Introduction: Home Made Electric Glass Fusing Kiln

Good evening anyone interested,

My name is Dave and I am from Bristol in the UK. Before Christmas I was out shopping in a market with my daughter Ava (8 yrs old) when she spotted some fused glass jewellery on a stand. Ava thought it was fantastic and immediately wanted to know if it was possible for her to make some. Obviously, I said yes without thinking as we make lots of interesting and arty stuff together. Once home I looked into the subject and realised we were going to need some type of Kiln to fuse the glass. I looked into the cost of a kiln and to be honest found the prices quite offensive so we (Ava & me) decided the way forward was to build a glass fusing kiln from scratch.

The first issue was an enclosure - luckily this was solved by my work. They were dumping a large aluminium radio test enclosure which seemed perfect. The enclosure already had an aluminium control box on the side and was generally very robust. The enclosure didn't have a lid but was otherwise good. I did some reading around and decided early on to heat the kiln from the top as this gives the glass a better gloss finish. So I knew from day one I was going to have to fabricate a top lid with integrated heating system. To fuse glass you need a sustained temperature of about 800C and aluminium melts at about 660C - so a small problem existed. The enclosure was going to have to be very well insulated and to achieve this I used a combination of ceramic fire brick, ceramic blanket and high temperature adhesive. To fuse glass you don't just turn on the heat full power and sit back. You have to increase the temperature slowly and more importantly reduce the temperature slowly to prevent thermal shock of the glass. To control this process I used an Altec PC 410 multi-program multi-step industrial temperature controller connected to a K-type thermocouple.

I hope you enjoy the series of videos and images I have included to describe my Kiln building project. Please if anyone has any questions or comments please feel free to get in touch and I will be more than happy to try and help.

Please remember if you attempt to build any type of kiln the resulting temperatures can be extremely dangerous and could result in serious injury. Not to mention the use of mains electricity in high current applications.

Step 1: Initial Look at the Enclosure & Temperature Controller

I have link to a video here which show the enclosure before I started to line it with insulation and also a look at the Altec PC 410 industrial heating controller.
My initial though was to line the enclosure with large bricks. However, these subsequently became difficult and expensive to get hold of. I found a supplier of standard size ceramic insulation bricks in Bristol and the guy did me a great deal with all the bricks and high temperature adhesive coming to under £100 cash - bargain !

(All the bricks, fire blanket and adhesive obtained from Paul at Complete Fire Protection (CFP) Bristol)

Video of initial look at enclosure and temperature controller :

Step 2: Enclosure Now Lined With Brick & Fire Blanket ...

After getting my hands on the ceramic fire insulation brick and ceramic fire blanket I set about lining the lower half of the box. So the box is initially lines with the blanket and then subsequently lined with the brick.

In order to make as much space as possible I cut the bricks down from the stock depth of 75mm to 50mm. The bricks can be cut using a standard hand saw. Do this outside as they create a massive amount of dust while cutting and I am sure you don't want to be breathing the dust. I made a simple wooden jig (see video) to get all the brick a consistent depth.

The bricks and blanket are all secured in place using a high temperature adhesive.

Video of lines enclosure :

Step 3: Construction of the Control Box

This section again features a video showing the completed control box that will drive the heating element.

Essentially the control box consists of the Altec temperature controller driven with a K-type thermocouple. The Altec then drives a 40A solid state relay which switches power to the heating element.

I have not added too many words here because I think the video covers things :

Step 4: The Construction of the Enclosure Lid

One of the most challenging aspects of building the kiln was construction of the lid section. I decided early on I wanted the heating element in the lid as this apparently would produce the best finish for the glass.

I decided to make the lid insulation from an array of the same ceramic fire brick used to line the lower enclosure. In order to hold everything together I went to a local metal supplier and got them to make me four corner brackets plus to long and two short straight sections and also cut a thin stop plate. The brackets and straight section were all cut from 2mm mild steel and the top plate from 1mm mild steel. The corner brackets and straight sections I drilled and screwed together around the brick secured with self thread cutting screws. The resultant lid is very sturdy if not a little on the heavy side. I also fitted a handle to the front which luckily came attached to the original enclosure obtained from work.

