Feeling pleased with myself...

[throbscottle]

Well, don't forget to check out these: https://www.instructables.com/howto/toner+transfer+pcb/ first! I got the idea of iron+laminator from this one: https://www.instructables.com/id/Easy-Consistent-Cheap-Toner-Transfer-Method-for-Si/
but I particularly like this one: https://www.instructables.com/id/Toner-transfer-for-PCB-Flamethrower-Style/

 

[Mosaic]

This might be handy....if I need to slow down the laminator motor.
https://lowpowerlab.com/blog/2013/09/09/laminator-dimmer-hack-for-pcb-or-stencil-toner-transfer/

this looks more complex
https://www.instructables.com/id/Modified-laminator-for-PCB-Toner-transfer/

 

[Mosaic]

Well, I got the laminator and I viewed various blogs & you tube videos on modding it for regular magazine paper use.
Here's the plan:

1) Add over temperature protection (for a failed/broken thermistor) as it has none.
2) Add an automatic forward /rev motor cycle option to create multiple, small, overlapping passes of toner transfer for a single pass of the copper clad board. Perhaps 1 sec forward, 3/4 sec back, ratio timer , thus slowing the speed down about 4 times.
Use a trimmer pot to permit adjustment for net slower operation with more cycles.
Since the motor is an AC synchronous unit, I can't use a triac chopper speed control.
3) Add a 2 minute cooldown over ride to permit roller cooldown while allowing the original temp setting (persistent) to remain. Add a beeper to signify when to shutdown power manually.

I plan to use a 12F675 PIC to do the job. The add on PCB will align with existing holes on the casing and be compatible with the 6 pin 0.1" pitch headers of the existing control board to permit simple plug & play.

I can publish the design and PIC code here when it's done.

 

[throbscottle]

Gosh, that sounds really ambitious! Good luck with it! Can I suggest though that you try giving it a run without modification first, just to see what happens?

 

[Mosaic]

Well, the mod is switchable via a tactile...so it can run either way anytime. The Blogs etc all mention that up to 20 passes are required, stock setup.
The problem is the PCB cools down when it comes in contact with the second pair of pressure rollers (which are cold). This means more pressure & passes are required.
Thus by keeping the PCB under the hot rollers with overlapping micropasses I expect to eliminate the heat losses and pressure losses incurred with manual passes. Thus the overall result should be realised much faster than 20 full passes. I am estimating 4 or 5 net passes. I'll get it optimized.

I begin the simulated design after this post.

 

[alec_t]

the motor is an AC synchronous unit

Is it reversible?

 

[Mosaic]

Yes...there is a relay that swaps the stator polarity. It has a 1.55uF 630V Poly snubber cap sitting on the relay terminals.

 

[BobW]

I've been using a GBC brand laminator for quite a while, and it works great. I did have some problems initially because of the thickness of the PCB. I had to open up the laminator and enlongate the openings for the bearing with a file. It's a fixed temperature laminator, and I found that when the "ready" light comes on, it's still not hot enough, and needs to warm up for about a 1/2 hour before using it. I use aluminum foil for the carrier, for maximum heat transfer.

 

[Mosaic]

I'd say that sounds like you're having to wait until the 'cooling rollers' warm up. Have a look inside and remove any heat shields preventing the 2nd pair of rollers from heating up.

 

[BobW]

There's only one pair of rollers in it. The 30 minute wait isn't a problem; it just requires planning. If I know that I'm going to be making a PCB, I power up the laminator at the beginning of the job, and It's hot by the time I need to use it. As far as the toner transfer method goes, this is the least troublesome part of the process.

The biggest problem that I've encountered is trying to get the toner to stick to the transfer paper. I use HP semi-gloss photo paper. I found that the toner would flake off the paper as it passes through the printer. The rubber rollers in the printer would pick it up and re-deposit it elsewhere on the paper, making a mess. I discovered that if I dampen a cloth with methanol, and wipe the paper with it (and letting it dry) before use, the toner adheres to the paper much better and the problem disappears. I could have tried a different brand of paper, but I like this stuff because once it's been "ironed" onto the PCB, all you have to do is soak it in water for 15 minutes, and the paper floats away, leaving all the toner sticking to the copper.

