kayleyvdb Posted August 13, 2020 Report Share Posted August 13, 2020 Hi all! I have a Skutt 818 with a digital TAP controller and a new type k thermocouple. I've completed two firings, one bisque, and one glaze, and both overfired. I placed a Cone 06 witness cone (it's all I had) in the cone 06 bisque fire and it melted completely. I placed cone 5, 6, 7 witness cones in the cone 6 glaze fire and all melted completely. Based on the shape of the cone 7 and the color of the plainsman m332 clay, I suspect the kiln reached cone 8. These are the firing schedules I used: Cone 06: ramp 100 degrees/hour to 200 degree setpoint. hold for one hour. ramp 200 degrees/hour to 1600 degree setpoint. ramp 500 degrees/hour to 1830 degree setpoint. hold for 15 minutes. Cone 6: ramp 200 degrees/hour to 220 degree setpoint. ramp 350 degrees/hour to 2000 degree setpoint. ramp 150 degrees/hour to 2190 degree setpoint. hold 15 minutes. ramp down 500 degrees/hour to 1900 degree setpoint. ramp down 125 degrees/hour to 1400 degree setpoint. My firing logs show that the kiln hit the proper temperature... but the witness cones tell a different story. Any idea why I'm experiencing this inconsistency? Any tips would be much appreciated! Thank you in advance. Kayley Link to comment Share on other sites More sharing options...
liambesaw Posted August 13, 2020 Report Share Posted August 13, 2020 I'm not familiar with the controller, does it have a thermocouple offset setting? If so you can dial it down a bit to match your cone results. Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 13, 2020 Report Share Posted August 13, 2020 1 hour ago, kayleyvdb said: ese are the firing schedules I used: Cone 06: ramp 100 degrees/hour to 200 degree setpoint. hold for one hour. ramp 200 degrees/hour to 1600 degree setpoint. ramp 500 degrees/hour to 1830 degree setpoint. hold for 15 minutes. Cone 6: ramp 200 degrees/hour to 220 degree setpoint. ramp 350 degrees/hour to 2000 degree setpoint. ramp 150 degrees/hour to 2190 degree setpoint. hold 15 minutes. ramp down 500 degrees/hour to 1900 degree setpoint. ramp down 125 degrees/hour to 1400 degree setpoint. To evaluate this you need to modify your schedules so the last 200 -250 degrees of you firing happens at about 108 degrees per hour. Take a look at the Orton chart, pick a speed and finish temperature for the last segment (generally 108 per hour for center column) fire that way and see if it’s over or under, might be right on. From there you can dial in any offsets needed. Digital controllerS can emulate cones but you must fire the last segment reasonably close in speed and temp per the cone chart else all bets are off. The last 200-250 degrees is where the most meaningful heatwork is done. Prior to that, not so much. also not sure why you want the hold at top temperature either as this will likely move one cone higher in fifteen minutes. My advice, dial it in plain Jane first, then you can fire with variations based on that knowledge. Link to comment Share on other sites More sharing options...
neilestrick Posted August 13, 2020 Report Share Posted August 13, 2020 At a final ramp of 500/hr I would expect it to be under-firing, not over-firing. But it's definitely a good idea to adjust the final ramp to 108F/hr and use the cone charts to make sure you're starting with numbers that will be more accurate. You'll also need to try it without the 15 minute hold, as that is adding almost a full cone of heat work. Get it dialed in first without holds and the appropriate ramp, and go from them. I think you will still need to adjust the thermocouple offset. Have you tried a pre-programmed firing schedule? Is this a wall mounted unit, or did you replace a Skutt KM kiln mounted controller with the TAP? Do you have a thermocouple protection tube? Link to comment Share on other sites More sharing options...
Sorcery Posted August 17, 2020 Report Share Posted August 17, 2020 On 8/13/2020 at 11:32 AM, kayleyvdb said: Any idea why I'm experiencing this inconsistency? It's only because you are not shutting it down yourself when you Witness the Cones bend. It doesn't matter how good any controller is, every firing should be manually ended by a human when the cones bend. You might have to begin by dedicating a couple hours near the end to watch. After a while you'll get it down to about 20 minutes or so. This "watch window" changes with the amount of wares in the kiln, element health, etc, but should remain within about 40 minutes. I guess most important is.... if only one thing fails in the controller, you can melt everything and destroy your kiln. That's why I would never leave it to shut itself off. Even if they claim "failsafe", planning for the worst is the best. Leaving a kiln to shut itself off is like using a tiger for a babysitter. Sorce Link to comment Share on other sites More sharing options...
