I'm finding that some of my schedules seem to be taking an awfully long time. A friend has the same size kiln (I know --no two kilns are the same but still.....i have the Olympic GF314ETLC) and the same firing schedule takes her 19 hours and takes me 23. I tried Spectrum's slumping schedule and it was a whooping 35 hours before the temp was back down under 100 degrees.

I posted it on my blog a few years back. It's probably gone through a bunch of revisions since then but most people customize it for their own use anyway...

http://www.morganica.com/bloggery/2008/glasswork/calculating-firing-time/
Cynthia Morgan
Marketeer, Webbist, Glassist
http://www.morganica.com/bloggery
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CH Glass
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Re: Schedule taking too long

Postby CH Glass » Fri Jun 22, 2012 8:02 pm

I'm a newbie, so this is probably obvious, but here goes.

I discovered, when running my first combing schedule, that my kiln would not actually heat as fast as what was programmed -- 600 degrees per hr. It did pretty well up to about 1475, but struggled the rest of the way to 1700. Just not enough amps to pull that off. I now let it get up to 1475 and then program a ramp at FULL for the rest of the way. It gets there when it gets there.

As the sheriff in Jaws says, "We're gonna need a bigger boat."

Morganica
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Re: Schedule taking too long

Postby Morganica » Fri Jun 22, 2012 9:09 pm

You may be a newbie, but I've seen it take loooooong time for even experienced folk to realize that your program can outrun your kiln. ;-)

Sometimes it's an amps problem, sometimes you've just got a whole bunch of mass in firebrick holding heat, a lot of airspace to heat up, and too few elements. And it's not a linear scale, either. If you've got a datalogger with one or two thermocouples, you can get a good idea of your kiln's firing profile(s) pretty easily. (And Bullseye offers a really nice technote about it)

If you don't, you can still profile your most popular firing schedules, albeit a little less accurately: Just record the temperature on the kiln controller readout periodically through a real firing of that schedule, with glass in the kiln. Check it, ideally at least every hour, then graph it. That'll give you an idea of how long it will take at each stage for that type of firing.

It's one reason you'll see schedules that don't go all the way back to room temperature, i.e. "200dph to 500F, OFF." The kiln's natural cooling rate is just as slow (or slower) than what you'd program, so there's no point in continuing.
Cynthia Morgan
Marketeer, Webbist, Glassist
http://www.morganica.com/bloggery
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"I wrote, therefore I was." (me)

DonnaG
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Re: Schedule taking too long

Postby DonnaG » Wed Jun 27, 2012 4:32 pm

Thanks for the link to the spreadsheet! I can't wait till tonight to 'test' out my kiln and programs --- after this I might actually start getting some sleep ----- or have time to cut more glass.

Mary Lou
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Location: Ontario, Canada

Re: Schedule taking too long

Postby Mary Lou » Wed Jun 27, 2012 6:22 pm

Cynthia, I downloaded your spreadsheet and it works great. Thanks for sharing. Mary Lou


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