Step 5: Choice of Heater and Mistakes Made

Ok, so now I had a fire brick lid all held together with mild steel and a handle - what I needed now was a heater. Having looked at commercial kilns I decided I needed a heater capable of delivering about 2.5KW of heat. Quite a few of kilns I had looked at used an inexpensive heating element which is essentially a coil of resistive wire which is rated at a give power at a given voltage. The element I initially chose was rated at 2.5KW at 220V AC (see the image attached).

I ordered the heater from China and it was <£5 .....

The heater looked good on arrival and I proceeded to chase out a channel in the fire brick lid with a Dremel and an abrasive tool. If you are going to chase out this ceramic brick DO NOT use a fluted metal cutting bit the brick although soft will blunt the cutting tool in about two minutes rendering useless - I found out the hard way. Use an abrasive grinding bit which works really well. The element was pinned into place using pins made from a slightly thicker version of the same resistive wire - so just about 2cm of wire with a short ninety degree bend at one end.

So I installed the element with feed wires through the lid to the top side. I plonked the lid onto the lower enclosure and connected it directly to the mains.

Sure enough the element heated up to a cherry red hot and the temperature measured by the thermocouple started to rise.

OK - two major problems became apparent :

1. No matter how much you pin the element in place it expands a great deal when it heats up. The element then sags as large hanging loops under the force of gravity. In my case the loops were hanging down some 15cm into the lower enclosure and even when the power is removed and the heater cools the heater only contracts slightly leaving the loops to flap about - it just didn't feel right to me and I wasn't happy with the heater solution.

2. The heater caused the chamber to climb rapidly in temperature until it reached about 300C where the rate of increase slowed. By about 550C the temperature was rising painfully slowly at maybe 1C/minute and was clearly not going to reach 800C in any sort of reasonable time. At this point I had taken delivery of a mains power meter. Attaching the power meter showed my heating element was actually only delivering about 1.2KW and NOT the specified 2.5KW as the supplier had stated ! I think the supplier was just selling 'an' element as various powers hoping that someone didn't check - well I did, complained and got a full refund :)

So the bottom line was I decided to ditch the first heating element and rethink the entire heating problem.

Step 6: Final Choice of Heater and Lid Construction

After ditching the first heating element I set about looking for another solution. After lots of research and surfing I picked up another bargain but this time it was a winner !

I found a supplier selling 400W 240V bar style heating elements. These still use a coil of resistive wire but contained within a high temperature glass tube and capped off with ceramic end caps with screw bolt style terminals. I picked up ten elements brand new and boxed for £13 (the lot) delivered from the UK - happy days ! After the low power issue with the first element the first thing I did was pop one of the new elements on the power meter and was happy to get a reading of ~426W.

The plan was to stack eight elements in parallel to give a total power of ~3.2KW

I used two sections of 25mm steel angle iron to support the eight elements. Steel is not a very good conductor of electricity and even worse when hot. So I faced the steel angle with 10mm strips of copper plate to act as bus bars to conduct power efficiently to the heating elements. Each bus bar is then connected up through the lid using 2.5mm copper wire terminated with a ceramic connector block.

To fuse glass you need a temperature of about 800C and copper melts at 1085C. So I figured even if the top of the enclosure was 100-150C hotter than the temperature probe as long as I didn't go any hotter than about 850C the copper would be fine - this has proved to be the case with no issues to report.

Step 7: Finished Kiln and Some Temperature Data

Without adding too many words here is a short video showing the finished Kiln :

The lid is now attached with rear hinges and the heater has been fitted. The underside of the lid has been lined with more ceramic fire blanket mainly to stop metal oxide from falling into the glass chamber during heating.

The Altec temperature controller has an automatic tuning mode which learns the characteristics of the chamber and then automatically updates the control loop PIC parameters. This worked extremely well and after calibration the temperature matches the set point to within +/-1C and even when the sequence is put into hold mode the temperature only overshoots by 1C for about ten seconds - very impressive I thought.

Step 8: Temperature Results From the Kiln

One of the first things I did was to run the kiln at full power and record the temperature at one minute intervals up to 820C and then kill the power and measure the natural fall in temperature again at one minute intervals.

