I just want to share a few photos of my kiln vent project.
The pin and its bushing were machined out of mild steel. The round foot - aluminum.
I didn't machine the circular top collar: I just found it in my scrap bin and used "as is" (the holes drilled in the collar do not interfere with its function, so I just left them alone).
I used the vent during several firings, then sandblasted the newly formed rust away and painted everything to finish the project. The pin was not painted. I blackened it to protect against rusting (it was heated, and used machine oil was rubbed into the surface). It looks like rust on the photos, but it's not. The inside of the bushing should be done the same way.
As you can see, magnets are used to regulate fresh air intake.
P.S. If I ever make one again, I'll use aluminum or stainless steel for everything (except the connection to the galvanized exhaust). Naturally, I'll have to make some kind of shutters instead of magnets then. This would require no painting and won't rust.
Posted by MichaelP
on 02 September 2013 - 01:36 AM
Here is something else that can be helpful to program Cone 5-6 in digitally controlled kilns. This is a way to emulate Cone Firing while making a custom program in Ramp and Hold Mode of Skutt and other controllers, including PIDs.
Choose the rate of the temperature increase during the last 200F of firing and see what temperature your kiln should reach to achieve Cone 5, 5 1/2 or 6. Each graph corresponds to one of the Cone #.
This is based on the data provided by Orton for self-supporting cones.
I'd like to post my notes on programming a simple Ramp and Soak PID temperature controller for Bisque (Cone 05) and Glaze (Cone 5-6) Firing. The Glaze Firing Schedule was adopted from the book "Mastering Cone 6 Glazes" by John Hesselberth and Ron Roy. The Bisque Firing Schedule is based on suggestions found in many books and other sources of information.
Note that the controller is programmed in Celsius. The controller operates an SSR (Solid State Relay) which switches the kiln on and off (Note: if you use a mechanical or mercury relay, use Cycle Time value from 20 to 40 instead of "5" in the PID setup).
My controller is capable of programming 50 steps. I allocated steps 1 through 7 for Bisque Firing program and steps 15 through 21 for Glaze firing.
I hope someone may find these notes helpful for setting and programming his/her own PID controller.It'll be quite easy to substitute the temperature and time values if you want to change the curves.
Thank you for your suggestions. I finished the installation last night. It was really easy and uneventful. For the completeness sake (in case other people find it helpful), let me describe the procedure.
I installed my thermocouple at, roughly, the same level with the Sitter, but on the adjacent wall. My peep holes are to the left of the control box, and the thermocouple is to the right of it.
I measured the distance between the upper rim of the chamber to the midpoint of a brick, transferred the measurements outside and drilled from the outside in. Before drilling, make sure the termocouple is not going to be at the same level as your shelf when the shelf is rested on your posts. This will keep the thermocouple away from the large mass of the shelf that heats and cools slowly and may therefore affect reading.
A smaller pilot drill was followed by a 15/32" drill. As always with drilling stainless steel, you need to use slower speed and a sharp drill (preferably, with a 135 degree point) and apply definitive pressure so that the drill grabs the metal right away. If you rub the drill against stainless steel, the drill will dull, stainless steel will work harden and make further drilling much more difficult.
Then I inserted the thermocouple with a nice reasonably tight fit. A made it so that it protrudes into the chamber a healthy 1 3/4" (approximately, as much as the Sitter does). Then I tried inserting a kiln shelf to check if the thermocouple doesn't interfere with its insertion. Such a significant protrusion of the thermocouple will insure a more true temperature reading. Besides, it played well with the lengths of the thermocouple insulation rings (by the way, I needed to remove two one them to fit my wall thickness). Then I attached the thermocouple to the terminal block to mark the block holes location and took the block away. Then I drilled very small holes and re-attached the block with sheet metal screws. Finally, I cut extra protruding thermocouple wires using an angle grinder with a cutting wheel attached.
This is a permanent installation to automatically control firing cycles. I did use peep holes for taking occasional temperature readings before though. But thank you for your suggestion anyway.
I'm in the process of finishing a DIY programmable controller box for my kiln. The kiln has the Sitter, and I'm not going to make any changes to the kiln. However, I need to install a thermocouple, so drilling a hole for it will be my next step. The kiln is an Evenheat 18"dia x 20" octagonal one. It has a stainless steel outside shell and 4"-high extension ring.
First, I thought about drilling a hole just below the Sitter cone holder. Then I decided not to attempt getting inside the control box and, instead, drill a hole in the ajacent wall. It would be easier to drill the lid, but I don't think measuring temperature on the top where it's higher is a good idea (no downdraft vent yet). Yes, I can make adjustments, but I'd rather know the actual temperature in the middle of the kiln (approx., the Sitter cone level). Besides, the lid is not covered with a metal shell, so attaching terminal plate to it will be very problematic.
Have you ever done it? What area did you choose for the thermocouple?
Did you use any refractory compound to seal around the thermocouple's insulation rings or went with just a reasonably close fit? I think sealing the space around is not a good idea since the thermocouple may need to be replaced at one point.
What are your thoughts, ideas and hints? It sounds like an easy and very straight forward procedure, but it's always better to get a second opinion.