Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

When a laminator's net roller speed is modified, you also modify the
heat energy transfer to the rollers as the same surface of the roller
sees more radiant heat in a given time. Thus it gets hotter without even
upgrading the heater.
Now if you run the rollers too slow, the roller area being heated vs the
roller area being sensed will have a hi temperature delta and you could
burn the rollers. If the gears are exposed to some of this heat
conducted by the roller shaft, thermoplastic gears can 'become' plastic
and fail.

I encountered this heat delta effect when I was developing & monitoring
my Apache/Trulam mod with a FLIR camera. To eliminate this heat spike,
whenever the mod. reverses the roller it cuts the heater. This seems to
work well to date with no roller damage and good transfers. Thus running
the laminator at 'normal' speed during the heat up phase and then
'slowing' the rollers just for the Toner Transfer phase and returning
the laminator to normal speed afterward keeps the rollers from seeing
too much of a heat delta cycle and they suffer less degradation.

For the different laminators being modified, cheaper units seem to have
cheaper materials in them, with less accurate controls. Thus it's trial
and error as to how slow and how hot you can go before you exceed the
design spec enough to destroy the laminator and make a fire hazard.

Rob's approach eliminates this risk but is not 'over the counter'
repeatable for everyone and is certainly more time consuming when you
have a batch to run!

I shipped a built Apache/Trulam mod. to Italy yesterday based on the
newer layout with the SMT PIC. It uses low ESR SMT bypass caps and wider
power rail traces as well to mitigate PIC resets due to transient power
spijes as are generated from the relay and heater switching.