What is etching and what is spray etching?

Etching is the process of eating away a pattern on a target material by using an etchant liquid that attacks the target material.

The most common target materials are copper and brass. The most common etchant liquids are ferric chloride, ammonium persulphate and cupric chloride

On a hobby scale it is common to submerge the target into a container filled with the etchant. This can be very slow and is often sped up by either mechanical agitation or using an aquarium / fish-tank bubbler. Even with the speed up from sloshing the container around this process can take 10-15 minutes for a PCB or over an hour for a thick brass plate.

The spray etching method uses the same etchant liquid as the submersion method, but instead sprays the liquid onto the target. This can speed up the process by an order of magnitude.

The advantages that spray etching has over the more mundane submersion method of etching is
  1. Faster
  2. Less manually intensive
  3. More uniform etch
  4. Produces sharper edges / better detail

Where are spray etchers used?

  • Manufacturing PCB (Printed Circuit Boards)
  • Etching plates for intaglio printmaking
  • Etching brass nameplates / plaques
  • Photochemical machining of mechanical parts (often used in model trains)
  • Etching jewellery
  • Etching stencils (if you can't afford a laser cutter hint hint)
  • Automatically generating traffic by showing friendly site logos made from brass

Why a ROTARY spray etcher?

This rotary spray etcher can be built for between $50 and $100, depending on where you need to source your material. This is a lot less than the $300 plus that other spray etching machines would cost. It is also quicker and easier to build as long as someone else has made all the errors along the way FOR you.


Well here is where I get to say "follow me on this remarkable journey of discovery"

Step 1:

Background / Prior Art

Types of spray etchers

There are two main methods of building spray etch machines.
  1. A pressure pump and nozzles
  2. Rotary spray etchers that rely on centrifugal force

Pressure Pump Versions

This is the method that commercial PCB manufacturing equipment uses. In an industrial setting where reliability, throughput and lowest level of operator skill are valued over cost and size, it wins hands down.

This method is also fairly well represented in DIY projects on the web with at least three projects showing up with only a cursory search in google.

  1. Proto Trains design dates from 1996 but first appeared on the web in around 2002.
  2. Adam Seychell dates from June 2007. (Unfortunately missing in action at the moment and on the way-back machine without pictures.)
  3. Crreed on Instructables from Instructables dating from 2012

The commercial machines and the three DIY projects all approach the uniformity problem differently. Having some relative movement between the nozzle and target removes problems with high pressure spots. Having the target in a horizontal orientation reduces undercut.

Nozzle Target Target
Industrial Stationary Moving Horizontal
Proto Trains Stationary Moving (rotating) Vertical
Adam Seychell Moving Stationary Horizontal
Ccreed Stationary Stationary Vertical

Rotary Spray Nozzle Versions

Rotary spray etchers are a whole different kettle of fish when it comes to DIY projects. It seems that although newsgroups are littered with people starting a project to build one, only one DIY project seems to have been published on the web to look at. It is also not the easiest thing to find as it is in German and “spray etcher” will not turn it up in a google search.

Spruhatzanlage use google translate or BableFish to make a bit more sense of it

The German site although very professionally done and full of helpful pictures, does not address the pitfalls of building one yourself.

Pressure Pump Vs Rotary

Pressure Pump

  • Can be scaled up
  • Can be built with target in horizontal position (reduces undercut)
  • Can achieve higher uniformity of etch if either target or nozzle are moving

  • Expensive to build (relative to rotary)
  • Difficult to find suitable pumps (Seychell recomends against Shurflo)
  • Labour intensive to build (relative to rotary)
  • Poor uniformity with static nozzle/target
  • Risk of hoses coming loose and coating your workshop in etchant with some Spray Etcher designs

Rotary Spray

  • Cheap to build
  • Easy to build
  • Excellent uniformity over a small area
  • Lower risk of accidents spraying etchant around