neilestrick Posted August 17, 2020 Report Share Posted August 17, 2020 53 minutes ago, Sorcery said: It's only because you are not shutting it down yourself when you Witness the Cones bend. It doesn't matter how good any controller is, every firing should be manually ended by a human when the cones bend. You might have to begin by dedicating a couple hours near the end to watch. After a while you'll get it down to about 20 minutes or so. This "watch window" changes with the amount of wares in the kiln, element health, etc, but should remain within about 40 minutes. I guess most important is.... if only one thing fails in the controller, you can melt everything and destroy your kiln. That's why I would never leave it to shut itself off. Even if they claim "failsafe", planning for the worst is the best. Leaving a kiln to shut itself off is like using a tiger for a babysitter. Sorce I respectfully disagree. One of the main reasons for having a digital controller is so you don't have to watch cones bend. Yes, you should verify that the kiln did indeed shut off when it was supposed to in case you messed up the programming or something went terribly wrong with the system (rare), but there is no need to watch cones bend and shut it off manually. Once you have everything dialed in with your programming and thermocouple calibration there's no need to watch cones. Sure, you can put them in the kiln to verify things if you want to (you don't have to), but it's okay to put a good amount of trust in the controller. Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 17, 2020 Report Share Posted August 17, 2020 6 minutes ago, neilestrick said: but it's okay to put a good amount of trust in the controller. @Sorcery The fact is most people do and the controls have proven reliable. Can anything guarantee your kiln will shut off, short answer is no unless you always faithfully shut it off yourself, but then again lots have forgotten on occasion to do that. Fortunately controllers have programming which means set point shutoff and also rate errors which mean at some point if your kiln can not maintain a rate then an error will shut it off and a high limit to ensure your kiln will not exceed a certain temperature. So they are reasonably reliable and pretty darn safe in a reasonably maintained kiln. Always good to know when to expect a kiln to shutoff though ......... and then check on it. Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 23, 2020 Author Report Share Posted August 23, 2020 Hi all! Thank you so much for your replies. My apologies for taking so long to get back and answer your questions. It's a tabletop TAP controller by SDS industries (https://www.kilncontrol.com/). I purchased the panel and my husband build the box according to Evenheat's specs. It doesn't come with pre-programmed firing schedules, unfortunately. I don't have a thermocouple protection tube — I've fit the thermocouple into place with pieces of kiln brick. I adjusted my cone 6 glaze firing schedule and did a test firing and it's unfortunately still overfiring. Cones 5, 6, and 7 are fully melted. I've used large orton witness cones. From what I've gathered here, the next option is to adjust the thermocouple offset? Here's my new firing schedule: Ramp 100 degrees/hour to 220 degree setpoint. Ramp 350 degrees/hour to 1724 degree setpoint. Ramp 270 degrees/hour to 1994 degree setpoint. Ramp 108 degrees/hour to 2210 degree setpoint. Hold for 20 minutes. Ramp down 500 degrees/hour to 1900 degree setpoint. Ramp down 175 degrees/hour to 1450 degree setpoint. Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 23, 2020 Report Share Posted August 23, 2020 57 minutes ago, kayleyvdb said: Hold for 20 minutes So it seams quite a bit out of calibration. Two questions and a request before we confirm the baseline. First post a picture of your thermocouple including location in the kiln and how far it extends into the kiln. Get rid of the hold for now and even the slow cool at this point until you can dial this in to terminate accurately. ........ and this one is gonna be tough, tell us what the total time for the firing actually ended up, for your next fire using the same schedule without the holds. Before you offset the controller a bunch we should be sure your kiln is actually following the schedule. As kilns get older they lose power and some controllers have difficulty detecting this and trend toward over firing. If you can jot down some real data at real times through the firing that would be great but if we had to pick, the rate the kiln is actually able to achieve during the last segment is key. (Last 200 degrees) when kiln elements wear sufficiently (10%), they often overfire as the actual rate they are firing decreases, firings take longer and the accumulated heatwork from the slowdown tends to be excessive. Just some things to check before you dial in large offsets. Better to get this right. Pictures of the cones would be great as well. Last outside thought, please be sure that if you are using a type K thermocouple, the tap unit is set for it and not type R for instance. Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 23, 2020 Author Report Share Posted August 23, 2020 32 minutes ago, Bill Kielb said: First post a picture of your thermocouple including location in the kiln and how far it extends into the kiln. Get rid of the hold for now and even the slow cool at this point until you can dial this in to terminate accurately. ........ and this one is gonna be tough, tell us what the total time for the firing actually ended up, for your next fire using the same schedule without the holds. Thank you, Bill! I’ll give it another go without the holds and ramp down and report back. Here’s some more info and photos of the thermocouple, cones, and firing log. It looks like the kiln hit the top temperature around 9 hours. The elements are new and have been used 5 times, same with the thermocouple and all the electronics in the controller. I’ve confirmed that the TAP is set for type K. Another thing that might be worth mentioning, the kiln lid is lifting about a quarter inch on the right hand side (above the thermocouple) over firing. My husband is theorizing that the draft escaping on that side could also be contributing to the overfiring. Thoughts? Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 23, 2020 Author Report Share Posted August 23, 2020 29 minutes ago, Bill Kielb said: Oops - ran out of image space! Here are the very melted cones. :( Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 23, 2020 Author Report Share Posted August 23, 2020 29 minutes ago, Bill Kielb said: Oops - ran out of image space! Here are the very melted cones. :( Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 23, 2020 Report Share Posted August 23, 2020 9 minutes ago, kayleyvdb said: the kiln lid is lifting about a quarter inch on the right hand side 1/4” is pretty big so that definitely can have an influence. 9 hours eleven minutes to 2099 instead of eight hours forty one minutes to 2210 is significant ........ and 2210 is actually short of 2232 which would be cone six at 108 per hour last segment. Definitely fix the gap for the next firing. Lids warp when heated so often the hinges often can be carefully loosened when the kiln is fairly hot to get this gap to decrease or go away. Your control isn’t making setpoint or within a few degrees of it so there is definitely a reason. Less than an hour over calculated time is not that significant but terminating well before setpoint tells us the control is having difficulty firing for some reason and it is falling outside the firing logic. Still can offset, but for sure I would suggest fixing the gap if significant before you calibrate. Just occurred is there a tcouple offset in it already? cones are smashed, tcouple looks great so no issue there. It is sandwiched between two elements and in direct sight of them but this would tend to terminate your firings earlier as in underfired. Link to comment Share on other sites More sharing options...
neilestrick Posted August 23, 2020 Report Share Posted August 23, 2020 It definitely needs some calibration. While calibrating, don't do any hold times. That 20 minute hold at the peak equals about 1 cone, but it's not an exact thing, so until you get it dialed in don't use any holds. Have you tried changing the thermocouple? It's possible for it to have a crack in the weld that's not visible when cold, but opens up when it gets hot and causes bad readings. Also check the TC wire connections at the ceramic block and make sure the wires haven't broken at the screws. Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 23, 2020 Author Report Share Posted August 23, 2020 58 minutes ago, Bill Kielb said: 2210 is actually short of 2232 which would be cone six at 108 per hour last segment. Definitely fix the gap for the next firing. Your control isn’t making setpoint or within a few degrees of it so there is definitely a reason. Less than an hour over calculated time is not that significant but terminating well before setpoint tells us the control is having difficulty firing for some reason and it is falling outside the firing logic. The kiln actually was reaching set point! I programmed it to hit 2210 with a 20 minute hold, based on Orton’s charts and info. They list 2228 as the set point temperature for a 108 degree ramp with large witness cones, and recommend dropping the set point temperature 18 degrees for a 20 minute hold, which is where my 2210 degree setpoint came from. For my next firing, I’ll adjust the lid and make the setpoint 2228 with no hold. There is no thermocouple offset programmed right now. Does this information change anything? Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 23, 2020 Author Report Share Posted August 23, 2020 22 minutes ago, neilestrick said: It definitely needs some calibration. While calibrating, don't do any hold times. That 20 minute hold at the peak equals about 1 cone, but it's not an exact thing, so until you get it dialed in don't use any holds. Have you tried changing the thermocouple? It's possible for it to have a crack in the weld that's not visible when cold, but opens up when it gets hot and causes bad readings. Also check the TC wire connections at the ceramic block and make sure the wires haven't broken at the screws. Roger that on the no holds! The thermocouple is new and just installed so I really hope that isn’t the issue. Thanks for your reply! Link to comment Share on other sites More sharing options...
