PeterH
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Posts posted by PeterH
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On 12/12/2023 at 6:34 AM, Lilith Rockett said:
The kiln worked fine for a decade and then this started after the last element change.
>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?
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3 hours ago, Jeff Longtin said:
(And all referred to molds as "moulds".)
Well it is the UK spelling.
- Jeff Longtin and Chilly
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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.
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2 hours ago, Hulk said:
Added: Forum internal search feature only returns "open" (UNarchived) threads; to search all, try using an external search engine, and include community.ceramicartsdaily.org in your search string...
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.
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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
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6 hours ago, Clay17 said:
Genesis 1 Controller
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.
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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.pdfThis 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. -
On 12/8/2023 at 9:58 AM, giorgiodidon said:
thank you all for answers, after all, it was a soap problem i thought it was dry, but in some ways it sealed surface, solved using a wet sponge cleaning the surface! it works well
giorgio
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 -
1 hour ago, jay_klay_studio said:
I know it's not quite the same, but I'm working on a way to select a segment to horizontally align target with actual. Meaning, you select segment 6, and the graph lines shift so that the start of segment 6 is aligned (but the lines are unbroken). I agree that visualizing the delta in time between each segment could be handy, but IMO, it's a little confusing to see the target graph line broken up like that.
Personally I like it because it's a reminder that a lag-less model doesn't fit the data there.
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Straight-line approximation to with-lag format with some decorations. Lags shown both on the x-axis and by shading on the xy plane.
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13 hours ago, jay_klay_studio said:
Update, tried the colors and from an aesthetic sense I like the old ones, but from a purely scientific perspective, I dig the extra info you get here:
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!
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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.
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59 minutes ago, neilestrick said:
I think maybe you're assuming that the kiln is staying exactly on track with the program? Unless it's a fairly slow program or a small but powerful kiln, it rarely does.
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.
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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.
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Looking at the table Orton Cone Chart I'm surprised/confused that the heating rate assumed for small cones is so much faster than for regular ones.
https://www.ortonceramic.com/_files/ugd/7c9d79_11dd303c800c46b08d3a05178a02d99c.pdf
Small at 300°C/hr and regular at 15°C/hr, 60°C/hr & 150°C/hr.Is there a simple explanation?
I note that a footnote states the small cones were fired in a gas kiln, while bars are typically used in a electric kilnsitter.
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If the slip is pourable when you come to emptying the mould then an airlock is a possibility. As is narrowing of the opening if the walls are too thick.
However if the glaze is gelling it's a different problem -- think thixotropic house paint which sets on standing.
The long-term answer is to adjust the slip until it doesn't gel during the time you are casting. Stirring the slip well just before casting (without introducing bubbles) can also give you a little extra time. While Jeff's stirring approach can break the gel in the mould.
Long ago I was using a mould with a long thinnish neck very next like this, and an unsatisfactory ready-mixed slip:
Pushing the handle of an artists paintbrush down the centre of neck and pushing it up and down for a while (while avoiding the sides) broke the gel in the neck for long enough for the mould to be emptied.
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Congratulations. Fingers crossed.
Presumably you improved some connections and/or the last switch you examined?
But there are two pretty independent sets of (switch + element-pair), and some thing(s) have affected both of them.
Maybe where two wires shared the same switch terminal (presumably on the switch you have just re-connected)?
PS Reminds me of my software days.
Heisenbug https://en.wikipedia.org/wiki/Heisenbug
In computer programming jargon, a heisenbug is a software bug that seems to disappear or alter its behavior when one attempts to study it. -
10 hours ago, PotteryEnabler said:
I suspect the kiln was wired slightly differently than the diagram originally. I'm guessing that it was a difference in how they wired it to get a single element on the bottom rather than the middle to be On element during a Medium fire. With the way the diagram is, I think the bottom elements ( 2& 4) are the ones firing with the medium switch, is that correct? That's also why it is so confusing that my elements 1 & 3 came on only when following that diagram.
9 hours ago, PotteryEnabler said:That's what is so frustrating about the process here, is that I see the diagram, understand the flow, it looks like it should work, tests out ok (in my limited ability to know how to test circuits)...but doesn't work.
Idle thoughts ... sometimes you can error-guess, sometimes you need more data
What tests have you been doing, and are they on the powered or unpowered kiln? Do you have a multimeter?
Lets assume that the wiring corresponds to the diagram, and the components work.
With the kiln unplugged and the meter measuring resistance you should be able to test for continuity ("zero" resistance) between the L1,Ll2 or neutral at the plug and the ends of the elements. Repeat with the 4-way switches in each position.
So with one switch off there are 12 measurements for each position of the active switch.
(L1,L2, neutral)x(both ends of top element, both ends of bottom element) = 3x4 = 12
... if, as looks likely, the "middle" ends of pairs of elements are physically connected (e.g. go into the same switch connector) this reduces to 3x3 = 9.Basically demonstrating the the connections shown in red are there, and no other connections exist from an element end to the plug's L1, L2 & neutral.
If some connections aren't there, trace them from L1/L2/neutral through the wiring, and see where connectivity is lost.If spurious connections exist, think about it.
PS Two wiring diagrams for the A88B at https://eadn-wc04-7751283.nxedge.io/wp-content/uploads/A82WD.pdf
One for push-on terminals and the other for screw-on terminals.
It also has a legend converting the b&w line-type to wire colour. I'd be inclined to colour-in a copy.
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Two answers in one.
Digitalfire https://digitalfire.com/ is a mine of pottery information, for example
Underglaze
https://digitalfire.com/glossary/underglaze -
9 hours ago, PotteryEnabler said:
Only the first and third elements out of four are turning red despite being on High. All elements are intact. Full power coming through the two hot lines all the way to the control box. Neutral and ground intact.
It looks to me like the top element (in the diagram, not necessarily in the kiln) is only fed by one of the 120v lines (the upper one in the stylised plug/socket). Although you say that both 120v lines are getting to the controller, is the upper one also getting to the switches and/or elements?
PS
>I have peered closely at that wiring diagram and wished for higher resolution a lot the past few days
For a different kiln, but probably/possibly the same circuit
https://content.invisioncic.com/r278179/monthly_2021_11/AFFD763E-B04E-4A36-A21B-049717307DB1.jpeg.d8d19f63656d62487cfde60f695535d2.jpeg
... asking for coloured felt-tips on the different styles of dashed lines
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Something to keep at the back of your mind.
IF the 4-way switches need replacing
OR you don't have a 4-wire 240v circuit (L1,L2, Neutral, Ground wires)
... you can change to using infinite switches ( which also gives you finer temperature control)
As (in some cases) recommended by the experts, and apparently Paragon (who seem to no longer stock 4-way switches).... and Paragon don't seem to sell replacement 4-way switches anymore
https://paragonweb.com/product-category/parts/switches/... remembering that a generic infinite switch from a high-volume supplier may be cheaper than one from Paragon.
Any problems with Skutt APM elements purchased after July 2022?
in Equipment Use and Repair
Posted
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?