Improving heat distribution

[bgrigoriu]

Hi everyone, Just received my T962 and doing some initial testing. After reading a lot of post the thing that was still apparent for me is that the heat distribution is uneven. Using a fan improves it but power is insufficient to heat-up enough fast and high.
Did anyone test adding one/two lamps (apart from the issues regarding power dissipation over the triac) ? Does it improves anything ? I am not a fan of radical changes but mechanically it is do-able. I would like to spare time if anyone has already done it (Just ADDING the same type of lamp).

Second question: it seems evident that there is left to right gradient of temp . Did somebody has an sound explanation for this ?

[affetus]

I don't understand what you mean with "seal the airflow so that air is not sucked from outside the chamber during cooldown" : the air will be sucked from where in your new design ?

Maybe there are variations in the manufacturing process, but in my unit the rear fan was not completely sealed to the plate which holds the slats, so there was air leakage from the inside of the main chassis, i.e. the space which also contains the electronics.

[xnk]

Yeah it seems to be a bit of hit-or-miss how well things are put together, some units have wide gaps, others not so much. The whole concept of placing the electronics on top of the oven is a bit sub-optimal, and their mitigation using that really annoying 40mm system fan to cool the electronics seems to be a bit of an afterthought (that somehow stuck).

On 10 Feb 2022, at 08:48, affetus @.***> wrote:

I don't understand what you mean with "seal the airflow so that air is not sucked from outside the chamber during cooldown" : the air will be sucked from where in your new design ?

Maybe there are variations in the manufacturing process, but in my unit the rear fan was not completely sealed to the plate which holds the slats, so there was air leakage from the inside of the main chassis, i.e. the space which also contains the electronics.

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[xnk]

You go right ahead and modify :) Although you don’t even need to modify the firmware in order to turn the fan circulation off. Fan will still turn on if temperature overshoots the curve during reflow though so I’m going to experiment with only allowing the fan to increase above idle during the cooling phase.

On 10 Feb 2022, at 08:40, zian31 @.***> wrote:

Thanks xnk ! (so I'll modify your firmware, hope you are ok with that ;) )

This is exactly what I am planning to do for my T-962, as soon as I get the parts I need. Plus, assemble new thermal insulation and seal the airflow so that air is not sucked from outside the chamber during cooldown.

I don't understand what you mean with "seal the airflow so that air is not sucked from outside the chamber during cooldown" : the air will be sucked from where in your new design ? One of my interrogation will be that during cooldown, air will come from down to up (and rear Fan is at 100% during cooldown), with old T-962 it was from up to down directly on PCB, here PCB could be a kind of "barrier" in air flow. I forget to write another thing in my new design :

2 Thermocouples used directly put on 2 angles of the PCB (orginal 2 Thermocouples close to IR lamp will be disconnected, because these one don't represent usable temperature) — Reply to this email directly, view it on GitHub https://github.com/UnifiedEngineering/T-962-improvements/issues/210#issuecomment-1034587275, or unsubscribe https://github.com/notifications/unsubscribe-auth/AAYSRD3E4EK5RBR4MCARIJLU2NTWVANCNFSM47FKPAPA. Triage notifications on the go with GitHub Mobile for iOS https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675 or Android https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub. You are receiving this because you commented.

[zian31]

Now I understand what you mean : you want that during cooldown, air comes only from back of the PCB, and not from other place in the T-962 (moreover because slats are limiting the good air way) ? Another solution could be one or two servo-motor to open the slats just during cooldown, with kind of "wires" to pull slats ? I prefer to try that :)

Have you seen this slow convection Fan inside (working during all reflow) close to lamp IR (Jerry Walker) : https://www.youtube.com/watch?v=9026Odx_jOw&t=960s Or maybe will you use another AC motor ? I think Jerry Walkeris true when saying slow rotation is important, if it's too fast it's not working well...

[affetus]

Yes I have seen the video from his T-962A and I will try to apply that exact method for T-962.

The heating power of the smaller model is a bit underrated (about 670W), so I am trying to prevent all cool air from entering during the reflow and the air mixer should help in that. The goal is to not pull air from under the PCB but just circulate the hot air around like in a household convection oven.