I then plotted the results - this data allows me to work out the maximum rate of heating / cooling at any point on the firing sequence to subsequently optimise the design of the glass firing sequence programmed into the Altec PID controller.

Step 9: First Result From the Kiln .....

Here is the first result from the kiln .....

The pendant on the left came from the microwave kiln I had been using and the pendant on the right from the new traditional kiln which has been the subject of this article.

The right hand pendant show much better shape, colour and no trapped air bubbles :)

Step 10: Conclusion .....

I have had a lot of fun building this kiln and have learned many new skills.

I realise that there is not a huge amount of construction detail in this article so if anyone has got this far and wants to know more about any aspect of the project please feel free to contact me.

One piece of advice I will give ....... when a top loading kiln is at 820C DON'T lift the lid and shove your head in to have a look at the work inside - bad idea, just a thought !

Comments

author
GamersU1 (author)2017-09-03

What terminals did you use for the heating elements?

author
dtrewren (author)GamersU12017-09-03

The heating elements I used had bolt terminals at each end complete with a nut and washer (see step 6). I fabricated two steel angle bus bars. Steel is not a particularly good conductor of electricity especially at temperature so I faced the steel bus bars in copper plate (melting point 1085C. The bus bars were then bolted into the firebrick lid, the bolts being seated into holes in the firebrick filled with high temperature adhesive. The same adhesive used to bond the firebricks together - hope that makes sense ?

author
GamersU1 (author)dtrewren2017-09-03

That makes sense, except that the ones that i found (since the ones you referenced were no longer available) do not have the same terminals as yours. These are the ones that i found but without the terminals (i think): http://www.ebay.co.uk/itm/4x-400W-Halogen-Heater-Replacement-Tubes-195mm-Fire-Bar-Heater-Lamp-Element-Bulb-/331567729860?hash=item4d32fa0cc4:g:oFwAAOSwNSxVZvWN
Anyway, thanks for replying quickly. idk if these will work. Let me know if the don't.
Thanks

author
dtrewren (author)GamersU12017-09-04

Hi, yes I have some of the same elements. They will work fine in terms of heating the kiln. The only thing that needs addressing is how to mount the elements. The elements you have clip into a ceramic spring loaded holder with a connecting wire. The ceramic holder will probably be up to the 800C+ at the top of the kiln but the wiring (outer coating) will probably break down. So you need to make sire the wiring is protected either by running it inside the brick or by surrounding the inner wire in ceramic sleeving. You can buy ceramic sleeve on ebay. I used the sleeve to run the copper connecting wires out of the lid and into the small terminal box on the top of the kiln lid. The ceramic sleeve prevents the copper wire shorting with the metal lid or terminal box.

author
GamersU1 (author)2017-09-01

Just a question, how much did the final build cost? thinking of building my own so I wanted to know how high I should set my budget.

author
dtrewren (author)GamersU12017-09-03

I would say the entire project cost me about £250. Of that about £100 was fire brick, fire blanket and heat tolerant adhesive. The controller was about £80 and the remaining £70 on the rest of the parts. Take into account though, I didn't have to buy the enclosure as this was a scrapped item from my work. Almost all of the small parts I sourced from ebay.

author
zact01 (author)2017-08-19

great instructable thank you. when you were testing the quarts tubes did u just plug them in to mains or was there ohter stuff involved ? when using the quarts tubes did u have a ssr direct mains to the tubes or did they need other stuff between?

sorry if this is coverd abobve. thank you again for the epic instructions

author
dtrewren (author)zact012017-08-20

Hello zact01, the heater elements are rated for 240V so are connected directly to the mains but via a circuit breaker for safety (see the schematic I included in the Instructable). The SSR is rated at over 300V and 40A so is switching 240V mains directly to the heater elements. Again everything is protected using a 20A thermal circuit breaker.

Hope that helps, please fire away if you have any other questions.

Cheers,

Dave

author
zact01 (author)dtrewren2017-08-20

thank you so much ive been very confused as to how htis works.

author
GippoPippo (author)2017-05-17

Hi Dave,

I see, from the Kiln heating temperature profile picture, that your oven, controlled by Altec pc 410, reaches 800 °C.

