Stop-gap PCB creation (has stopped)


This is a year-old post that I never published. I guess I was waiting to be able to snap some pictures, but that never happened. Most of these components have been e-wasted by now.

I’ve talked about various avenues of rapid prototyping circuit boards before, and not really come up with any definitive solutions.

My current favourite possibility is using a dye-sublimation printer, but they’re fairly difficult to get ahold of. I’m not willing to throw money at the solution just yet.

In the meantime, one of the more reliable methods is toner transfer, using a clothing iron. There are two easily-controlled variables that affect the transfer quality. There are a lot more than two, but those are the ones that involve a human element.

As a solution to that, I started work on my own laminator. I took the fuser from a laser printer and mounted it to a board.

Mounting and getting it working independently had a fairly involved process. First I needed to drive the motor.

It required a lot of torque and I have no access to any simple motor that can handle that. The only thing I have that comes close is one of my brushless DC motors, but man, I don’t want to use complicated driving circuitry for that. What I ended up doing is mating a simple 12v DC motor to the gearing for one of those motors. I laser cut a bracket that has mounting holes for both sides, ground down a shaft, and it seems to work. A very consistent and slow speed, and huge amounts of torque.

The next step was the heating element. I ran it off one of the 30v supplies we have kicking around, and it got to the “reasonably warm” level while drawing just over 1 amp. Fortunately (or unfortunately, depending on your perspective), a local e-cycle company was closing down and had an impromptu fire-sale. I picked up a 60v power supply that was labelled “broken” for free. Replaced a PTC (that literally crumbled away in my hands), and it was good to go again. The new supply got it to “properly hot” in a minute or less.

The next step was measuring the temperature. The fuser had a thermister output that starting at around 33kohms. As it gets hotter, the resistance drops. I measured around 19kohms when it was “slightly hot”. That’s the totally objective temperature description I’m going with here.

I used a voltage divider with a 100k potentiometer to tune it to 0xFF at room temperature. The reasoning being that I didn’t actually need to know the “proper” lamination temperature, just the relative values that apply to this system.

So I had the whole system, the drive motor, the heater element, the temperature measurement. It turns out that while my system is 0xFF at room temperature, everything melts at 0xA0. That’s not very hot at all! I think. I have no idea what that translates to in real measurements.

There is another printer kicking around that I should be able to pull the fuser out of. The rollers didn’t really feel that hot overall when they melted, so it’s possible that it was just because I wasn’t running the motor at the same time.

Fortunately, there’s no shortage of old laser printers destined for the scrapheap.

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