Homebrew PCBs

Ancel,

That makes sense. I am beginning to see why the laser printers I have 
looked at use heaters inside the rollers.

Harvey


On 1/1/2017 7:07 AM, mosaicmerc@... [Homebrew_PCBs] wrote:
>
> Harvey asked :
> >>I am not sure I understand why slowing the rollers causes them to 
> pick up more heat energy. In my  laminator (Harbor Freight) there are 
> two heaters, placed on opposite sides fo the rollers. The heaters are 
> attached to aluminum structures that enclose the roller assembly all 
> around, except for the slots for the paper path.<<
>
> During development of the Apache PCB mod, I effectively slowed the 
> rollers to a  net zero movement.
>
> Before long the rollers' area closest to the heaters started to smoke 
> a lot.
>
> When I powered down cooled and dismantled the rollers they had 
> developed a white powdery surface which shed when wiped. After 
> cleaning this sediment the rollers had become oval shaped and frangible.
>
> I swapped them out with the 'cold rollers' (quad roller laminator) and 
> wrapped them in kapton tape to keep them serviceable.
>
> In summary; the reflected heat from the metal enclosure is not as much 
> as the direct radiant heat from the heater coils and (with an almost 
> parked roller)  this creates a temperature on the roller surface than 
> can  exceed the roller's spec, if the roller does not rotate away from 
> the heater and cool off.
> Because the temp sensor is on the exposed  side of the roller away 
> from the heaters, it depends on the hot side of the roller rotating 
> into contact with it, if this doesn't happen fast enough, the temp 
> sensor sees a temp well below the hottest part of the rollers and does 
> NOT shut off the heater, resulting in overheating.
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