[chbot] Chchrobotics Digest, Vol 159, Issue 6

Mon Dec 7 10:16:41 GMT 2020

Thanks Robin

I'm using the last of my ammonium persulfate now. I'll try that next time as I
have both here. 

Thanking you
Wallace Weideman
Marshland Engineering
704 Marshland Road
Styx
Christchurch
03 3237449
www.marshland.co.nz

On 7/12/2020 at 7:22 p.m., chchrobotics-request at lists.ourshack.com wrote:
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>Today's Topics:
>
>   1. Re: chemical milling (Mark Atherton)
>   2. Re: chemical milling (Mark Atherton)
>   3. Re: chemical milling (Ivo Gorny)
>   4. Re: chemical milling (Andy Gardner)
>   5. more chemical milling (Mark Atherton)
>   6. Re: Ferric Chloride (Robin Gilks)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Mon, 7 Dec 2020 13:02:51 +1300
>From: Mark Atherton <markaren1 at xtra.co.nz>
>To: chchrobotics at lists.ourshack.com
>Subject: Re: [chbot] chemical milling
>Message-ID: <4d4e9300-a73d-d716-cfef-db55fa621ad7 at xtra.co.nz>
>Content-Type: text/plain; charset=utf-8; format=flowed
>
>David, Andrew,
>
>Comments and links appreciated.
>
>I have heard similar warnings about laser-cutting Cu before, but am not 
>sure if it is urban legend or not.
>
>The beam out of a 70W or so CO2 LASER emerges as a cylinder a few mm 
>diameter (maybe 4mm?), and around 10um wavelength. The light then 
>bounces around fixed and movable mirrors until it hits the final mirror 
>where is is directed down, towards the bed. On it's way down, it passes 
>through a convex lens, focussing the beam, and increasing the power 
>density at some focal point - maybe 50mm.
>
>This is where you now have many tens of watts of coherent light arriving 
>at a final diameter of perhaps 50 microns. This is an incredible power 
>density, and the very reason that the laser-cutter can do useful work.
>
>So now we hit a piece of reflective material; some of the energy does 
>useful work, lots gets reflected. The focus has been lost with this 
>reflected beam, and it rattles around inside the cutting chamber. Some 
>of the energy hits the perspex observation window. Perspex however is 
>opaque to 10um and converts any remaining reflections into heat.
>
>Even directly under the cutting head, perspex can only be cut to maybe 
>10mm (if you are using a slow head), but the reflections are going to be 
>several orders of magnitude lower than this.
>
>I am not advocating using an LC with the lid open and the safeties 
>disabled, but I can't see many problems with running a LASER over 
>something reflective within the context above.
>
>Anyway, appreciate anyone pointing out holes in my argument since this 
>is a safety issue.
>
>Regards,
>
>Mark
>
>
>
>
>Thanks for you comments.
>
>On 7/12/2020 12:13 PM, David Closey wrote:
>> Mark
>> I have tried exactly as you suggest
>> Paint over copper then laser off and etch
>> It is written up in a few places on the web (see below)
>> 
>> I had some success but resolution was a bit to be desired
>> (I couldn’t do smd parts) so was not much of an advantage over std methods
>> 
>> I found the same with milling pcbs
>> Résolution was limited to through hole
>> 
>> I think Russel’s method with screen printing resist and using the 
>> transparency from rs components is most exciting for home prototyping
>> 
>> Be interested to hear how you get on
>> 
>>
https://www.instructables.com/Custom-PCB-Prototyping-using-a-Laser-Cutter/?amp_page=true
>> 
>> 
>> David
>> 
>> 
>> Sent from my iPhone
>> 
>> On 7/12/2020, at 10:43, Mark Atherton <markaren1 at xtra.co.nz 
>> <mailto:markaren1 at xtra.co.nz>> wrote:
