Laboratory oven -> Reflow oven?

[JaspaJami]

I have one Heraeus T5028 laboratory oven at warehouse without any use. Last time it was used as a egg incubator (this picture is not from my oven, but its same).
http://www.handelskontor-freitag.de/Verkauft/Heraeus-Waermeschrank-ST-5028-250-C-Heissluft-Sterilisator.html

Its quite big from inside, about 29 liters, and its no powerfull at all with about 800w.

But its quite nice looking, its very well insulated already. There is small latch top of the oven that can be opened.

What do you think? Can this be reused as a reflow oven? Is glass door how handy, this doesn't have that. For sure this need new heating elements.

[Pinkus]

A glass window is a must in my opinion as different PCBs need a different profile and you need to check the PCB / soldering during the reflow phase. Especially with prototypes this is very helpful. Of course you can work without a window but you will miss it.
Also 29 liters volume is quite large - maybe too large to run a standard temperature profile.

[wraper]

Won't work. Too large volume, too little power. It should have like 8 times more power to do the job.

[JaspaJami]

maybe too large to run a standard temperature profile.

Why, if i have power to compensate that?

Of course it easier to stay in 1 phase, 16A, 230VAC. But i have 3 phase, 16A, 400VAC at lab (and if needed even more, because i dont have yet cables to coming lab and i have 3x35A fuses to house).

But yes, i agree, it is kind a large. But another oven + insulation is quite costly. Mostly im thinking of that window. I havent checked if its easy to make window to this oven (there is also models with window).

[JaspaJami]

Won't work. Too large volume, too little power. It should have like 8 times more power to do the job.

Idea was to but totally new heating elements. I can easily but at least 3500w. If needed, with 3 phase much more.

[Richard Crowley]

Isn't it also an issue with the thermal inertia of a large oven?
You can't control the fast temperature profile on the typical curve with a big oven like that.

[ElektroQuark]

That oven is sloooooow. It has to much thermal inertia.
Home little ovens are slow too (take a look at my Youtube channel where I test one that finally gets modified).

[wraper]

But yes, i agree, it is kind a large. But another oven + insulation is quite costly. Mostly im thinking of that window. I havent checked if its easy to make window to this oven (there is also models with window).

Thermal insulation is an enemy in this case. What you want is oven that heats up very fast and cools down fast as well.

[JaspaJami]

That oven is sloooooow. It has to much thermal inertia.
Home little ovens are slow too (take a look at my Youtube channel where I test one that finally gets modified).

I did check them. Well i dont speak spanish but final modification was to add more power, those quartz heaters. Same idea was for me.

So idea was, is it possible or wise to modify this oven to reflow oven. Better reflective insulation to inside, maybe 3500w of quartz tubes for heating, aluminium/copper plate for the pcb:s

[jmelson]

The only way to use this is to preheat the oven, and then slide each board in for a set time, and remove.
That doesn't allow you to do the ramp - hold at 180 C - ramp - hold at 240 C (or whatever) - cool
profile.  But, lots of people have reported pretty good results with kitchen pans on a hotplate, so it likely will work once you find the right combination of temperature and time.

You will have to come up with some scheme to place the board in a hot oven and then remove the board without jostling it too much, while the solder is liquid.

I cool the boards on the oven rack until it is down to around 100 C before removing from the oven.  My toaster oven heats and cools the boards a lot faster that your lab oven could, by IR radiation.

Jon

[JaspaJami]

My toaster oven heats and cools the boards a lot faster that your lab oven could, by IR radiation.

Cooling down fast can be a problem. But i don't exactly understand why this would be so much slower to heat up? If i use similar heaters but more power to compensate that volume. And most likely stronger insulation.

[JaspaJami]

I think that even if i dont use this i have to make a test Install 3500/3600w of heating power and then measure how fast it can heat up.

[wraper]

My toaster oven heats and cools the boards a lot faster that your lab oven could, by IR radiation.