 

[Mosaic]

Hmm, seems like your semi-gloss paper doesn't bind to the toner as much as magazine paper so u don't need as much heat & pressure to transfer to the PCB. Flaking while printing is sometimes happens when I run baking parchment thru the printer.
The toner flakes off the parchment during handling to attach to the pcb.

Edit:
Cleaning the parchment with isopropyl solved the flaking! But I still need multiple laminator passes for adhesion to the copper. How do u clean your copper clad before toner application?

 

[BobW]

Hmm, seems like your semi-gloss paper doesn't bind to the toner as much as magazine paper so u don't need as much heat & pressure to transfer to the PCB.

I'm not sure about that. There are really two separate processes going on. Just because the toner doesn't still well to the paper, it's no guarantee that it will stick well to the copper.

When the paper passes through the fuser unit of the printer, the toner melts and sticks to the paper (assuming that the paper has a good surface to adhere to). Later, when the paper and PCB are passed through the laminator, the toner re-melts and, as it cools, adheres to both the board and paper, gluing everything together. The coating on the paper is water soluble, so that when it's placed in a water bath, the paper coating dissolves, separating the toner from the paper, leaving the toner on the PCB. Because of the water soluble coating on the paper, it's guaranteed that the toner will easily separate from the paper. How well the toner sticks to the copper will depend on how hot the laminator was, the characteristics of the toner, and the surface condition of the copper.

To clean the copper, I use water, dish detergent, and a green Scotchbrite pad. Nothing fancy. Scrub well. Rinse with water and dry with a paper towel. And of course, once it's clean and dry, don't let it touch anything.

Regarding the laminator, I usually run the board through twice, but I suspect that a single pass would be sufficient. The thing is stinking hot, and you can barely hold onto the board when it comes out. When you run your fingers over the paper & board assembly after the first pass, you can feel that everything seems well stuck together. Still, it does no harm to run it through a second time just to be sure.

Of course there are many variables that can affect results. I remember reading several years ago, that Hewlett Packard printers, because of their toner formulation, work especially well for toner transfer, and that is the brand that I have. So that may contribute to my positive results.

I rarely make big boards. In the last few years, I'm sure I've never done anything bigger than 4x4 inches. If I wanted to make something bigger, I'd likely send it out to a commercial fabricator.

FYI the paper that I use is HP product No. Q2509AC. I don't know if it's still available. I bought a large package several years ago, and I'm still working my way through it. I also have some of the Pulsar toner transfer stuff, but the toner adhesion was far worse than with the HP paper. Now that I know about the alcohol wipe trick, I'll probably give the Pulsar paper another try next time I make a PC board.

 

[Mosaic]

Well, perhaps your laminator is hotter or slower than the Apache which is about 200C.

I completed the laminator mod simulation last night and the uC coding. I am designing the PCB for it now and I should have results soon!

 

[throbscottle]

Cool! Watching this space with interest

 

[Mosaic]

Throbscottle: I'll do a thru hole prototype so it's easy to duplicate.

Edit:
This is the PCB design. I'll build it tonite or tomorrow.

 

[Mosaic]

Just a note:

By using isopropyl wiped parchment stuck with tape to regular paper as a vehicle I got very good toner transfer to the copper (10 x thru the laminator) . B4 the laminator step the copper was cleaned with 320 grit sandpaper and then wiped down clean with more isopropyl (in tissue paper).
Popped into a gentle bath of dilute nitric @ 1160 spec. gravity yielded a good etch 20 mins later, including the text and numbering etched into the copper as per the design shown.

 

[BobW]

BTW, this recently came up on another forum. If your isopropyl alcohol is less than 99% pure (ie., lab grade) then it is likely to contain contaminants such as amyl alcohol which may leave an oily residue when used for cleaning.

 

[Mosaic]

I used 90% in a gallon jug, pharmaceutical grade.

 

[throbscottle]

Think it's time I started looking at getting an old laminator so I can hack it... (don't think Mrs would be too impressed if I did Things to the regular one, even though it was cheap!)

 

[Mosaic]

BTW BobW...it seems that GBC has changed their laminators and the <$100 units don't work for PCB anymore...
https://ultrakeet.com.au/write-ups/superFuserV2