  • Can not be scaled up in size a great deal
  • Target can only be vertical
  • very difficult to get working well (until now)
<p>Adam has a new website it seems</p><p><a href="http://home.exetel.com.au/adam.seychell/PCB/SprayEtcher/index.html" rel="nofollow">http://home.exetel.com.au/adam.seychell/PCB/SprayE...</a></p><p>Appears he changed ISPs</p><p>Very neat idea, excellent documentation, top work mate.</p>
<p>Very nice work. Thank you for sharing.</p><p>Been looking for parts in the US. Our standard 3/4&quot; PVC pipe comes in two different versions, 20.4mmID / 26.6mmOD and 22.8mmID / 26.6mmOD. The most common version is close to your specs, 20.4mmID / 26.6mmOD. I ask because your photos look very much like the thin wall version available here. Would you please confirm that you used a 20mm ID/ 27mm OD? Your write-up mentions both 26mm and 27mm OD. Do you think the thin wall (22.8mmID / 26.6mmOD) we have here would work as well? I would prefer to follow your proven approach and would appreciate clarification only because the photos appear as a thin wall PVC tube.</p><p>Also, you mentioned in one of your responses to a question that a center hole in the impeller is an issue. Did I understand that correctly? Attached are photos of the two impellers under consideration. If the center hole is and issue it should be fairly simple to plug. </p><p>Thank you again for sharing your idea and work.</p>
<p>The size of the PVC is not that critical. You can get by with anything in the approximate range. Thin wall is slightly better as it will need less unblocking with heavy use.</p><p>The impellers NEED a hole in the middle rather than at the edge. You need that lip on the edge to stop the fluid being flung back out when centripetal force is pushing the fluid to the outside of the tube.</p>
<p>I'm wondering if anyone would build one and sell it to me or has seen any similar I could purchase? I'm a metalsmith and I really need one, but I'd rather have someone else build it for me. </p>
<p>Bungard sell a smallish spray etcher for a few $K</p>
<p>Hi, after experimenting with &quot;thick&quot; tubes for plumbers I have finally used &quot;thin&quot; carbon tubes for modellers. Holes are crucial so I did drilling work on my lathe with DIY drill on support. Hole dia is 0.8mm distance in row 6mm and three rows 120&deg; each with hole offset 2mm. Spray tubes are counterrotating so when in the half time is work turned over then etch uniformity is even beter. Now I am working on the electonics. When finished I&acute; ll give some results.<br>Regards from Brno, Moravia( Czech Rep.)</p>
regarding a sophisticated impeller/fan . There a lot of activity / enthusiasts that are building at home made 3D printers (also there is a group on yahoo). Also are available commercial services for this. On a such a printer can be made this impeller fairly easy . Also I am interested to participate on this &quot;improvement&quot;. <br>Regards, <br>Daniel
Daniel, <br> <br>It seems there is a fair bit of interest happening. I am going to try find someone local with a 3D printer to come up with a printable design for it. <br> <br>It should make easier one of the more fiddly parts of the build. <br> <br>I have also had feedback from a few people to make the etcher easier to keep clean.
<p>I am designing a spray tube using a 3D printed impeller. In fact, I'm reproducing you basic design, but using only off-the-shelf (in the UK) parts and 3D printed widgets. I will obviously write and instructable and share all design files (including source code) with everyone when I am done.</p><p>I printed my first impeller last night at my local makerspace (SoMakeIt in Southampton) since my 3D printer is not working so well right now, but I seemed to have screwed up my maths (in openscad) and it doesn't fit my tube...more work to do. I'll keep you all posted!</p>
<p>What a pleasant surprise to read your reply now after 2 years ! This idea (with printed propeller) has been sitting in my to do list until now. Hopefully soon I will be able to print myself that impeller. Could you post / share a image with your design ? </p>
<p>Sure, when I get it to work, I'll post up the files to reproduce. I'm starting with the spray tube, as this is the hardest part. I'm not decided how to drive the thing yet, so I'll make a prototype top cap that can accept a screw or stud, so I can just use a variable speed drill to play with it. I found the openscad bug last night - pretty easy to fix. I will reprint next week and try again...</p>
