do not ask why, I am about to build (Arduino based) reflow oven from scratch (i.e. no toaster oven conversion) and would like to hear your opinion or advice on hardware design.
There are many DIY toaster oven conversion projects documented on the Internet. Ovens have their form factor set by manufacturer with respect to food processing - from specialized low-profile pizza stoves to high-volume chicken grills...
General advice for reflow ovens is to "keep the internal volume low" to keep thermal inertia low for better control characteristics. Keeping the volume low comes down to reducing chamber dimensions.
Question: Having traditional design in mind (insulated chamber with reflective surface applied, with bottom and top IR quartz heater elements and tray in between), are there optimal recommended or safe distances? I mean a) distance from heater elements to top and bottom chassis walls and b) distance from heater elements to tray?
My oven will have 3x 300W quartz elements on the bottom, 3x elements on the top, max PCB size 30x20 cm (12x8"), convection fan.
qwertysimo:
are there optimal recommended or safe distances
That depends one the type of heater elements. The distance has to be high enough to distribute the heat evenly, but close enough to heat the pcb to the desired temperatures in the required time.
Keep in mind, that the fan has to be able to withstand the temperatures.
Heater elements are IR quartz tubes, 300W, 33 cm (13") long, 3 at the top, 3 at the bottom, total of 1800 W.
Internal fan will be DIY full aluminium impeller, no plastic.
In this moment, my chamber design is 31 x 25 x 20 cm (12 x 10 x 8") (w x d x h) what gives volume of 15,5 liters. Elements are placed 3 cm (1,2") from the chassis bottom and top. Tray is 7 cm (2,75") from bottom and top elements. Elements are spaced 6.5 cm (2,5"). Screen attached.
The distance has to be high enough to distribute the heat evenly, but close enough to heat the pcb to the desired temperatures in the required time.
The data sheets for the components you are going to solder will give the heat profile for those components. A reflow oven is not just heat and forget. Basically heat slowly to a given temp for a few seconds and then begin cooling.