>> 
>>> Thanks Andrew,
>>>
>>> The hydrogen peroxide/hydrochloric acid solution looks most 
>>> interesting; never heard of it before.
>>>
>>> My largest complaint back-in-the-day when using Ferric Chloride was 
>>> the indelible orange-stain that the spills caused.
>>>
>>> Anyway, I am looking into chemical-milling some thin copper sheet, and 
>>> you may have solved one of the issues.
>>>
>>> Just wondering about spraying a thin layer of paint on the copper. 
>>> Removing the 'resist' using a laser cutter, then etching the remaining 
>>> piece.
>>>
>>> Anyone have any experience with a similar process ??
>>>
>>> -Mark
>>>
>>>
>>>> On 07 December 2020 at 09:14 Andrew Errington <erringtona at gmail.com 
>>>> <mailto:erringtona at gmail.com>> wrote:
>>>>
>>>> Ferric chloride is nasty, and becoming increasingly difficult to get.
>>>>
>>>> Try hydrogen peroxide and hydrochloric acid (or hydrogen peroxide and 
>>>> vinegar). Instructions on the web. I have tried it and it works.
>>>>
>>>> Andrew
>>>>
>>>> On Mon, 7 Dec 2020, 08:56 Marshland Engineering, < 
>>>> marshland at marshland.co.nz <mailto:marshland at marshland.co.nz>> wrote:
>>>>
>>>>     Is this Ferric Chloride still available in NZ ?
>>>>
>>>>     I have some ammonium persulfate but FC works at room temperature
>>>>     which makes
>>>>     it easier.
>>>>
>>>>     Cheers Wallace
>
>
>
>------------------------------
>
>Message: 2
>Date: Mon, 7 Dec 2020 13:09:34 +1300
>From: Mark Atherton <markaren1 at xtra.co.nz>
>To: chchrobotics at lists.ourshack.com
>Subject: Re: [chbot] chemical milling
>Message-ID: <78732e30-c722-d2ba-cd72-7c57beec87d7 at xtra.co.nz>
>Content-Type: text/plain; charset=utf-8; format=flowed
>
>In the order of 500u copper. Also wondering if I can chemically-mill 
>nickel. Piece is likely to be 20mm dia, with a 750u hole in the centre. 
>Final application is a wehnelt cylinder.
>
>-Mark
>
>On 7/12/2020 12:19 PM, ceo at andygardner.com wrote:
>> 
>> Copper thickness? (Thinness?)
>> 
>> Do you have a rough sketch of what you need?
>> 
>> 
>> 
>> On 7/12/20 12:09 pm, Mark Atherton wrote:
>>> ERT
>>>
>>> On 7/12/2020 12:05 PM, ceo at andygardner.com wrote:
>>>>
>>>> Are you milling a channel in the copper or want to eat right through 
>>>> to the other side?
>
>
>
>------------------------------
>
>Message: 3
>Date: Mon, 7 Dec 2020 13:44:06 +1300
>From: Ivo Gorny <ivo.gorny at callaghaninnovation.govt.nz>
>To: Christchurch Robotics <chchrobotics at lists.ourshack.com>
>Subject: Re: [chbot] chemical milling
>Message-ID:
>	<CALqFeKwobvc70eQUQUfx+yA4fgfuryh9L=KhLnnyX5+Xrm3Rnw at mail.gmail.com>
>Content-Type: text/plain; charset="utf-8"
>
>Just to but a different opinion on the table:
>
>I have done a lot of home brew PCBs, and tested a variety of etchants - my
>preferred process, using a self-built double sided UV exposure box with
>vacuum pump, is:
>
>1) Create the layout and print it on a transparent paper (like architects
>use). Laser printer setting on 'Black as possible'.
>2) Use a UV sensitive film and expose the layout as a contrast enhancement
>to the film. Do twice, if two sided layout.
>3) develop like regular B&W film (yeah, that vinegar smell again) - and dry
>properly.
>4) expose the PCB. Now, I buy photosensitive PCBs, but one can easily buy
>the spray with the photoresist and coat your PCB (or copper sheet metal)
>yourself. tested that successfully.
>5) develop the photoresist.
>6) Etch the PCB. I have best results with Ferric Chloride, at ~60°C and
>slight movement. I am very careful not to drip or splash around, oh, and