Cooling down fast can be a problem. But i don't exactly understand why this would be so much slower to heat up? If i use similar heaters but more power to compensate that volume. And most likely stronger insulation.

And where the heat goes away except opening the door in a right moment. It simpler to build an oven from a ground up rather that modifying this thing to work decently.

[JaspaJami]

For cooling down door opening can be automated also.

[wraper]

For cooling down door opening can be automated also.

First of all, it's not a right way to do the thing. Secondly, you'll end up attaching a rocket engine to this poor oven in effort making it do the task.

[JaspaJami]

i believe that its not maybe good idea to use this. But i think i can anyway test (even just for the curiosity) what kind of heating ramp i can achieve. Only parts that i need for that what i dont allready have are those quartz heating tubes. And most likely i need them anyway in another oven.

Oven most likely have to order from outside of Finland. Those ovens are not very popular here and very hard to find.

[ar__systems]

Please don't use quartz heating tube. They are the worst. They heat via IR, leading to very uneven temperatures on the PCB.

[JaspaJami]

Please don't use quartz heating tube. They are the worst. They heat via IR, leading to very uneven temperatures on the PCB.

When then i have misunderstand. What kind of heaters you recommend?

EDIT: reason why i thought quartz would be ok was this one i think

"Type of element - the elements should ideally be quick to heat up and cool down. Resistive heating elements are extremely slow to heat up and cool down, and make it difficult to follow a reflow profile. Infrared elements are usually a poor choice because they heat up dark components before lighter or shiny ones. Commercial ovens use infrared elements, but only to heat the air which is then blown onto the boards. The compromise is to use quartz infrared elements which emit less IR. They are typically shielded with a perforated steel sheet which limits direct radiation. Also, Controleo3 will limit how much the top element is used to further reduce uneven heating."

http://www.whizoo.com/reflowoven

[ElektroQuark]

I used common halogen lamps.

[wraper]

Resistive heating elements are extremely slow to heat up and cool down, and make it difficult to follow a reflow profile.

Please tell me which heating elements are not resistive. Like inductive or which don't use electricity?

[JaspaJami]

Resistive heating elements are extremely slow to heat up and cool down, and make it difficult to follow a reflow profile.

Please tell me which heating elements are not resistive. Like inductive or which don't use electricity?

Thats not my text Putting fire under the oven?


But i think its quite clear what kind of heating elements that text is meaning by that.

[luiHS]

 

A sterilization furnace like that has no control to apply a welding curve, nor fans to maintain precise control of temperature.

I would not use it to solder electronic components. In addition, today you have the T962 Chinese ovens, which are very economical and are made expressly for soldering electronic circuits.  I have a T962A and T962C, and I am very happy, they work very well, I also had the smallest model that I sold to buy the biggest ones.

[JaspaJami]

A sterilization furnace like that has no control to apply a welding curve, nor fans to maintain precise control of temperature.

For sure, but question was that could this be modified to that use.

In addition, today you have the T962 Chinese ovens, which are very economical and are made expressly for soldering electronic circuits.  I have a T962A and T962C, and I am very happy, they work very well, I also had the smallest model that I sold to buy the biggest ones.

Thanks, have to check more of those. If the really work price is not so bad

[SMdude]

I have a T962A and it works quite well for what I do with it.
Do some research, there are some modifications and modified firmware for them, which after that has been done work well.

To modify the oven you already have, you would be better off just starting from scratch and making your own.

Keep it for drying moisture from boards and components.

[JaspaJami]

Keep it for drying moisture from boards and components.

Thats maybe best one

Thanks for the help for everyone. Where i can find info of those different models of those T-9xxx ovens? And what modifications are recommended

EDIT: seems that here is quite good info about T-962A oven: https://esden.net/2017/11/27/upgrading-a-t962a-reflow-oven/

EDIT2: https://github.com/UnifiedEngineering/T-962-improvements

[luiHS]

A sterilization furnace like that has no control to apply a welding curve, nor fans to maintain precise control of temperature.

