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Exhaust on Reflow Oven

Rob

#35057

Exhaust on Reflow Oven | 21 June, 2005

Hi,

What will be the effect in my soldering if my Reflow Oven's Exhaust system is not properly extracting air from the chamber. Recommended is 100 CFM but I am measuring 45 CFM.

thanks,

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??

#35058

Exhaust on Reflow Oven | 21 June, 2005

i dont think it causes and soldering effects but i do believe that the fumes will escape out into your factory.

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#35059

Exhaust on Reflow Oven | 21 June, 2005

I have a self contained fume filtration system (for sale)for reflow ovens that will maintain your desired cfm. What I have heard from customer's is that there will be variations in your profiles thus causing some defects.

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Dreamsniper

#35060

Exhaust on Reflow Oven | 21 June, 2005

Defects will result, Your cooling rate is affected because the hot air is not circulated properly. Outgassing will appear and you'll have pin holes / blow holes, disturbed joint etc.

Correct me guys if i'm wrong.

Thanks

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#35063

Exhaust on Reflow Oven | 21 June, 2005

The 2 issues are:

-1 Enough flow to keep all fumes from reaching people. -2 Consistent amount of heat removal to keep the temperature steady.

If the 45 CFM is steady and keeps all fumes away from people all is well.

Jerry

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slthomas

#35064

Exhaust on Reflow Oven | 21 June, 2005

I'm inclined to believe along with others that if you don't smell it, and the flow rate is consistent (hence, your profiles aren't suffering from fluctuations in temperature due to fluctuations in circulation) you're probably OK.

It does beg the question "If I can't smell it, is it not there?", however.

Is it possible that someone tweeked your exhaust or cooling fan settings w/o telling you?

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#35065

Exhaust on Reflow Oven | 21 June, 2005

This is basically the reply that I had from Heller ovens regading this - "The recommended air flow is at the back of the machine near the vent. From the book I copied from you it should be 500 CFM. If you do not achieve this figure, it not a great issue. What is more important, is that new air is being drawn into the oven at both ends. If you take a tissue and hold it near the end, you need to ensure it is getting drawn in, not blowing out." We had to move our whole facility and commission a new line some years ago. The ducting had to go up an extra floor. I could not achieve the 500cfm required and duly get an airflow expert in. His opinion was that you could never achieve 500cfm, even with a jet engine attached, as the outlet on the oven was too small - he said, "remember you are talking volume, not pressure". After more conversation with Heller, they basically stated that the CFM required is very forgiving. If you can smell it and the oven is hot to the touch, then you have insufficient exhausting. If your reflow zones are running over 60% power consumption then you are exhausting too much. You can increase your cfm by removing any flexible ducting, (like Robbie the Robot arms), from the system or stretching it to the max. Also removing any elbows and joins, if practical will help. Remove any damping mechanisms, even if they are fully open. What does your oven manufacturer say? It's all a bit inexact innit? An issue with a tissue. Cheers.

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slthomas

#35094

Exhaust on Reflow Oven | 22 June, 2005

"His opinion was that you could never achieve 500cfm, even with a jet engine attached, as the outlet on the oven was too small..."

I had that experience with a washer that blew steam out of the entrance. He said we'd collapse the pipe before we ever got the specified flow through it. We just started referring to the machine as "the sauna" and decided it was a feature, not a bug.

Our 3 Hellers used 100cfm, I think, and we had one that fouled the air with no-clean fumes no matter what we did. I could run 200cfm through the stack with a new blower AND roof unit, clean impeller, clean filters, clean baffles, etc., and it still blew fumes (and puffed on the tissue). Never figured it out. We outsourced and now it's someone else's problem.

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richard

#35174

Exhaust on Reflow Oven | 26 June, 2005

Hi

What is CFM and how do you measure it?

Richard

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#35178

Exhaust on Reflow Oven | 27 June, 2005

reflow oven profiler

Reflow Oven