>the halflife of the solution can greatly be enhanced by adding a bit of
>Hydrochloric Acid when it starts to look more muddy green then yellow. All
>other chemicals are too expensive or dangerous and do not offer the
>halflife.
>
>The detail level goes down to track/gap widths of 0.4..0.5mm. But with
>cheap PCBs available from China nowadays, I am not doing it very often...
>
>The challenge is to get the chemicals for the film nowadays...
>
>If the layout is simple, it can be cut out of plack paper and glued on
>clear film, cutting out the step of producing a film.
>
>Ivo
>
>On Mon, 7 Dec 2020 at 13:10, Mark Atherton <markaren1 at xtra.co.nz> wrote:
>
>> In the order of 500u copper. Also wondering if I can chemically-mill
>> nickel. Piece is likely to be 20mm dia, with a 750u hole in the centre.
>> Final application is a wehnelt cylinder.
>>
>> -Mark
>>
>> On 7/12/2020 12:19 PM, ceo at andygardner.com wrote:
>> >
>> > Copper thickness? (Thinness?)
>> >
>> > Do you have a rough sketch of what you need?
>> >
>> >
>> >
>> > On 7/12/20 12:09 pm, Mark Atherton wrote:
>> >> ERT
>> >>
>> >> On 7/12/2020 12:05 PM, ceo at andygardner.com wrote:
>> >>>
>> >>> Are you milling a channel in the copper or want to eat right through
>> >>> to the other side?
>>
>> _______________________________________________
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>------------------------------
>
>Message: 4
>Date: Mon, 7 Dec 2020 13:57:04 +1300
>From: Andy Gardner <ceo at andygardner.com>
>To: chchrobotics at lists.ourshack.com
>Subject: Re: [chbot] chemical milling
>Message-ID: <1f003311-5fa3-7a9d-85f7-67badd6a0ffe at andygardner.com>
>Content-Type: text/plain; charset=utf-8; format=flowed
>
>
>Sounds like a job for a spark eroder?
>
>On 7/12/20 1:09 pm, Mark Atherton wrote:
>> In the order of 500u copper. Also wondering if I can chemically-mill
nickel. Piece is likely to be 20mm dia, with a 750u hole in the centre. Final
application is a wehnelt cylinder.
>> 
>
>
>
>
>------------------------------
>
>Message: 5
>Date: Mon, 7 Dec 2020 14:09:04 +1300
>From: Mark Atherton <markaren1 at xtra.co.nz>
>To: Christchurch Robotics <chchrobotics at lists.linuxnut.co.nz>
>Subject: [chbot] more chemical milling
>Message-ID: <9bec3096-2dcc-82fd-fe70-7aa785c32443 at xtra.co.nz>
>Content-Type: text/plain; charset=utf-8; format=flowed
>
>https://www.microchemicals.com/technical_information/wet_etching_metals_al_au_cu_cr_ni_ti_ag.pdf
>
>.. and several references to Hydrofluoric Acid.
>
>eek.
>
>-Mark
>
>
>
>
>
>------------------------------
>
>Message: 6
>Date: Mon, 7 Dec 2020 19:21:50 +1300
>From: "Robin Gilks" <robin at gilks.org>
>To: marshland at marshland.co.nz, "Christchurch Robotics"
>	<chchrobotics at lists.ourshack.com>
>Subject: Re: [chbot] Ferric Chloride
>Message-ID: <cbfa757929f62b0034b808de4fb4be77.squirrel at gilks.ath.cx>
>Content-Type: text/plain;charset=iso-8859-1
>
>
>> Is this Ferric Chloride still available in NZ ?
>>
>> I have some ammonium persulfate but FC works at room temperature which
>> makes
>> it easier.
>>
>> Cheers Wallace
>
>I had reasonable luck with hydrochloric acid (from pool shop - Ph
>adjuster) and copper sulphate (PGG Wrightson - fungicide).
>
>Careful how you store the mix though as the fumes (open top etch tank)
>made all the steel in my garage go rusty.
>
>-- 
>Robin Gilks
>
>
>
>
>
>------------------------------
>
>Subject: Digest Footer
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>------------------------------
>
>End of Chchrobotics Digest, Vol 159, Issue 6
>********************************************