The data sheet on the back of the pc 410 (see attached picture) says that the max controlled temperature is 400 °C.

How was it possible to rise the max controlled temperature from 400 °C to 800 °C?

Kind regards

Beppe

PC 410.jpeg
author
dtrewren (author)GippoPippo2017-05-17

Hello Beppe,

The controller doesn't really have a concept of temperature but allows a large selection of thermocouples to be used each with its own resistance v temperature characteristic. I have attached a link to the manual - if you look at the very last page there is a table with measurement ranges depending on which thermocouple you are using. I used a type K range -255 to 1395 C, this type has to be selected in the controller menu system.

My controller didn't have a sticker as your does. I suspect the temperature range given is based on the thermocouple supplied and not the controller. Selecting the type K (cAtc) coupler I used the controller works perfectly up to 800 C. Many of these controllers are out there say on ebay and are programmed for specific industrial tasks and I suspect the 0 - 400C range relates to its task - maybe a flow soldering or soldering re-flow machine ?

Link : https://xmoddz.com/images/PC900-410-Manual-XModdz....

Cheers,

Dave

author
GippoPippo (author)dtrewren2017-05-29

Hi Dave,

sorry to disturb you again but I need an information in order to follow up with my project. Do you remember where have you bought your Altec PC 410 Controller? I have just received the controller that I bought from China, it was supposed to be an Altec PC410 but actually it is a fake and I have to find a trusted seller to by another one.

Thanks again

Beppe

author
dtrewren (author)GippoPippo2017-05-29

Hello Beppe,
Oh dear that's a real pain ! I bought mine via Amazon. It was a bit more expensive at £80 but I figured if there was a problem I could send it back.

author
GippoPippo (author)dtrewren2017-05-18

Hi Dave,

thanks a lot for your useful information.

My project is to build a oven for both melting metal and thermal treatment of metals. The max temperature I need is 1250 C, a K thermocouple would be fine. I had ordered a PD 410 (that I have not yet received) but only after the order I noted on the web a picture of the the sticker that I posted above so I had a doubt about the real temperature range.

Well, I have not wasted my money!

These will be my first project with a PID, in the next week I will start some test taking your project as a model.

I will inform you about my progress and may be ask you for some additional tip (if it is possible).

Many thanks

Beppe

author
dtrewren (author)GippoPippo2017-05-18

Hello Beppe,

No problem - I had a bit more of a think about your controller. The label says K type thermocouple. So I suspect the range 0 to 400 C has been set using the setpoint high limit (SP H) and setpoint low limit (SP L) which can be found on page 16 of the manual in the parameter list. I seem to remember setting these to 0 C and 850 C for my kiln so that if left working alone the temperature can never exceed 850 C.

Cheers,

Dave

author
Sharonscott (author)2017-02-05

hi Dave

I was wondering if you're still happy with the kiln. And if there would be anything you would change. As my husband was thinking about making one and I thought a would check before he ordered all the parts .

Kind regards

Sharon , fellow Bristolian ??

author
dtrewren (author)Sharonscott2017-02-05

Hello Sharon,

Yes, still happy with the kiln and it is working well. I had one heater element burn out and had to be replaced but I think that was my fault as I tapped it quite hard while lifting out work and may have cracked it. The maybe a better way of supporting the elements but I have not come up with anything making it worth stripping down and replacing.

If you are local in Bristol your husband is more than welcome to come over and have a look ?

Cheers,

Dave

author
Sharonscott (author)dtrewren2017-02-06

Hi Dave.
That would be great if my husband could come and take a look. Would you mind e mailing him your mobile number so rob could contact you please. His e mail address is rob.scott0069@gmail.com
Many thanks
Sharon ??

author
dtrewren (author)Sharonscott2017-02-07

Hello Sharon, sure no problem. I am in California until the 14th but when I return we can arrange a visit so Rob can check out the kiln first hand. I will email him my number.
Cheers, Dave

author
danwood76 made it! (author)2016-08-02

Hi Dave,

I built a fusing kiln very similar to yours earlier this year, reading your instructable gave me great pointers and ideas on how to complete the project (all in all it took me around 6 months from start to finish, much to the disappointment of my better half :-)).

