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New L & L kiln


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57 minutes ago, neilestrick said:

. It can keep up 300F/hr up to 2100F, though. That I've tested. When I fire I ramp at 300F/hr to 2030F, then I ramp at 108F/hr to 2230F. At the peak of my last firing, which was a pretty full load, it was running 93% top, 47% middle, 90% bottom.

Those are still really good numbers in my experience. I used to even things out  as a last resort by dropping the relay cycle time on the old V6cf to ten seconds so I was curious how much the SSR’s would improve this. Pretty impressive IMO.

Thanks for sharing.

Edited by Bill Kielb
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3 hours ago, neilestrick said:

 

One of the cool things about the SSR's is if you get really close to the kiln you can hear the elements buzz in a pulsing rhythm as the relays cycle twice per second. It's like a faint drum beat.

Time to get your banjo out!

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2 hours ago, Bill Kielb said:

I used to even things out  as a last resort by dropping the relay cycle time on the old V6cf to ten seconds so I was curious how much the SSR’s would improve this.

The SSR's are really good at keeping it even. In looking at my last few firings, the temp difference between the 3 sections during the final slow rap is never more than 2F degrees. During the faster ramp it's mostly even, but in every firing there's a couple hundred degrees at some point where the spread gets to 10F degrees. It's interesting to see how that varies from firing to firing.  Sometimes it goes uneven at 1600F, sometimes at 1900F. It's clear that how each batch is loaded affects what happens during the ramps.

I was also surprised that during the final 108F/hr ramp the relay % doesn't vary much over the 200 degrees. It's only 2-4% difference. I would have thought it would be working a lot harder at the peak. 200 degrees is a big climb, after all. I suppose that during the slow ramp the bricks and ware are much closer to the air temp, so they're not just sucking up every bit of energy the elements put out and the elements don't have to work nearly as hard to make gains in temperature despite it getting hotter. I've also seen in several firings that the top section is clearly dealing with heat loss out the lid during the final ramp, as it tends to increase more than the bottom and middle by the end of the ramp.

It's fun to geek out on a spread sheet!

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5 minutes ago, neilestrick said:

I suppose that during the slow ramp the bricks and ware are much closer to the air temp, so they're not just sucking up every bit of energy the elements put out and the elements don't have to work nearly as hard to make gains in temperature despite it getting hotter.

Feels weird to self-quote, but this made me think of a phenomenon we see in wood burning kilns and sometimes in gas salt kilns, too- kilns that have hard brick interiors. There's often a point at which the kilns stall out, where the mass of the bricks are sucking up all the energy. Then, once the bricks become saturated with heat they start radiating and the kiln climbs easily.

In grad school we had a shino kiln that had 18" thick walls- 9" of hard brick interior and 9" of soft brick exterior. The idea was that you'd fire really slow, like over two or three days days so the hard bricks got super saturated with heat, and then it takes days for the kiln to cool, which gives great color in shino glazes. Anyway, my fried was firing the kiln and had it climbing really slowly. After a day or two the kiln was at about cone 6 and should have continued for another full day at that rate of climb, and needed turning up a couple more times. So he went home and went to bed that night and in the morning the kiln had flattened cone 11. We figure it got to cone 14 or higher. The bricks had become saturated and the kiln rocketed up.

Anyway, this just popped into my head when I was looking at my firing reports.

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2 minutes ago, neilestrick said:

I was also surprised that during the final 108F/hr ramp the relay % doesn't vary much over the 200 degrees. It's only 2-4% difference. I would have thought it would be working a lot harder at the peak. 200 degrees is a big climb, after all. I suppose that during the slow ramp the bricks and ware are much closer to the air temp, so they're not just sucking up every bit of energy the elements put out and the elements don't have to work nearly as hard to make gains in temperature despite it getting hotter. I've also seen in several firings that the top section is clearly dealing with heat loss out the lid during the final ramp, as it tends to increase more than the bottom and middle by the end of the ramp.

I like it! Backs up the theory that slow is sort of everything for more even firing.  As far as more energy it’s still the shell losses and the mass of the kiln so that makes complete sense to me. At lower temps the difference in energy between the elements and everything to be heated is greatest, so that and a relatively fast rate has to be some sort of exponential relationship. Later the elements and wares are closer in temperature while shell loses are close to a linear percentage so easier to maintain a slower rate...... as long as the relays can cycle fast enough. That old ten second minimum was likely there to save relays and also likely helped prevent some overshoot in the early stages but may have caused some undershoot later on made up by longer relay on time.

The percentage activation is golden and is a nice indicator of the loading. This process from basically zero to 2000 is tough to tune as it’s changing significantly and loading changes the effect on the zones. Anyone who has spent an afternoon tuning a pid module for something simpler would understand.

The lid makes total sense to me and aligns with IR camera stuff we have taken as well.

We should take the data and curve fit it ............. why? Geek alarm, never mind.

Nice data, thanks again!