<p>My ideea would be to print only the impeller and not the hole tube. Printing all tube may not be balanced at high speed. On the other hand an idea would be to print inside of tube an archimedes screw : http://www.thingiverse.com/thing:79245</p>
<p>Yeah, sure. I want to use ordinary 34 mm (out diameter) PVC waste pipe, as available in the UK for very little for the tube. You can look at my current effort (sorry, it's very rough at the minute) on my github here: </p><p><a href="https://github.com/daverowntree/spray_etcher" rel="nofollow">https://github.com/daverowntree/spray_etcher</a></p><p>This is not released, finished or tested. I printed an earlier design, but then I changed my mind :) I may also add a little bit of a twist (configurable) to the impeller blades later. You will need to install OpenSCAD to compile the design and export as STL (change the argument to platter=true in the body module at the top, then hit compile, and export STL) I will ALWAYS release full OpenSCAD source, rather than a bunch of crappy STLs for my work. There is much more to come when I get round to uploading more to this repo, so watch this space!</p><p>Also, I am contemplating the archimedes screw idea...it is...interesting :)</p>
<p>Hello, </p><p>Sorry for late reply. Regarding type of impeller I was thinking about more something like this :</p><p><a href="http://www.simerics.com/simulation-gallery/centrifugal-pump/" rel="nofollow">http://www.simerics.com/simulation-gallery/centrif...</a></p><p>But of course to rotate in oposite direction.</p><p>DAniel</p>
<p>People have experimented with screws inside the tube. They seem to be no more effective than the dams.</p>
<p>I want to see all the above! This list is (a subset of) my wishlist, so any details you can publish would be awesome :D</p>
<p>Anybody having issues with sprayer holes getting blocked with debris? Maybe some kind of online filter may work... Working on it.</p>
<p>Only if I let the solution get very thick with spent brass and leave it unused for a long period.</p><p>With fresh ferric or any CuCl I have not had blockages.</p>
This instructable rules, thanks! I was wondering, for heating, is there any reason you couldn't use a glass aquarium heater? I'm currently testing out various tubes and configurations in preparation for building my own etchinator, it seems the spray tubes are pretty finicky to get going. I've tried both a 22mm OD / 15mm ID tube and a 34mm OD / 28mm ID tube and the smaller definitely doesn't work as well as the larger one - however i still can't get the larger one to spray all the way up the tube. I bought two of <a href="http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?refineValue=JOHNSON+MOTORS%2CINC.&refineType=String&langId=-1&from=mflisting&productId=2167437&catalogId=1000&sub_attr_name=Manufacturer&storeId=10001&ddkey=http:StoreCatalogDrillDownView" rel="nofollow">these</a> motors which looks like they should be quite perfect, no? I too had problems making a good impeller, best i've tried is getting a fan like <a href="http://www.newegg.com/Product/Product.aspx?Item=N82E16835119098" rel="nofollow">this</a>, rip out the fan part and glue it upside down to a piece of plastic covering the bottom of the tube. Figuring out how far up the tube the water/spray is going to reach and calculating the drop of the water over distance seems really hard - any way of doing this without experimenting? I'm currently prototyping in a plastic tub but would like to migrate the project to a larger glass aquarium i bought second hand.
Yes, you can use an aquarium heater. Just make sure it is compatible with your etchant. <br> <br>Is there a ring plastic at the bottom of your tube with just a hole in the center? You can't get the water to travel all the way up the tube without this ring preventing the water from going out the bottom also.
Well it's a plastic circle with a 6.35mm hole in the bottom and the fan glued as an impeller on the inside - picture attached. The impeller is the most confusing part to me so i'm not sure i did this right..
At a guess I would say try increasing the size of the hole. <br> <br>All my iterations where done experimentally so I can't give you any maths. However the tubes throw out a LOT of liquid and I would think that the 6.35mm hole is becoming a bottle neck.
First pic! (Sorry, tomorrow i will post a better pic)
Fabulous work. It almost looks radioactive with that green back lighting. <br> <br>Is that CuCl etchant full density yet, or are you still using H2O2 in it?
