Help Etching Aluminium Enclosure

[MetalGod]

I've got my laser printer up and running again so I decided to design a graphic for a simple treble boost pedal.  Printed out the P'n'P in the usual manner as I would for PCBs then ironed it onto the alu box. 

I prepared the box by scrubbing it with wire wool then drying it with a dry cloth.  Problem is that the P'n'P is not sticking at all.

Any ideas what I'm doing wrong here?

[$uperpuma]

I've found that if you make sure the metal is sanded completely flat, go over the metal with some acetone after sanding, and make sure the metal is very hot... I've also found that putting painters tape over the graphics areas helps some, but thats not absolutely necessary... maybe the Acid King will chime in...

[markm]

Here's what ya gotta do....
Go here>>>>http://aronnelson.com/gallery/Acid-Graphics
.....and see if that helps you.
If you have any questions, ask away!
Remember, be very careful of the brown acid! 

[MetalGod]

Here's what ya gotta do....
Go here>>>>http://aronnelson.com/gallery/Acid-Graphics
.....and see if that helps you.
If you have any questions, ask away!
Remember, be very careful of the brown acid! 

read that mate - those were the instructions I followed.

any other suggestions?

the only thing I can think of is maybe the toner in the laser printer not being dark enough - would that matter at all?

[markm]

I prepared the box by scrubbing it with wire wool then drying it with a dry cloth.  Problem is that the P'n'P is not sticking at all.
Any ideas what I'm doing wrong here?

Well, unfortunately scrubbing with steel wool and wiping with a dry cloth are not enough to prep aluminum for PNP transfer.... as you found out 
I would suggest sanding the top down so it is completely flat, clean and free of even the smallest imperfection then see
how that does.

[MetalGod]

do you think that sanding with wet & dry (or 600 grit as you call it) is essential to this working?

I'll get some tomorrow and give it another bash.

[markm]

do you think that sanding with wet & dry (or 600 grit as you call it) is essential to this working?

I'll get some tomorrow and give it another bash.

Yes Sir, absolutely.
I would suggest getting it smooth first with 220, move up to 400 to get some of the deeper 220 scratches out of it and from there you could do your transfer -or- move to 600 then do the PNP.
I think the cleaner and smoother the surface is the better the transfer.
Just imagine how smooth a copper clad PCB blank is before you iron on your PNP.....that's how you want the top of the enclosure to look. Remember though, it needs to remain squeaky clean and free of dirt and grease to stick.
Hope this helps!

[MetalGod]

I'll report back and let you know how I get on - might as well go all out and use some lighter fluid to clean it in the final stages too.

damn you for making those etched enclosures look so damn good 

[mojotron]

As far as 'cleaning' goes - doing a good cleaning once with soap/water then twice (or 3 times) with pure acetone is about as effective as anything for working with PNP - I don't like how expensive lighter fluid is. I just keep cleaning until a paper towel looks fairly clean after cleaning - then I know I'm ready for the PNP transfer. The cleaning is really the critical step for me.

On sanding, a rubber (or wood) sanding block is a great tool for getting a flat surface. It is nearly impossible to improve the 'flat-ness' of a surface without sanding with a flat surface.

[markm]

On sanding, a rubber (or wood) sanding block is a great tool for getting a flat surface. It is nearly impossible to improve the 'flat-ness' of a surface without sanding with a flat surface.

Very true indeed.
The secret to a good etch is good surface preperation.
There's no way around it.

This is what you want it to look like;

[MetalGod]

cheers for the pic - I've got the pedal prepared again with the wet & dry, just sanded off the black primer with some 600-grade.  off to the shops now to get some lighter fluid to clean the surface then try ironing this thing onto the pedal.

[MetalGod]

ok, I've sucessfully got the PNP design ironed on the case - thanks for the help, you were right - there are no shortcuts with this method.

I've got a few small spots to touch up before etching but I should be good to go tomorrow night 

any tips on the actual etching? - I'm sure I read a thread a while back where someone reported that it was better when the solution wasn't 100% fresh.  I recall they advised putting an old penny in the solution beforehand to slightly weaken it. 

Thanks 

[$uperpuma]

checkout Mark's tutorial, it tells you everything you need to know...EVERYTHING...

[MR COFFEE]

Obviously Mark gets great results with his method.

But here's a couple of variants I have used

1 - Iron on a second blank pnp sheet to thicken up the resist The blue powder stuff soaks into the laser toner and makes it a bit thicker

2 - If you aren't in too much of a hurry, you can apply the etchant with a small hobby type paint brush and sometimes this gets better resolution. This keeps the box from getting too hot or the etched aluminum residue from globbing up.

Never done the penny, but I think a less active etchant is less likely to overheat the box on you. FWIW

Lighter fluid is sold in paint stores as naptha - it costs a lot less. I use acetone myself.

mr coffee

[MetalGod]

I etched the box last night and sanded it down, looks great. 

Thanks to everyone who replied/helped.

I'd post some pix but I dropped my digital camera the other day and broke the lens (doh!).

I gave it too much time in the ferric chloride (kept taking it out to check), there was some pitting on the surface.  It's a learning curve, next time I'll know what NOT to do.

[markm]

Yeah, it does take some doing to know just when your etch is "done".
Sometime you can clean up some of the pits by sanding the top just a little bit.
Don't go to far though or you'll ruin the etch.

[lumpymusic]

Obviously Mark gets great results with his method.

But here's a couple of variants I have used

1 - Iron on a second blank pnp sheet to thicken up the resist
The blue powder stuff soaks into the laser toner and makes it a bit thicker

Explain further, please?

Doesn't that give you an entire face of the box covered with resist?


Lumpy

[MR COFFEE]

there was some pitting on the surface.

That's why I use the second application of PnP - it thickens the resist and gives less pitting.

Explain further, please?

Doesn't that give you an entire face of the box covered with resist?

No.
Think about it this way - when you print onto PnP, then iron it on, the blue powder on the sheet melts into the laser toner and becomes the resist for etching. When you peel off the PnP, the places with toner stick (hopefully) to your board or box and the rest of the PnP blue powder stays on the clear substrate you peel off. When you iron an additional blank sheet of PnP onto the resist (laser toner + blue powder already on a board or aluminum enclosure), the powder fuses into the toner to make a thicker resist coating. Then you peel off the clear substrate film as usual, and the blue powder sticks to the film anywhere you don't have toner and peels off as usual. That includes holes in the resist, so it doesn't substitute for touch up with a paint brush where the hole is a defect of printing or adhesion of the PnP pattern, but it does mean you can leave the board in the etchant longer without the etchant causing pinholes because the resist was just a tad too thin here and there and a few etchant molecules sneaked through. Works well for etching PCBs with thicker foils (like for power amps and power supplies where you need the greater current-carrying capacity), too.

I've never tried more than one additional sheet of PnP, so I don't know how far you could stretch this concept for really deep etching of aluminum boxes or panels. Maybe somebody here will try and see how far you can go.

The PnP is just one way to transfer the laser toner pattern to the metal - some people use other kinds of printable media (i.e., the Goutee method). The PnP advantage is that the blue powder (seems, anyway) to make the laser toner resist a bit more robust. Some other systems use films that you iron onto the toner and adhere to the toner (the name escapes me at the moment). Same idea. Thicker resist "resists" better.

mr coffee

[markm]

MR.COFFEE,
Very interesting idea and a good one at that!
I'll have to give it a try.
Thanks for sharing 

[jmdfd415]

What kind of software do you guys use to design your enclosures?