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I guess I am trying to settle my conflict between the firing of the old manual electric and this new beast. I used to fire by a schedule writing everything down for years, then about 10 years ago, just flew by the seat of my pants. Looked in the mirror, saw a color and decided if it was too soon or not soon enough.  It was more of art, than science. I hit my target of hard ^6, then dropped to yellow orange quickly to hold for 30 minutes or so, then dropped to red orange to slow down below dull red. then shut off. Took notes when changing elements on resistance, then would check the resistance every 10 firings or so unless something seemed suspicious in a firing. 

This new thing, seems to be turn me on, let me go. You're not needed.

 

Hmmm

best,

Pres

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37 minutes ago, Pres said:

I hit my target of hard ^6, then dropped to yellow orange quickly to hold for 30 minutes or so, then dropped to red orange to slow down below dull red. then shut off.

You can still fire by color if you want to. Set it to cone 7 medium speed, then manually turn it off when it hits the color you want.

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I understand that I can do things like that. I believe that I will have to see what the present settings do, look at what I see going on, and then set up some sort of custom setting that allows me to fire up, and fire down the way I was used to doing it. I knew that there would be a learning curve, after all it took me 25 years or so to get to where I could fire the old one intuitively. Hopefully this one will not take that long!

 

best,

Pres

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22 hours ago, neilestrick said:

{snip} At 2000F and a rate of 350F/hr, the bottom section will be on 100%, the top at about 97%, and the middle at about 45%, and the three sections will be dead even in temp. {endsnip}

This is an interesting and useful discussion. I too have noticed the top and bottom sections "working" harder than the middle, but didn't put it together the way you just did. I wonder if this is where Skutt gets it by putting hotter elements at top and bottom? If one paid extra for a Skutt with 3-zone control and the touchscreen, would the data dump show the top and bottom sections at lower percentages, closer to the middle section to maintain even temperature?

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2 hours ago, Dick White said:

This is an interesting and useful discussion. I too have noticed the top and bottom sections "working" harder than the middle, but didn't put it together the way you just did. I wonder if this is where Skutt gets it by putting hotter elements at top and bottom? If one paid extra for a Skutt with 3-zone control and the touchscreen, would the data dump show the top and bottom sections at lower percentages, closer to the middle section to maintain even temperature?

Skutt does the graded elements to compensate for the fact that most of their kilns are single zone, and the controller doesn't know what's happening in the top and bottom sections of the kiln. It's not nearly as precise at keeping things even as zone control, though, so you still have to be careful how you load the kiln. If you run zone control with graded elements, the top and bottom sections won't have to work as hard as with equal elements since they're running hotter. The total power consumption would probably be about the same, since the total wattage is the same with either setup. It's hard to estimate just how much of a difference it would make. I think it would take a real world test to find out. My gut says it would be more like 75% instead of 85%. I think to get them all to run totally even, you'd have to have a drastic power difference between the middle and the other sections.

The Skutt 1231PK runs 3 different elements. I think some of the older Cress kilns do that, too, even on 27" tall kilns.

L&L has always run equal elements because it greatly simplifies everything when it comes to elements. No worries about getting the wrong elements in the wrong place, etc. And as a repair person the math is easier if you need to calculate element resistance on the fly. TBH, I haven't noticed the middle section elements wearing that much differently than the top and bottom on my L&L kilns, and I've always gotten about 150 firings between element changes, so it's not really a big deal. I think that just being in the heat degrades the elements a lot, even if they're not working hard to create the heat.

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Set the cone setting to -20 before the last glaze firing. Cone 7 was down, but less than the previous firing. I believe my next step will be another 20 for -40. I am closing in on the firing, and will start setting up my own schedule as soon as I graph out my present factors and figure in a slow cooling cycle. All in all, getting better, even though I know I am overfiring even though to look at the pieces it is hard to discern anything in the clay or glaze. 

 

best,

Pres

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1 hour ago, Pres said:

Set the cone setting to -20 before the last glaze firing. Cone 7 was down, but less than the previous firing. I believe my next step will be another 20 for -40.

Wow, seems sort of excessively off. So I wonder if similar applies to bisque?  Any chance the operating voltage is low by 10%, maybe worn breaker? Just seems a lot for a new kiln.

Edited by Bill Kielb
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Last bisque looked to have fired to ^04 with a ^06 setting and no cone adjustment. Yes, I agree with the adjustment being excessive, but don't have any other alternatives. I have looked over everything, and believe I am on the right track, but time will tell.

 

best,

Pres

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Mine is about 30 degrees off at cone 6, about 10 degrees at cone 04. No voltage issues, plenty of power. I've had several customers in the past 6 months experience the same thing. I think it's just a difference with the programming in the controller. I even used my old TC blocks just to see if that made a difference, since they have a different terminal material.

@Pres If you plan to do your own program anyway, just run a firing with cones you can see, and shut the kiln down manually when the cones drop and use that temp as the peak for your firings. That's what I do for my glaze firings.

 

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