Lol, thanks. It's CuCl + H2O2, with a white back light (so i can see when the work it's done..) ,
Cool. If you are after absolute best results then measure and titrate the CuCl (as per Adam Seychell guide) and go easy on the H2O2. Too high an acid and too much free oxygen causes the etchant to be very aggressive. Very high Acid and O2 will also cause a lot of fuming and will rust your motors. <br> <br>It also saves money on H2O2 :)
Acid-motor issue fixed. The holes in the pvc conduit where way too high, now my motor is pretty safe from it. :)
A preview of the working machine: http://www.youtube.com/watch?v=f7xyQUiLLsA
Hello, thanks for this beautiful design, i'm almost done with my own etchinator with a few mods, in the next week i will be showing some pics.
Your Instructables are top shelf there, Mr. cunning_fellow. Never new Aussies could be so creative:) More please!
We don't just spend all day saying &quot;Crikey mate a stingray just got me&quot; <br> <br>We have to fill in the rest of our days somehow. <br> <br>There is a new instructable on the burner I want to try get done for the Zing competition. However it's pretty hard slog when all your parts from digikey have to come via kangaroo.
And, I suppose, why a great sense of humour is also required. I'd put a vote in for you, but for some reason, can't bring myself to do that just yet:) Good luck. I'm looking forward to seeing it.
Total Awesome Instructable. Would love to see your through hole plating setup next
Great instructable! Could you please put up a video showing it in action?
Bri-Wiz, <br> <br>It no so exciting to watch the machine run in a video. I will try do a video of its use though. I will just cut/FF/timelapse the boring &quot;spray&quot; part.
I know the video may seem boring to professionals but for us poor laymen it will be fascinating and inspiring especially as this is a beautifully built apparatus!
&gt;If this project is well received and people seem keen I have another few projects about home brew PCB manufacturing equipment<br> <br> Yes Yes Yes!
SDX, <br> <br>Stay tuned. About 10 people so far have told me they have built or are building The Etchinator and I have some feedback to improve the design. <br> <br>I am also working on the write if for another few pieces of equipment at the moment.
I am in the process of constructing an etchinator, with the goal of eventually scaling it up by using a row of spray tubes with blinds between them to control the angle. I have constructed one impeller out of plexiglass, and am still trouble-shooting it, but wonder, what do you imagine the fan looking like in a perfect world? Is it still based on fluid entering through a small hole in the end, or does it pull fluid in from the sides? <br>Thanks so much, <br>Cat
Cat,<br> <br> I would suggest having a look at Adam Seychells spray etcher on the way back machine. &nbsp;The photos have gone AWOL, but the descriptions are all there.<br> <br> Economics is not very kind to &ldquo;scaling up&rdquo; the design I show here.<br> <br> With the spray tube etcher here there is one motor (the expensive part) per tube.&nbsp; If you scale up to 10 tubes you need 10 motors.&nbsp; In contrast pump/nozzle type spray etcher still only needs one pump.<br> <br> Although the original motors I bought years ago where $5, recently the cheapest reliable source of motors I have found outside the US is $12.&nbsp; This means a 10 tube etcher would be $120 just in motors.&nbsp; Motors alone you are spending more in parts than a diaphragm pump.<br> <br> Aside from the low cost of the small version, the etchinator comes out favourably because you don't need to construct a tank.&nbsp; The HDPE storage crate make a very convenient liquid tight container.&nbsp; If you are scaling up you are going to have to make your own PVC tank.&nbsp; The Etchinator style has lost both advantages now.&nbsp; It's no longer easier to build and it will be more expensive.<br> <br> WRT you question about the impeller.&nbsp; I am looking at axial inflow radial outflow styles.&nbsp; Look at a car turbo charger photo off google to get an idea.&nbsp; There is still a small inlet hole but the impeller blades come down and face forward.<br> <br> Also if you DO decide to scale up the spray tube etcher, you probably don't need the blinds.&nbsp; The angle issue I show in the digram on step.4 is not really about the angle of the impact causing undercutting. It is the angle of the impact having less force therefore a slower etch (poor uniformity).&nbsp; Any overlap from not having &ldquo;blinds&rdquo; will cause faster etching.&nbsp; If you just work out how far apart to have tubes to balance out the speed-up and the slow-down your should be right :)<br> <br> But really I do recommend a pump version for anything much larger than what is shown.&nbsp; The pump&nbsp; version on a large scale will be<br> <br> Cheaper<br> Easier to construct<br> Very marginally better results (Adams style, Creeds style will be MUCH worse)<br> Easier to automate
