Pid controled forge problem.

[JTknives]

Well i think my pid controlled forge has a problem. Or maybe it's just me. I did move the gas inlet to the burner and not the blower as i was smelling leaking gas. But last night i was doing some forging and started up the forge and set it to 2000 deg and let it warm up. I only have one speed controll connected right now so it pulses on and off. So after it warned up i started forging and after say like 5 min i noticed that the forge was pulsing on and off like every sec. I looked at the temp and it was smack on 2k and so i watched it for 5 min and it very only 1 deg in the plus or minus. I could not beleave it. The inside of the forge was an amazing even color. So i finished forging and then ground the knife and went to heat treat. I set it to 1525 at the same thing held it spot on what i set it to. I was shocked. The heat treat oven at work cant hold a temp that close. But my question is this. Is it bad that it is turning on and off every 1 to 2 sec. And how do i change the margin of its holding temp.

 

[efleming]

But my question is this. Is it bad that it is turning on and off every 1 to 2 sec. And how do i change the margin of its holding temp.

Hello JT,

Is your entire flame turning on and off every 1 to 2 seconds or are you running a bypass system that simply allows your flame to keep burning at a reduced rate each time the solenoid clicks on and off? It is very normal for the solenoid to click on and off every 1-2 seconds to hold the heat within a few degrees of set temp. If you do not have a bypass that keeps the flame lit between on/off cycles, id be concerned when you are running at lower heats. Here is a pic of my bypass setup to give you an idea of what I mean. Can you post a pic of yours?

Eric

 

[sharpeknives]

Can't you set the margine of temp with the controler. I don't think the cycleing every second would hurt anything. Course I have been known to be wrong.

 

[JTknives]

I do have a bypass system but i have not installed another fan speed controller for the low burn yet. It seams to be working great at the higher temps but ya i would worry about lower temps and not lighting the gas. I was just wondering if that kind of cycle rate is normal or am i going to damage my gas valve. But i am impressed with how much control you have with the pid. Now i am not guessing at my heat treat temps.

 

[efleming]

I agree JT. Fantastic control with this setup. I'm experiencing a +- 1 degree variation typically. No more guessing. My first solenoid stays on the entire time as a safety shutoff in the event of a power failure. My second solenoid valve cycles every 1 second or so. This is quite normal to maintain that kind of temperature control.

Eric

 

[Fred.Rowe]

JT,

How do you have your fan wired? Do you have a rheostat on the high fan side with no rheostat on the low burn side?

If that be the case; move the rheostat to the low fan side and run the high side fan at full power.

The way you have your post worded, says your fan is cycling off and on.

This should not be the case.

Fred

 

[Stacy E. Apelt - Bladesmith]

Yeah, Fred, I was worried about that, too.

JT you can set the range for the PID so the oven holds at +/- 5 degrees and will take a little longer between cycles. I explained that in the paperwork and schematics I sent you ( has the second controller got there yet?). The only real worry on the cycling is the solenoid wearing out. The SSR is rated at something like 100,000 cycles, and the PID doesn't care how often it cycles. The fan only goes from low to high (when you have the other controller installed) and it won't be affected. With the PID set at an exact number, and the system fully soaked, a 1 degree range is not unusual.

I sent a full schematic diagram to JT for him to clean up with a drawing program. I will post it here when he has it done. I have also made a setup and calibration procedure tutorial to post with it.
I have a little more to do on "The Ultimate Controller Box", and it will be ready to unveil ( by summer, for sure). If I was the sort that cared ,I'd patent it, but I'd rather give it away to the knife community.
Stay tuned kids.

Stacy