PeterH

I had a vague memory of possibly related postings using IR thermometers and/or IR cameras. Having been impressed by images such as this one showing an overheated relay lead. Turns out it was from one of your postings, What's your current position on these techniques? PS I also have a vague feeling that some mobiles were sufficiently sensitive to IR to give useful images.

Help, I'm having trouble understanding these figures. Problem 1. 28+23+28=79Aamps, but the 240V kiln seems to be rated at 60amps. https://www.sheffield-pottery.com/SKUTT-KM1231-3PK-240V-1PH-p/skkm12313pk.htm ... note that 79/sqrt(2)=55.9, so it might be interesting to know if the current sensor is reading RMS or not. Problem 2 Currents of 28+23+28 indicate that the centre section has a higher resistance than the end sections. But the ends seem to have 2x 8.9ohm elements in parallel, and the centre 3x 11.3 ohm elements in parallel. https://skutt.com/images/KM1231PK-1PH-and-3PH.pdf https://www.armadilloclay.com/uploads/5/1/2/8/51288343/element_resistence.pdf So, ends should be 8.9/2=4.45ohms & the centre=11.3/3=3.76...ohms. ... where the centre has a lower resistance than the ends ... and the currents are very high at 240*2/8.9=53.9amps, 240*3/11.3=63.7amps and 240*2/8.9=53.9amps compared to 28-23-28.

You may find these of interest if you are going to make your own paperclay. HOW TO MAKE PAPERCLAY | Chris Campbell http://www.ccpottery.com/colored-clay-lessons--chris/how-to-make-paperclay-.html Great if you have a heavy-duty mixed. If you don't you may have to resort to adding the damp paper-pulp to a pre-made thick clay slip, or adding dry clay powder to a wetter paper-pulp mix. In either case it will take longer to dry on a plaster slab due the the greater water content. Making Paper Clay Storage Easier and Less Stinky https://ceramicartsnetwork.org/daily/article/Making-Paper-Clay-Storage-Easier-and-Less-Stinky

Interesting to be reminded of prior work, but from pp74-75 of the 2nd edition of Contemporary Studio Porcelain by Peter Lane (2003). The methods used to make the components for constructing his sculptural installations were developed during a ten-year period of intensive experimentation and intensive research. ... The procedure of actually casting thin slabs of porcelain is the the most difficult part of the whole process of manufacture because small mistakes can create big problems. The most common faults resulting from incorrect casting are: cracking, warping, and distortion with corners curling to destroy the flatness. The details of the process cover about a page of A4. Rolling paperclay seems likely to be a lot easier and more fault-tolerant. PS If you are interested in the book, it's available from A$40 via https://www.bookfinder.com/search/?full=on&ac=sl&st=sl&ref=bf_s2_a1_t1_1&qi=iA,O6ra27IBsie2OptRYjTAhne4_1702997710_1:9810:16802 ... check against other sources such as Amazon

I would take a very careful look at Neil's suggestion. A very plausible cause of baffling problems, and you can check if it's causing your problems with a very simple wiring change. As Neil says it's a long shot, but if electrical interference is the cause it's going to be practically impossible to identify by normal diagnostic procedures. To me trying his suggested fix is a no-brainer, the cost/potential-benefit is so one-sided. ... but I'd continue exploring other options in case it doesn't work out.