I loosely based my project on your design. I had my casing fabricated by a local metal worker and based my insulation layering on your setup (case | ceramic fibre | IFB). I also built a frame around it with castors so its easily movable (I think in total it weighs in at around 90kg so the castors are a necessity).

I had really good results from the cheapo coil heating elements off eBay, the ones I got pump out their specified power and get the kiln up to temperature easily. Maybe you had a bad batch?

My partner loves her kiln anyway, she has produced over 10 full firings (up to 9 items in each firing) making loads of different things all fused perfectly.

I would just like to say thank you for your effort in this build and write up, it really helped! I may document my project and upload it if I get some free time (I took lots of pictures).

Danny

IMG_2140_cropped.JPG
author
dtrewren (author)danwood762016-08-05

Hi Danny,

That is an outstanding effort - I have to say you have obviously put in the time because the kiln really looks great, a very professional job. Can you post a couple of images showing the inside and the distribution of the heating elements ? The first lot of heaters I got hold of just didn't produce the rated output power. Also they were difficult to mount in the lid because of the amount of sag when hot. I found the glass encased heaters much easier to work with and had reliable power output. I have been running mine for over a year now with dozens of firings - so far so good.

A very good job, I bet the other half was very pleased with the result !

Cheers,

Dave

author
yonasjob (author)2016-06-14

hello I made glass fusing machine big size 1250x1000x600mm for fusing glass basin. it didn't work could you help me I will send pictures

author
dtrewren (author)yonasjob2016-06-14

Hi yonasjob,

Sure I will help if I can, please send some pictures .....

author
matrixmechanics (author)2016-04-17

Hello I want to build a kiln that can plug into a 110volt outlet. Can someone please recomened a programable controller that will work well for me. Thank you.

author
dtrewren made it! (author)matrixmechanics2016-04-18

Hi matrixmechanics,

The Altec410 controller I used in this project is rated for an input 100 - 250v AC, see the attached image. Therefore, you are fine to use this controller for a Kiln design on a 110VAC supply. I suspect this will be try of the entire Altec controller range - but check first or send me the model number.

Cheers,

Dave

Altec 410.jpg
author
dpswords (author)2015-12-24

hi dave

awesome project. Im thinking about doint the same thing any mord info on the actual build details. Cant believe how expensive a glass kiln is in the UK. The electrics are the big financial issue. Im new to this glass melting stuff but dont understand what u cant do I.e only fusing no casting? On certain kiln types it seems, anyhoo big respect on sharing your electric kiln project.

thanks

dodgy dave the builder

author
dpswords (author)dpswords2015-12-31

Hi dave
many thanks for the diagram greatly appreciated. How do I give u my email address without publishing it here? Im contactable via my website basicplumbingcourse.com
thanks
Dave

author
dpswords (author)dpswords2015-12-30

Hi dave
Thanks for your reply, been having a bit of time off with no email bliss. Im really interested in all the build details to replicate what u built as it obviously works. Really keen to build it asap.
I have taken on board your comment on the max temp on some copper parts you used. So I guess its a parts list and how to wire it all together are the important things but any info would be greatly appreciated as I have no idea how to build this but used to following instructions from structural engineers etc. Think I will leave the glass slumping for now and keen to build this as my hot pot for microwave glass melting is a bit of a nightmare to get it right.

have a good new year and many thanks for you help.
dave

author
dtrewren made it! (author)dpswords2015-12-30

Hi Dave,

Sure I can help you with construction detail. I have attached a electrical schematic based around the Altec temperature controller I used. I don't have a comprehensive parts list as such as just picked things up ad-hoc as I found them.

Would is be easier if you contacted me directly (via email) rather than using the forum ?

Cheers,

Dave

Kiln schematic.jpg
author
dtrewren (author)dpswords2015-12-25

Hi Dodgy Dave,

Sure I can give more build details - which specific aspect of the build would you like to know more about ? You are right the cost of kilns in the UK is crazy, they are so much cheaper in the US. The problem is by the time you have paid import duty, VAT and shipping something of that weight I am not sure how much of a saving you will see. The only thing of value in the electrics is the temperature controller which is about £50. Most of the other electrical items are quite cheap - for example the solid state relay is under £5 ! The heating elements were on a few pounds each.