neilestrick Posted August 23, 2020 Report Share Posted August 23, 2020 @kayleyvdb So the 9:11 to 2099 wasn't the peak, it actually got to 2210? I think that photo confused us. So yes, if it's getting to 2210, try it all the way to 2232 without a hold and see what that gets you. From there you can either do a thermocouple offset if it's also off at low fire temps, or a cone offset if it's only off at cone 6. Not likely a bad TC then. Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 23, 2020 Report Share Posted August 23, 2020 2 hours ago, kayleyvdb said: Does this information change anything? Yes, by the screen pic it seems you ended at 2099 but maybe that was after holding for twenty minutes at 2110? Best plan is to try to fix the lid gap and offset from those results. Your tap controller should display each segment if you touch the graphic along the segments the info should pop up and maybe provide some more insight in what speed it actually fired. This could be very helpful to know for the last segment. Your offset is limited to +/- 50 degrees so hopefully the kiln lid will help a bunch and bring this much closer. Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 24, 2020 Author Report Share Posted August 24, 2020 19 hours ago, Bill Kielb said: Best plan is to try to fix the lid gap and offset from those results. Your tap controller should display each segment if you touch the graphic along the segments the info should pop up and maybe provide some more insight in what speed it actually fired. This could be very helpful to know for the last segment. Thank you, Bill! I ran another firing after adjusting the lid. There’s still a small gap in the very front but it’s much better. It’s about 1/8” now. According to the firing log, it followed the schedule perfectly. It took 8 hours and 40 minutes. I’ve shared two photos of the firing log, one to show the entire firing (ignore the time and temp stamp) and one to show the end of the firing. The cones are all melted again, but they aren’t as destroyed (I hope). I’ve included a side by side comparison of my previous firing (left) and this firing (right). I’d like to run another test today with an offset, but am unsure what offset to program. Is this the next best step? If so, any tips on how to determiwne the best offset to try? Thank you again for all your help. I appreciate it so much! Link to comment Share on other sites More sharing options...
neilestrick Posted August 24, 2020 Report Share Posted August 24, 2020 @kayleyvdb Have your cones ever gotten wet? There's a lot of lumpiness in them that isn't normally there. Can you post a clearer, closer picture of them? Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 24, 2020 Author Report Share Posted August 24, 2020 1 minute ago, neilestrick said: @kayleyvdb Have your cones ever gotten wet? There's a lot of lumpiness in them that isn't normally there. Can you post a clearer, closer picture of them? They haven’t! Here’s a new photo ... the cones from the firing with the hold are on the left. The most recent firing is on the right. Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 24, 2020 Report Share Posted August 24, 2020 5 hours ago, kayleyvdb said: I’d like to run another test today with an offset, but am unsure what offset to program. Is this the next best step? If so, any tips on how to determiwne the best offset to try? Much better! Maybe run an empty glaze with extra shelves in there to load it a bit to get an idea without firing finished work. My guess, I would start at ten degrees. So a positive offset in your case of plus ten. Total guess though. much better result!!! Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 24, 2020 Author Report Share Posted August 24, 2020 1 hour ago, Bill Kielb said: Much better! Maybe run an empty glaze with extra shelves in there to load it a bit to get an idea without firing finished work. My guess, I would start at ten degrees. So a positive offset in your case of plus ten. Total guess though. much better result!!! Thank you! I‘ve been loading the kiln with some mugs that didn’t turn out the way I had hoped just to mimic an actual firing, so hopefully the results I’m getting are as accurate as possible! I’m currently firing with a 50 degree offset thinking I’ll work my way down from there. Then I’ll have to check my bisque firing schedule and cross my fingers it’s calibrated for that as well! Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 25, 2020 Report Share Posted August 25, 2020 1 hour ago, kayleyvdb said: I’m currently firing with a 50 degree offset thinking I’ll work my way down from there If fifty degrees doesn’t do it then we will need to see if your thermocouple is out of calibration (super rare) and if the software is up to date in the tap. I just looked and it appears they have had several. They appear free to download. Link to comment Share on other sites More sharing options...
kayleyvdb Posted August 25, 2020 Author Report Share Posted August 25, 2020 8 minutes ago, Bill Kielb said: If fifty degrees doesn’t do it then we will need to see if your thermocouple is out of calibration (super rare) and if the software is up to date in the tap. I just looked and it appears they have had several. They appear free to download. Fingers crossed! The software should be up to date because I ordered it a little over a month ago. Thanks again for all your help! Link to comment Share on other sites More sharing options...
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