I'm certain you will enjoy experimenting with paperclay. Just measured my printer paper, it's 0.06mm thick (a stack of 500 sheets measures 3cm). I cannot see you getting anywhere near that. OTOH playing with home-made paperclay years ago I achieved 2-3m very easily with a rolling pin. I just rolled it out on under a cloth on a slightly porous surface and draped it onto a balloon. Handling thin sheets, especially when drying, may be an issue. Pouring slip seems to be trying to cast it. I cannot see you getting thin sheets this way -- or getting them off the casting surface either. Weakly related article. THE MAKING OF PAPERCLAY PORCELAIN BANNERS https://www.grahamhay.com.au/harrison1998.html I mention it because he achieves 1.0-1.5mm with rolling. Which I suspect you could do with most paperclays. Using a light weight cellulose/cement batt as a backing, spread a jumbo garbage bag over the batt, held in place with paper clips. Spead a layer of paper clay mix fairly evenly over the plastic sheet with a spatula. Place another sheet of plastic garbage bag over the top and roll out the clay in all directions with as much pressure as you can muster until it oozes out off the batt on all sides. Alternatively, the batt can be placed on the slab roller and reduced in that way. Keep rolling until it is as thin as you can get it. PS Not relevant to you, but an interesting idea I haven't seen before, using ceramic fibre to strengthen the clay during firing (after the paper has burnt out). He apparently needed to do this because he was using very highly/deeply textured sheets. Firing is to Orton Cone 8 in 4 to 8 hours, depending on the decoration. If the marks are many and vigorous, a longer firing is required to stop the tile splitting up along the incisions. This is why the ceramic fibre is added, as it doesn't bum out like the paper but persists. The paper does a sterling job at room temperature of binding the surface together but the tell tale waft of smoke at 250,C spells its end, and that is when the normal paperclay tile will crack if the fibre isn't added, as the fibre remains intact until elevated temperatures resisting any tendency in the tile to crack apart along the stress lines created in the decoration. Eventually the ceramic fibres dissolve into the ceramic body glass, which is created by the high proportion of nepheline syenite in the recipe.

Maybe this one?

If the only fault is the elements -- and they are run at the correct voltage -- surely they must be drawing the wrong currents. That's all an element does, turn electricity into heat. So using current-sensing to measure the per-section currents when at full blast gives an end-to-end test of the elements. (Providing that the current sensing is wired correctly.) If the elements -- when fully powered -- are meeting the design specification for power output, then it looks like their duty-cycles aren't correct for at least part of the firing. PS Question for the experts. Do the solid-state relays switch at a sufficiently high frequency for the current sensing to accurately measure the time-averaged current?

>I use zone control and my center elements do not seem to be able to keep up, so the kiln continually stalls out, usually without an error code. >Even in single zone the center section of my 1231 pk fires cooler than the top and bottom. The single-zone result is surprising, as presumably the different element resistances in the top/bottom & centre sections are designed to avoid/reduce temperature differences between sections. [Presumably with caveats about extreme differences in the loading of the sections.] So checking that the various sections are drawing their design power when the kiln is running "flat-out" seems a good first step. The current sensing technology provides a per-section current measurement, and an eyeball check can confirm that the current-sensing loops are indeed round the wires going to the appropriate elements. What currents do you get for the three sections?

Well it is the UK spelling.

Rightly lots of talk about measuring resistances, voltages and currents with a meter, but doesn't this kiln have current sensing technology? https://skutt.com/products-page/ceramic-kilns/km-1231pk/ What does this say about the power going into each section at full blast? And I suspect that it should be pretty easy to eyeball that the current sensors are reading from the right elements.

Good advice, but I think it should be site:community.ceramicartsdaily.org For example google PeterH community.ceramicartsdaily.org gave me 76,400 hits, while google PeterH site:community.ceramicartsdaily.org gave me 186 hits PS Note that these figures vary between users and invocations. A second call produced 957 & 76,400.

Just a possibility: is the zener diode called a surge protector in Shimpo-speak (as they can be use to provide over-voltage protection)? https://kruegerpottery.com/collections/vl-lite-parts/products/rzzaa005394-vl_lite

If you are going to plot the planned and actual points on the same x-axis without registering them I think you need to show both "Actual start of segment X" and "Planned start of segment X" to clarify the situation somewhat. After pondering on your previous comments I've changed my suggested plot slightly, and the rationale quite a bit. Using this presentation (with or without the shading) For segments without a lag there is isn't a dogleg. For segments with a lag there is a dogleg. In either case the green line within that segment corresponds exactly to the "target" temperature profile actually produced by the controller for that segment in this firing.