My Kiln is good to about 850C at the bottom of the kiln. I think it would go higher but I have used copper bus bars in the lid section and copper melts at 1085C so I have to be careful not to get too close to that temperature. For glass fusing, glass casting and slumping 850C as a top temperature is just fine. For metal casting I think you might have to rethink the design.

Let me know where you need more detail ....

Cheers,

Dave

author
dtrewren (author)2015-12-16

Hi Hampy,

I had a look at your microwave glass fusing experiment with temperature control. One question - what was the compressed air for, couldn't see what it was being used for ?

I played around with using microwaves for fusing with vary degrees of success. I have found the electric kiln built in this instructable produces very consistent results time after time. I must of used the kiln well over fifty times now and it has never let me down.

Cheer,

Dave

author
HampyD (author)dtrewren2015-12-18

Hi Dave,

the compressed air is good for cooling the magnetron in the microwave after a long time working with maximum power. Without cooling it would be to hot after a period of 40 until 60 minutes.

Cheer,

Hampy

author
NagarajanK (author)2015-03-19

Thank you for giving this. i was searching for the same requirement. I want to build a kiln for fusing 2 inch thick 16 inch dia plate glass for telescope mirror having inner size of L=19inchs, B=19inchs and H=8 or 9 inches which ever is permissibly lower. i fairly got the construction part but confused with element and power requirement. as per some literature it needs up to 8000w but commercial ones are around 3000-3500 watts. since i don't have the subject background im struggling. can you help me to choose correct element size, wattage and breaker. i measured my house socket voltage is 217 V. rest of the connections and circuit i can manage comfortably

author
dtrewren (author)NagarajanK2015-03-20

Hello NagarajanK,

I hope I can help. Choosing the heating elements was
one of the most time consuming exercises. In the end I used these
elements :

http://www.ebay.co.uk/itm/331464454384?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

These elements are quite short as my kiln opening is only
23cm by 35cm. Your kiln is considerably larger so you might need to find
longer elements. There are lots of Quartz and Infra Red elements on the
market. The tricky bit is not the heater but the means of getting power
to it. Most heater end connectors and cables are not designed to
withstand 800C and above. This is why I chose elements with bolt type
terminals at the ends to I could build my own bus bar style connectors to hold
all the elements in place. If you use a standard push fit type connector
it will need to be buried in either fire brick or fire blanket to protect it
from heat.

I used eight elements giving me a total of 8 x 400 =
3200W. I get a little less than this because of the voltage drop out to
my workshop. My final voltage is about 225V so the current (assuming a
resistive load) is 3200 / 225 = 14.2A. I used a mains switch rated at 20A
and a circuit breaker rated at 20A. However, my workshop ring main has a
circuit breaker rated at 16A so this would trip first if there was a problem.

All the connector blocks I used were rated at 30A and all
the hook up wire is rated at 16A at 250V.

The solid state relay I used is rated at 40A at 380V so more
than capable of switch the heater load.

Please ask away if you have more specific questions.

Cheers,


Dave

author
NagarajanK (author)dtrewren2015-03-23

small correction 13.225 Ohms was calculated based on 230V and 4000 Watts. so if the voltage drops to 217-220 the wattage will be 3560.605-3659.735 respectively which is more than the design valye of 3515 Watts. Well its not a small correction actually a blunder.

Thanks
Nagarajan K

author
BShaveta (author)NagarajanK2015-12-17

Hi Nagarajan! Are you from india? Need some help regarding glass kiln construction. Thanks Shaveta

author
NagarajanK (author)dtrewren2015-03-24

Dear Mr.Dave,
I found another information today. after comparing pictures of your element and the one i planed i found both are diffrent. yours was a medium wave and the one i posted is short wave. short waves tubes gives narrow emission which is good for spot heating but for glass we need wide uniform heating. Profusion 16 kiln also uses medium wave tube as seen in the picture and these are made to order according to size and length. The new vendor suggesting me to go for 500Watts X 8 (19 inch tube + extra for connector) rated for 110V connected in series for optimal surface loading. He promised to send me drawing and quote. He could be either suggesting the right thing or taking me for ride by selling 8 tubes instead of 4. Don't know whether to trust or not. Could you check his suggesting is right or am i being taken for a ride. Every reply from excites me to complete this project.

