Junk ScAmazon Laminator

[SenseofScale]

I recently bought a laminator for making PCBs. I know, "have them made in China", but I'm not an EE, just a "hobbyist."

The laminator I pulled the trigger on supposedly had a feature to allow the user to select two different temperature settings, via a switch for 3 or 5 mil pouches.
https://www.amazon.com/gp/product/B01M0FNZD1/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Anyway, just about as soon as I received it, I took it apart and noticed something interesting. The 3/5 mil selector switch is jumpered, such that choosing 3 or 5 mil merely turns the unit on. I was surprised and seriously considered returning it, even though it won't matter for what I'm going to do to/with it.

Anyway, here are some pics and a schematic of the internals.

EDIT: I goofed on the schematic. Removed it and reattached the correct one. Also, the thermostats are closed, and open after the unit comes up to temperature.

[Kean]

By any chance is there a diode under the heatshrink on one side of the switch?

[Gyro]

Not if it's still going to run the synchronous motor.

[Kean]

Not if it's still going to run the synchronous motor.

Fair enough... the heatshrink just looked a bit more bulky on the right hand switch terminal, like something might be hiding in there.

[SenseofScale]

By any chance is there a diode under the heatshrink on one side of the switch?

Nothing under the heat shrink. Think they may have put thicker shrink there so it can rest against the motor. They wanted to make sure it was protected  .

[Gyro]

It looks as if it's supposed to keep the temperature in the middle of the 120'C to 140'C range.  Below 120'C both thermostats are closed so the element gets full wave mains, above 120'C one thermostat opens and drops the heating power to half wave mains and of course above 140'C off.

It's a little bit elegant - as in not being just simple on-off heater cycling. You could probably turn it into a two temperature basic on-off cycling but you'd have to have the motor running continuously.

In the old days, they had a proper triac circuit and thermistor of course. 

They missed the reverse voltage protection on the Red LED too.

[SenseofScale]

It looks as if it's supposed to keep the temperature in the middle of the 120'C to 140'C range.  Below 120'C both thermostats are closed so the element gets full wave mains, above 120'C one thermostat opens and drops the heating power to half wave mains and of course above 140'C off.

It's a little bit elegant - as in not being just simple on-off heater cycling. You could probably turn it into a two temperature basic on-off cycling but you'd have to have the motor running continuously.

In the old days, they had a proper triac circuit and thermistor of course. 

They missed the reverse voltage protection too.

That appears to be how it functions. The temperature values are made up and probably lower than the ones I chose. I'd have to cut some wiring or destroy a crimp to remove one of the end caps to slide the thermostats out to actually read the values. The thermostat, whose opening up activates the "ready" LED, comes up to temperature first and the other one opens up a little later as the temperature more slowly reaches its opening temperature, due to only half of the AC cycles doing the heating.

Do you mean the reverse voltage protection on the power indicator LED? I wondered about that. Some reviewers say theirs quit working after a month or shorter. I wonder if their power LEDs had merely quit.

Edit: Saw your edit.

I took the motor end off, which gave me enough room to take the thermostat switches out. They are 110° C and 120° C rated switches. They're also not in the positions I figured they were. The 120° C switch is actually attached to the "ready" LED. The 120° C switch must have a much larger hysteresis as it never turns back on while the unit is running, but the 110° C can be heard clicking on and off. Or they're just that poor quality.

[Domagoj T]

I have one that mechanically looks almost exactly the same. The difference is that mine has two switches, one for motor alone the another one for heating elements. It works fine, but I'm considering replacing the thermostats to crank the temp up by 20-ish °C. It struggles on thicker and larger boards so I need some hot air assist.
Also, yours has the same outfeed fins as mine. I filed mine down a bit so the boards can pass through them more easily.

[Gyro]

The only reasons I can think of for them quitting (I suspect the power LED alone wouldn't be seen as a total quit).

- Thermal Fuse rating a bit too close to operating temperature (something to think about if trying to squeeze some more heat out of it).
- Motor winding failure
- Plastic gears getting chewed up.
- Thermostat contacts?

[SenseofScale]

The only reasons I can think of for them quitting (I suspect the power LED alone wouldn't be seen as a total quit).

- Thermal Fuse rating a bit too close to operating temperature (something to think about if trying to squeeze some more heat out of it).
- Motor winding failure
- Plastic gears getting chewed up.
- Thermostat contacts?

I repair things for a living. Some people, or at least some of the people I work around, would think it's broken just because the light wasn't coming on.

[SenseofScale]

I have one that mechanically looks almost exactly the same. The difference is that mine has two switches, one for motor alone the another one for heating elements. It works fine, but I'm considering replacing the thermostats to crank the temp up by 20-ish °C. It struggles on thicker and larger boards so I need some hot air assist.
Also, yours has the same outfeed fins as mine. I filed mine down a bit so the boards can pass through them more easily.

I think I may do the same but I would like to retain it's functionality as a laminator and maybe have temperature control. I did some testing and mine survived a 67° C increase in temperature, controlled by an external controller and SSR. After a bit of drill "milling", followed by some filing, I was able to press fit an RTD into the same channel as the thermal fuse. I didn't have any thermal paste handy, so I gooped some silicone vacuum grease as a temp stand in. The reading you see in the pic is farhenheit and works out to about 140.5° C. When the laminator controls itself, my RTD is averaging about 96° C at the same location. I pushed the temp to 163°C and let it run for about ten minutes without issue. The rollers expand a bit as they heat up, so the increased friction caused the motor/gears to creak a bit.

This isn't a permanent solution. Although these parts are second hand and were basically free (aside from the SSR), this is over kill and I would rather have these parts for whatever else comes along. I was thinking about implementing something more along the lines of a triac, thermister, a pot, etc.

Two passes transferred toner onto the board in the picture at 140.5° C. Yes, this mask is the negative of what one would want for toner transfer.

Also, the thermal fuse survived.

[blacksheeplogic]

This post seems to be nothing but whining for the sake of it.

So they tweaked the design and no longer needed to switch between 3mm and a 5mm setting and jumpered the switch to reuse the existing parts & case - so what's the problem? Does it work? It was built to a price point, Stop whining if it works you bought it because it was cheap, the manufacture meet the price point and function.

[SenseofScale]

This post seems to be nothing but whining for the sake of it.

So they tweaked the design and no longer needed to switch between 3mm and a 5mm setting and jumpered the switch to reuse the existing parts & case - so what's the problem? Does it work? It was built to a price point, Stop whining if it works you bought it because it was cheap, the manufacture meet the price point and function.

The only problem is that switches that do nothing cause operator confusion and it seems sleazy to me to advertise and lie, outright, about a feature that doesn't exist.

Aside from that, I bought it and kept it   . Someone piss in your cheerios   ?