The slats will stay closed nicely unless the rear fan runs with a higher speed, so I don’t think any extra control is needed for them. This also means that using the rear fan for circulation does not work, as it requires a higher flow to open the slats (especially if there are air leaks which I mentioned earlier).

Problem is that the rear fan is so thick that it limits the slats from opening completely. It is possible to increase the slat opening angle a bit (about 1.5mm) by removing four fiber washers which are between the fan and the chassis rear plate, but it requires some machining of either the chassis or the fan frame because those washers were used to add a small gap to fit the fan better. I need to investigate this more, maybe there is a way to modify the slats a bit in a way that they open up more, still sealing the airway when in a closed position.

[zian31]

Ok, I believed that slats were no fully openned during 100% PWM power with rear fan, so no need of extra servo-motors. I've now read that slats are 400mils openned, it should be enough compared to ES technical special new piece (with other air way direction) : https://www.estechnical.co.uk/images/pdfs/Addendum_-_T962A_A_Fan_and_air_path_modification.pdf

So as you, I will put some aluminium to seal the air flow.

And the main modification is this new inside little fan motor : do you already find one ? It should also be thermally isolated. I think I will make it work all the time (so not with a firmware command), but I hesitate to find one with DC 12V or AC 230V. I also use a T-962+ I've added a "pnoxi" board.

[affetus]

I will use Mabuchi RF-500TB-12560 motor mounted on 25mm long standoffs so there is room for the insulation wool + aluminum tape to fit between the motor and the reflow chamber upper plate. Then a 2mm to 3mm shaft adapter which goes through the wool and rotates the air circulator blade. This should keep the motor cool enough, I will not plan to use the oven for production so the duty cycle will be very very low. Just need to make sure there is a bit of clearance for the shaft so that it does not catch the wool fibers when it rotates.

[zian31]

Perfect ! I'd be interested with your 2mm to 3mm shaft adapter reference and also your helix or blade reference :) I think I will also use a 25mm metallic tube arround the shaft to protect from wool shaft catching.

[affetus]

This is what I will use as the adapter, motor shaft is 2mm:

https://www.aliexpress.com/item/1005002911230673.html

On the blade side, I will probably just use a regular M3 screw (so I ordered 2mm to 3mm adapters) and the blade will mount with help of star washers and a nut to lock it in place.

Blade design will need some more thinking but I will use Jerry’s design (from the Youtube video) as the starting point, as he had good results with it in T-962A.

[GitLang]

Werner, how are you going to control the temperature if you have no forced cooling element?. Without it, you have fast heat in from the lamps and very slow heat out from thermal insulation losses. I've tried to do this in the past, and it just cannot work unless you are on an extremely slow control bandwidth. For the job we did controlling a standards room with +/- 0.2F. the cooling apparatus was as much power as the heating. If you put energy in you have got to take it out, and unless you want to get into very non-linear control and stability problems, keep the cooling!. In fact, some schemes will heat the target with more power than required then control temperature with heat extraction..

[xnk]

What I meant was that the PID regulator wouldn’t be allowed to turn the fan on until the reflow profile has hit the peak temperature. Normally the fan shouldn’t turn on during the ramp-up but I’ve seen it happen on the T-962A+ where the PID regulator hasn’t been tuned properly. During the ramp-down the cooling fan has to run.

On 10 Feb 2022, at 16:10, Optician @.***> wrote:

Werner, how are you going to control the temperature if you have no forced cooling element?. Without it, you have fast heat in from the lamps and very slow heat out from thermal insulation losses. I've tried to do this in the past, and it just cannot work unless you are on an extremely slow control bandwidth. For the job we did controlling a standards room with +/- 0.2F. the cooling apparatus was as much power as the heating. If you put energy in you have got to take it out, and unless you want to get into very non-linear control and stability problems, keep the cooling!. In fact, some schemes will heat the target with more power than required then control temperature with heat extraction..

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[zian31]

the direction of airflow is important, and I can only agree that I had huge issues with the T-962A+ which also had the new “improved” airflow. It looked like the solder oxidised really bad despite reachine the correct temperature. Reversing the airflow using a similar modification as estechnical describes resolved that issue for me. Pulling in even small amounts of cool air directly below the PCB seems to be messing things up. The original firmware really isn’t impacted as the fan isn’t running during reflow.