Regards
Nagarajan K

author
NagarajanK (author)dtrewren2015-03-23

Dear Mr.Dave,
        Apologies  for the delay as i was out of station. i don't want to write in hurry. After seeing your kiln i dropped the coil element for Quartz tube. i made some enquirey and found a vendor and he suggested same type as yours but my kiln width is 19inches so choose one close to my requirement, an 18 inches tube 1000Watts at 230 V. funny thing is cost of the tube is based on size not wattage (Euro 40.42). 600, 800, 1000W all costs same. i choose to go for 1000W X 4. it looks similar to this.

http://tinyurl.com/qd5hfoz


   I arived at the 3515 wattage @13.225 Ohms and  230v requirement based on 

http://www.joppaglass.com/.../dudleys_element_paper_2012.pdf

http://www.euclids.com/Html%20pages/element-design.htm

but my average output at my house  is 217 to 221 which will bring the wattage to 3560.605 - 3659.735 Watts respectively which is slightly more than the calculated requirement of 3515 Watts. I don't want to calculate ohms based on 220 volts as it the over shoot amperage above 20A if their is any spike. i choose to make the insulation out of 3 inch ceramic fiber board as its lightweight as well as more efficient insulators as per Dudleys paper. I also found commercial kilns of my size with almost similar spec. the kiln will be bottom open as i guess hot air raises to the top and any gap at top increases heat loss than at the bottom. 

http://jenkenkilns.blogspot.in/p/profusion-series-af3p-16-square.html

http://www.paragonweb.com/Fusion-19.cfm

   For the ramp/soak controller i prefer to go with 

http://www.selec.com/pr502      (Euro 52)

but  vendor is suggesting some other brand which is twise the cost.
other things are 20A breaker, Ceramic thermostat etc. Can you confirm these values are correct and or the over all design is a dud. I profoundly thank you for the help. when i saw you mail felt like a thirst  person on desert finding an  oasis 

Nagarajan K





author
dtrewren (author)NagarajanK2015-03-23

Hello NagarajanK,

Very good, sounds like you have some very good information - I like the article I wish I had found this information before I started. I think the 3 inch fibre board is a very good idea. It is much better (maybe x5 times) than ceramic fire brick and much much lighter. My kiln although it works well is extremely heavy to the point where I can almost not move it on my own. The only question I would ask here ..... when I looked into using fibre board I was told it could not be used as the primary insulator. By that I mean I didn't think it could be used directly exposed to the heating elements - could be wrong here but that I what I was lead to believe, might be worth checking ?

Heating elements look great ! Just make sure you bury the end connectors and wire into the insulation - I doubt they will like 800C+

Your power calculations look ok, I think you will have more than enought power. I wanted to run my kiln from a standard UK 13A mains power outlet and I an at about 13-14A. The circuit breaker I used was one like this :

http://www.ebay.co.uk/itm/Joemex-Pe74-20a-Circuit-...

I did not use a ceramic thermocouple but used this K-type device which is specified up to 1200C

http://www.ebay.co.uk/itm/281079355002

The thermocouple has worked perfectly, I have never taken the temperature over 850C at the bottom of the kiln as the conductors at the top of the kiln are copper and will melt at ~1060C.

Your PID temperature control unit looks fine. There are many on the market and they all do basically the same thing.

Look forward to seeing some photos and an Inststructable :)

Cheers,

Dave

author
HampyD (author)2015-12-16

Hello,

very instructive your kiln project. If you interested in my project look to youtube:

Mikrowellen-Fusingofen

Cheers

Hampy

author
hopeof1 (author)2015-10-08

Dave,

Thanks a lot for the schematic.

author
dtrewren made it! (author)2015-09-30

Hello Jahn,

Sorry for the delay, I was on holiday in France. I have drawn a schematic of the kiln based around the Altec PC410 PID controller I used. If you have questions please fire away. Please be careful if you build your own kiln - whether you are experienced or not live mains can and will kill.

