Takt time (without a google search) is the rate (amount of time per pc.) at which stuff gets made on an assembly line, a workcell, a hi-speed SMT line, CNC machine cell, etc....
Takt time is governed by the gate (the slowest person, machine, etc. in your workcell).
A reflow oven has no stops - it is a continuous process where you can shove boards in there literally back-to-back (not recommended, but do-able).
I guess if you really wanted to get technical, you can go back to your 6th grade algerbra class, and use the distance formula D=vt...That way, you can derive a time, based on the total travel length of the oven and conveyor speed. So, for example, 1 board by itself on a 12 ft. oven, and a conveyor speed of 36"/min. (3FPM) would take t=d/v= 12/3 =4 min. or 240 seconds...that is not takt time, though, 'cause your oven isn't "fully loaded."
To get a takt time, the assembly line (or oven) has to be "wet" (fully loaded), and you'll have to assume that boards are coming into your oven at a consistent rate, and they're being spaced apart consistently. Now, you've got your "oven takt time" (ie a PCB will come out every X number of minutes or seconds)...
So, for example, say your oven is fully loaded, and you're running at 3 FPM (36"/ min.). Say your boards are spaced 5" apart ALL THE TIME. T=5/36=0.138 min. = 8.33 seconds. So, you'll have a board come out every 8.3 seconds.
Again, to get accurate numbers, there's lots of assumptions here, and you'd have to be working in this manufacturing "utopia" where people are loading boards at a consistent rate, and consistent spacing..
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