Hoping that the problem of "solder oxidised really bad" is only due to "small amounts of cool air directly below the PCB" during first phase before hitting the peak temperature, and not due to something else : another reason can appears during the starting of cooldown => with old T962 cool air is arriving directly on PCB top, but with new T962+ cool air is arriving on PCB bottom (not directly on PCB top) and some bad air circles turbulences could be created ?

[zian31]

Blade design will need some more thinking but I will use Jerry’s design (from the Youtube video) as the starting point, as he had good results with it in T-962A. What do you think about these 4 leaves blades : https://aliexpress.com/item/4000977277776.html

[affetus]

Blade design will need some more thinking but I will use Jerry’s design (from the Youtube video) as the starting point, as he had good results with it in T-962A. What do you think about these 4 leaves blades : https://aliexpress.com/item/4000977277776.html

Might be quick and easy, but looks like they may create too much draft (i.e. pull air from the bottom or push it towards bottom. It may be better to use a blade which doesn't act like a fan, but rather as an air mixer. The air circulation doesn't have to be strong, it is enough to just mix the air inside the chamber.

[jakorten]

Wow, great work @DimaSM338 do you also happen to have a part number for the heat sink? I could not find it. Or [bgrigoriu] do you have a suggestion? I still could dive into my parts 'heap' and might find one that fits, but ordering one would be easier/more reliable.

[DimaSM338]

Wow, great work @DimaSM338 do you also happen to have a part number for the heat sink?

Wow great job @DimaSM338 do you also have the part number for the radiator?

Unfortunately, I do not remember the model number of the radiator. I wrote its dimensions above - Radiator size 37x30x15 mm and provided a profile picture. Choose a similar one.

Unfortunately, due to the war in my country, I do not follow the topic. Can you tell me if you managed to connect the oven to a Windows PC?

[jakorten]

Thanks Dimas, It should work without any problems. Windows sees the USB FTDI converter at least (but I use a Mac, Parallels sees the FTDI converter and asks me if I want it in Windows or macOS).

I'll try, I already got the new Triac from Farnell.

Really hope the war will end sooner than later!

[DimaSM338]

Good day to you all. Regarding the Windows oven connection. I could not establish a connection. Although I tried very hard, I even wanted to understand the code. That's why I asked, maybe there is already a solution

Швець Дмитро тел//vib//telegram.: +38 067 811-08-76

вс, 3 сент. 2023 г. в 10:19, Johan Korten @.***>:

Thanks Dimas, It should work without any problems. Windows sees the USB FTDI converter at least (but I use a Mac, Parallels sees the FTDI converter and asks me if I want it in Windows or macOS).

I'll try, I already got the new Triac from Farnell.

Really hope the war will end sooner than later!

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[PerennialNovice]

Concerning the windows connection, someone recently posted a link of another heavily modified T962 https://en.gradient-sg.com/t962/ They also somehow control the oven via PC (but I think there is a bluetooth module used to do so...

maybe it helps?

[zian31]

Concerning the windows connection, someone recently posted a link of another heavily modified T962 https://en.gradient-sg.com/t962/ They also somehow control the oven via PC (but I think there is a bluetooth module used to do so...

maybe it helps?

Very interesting ! What a job !

After reading all this page, i'm wondering if they use the older or newer T-962, or the modified newer T-962 (fan direction inverted with unmount and reverted remount).

But one thing is sure : they don't use the PWM fan during heating to mix the heat inside, the curves show PWM fan = 0% during heating, so they find THE solution to avoid mixing the heat inside with little PWM fan during heating (or using a little fan blade to mix heat) ?

EDIT : I've done this little drawn :

[darkroomai]

The unit I received this month (Feb 2024) definitely blows the air out the back. From the EST modification PDF:

"Our testing has shown the direction of the air flow within the oven has a large effect on the overall performance of the reflow oven."

"14. Find the marking on the fan which shows the direction of airflow and fan rotation. Refit the fan to the rear panel of the oven - ensuring that the airflow arrow points away from the rear panel (airflow directed into the oven chamber)."

This modification they recommend is only for the new version with the airflow OUT the back, but not for the earlier version with the airflow coming IN the back.

The airflow mod seems pretty invasive, so I'll hold off on that for now.