Cheers,

Dave

Kiln schematic.jpg
author
hopeof1 (author)2015-09-27

Thank you for your nice kiln project (Home made electric glass fusing kiln).

Is there an electric schematic available( drawn by hand only is OK)?

Thanks

BR,

Jahn

author
zozlefou (author)2015-06-05

I Mr.dave
i would like to know how much did you spend for the kiln and if it possible to have the shema of electricity ?. Very nice project end up very clean . im also build a kiln is a little bit different ( front door for glass blowing ) and not clean like yours ahahaha . (sorry for my english is not my first language) thank you

author
dtrewren (author)zozlefou2015-07-05

Hello zozlefou,

Sorry for the very slow response - didn't get post email for some reason ....

I was lucky in that the main enclosure was obtained from work as was being scrapped. The bricks, tolerant adhesive and fire blanket cost around £100 in total. The PID controller was about £60 from ebay and the thermocouple about £10 also from ebay. So I suppose including other electrical items the entire build came to around £210 give or take a bit.

Hope this helps,

Dave

author
drbrodie (author)2015-06-04

Thanks for sharing your design. It's not clear to me what holds the fire bricks in the lid from falling. Is it simply the clamping force of the metal frame? Thanks in advance for your answer.

author
dtrewren (author)drbrodie2015-07-05

Hello drbrodie,

Sorry for the very slow reply - for some reason I didn't get an email informaing me of your post.

The bricks in the lid are first bonded together using a heat tolerant adhesive. The metal frame does hold the brick array reasonably firmly. However, the self tap bolts used to bolt the frame together extend into the brick array making up the lid and prevent it from slipping within the metal frame,

Hope this makes sense, please fire away if you need more detail.

Cheers,

Dave

author
dtrewren (author)2015-03-31

Hi Paul @ FirePlug,

Very pleased you like the design !

The insulating brick and fire blanket perform really well. Not surprisingly the hottest part of the kiln is the top of the lid. I have a contactless temperature gun and the top of the lid with the kiln at 800C reaches a temperature of about 120C. The sides of the enclosure towards the top reach about 70C - so you don't want to put your hand on the kiln but nothing is going to melt or catch fire :)

I did all the brick & blanket cutting outside with a basic dust mask. I would not recommend cutting or profiling inside. Aside from the health issues it makes a massive mess ! I would also recommend wearing some type of thin glove maybe surgical gloves when handling the blanket as it can get a bit itchy.

Thanks to you Paul and the other guys at FirePlug for your help and materials.

Cheers,

Dave & Ava

author
FirePlug3 (author)2015-03-31

Hi Dave

Paul here from Complete Fire Protection (FirePlug) Thank you for giving us a mention.

Very impressive what you have achieved with the glass fusing kiln. How has the fibre blanket and insulating bricks performed? Do you know what is the outer temperature of the box whilst the kiln is at full flow.

Just to put your mind at ease the Fibre Blanket is body soluble making this blanket safe should you accidentally inhale particles, However whilst working with fibre's of any kind you should always wear a mask. I would advise all budding instructables to always seek out Body soluble fibre blanket.

Thanks Dave your kiln looks fantastic and we are glad we could help in any way.

Regards

Paul

author
NagarajanK (author)2015-03-25

Dear Mr.Dave,

Thanks for the confirmation. at my home we have 3phase each phase with 32A. wall socket with dedicated line having 20A breaker. this line is not connected to any other device. usually for air-conditioner or water heaters. 3996W @ 230V is around 17A but available voltage is 217V. This i hope will keep the amps below 20A. before taking delivery ill check the the element resistance value which should be 5.791Ohms rated for 666W @ 115V ( hope my Ohms law calculation is correct :) but i learned resistance value changes in temperature. so i have to partially believe the vendor moreover its custom build. to measure the current i thing i have to go with a borrowed clamp meter from a friend, my multimeter is plain vanilla. PID controller model i choose with SSR support will take time for delivery as i don't want to go with mechanical relay. hoping to complete it within two weeks.

Nagarajan K

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