- Joined
- Jun 11, 2006
- Messages
- 8,650
So I know I have been absent lately and my build threads have been missed. I have been quite busy with switching departments at work and all the heat treating. So I figured it was time to Bring you along on a current project I’m undertaking.
This project started out with the desire to have a dedicated tempering oven. The wife was tired of having blades and chunks of steel in her oven. So I went looking for an oven to mod. This ended up leading me to a oven for sale on Craigslist. He wanted an ok amount of money for it but said it was 480v 3ph. I talked to him alittle bit about it and he said well make an offer. I kinda himhawed aroynd and he tossed out $50 and it’s yours. Sold I said I will be down tomorrow to get it.
This is the oven I got for $50
It has an internal size of 24”x24”x50 and has a circulation fan that draws the air from the bottom and blows it across the heating elements and back into the top of the oven through a big diffuser plate.
To my delight I discovered that the control panel ran off 12v and only the elaments where 480v 3ph.
I removed the elaments and reconfigured then to the lowest ohms possible and for 240v single phase. But that only netted me around 1600w of power.
I tried looking for a replacement 6kw watlow element but was shocked by the prices. Thy wanted like $1,500+ for one. So I kinda looked around and thought I had an idea what I would do. But the project ended up on the back burner so to speak. Then we almost had a catastrophe when the wife fired up her oven to cook something. I still had a large batch of blades in there cooling from there last temper cycle. We lucked out because she checked the oven as it was heating and found the blades. Blades where perfectly fine as thy where between 1/2” thick sheets of steel. But thy all got HRC tested agian just to make sure. Any way this sparked the build agian and brings us up current.
I went looking for elaments and had kinda thought I would use a furnace elament unit and almost bought it till I found out thy are only rated for 250°. So I started searching agian and came across these 5,000W finned elements rated at 800°.
We also bought another watlow pid to match the one it allrrady has.
These are currently on there way to me as we speak. So I started planning out how I was going to do the wiring. The plan was to use the 2 elaments in a duel set up so one pid controller could switch them from series to parallel and back. This would give me a high and low mode of sorts 10,000w and 5,000w. So when the oven hit 300° it would switch to 5000w mode and idle. That’s one reasion we bought the extra pid. The oven has 3 thermal couples built in. 2 in the bottom and one up top where the air enters befor the defuser. The pid on the controller runs off one of the lower TC’s and there is a safey sensor that’s wired to the upper TC that kicks the elaments off at X temp. This was to protect the elements and the parts thy where curing. My plan is to wire the second pid to the upper TC that way I can see the upper and lower temp and set a exceptable temp spread.
But in my research of what I thought was an SSR I found out it is a proportional output. Meaning the pid controller does not output and on/off command. It puts out a 4-20ma signal that this “SSR” sees and then sends out the appropriate power to match. 4ma=0% and 20ma=100%. So what this means is this oven does not cycle on and off, it adjusts the power output to match the temp needed. I am blown away, I can’t imagine how much this thing cost to have built for them and I picked it up for $50. What this effectily means is I can put blades in a cold oven and not wory about it over heating them as it heats up. This is crazy to me becaus I come from a pid world where it’s on or off. We are still going to install the second pid and run it off the upper TC and use it to replace the safety temp “sensor”. That sensor is only adjustable up to like 350° I think and it’s analog with an adjustment screw.
So I will post more pictures as I continue this build/mod. But I’m really excited about this type of controlling as it will open the door to other projects. I have a gas valve that takes the same 4-20ma to vary the output psi. So this has me thinking about building a forge control that varys the gas pressure to control the forge temp. Or even heat treat ovens. The possibilits are endless.
Thanks guys, hope it was not to boring - JT
This project started out with the desire to have a dedicated tempering oven. The wife was tired of having blades and chunks of steel in her oven. So I went looking for an oven to mod. This ended up leading me to a oven for sale on Craigslist. He wanted an ok amount of money for it but said it was 480v 3ph. I talked to him alittle bit about it and he said well make an offer. I kinda himhawed aroynd and he tossed out $50 and it’s yours. Sold I said I will be down tomorrow to get it.
This is the oven I got for $50
It has an internal size of 24”x24”x50 and has a circulation fan that draws the air from the bottom and blows it across the heating elements and back into the top of the oven through a big diffuser plate.
To my delight I discovered that the control panel ran off 12v and only the elaments where 480v 3ph.
I removed the elaments and reconfigured then to the lowest ohms possible and for 240v single phase. But that only netted me around 1600w of power.
I tried looking for a replacement 6kw watlow element but was shocked by the prices. Thy wanted like $1,500+ for one. So I kinda looked around and thought I had an idea what I would do. But the project ended up on the back burner so to speak. Then we almost had a catastrophe when the wife fired up her oven to cook something. I still had a large batch of blades in there cooling from there last temper cycle. We lucked out because she checked the oven as it was heating and found the blades. Blades where perfectly fine as thy where between 1/2” thick sheets of steel. But thy all got HRC tested agian just to make sure. Any way this sparked the build agian and brings us up current.
I went looking for elaments and had kinda thought I would use a furnace elament unit and almost bought it till I found out thy are only rated for 250°. So I started searching agian and came across these 5,000W finned elements rated at 800°.
We also bought another watlow pid to match the one it allrrady has.
These are currently on there way to me as we speak. So I started planning out how I was going to do the wiring. The plan was to use the 2 elaments in a duel set up so one pid controller could switch them from series to parallel and back. This would give me a high and low mode of sorts 10,000w and 5,000w. So when the oven hit 300° it would switch to 5000w mode and idle. That’s one reasion we bought the extra pid. The oven has 3 thermal couples built in. 2 in the bottom and one up top where the air enters befor the defuser. The pid on the controller runs off one of the lower TC’s and there is a safey sensor that’s wired to the upper TC that kicks the elaments off at X temp. This was to protect the elements and the parts thy where curing. My plan is to wire the second pid to the upper TC that way I can see the upper and lower temp and set a exceptable temp spread.
But in my research of what I thought was an SSR I found out it is a proportional output. Meaning the pid controller does not output and on/off command. It puts out a 4-20ma signal that this “SSR” sees and then sends out the appropriate power to match. 4ma=0% and 20ma=100%. So what this means is this oven does not cycle on and off, it adjusts the power output to match the temp needed. I am blown away, I can’t imagine how much this thing cost to have built for them and I picked it up for $50. What this effectily means is I can put blades in a cold oven and not wory about it over heating them as it heats up. This is crazy to me becaus I come from a pid world where it’s on or off. We are still going to install the second pid and run it off the upper TC and use it to replace the safety temp “sensor”. That sensor is only adjustable up to like 350° I think and it’s analog with an adjustment screw.
So I will post more pictures as I continue this build/mod. But I’m really excited about this type of controlling as it will open the door to other projects. I have a gas valve that takes the same 4-20ma to vary the output psi. So this has me thinking about building a forge control that varys the gas pressure to control the forge temp. Or even heat treat ovens. The possibilits are endless.
Thanks guys, hope it was not to boring - JT