For sure, but question was that could this be modified to that use.

It may be that you can add temperature sensors and electronic control with PID to apply a welding curve, but I do not think you can add fans. The precise and constant control requires both, heaters and coolers (fans).

[luiHS]

Keep it for drying moisture from boards and components.

Thats maybe best one

Thanks for the help for everyone. Where i can find info of those different models of those T-9xxx ovens? And what modifications are recommended

EDIT: seems that here is quite good info about T-962A oven: https://esden.net/2017/11/27/upgrading-a-t962a-reflow-oven/

EDIT2: https://github.com/UnifiedEngineering/T-962-improvements

You can find all the T962x on Aliexpress and Ebay. I ordered my T962C from a Chinese, but with shipping from Germany, ideal for Europe to avoid customs taxes.

On the improvement, one is to replace the masking tape with Kapton tape, for more precise control of temperature, improved performance and lower consumption. Also some firmware update. In any case, I have all my original T962x, never modified and work very well. I prefer not to modify them.

The only thing I do not like is that when the welding time is over (7 minutes), it starts beeping and does not stop until you press the STOP button. I guess it will be one of the improvements to the firmware update.

[wraper]

I have a T962A and T962C, and I am very happy, they work very well, I also had the smallest model that I sold to buy the biggest ones.

AFAIK they work 'well' only if you reflow single pieces of small boards. Once you start reflowing large boards, hot/cold spots become a huge problem.

[luiHS]

I have a T962A and T962C, and I am very happy, they work very well, I also had the smallest model that I sold to buy the biggest ones.

AFAIK they work 'well' only if you reflow single pieces of small boards. Once you start reflowing large boards, hot/cold spots become a huge problem.

Most of my PCB are 380 x 130 mm and everything works perfectly, I even have one of 367 x 177 mm, and there is no problem.

If you have problems with PCB that come out with unwelded components, it is because they are putting too many PCB or they are too big for the capacity of the oven. To avoid that problem, simply do not fill the baking tray beyond 60 or 70% of its capacity, or if you have PCB with many components, weld them one by one or more depending on the size of the PCB and the capacity of the oven.

Right now I am welding several of my PCB, all large, of the dimensions I have mentioned, in my T962C, and they all come out perfect.

[flasonsmts]

that reflow oven you suggested is not very good, it's infrared reflow oven , which is invented 60 years ago, the IR reflow oven has too much shortage like big components will take heat from small component, different color component got different heat , black got more, white or silver got few, this will make some component got too much heat increased too fast and be dsitroyed. the temperature diviation on is big different on PCB. So nowadays most reflow oven use the hot air convection heating method.

[Doctorandus_P]

from wat i know about all the different ovens it is best to start with a cheap oven as used in kitchens, and then extend it with a decent temperature controller.

With a hot air oven the temperature will be relatively evenly divided, except for near the hot air outlet. Sometimes these blow too hard and blow components off the pcb.

For an IR grill like oven (these are often the smallest) you can add a metal plate to shield your pcb from direct IR and add a small fan to stir the air a bit.
The motor is preferably outside of the heated compartment, with only yhe axle sticking through.

For really low budget, a scrapped combi mircowave with a worn out microwave tube would be an ideal start. It has the cabinet with look through door, heating elements, fans, relay's and even a low voltage power supply for the temperature controller, and storage space to put it in.

From what I've heard the cheaper purpose built ovens are not so good, unless modified extensively, and the professional ovens are pretty expensive. And that is why a kitchen oven is a decent start for a diy project.

[Savl]

Hi to every one.
I have T-962A+ reflow oven. It constantly beeping .
Immediately after selecting stand alone mode it start with reflow  (profile 1), I don’t even have time to enter menue to change the reflow  profile, it start to constantly beeping. During operation it stops about half the  cycle, then menu appear , then it starts again from the beginning.  Can anyone help, what may be the problem ?

Thank you in advance