What is your kiln make/model. Are the element resistances consistent with those in the kiln diagram. ... oops if it is a KM-1231PK the wiring diagram doesn't have resistances on it. https://skutt.com/images/KM1231PK-1PH-and-3PH.pdf This gives the resistances of the (normal?) elements https://www.armadilloclay.com/uploads/5/1/2/8/51288343/element_resistence.pdf ... but only gives 6 figures, while I believe that the KM-1231PK has 7 elements. https://community.ceramicartsdaily.org/topic/23960-a-few-questions-about-replacing-elements/?do=findComment&comment=194119 I order Skutt elements almost weekly. With modern kilns, the top/bottom elements are one for the top and one for the bottom. Always, for 27" and shorter kilns. The center elements make up the rest, whether that's 2, 3, or 4. The only exception are the KM1231PK models, which have 7 elements- 2 T/B, 2 intermediate, and 3 center.

What were you using the soap for? Soap reacts chemically with plaster to form insoluble "soap scum". Used correctly this is an effective way to seal a plaster master, but you don't want to let the soap react with your plaster mould. What is Potter's Soap, and how do you use it? https://www.artcoinc.com/potterssoap.php

Personally I like it because it's a reminder that a lag-less model doesn't fit the data there.

Straight-line approximation to with-lag format with some decorations. Lags shown both on the x-axis and by shading on the xy plane.

Obviously your choice, I just thought you might want to evaluate the alternative. Have to admit in this case it's a bit like looking at a 3D anaglyph without the coloured glasses!

The actual and target lines are made up of sections for each of the controller segments. So we have a lag-free target sections and with-lag actual sections. Naturally the two lines get progressively out of sync if any lag occurs. If you move the start-point of the each target section to the clock-time that that segment actually started you get a much clearer picture of what's actually going on, segment by segment. ... my straight-line approximation from a digitised image. With the gaps in the target-line representing the lag in that segment. Decoration: you might want to embolden the lag-periods on the x-axis, or shade a region of the xy plane. PS Here's a graph from my most recent firing (where it's clear that my kiln struggled to maintain ramp at peak but otherwise was pretty close): From this presentation segment 5 may be a bigger issue than segment 6.

You might also want to look at dry ready-mixes. This sort of thing https://www.potterycrafts.co.uk/Products/pottery-powdered-clays/P3103 Limoges Porcelain Casting Slip Recipe P3103 Limoges Porcelain Clay - 50kg Water - 18.5lt P3342 Soda Ash - nil P3344Soda Sil - nil Deflocculants are added in the spray drying of this clay so it is not necessary to add them.

How do you determine the start-time of the segments? Is it just when the end-temperature is reached in the CVS file? PS Minor point, but you might try changing the line colours to additive ones, which might show overlapping lines more clearly. Perhaps cyan & magenta, as some real-world yellows are a bit dodgy. The idea has some history in statistical presentations.

I freely defer to your knowledge in this area, but wouldn't 60 mins be a bit excessive? Note that the actual temperature is shown as significantly higher than the target temperature for the first ~600 mins. With the actual temperature shown peaking ~60 mins before the target peak temperature. So maybe the actual/target labels are the wrong way round. Switching the labels means that the registration of several kinks in the purple line (now the target temperature) with segment changes seems very plausible. But the two curves still seem (to me) to have registration problems, which might relate to skipping part of the program. I'm unsure if this could result in mis-attribution of the timings of readings on one of the curves. Of course then then thermal lag has to be allowed for. .

Am I having a senior moment, or does this graph have teething troubles? Shouldn't the major discontinuities in the target temperature line be at the segment-start times? ... and should the two peak temperatures differ by ~60mins? ... and did skipping part of the candle confuse the analysis?

Might also be worth also offering a (target-actual) plot. People tend to "see" the distance normal to the lines, rather than the distance parallel to the y-axis.