Thanks for the detailed response. I will look into Adam's design, and see what I can make of it. Cheers!
A few things to keep in mind if you DO build the pump version. <br> <br>The pump Creed used is apparently not etchant safe and will die a horrible death without modification. (See the link in Step.1 to Adams experience with the same pump). In that link Adam recommends FloJet instead (which is the brand proto-trains used). <br> <br>Hoses running outside of a containment vessel are not a great idea. Read the section &ldquo;Etching tank No.4&rdquo; in the proto-trains link in Step.1. Watch Creeds video and pause at 3:21. Now imagine that pressure relief hose on the OUTSIDE of the tank. That is the volume of corrosive fluid being splashed around the shop when the hoses let go. <br> <br>A second PVC containment vessel that contains ALL hoses and the pumps is probably a good plan. PVC is cheap and making the outer tank will only be expensive in time. Weigh that up against time cleaning up after a spill WHEN it happens. <br> <br>Finally these days if you look at that festering pit flea-bay and search for &ldquo;PCB Ceramic Spray Nozzle&rdquo; you actually find something. I have never bought or used these so I don't know what the quality is, but they are not too expensive to give a try.
I don't do enough etching to justify making one of these, but I just wanted to say that this is incredibly well documented and written. I also like seeing plastic used without a laser cutter (they can be such a crutch.) <br> <br>Did you etch the Hackaday logo from a solid sheet? How come it doesn't get massive undercuts? <br>
It gives a perfect opportunity to say to people &quot;Doubt but not using hand tools is an art.....&quot;. It is a shame a lot of people don't think it is an art well worth their learning. Obviously entering the Hurricane contest means I would love to have a working CNC mill or a laser cutter. I am glad however that I have spent the time learning to use ruler, saw and a file. <br> <br>The Hack-a-Day logo was made from the same 0.7mm (1/64&quot;) as the Instructable Robot. The lack of undercut is the &quot;extra way big&quot; advantage of spray etching. The droplets hitting the target at speed and close to perpendicular help etch directionality. <br> <br>If you tried to do the same etch depth (0.35mm) sloshing around in a container full of liquid, you would get about 0.2mm undercut. Sloshing gives a wanted to unwanted direction of etch ratio of about 3:1 on fresh etchant down to 2:1 on spent etchant. <br> <br>The Etchinator gives more like 10:1 down to 5:1. If you want better than that you are going to have to build something like Adam Seychell did.
Thanks everyone for the positive comments.
&quot;Mark the drill points at 6mm intervals along the first line. Mark the second line with the same 6mm intervals but offset by 2mm. Finally do the marking of the third line offset by another 2mm (4mm total).&quot; <br> <br>Making a note that the offset is vertical to better cover the item being etched would be a good idea. <br> <br>An easier way to ensure the motor couplers align with the tubes would be to turn a step on them. Use a ratcheting PVC pipe cutter (a good one) and you'll have perfectly straight pipe to coupler connections.
thanks, I will try draw up a diagram to clear that ambiguity up.
Forgot to mention that drilling the couplers on the lathe will make perfectly centered holes, as long as the tailstock is properly aligned.
Great instructable, terrific detail and all well done. <br> <br>Good old Reverse Garbage eh? They are not as good as they used to be but I have scored some nice material from them over the years. I miss them now I have moved to the country. <br> <br>With respect to posting your other projects - well just call me Colonel Mustard ;-)

About This Instructable




Bio: Just a guy really. Like building stuff and like to help other people build stuff too. If you really need to know, am male in ... More »
More by cunning_fellow:The Asteroid Belt My response to the WS2811 with an AVR thing The Etchinator - low cost PCB spray etcher (under $100) 
Add instructable to: