Difference between revisions of "Equipment/PCB etch station"

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[[File:Pcb labstation.jpg|thumb|right|Etch station]]
+
{{EquipmentInfobox
 +
|name=PCB etching station <!-- Name of the item. -->
 +
|image=PCB710S.jpg <!-- Image of the item. Leave with placeholder image if none exists. -->
 +
|model=PCB710S <!-- Model -->
 +
|category=Equipment <!-- Main category. Please leave alone to keep item in this category -->
 +
|subcat=Fabrication<!-- Sub-category if one exists. Please check main listing to see other categories contained within the main one -->
 +
|status=Good working order
 +
|consumables=Cupric Chloride, Developer<!-- Any items used up in normal operation, such as; ink, paper, saw-blades, cutting disks, oil, etc.. -->
 +
|accessories=Pump <!-- Any items associated with the equipment but not consumable, such as; drill bits, safety gloves, goggles, etc.. -->
 +
|reqtraining=no
 +
|trainlink=[http://wiki.london.hackspace.org.uk/view/Pcb_etching_instructions Etching instructions]<!-- If training is required, provide a link to training signup or contact page. Otherwise leave blank. -->
 +
|acnode=no
 +
|owner=Artag<!-- Provide a link to owners members page if other than LHS -->
 +
|origin=Pledge<!-- If via pledge, please link to the completed pledge page on the wiki -->
 +
|location=Ground Floor, Murder Kitchen<!-- Floor, room/zone and location within that area -->
 +
|maintainers=Artag, Mentar, Liam <!-- NO LINKS PLEASE; it currently breaks the template. If someone is nominated as managing the upkeep of this item, please list them here. -->
 +
|template_ver=1.1 <!-- Please do not change. Used for tracking out-of-date templates -->
 +
}}
 +
We have a [http://www.megauk.com/production_lines.php Mega Electronics PB710S PCB Production line] etching station, obtained by a [[Pledge:_PCB_Etch_Tank|Pledge]]
 +
 
 +
Note : see '''[[Pcb]]''' for other references
 +
 
 
==Important Warnings==
 
==Important Warnings==
  
−
* Do not put any water in the spray wash tanks at the moment : it will flow straight onto the floor.
+
* '''CLEAN UP AFTERWARDS'''
−
* Do not run any heater unless the tank is full of liquid. It should blow a thermal fuse before melting the tank, but that may involve replacing the heater. Keep unused heated tanks full of plain water until we have disabled the heaters.
+
* Do not run any heater unless the tank is full of liquid. It should blow a thermal fuse before melting the tank, but that may involve replacing the heater. Keep unused heated tanks full of plain water or disable the heaters by unplugging the associated connector inside the cupboard door.
 
* Do not etch anything except copper (other metals will pollute the etchant).
 
* Do not etch anything except copper (other metals will pollute the etchant).
 
* Do not drink the contents, even when there's no beer.
 
* Do not drink the contents, even when there's no beer.
 
* Do not allow children or drunken hackers to play with the tanks.  
 
* Do not allow children or drunken hackers to play with the tanks.  
 
* Check the power has been turned off after use.
 
* Check the power has been turned off after use.
 +
* Do not dip a basket soaked in one chemical into the tank of another chemical.
 +
* Read the [[Media:PB BENCH Line and PCB Labstation instructions.pdf|instructions (pdf)]]
 +
* '''CLEAN UP AFTERWARDS'''
 +
 +
==Less important warnings==
 +
 +
* You normally place boards to be etched in the plastic basket under a tank lid, then dip it into the tank. If the PCB is too close to the open end, it will fall out. You may have to drain the tank to retrieve it. You don't want to do this, so put the pcb well into the opening and don't tip it forwards as you remove the basket from the tank.
 +
* Very small PCBs may fall through the holes. A possible solution is to put them in fine-mesh envelopes before putting them in the basket. Finding a suitable envelope is left as an exercise for the user (hint - look on the [http://www.megauk.com Mega website]).
 +
 +
==Model==
 +
[[File:HackneyRoadEtchTank_small.jpg|thumb|right|The PCB station]]
 +
* Make: [http://www.megauk.com Mega Electronics]
 +
* Model: [http://www.megauk.com/production_lines.php PB710S] - PCB 7 tank production line with sink
 +
 +
Manual: [[File:PB_BENCH_Line_and_PCB_Labstation_instructions.pdf]]
 +
 +
==Controls==
 +
[[File:PCB_station_controls.jpg|right|thumb|Controls for the PCB station]]
 +
The leftmost button on the control panel is mains power. If you see it lit up when no-one is using the tank, please turn it off (but if someone _might_ be waiting for it to warm up, please check first!). Probably a good idea to switch off at the mains as well.
 +
 +
Each tank and rinser then has a control section. Working from left to right, these are:
 +
 +
* '''Developer''' - Heat button and 'heater active' light. Set to about 28&deg;C.  Heating not normally required.
 +
* '''Developer rinse''' - Spray button activates spray bar.
 +
* '''Etch''' - Heat button and 'heater active' light. Set to about 48&deg;C.  Takes about 15-20 minutes to get hot.
 +
** Air bubbler button - only active when heating is also on.
 +
* '''Etch rinse''' - Spray button activates spray bar.
 +
* '''Photoresist stripper''' - Heat button and 'heater active' light. Set to about 50&deg;C.  Optional.
 +
* '''Stripper rinse''' - Spray button activates spray bar.
 +
* '''Tinning''' - Heat button and 'heater active' light. Set to about 50&deg;C.  Optional.
 +
 +
The spray bars work best if only one is on at a time (and unless you're making a lot of boards at once, you probably only need one).
  
 
==Status==
 
==Status==
−
''We are currently planning on fixing-up the unit and working out how it should be configured: ''
+
=== 1st Tank - Developer ===
 +
Working SENO4006 (concentrate, fresh as of 20-FEB-2016)
 +
Resupply with:
 +
* [http://www.megauk.com/developers-pre-coated-boards.php Mega Electronics 690-849]
 +
* [http://www.rapidonline.com/Tools-Equipment/4006v05-Seno-Liquid-Developer-Concentrate-1ltr-for-10ltr-20ltrs-34-0790 Rapid 34-0790]
  
−
From a quick test it appears to have no major faults : it heats all the tanks, it bubbles, the spray wash solenoids click, and the tanks don't appear to leak. And the cupboard turned out to contain some developer and tin plating crystals!
+
=== 2nd Tank - Etchant ===
  
−
The tanks are currently full of water - very polluted by the previous contents. Don't expect it to etch ! The intention is to soak off the old contents, clean them out and then refill.
+
Now contains CuCl2 etchant at ~3M strength. Ready to use. (Heater does not seem to shut down by itself so make sure not to overheat the solution, being worked on)
  
−
The bench should be usable in the simplest form as soon as we've checked it out, but there are some things we can do to make the best of it. There's a need for a handful of plumbing and electrical accessories.
+
Resupply: instructions below!  Required materials are:
−
===Todo===
+
* HCl
−
====Urgent====
+
* Copper
−
* Check tank drains (clamped tubes inside cupboard) to make sure clamps and tubes are sound and not just about to fail.
+
* NaOH (for checking concentration)
−
* Check bubble bar carefully for an even flow : replace water in etch tank with clean, use torch to see if all holes are bubbling. If it's not fairly even, clean as described by Mike on the mailing list (but note warnings about damaging clamping nuts). If there are only minor problems with the bubble bar, try cleaning without removing (prick holes with pin, use cleaning crystals, run bubbler etc.). '''Warning - the bubble bar will only operate when the heater is on, and there MUST be plenty of water in the tank to operate the heater'''
 
−
* Flush all tanks another couple of times, scrubbing top area back into the water.
 
−
* Fill and use if desired
 
−
====Soon====
 
−
* Scrub out sink
 
−
* Connect waste pipe on back of cabinet. There are some random plumbing fittings in a bag in the cupboard and may be some more in the space, possibly under the lab 24 sink. In particular a rodding tee that was fitted to the outlet, and a new swept tee. Check under the hangar 23 sink for a spot to link in using that swept tee or some other fittings. A length of 1 1/4" pipe will be needed and maybe a few other fittings. A short flexible section or something easily disconnected would be a good idea.
 
−
* Connect cold water to wash tanks. This can probably be done using the tap just above the tank, if the pipes are long enough. BUT DON'T DO THIS UNTIL THE WASTE IS CONNECTED!!
 
−
* Build splashback if possible.
 
−
* Connect cold water to tap. Might be possible using a Y connector on the same supply as the wash tank, but a neater solution would be to add washing machine fittings to the side of the existing sink unit. Unfortunately there's a water heater in the cupboard just where you need to work.
 
−
* Connect hot water to tap. Probably not really needed since there's an adjacent sink, but would complete the job.
 
  
−
===Usage configuration===
+
''' DO NOT put Ferric Chloride in this tank !!!''' In fact, please don't use ferric chloride at all - it silts up the tank and is really difficult to clean up. If there is some reason why we wish to use it again, it may be possible to use the 4th tank for it.
−
* Since it's already stained there's no problem in putting ferric chloride in it if we have some available (it needs 5 litres but 3 or 4 would do).
 
−
* We can use a spare tank to start brewing the cupric chloride if we want to do that
 
−
* There were some chemicals in the cupboard - developer, tinner, stain remover.
 
−
* I (artag) have some date-expired mask stripper we can try in a strip tank
 
  
−
===Placement===
+
====CuCl2 Etchant====
−
* We need water and waste connections for the rinse tanks. These are simple washing machine fittings but we may need adapters for the supply pipework and a waste hose. I do have some plumbing fittings but we may need more.
 
−
** Depending on when you need these, I could go out and get these on Fri/Sat. -- Elliot
 
−
** I think we'll need at least one cold fitting, ideally another cold and a hot too, and a way to get 1.25" waste into the sink plumbing - possibly just a length of pipe, possibly some joints. May be easiest to put things in place and then find exactly what's needed.
 
−
* Where do we put it ? I suggested replacing the unit 23 sink, but short-term it could simply go next to it. Tools may need moving, though. Or it could be installed in the unit 23 toilet. Or it could be integrated into a darkroom build. Discuss ..
 
−
** I think it can fit next to the sink in the place of the metal cabinet that is there currently - it may be a bit longer and deeper but that shouldn't be a problem. Ideally it'd be nice to keep the sink for other chemical type experiments. If we can avoid talking about the darkroom then we can save ourselves a lot of hassle :-) -- Elliot.
 
−
* It would be nice to have power without using the extension lead. The existing ring main might be extended fairly easily to put sockets on the wall near the sink.
 
−
** Again, depending on when electrical stuff is needed, I could go out and get conduit/socket/back box/etc. on Fri/Sat. -- Elliot
 
−
** I see there's a bit of conduit near #23 back door. Needs a socket plate and probably some more 2.5mm wire to link into the ring. Could be patched up but a better plan might be to look at fixing a couple of electrical jobs and buy the bits at the best price rather than in small pieces.
 
  
−
==Model==
+
The bath for [[Project:PCB Making/Cupric_chloride_etchant|Cupric Chloride etch]] was prepared  using the slow method : leave some copper in acid, allow corrosion to occur generating some oxides, add further copper and acid as required. Water, acid, copper and hydrogen peroxide (if used) should be noted as it's easy to over-dilute if you just add stuff randomly.
−
* Make: [Mega Electronics]
+
 
−
* Model: [http://www.megauk.com/production_lines.php PB710S] - PCB 7 tank production line with sink
+
The preparation so far contains 540g copper, 2900ml 38% HCl, 1750ml water. SG is 1260. This is ready for use - air has been bubbled through it and it has reached the bright green colour indicating it has converted copper to cupric chloride. The acid concentration appears to be correct and I have reconnected the heater.  If the etchant is not bright green, please leave the small fishtank bubbler running. The bubbles will regenerate the etchant.
 +
 
 +
'''DO NOT ETCH ANYTHING EXCEPT COPPER IN THIS TANK'''
 +
 
 +
See [[File:CuCl.pdf]] for maintenance instructions. These are basically : Check colour. Bubble if dark. Titrate against 1 molar NaOH to check acid concentration (this only requires a check for precipitate, no need for acid indicator). Add HCl if necessary.
 +
 
 +
If you use it, don't rely on the small bubbler to provide agitation - keep it moving the whole time (and be careful your board doesn't walk out the end of the basket when you do that). The small bubbler is really only there to re-aerate the solution after use, as it's quiet enough to leave on.
 +
 
 +
=== 3rd Tank -  (water) stripper ===
 +
 
 +
Currently contains clean water (mainly to protect the heater if accidentally switched on
 +
 
 +
Stripper can be resupplied with:
 +
* [http://www.megauk.com/strippers.php Mega Electronics 600-019] PC155 Resist Strip 1 Ltr makes 5 Ltrs
 +
* [http://www.rapidonline.com/tools-equipment/etch-resist-stripper-75331 Rapid 34-0400]
 +
 
 +
=== 4th Tank - (Water) ===
 +
 
 +
Currently contains clean water (mainly to protect the heater if accidentally switched on
  
−
==Controls==
+
===Planned changes===
  
−
The leftmost button on the control panel is mains power. If you see it lit up when no-one is using the tank, please turn it off (but if someone _might_ be waiting for it to warm up, please check first!). Probably a good idea to switch off at the mains as well.
+
*<del>Use Cupric chloride in the etch tank rather than Ferric chloride, which is messier, requires frequent replacement and silts up the bubbler.</del> Has been done
 +
*Replace the bubbler in the bottom of the tank with a bar suspended from the basket, so that it's easier to clean.
 +
*Link both the large air pump and the small one into the same air supply so the cupric chloride can easily be regenerated (requires long slow bubbling rather than short fast bubbling)
 +
*It would be nice to have power without using the extension lead. The existing ring main might be extended fairly easily to put sockets on the wall near the sink.
  
−
Each tank and rinser then has a control section. Working from left to right, these are:
+
==Notes==
  
−
'''Developer'''. Heat button and 'heater active' light. Set to about 28C.  Heating not normally required.
+
The pump was replaced with a heavier duty medical unit mostly because it was cheap & available. The original was a fishtank pump and is still mounted on the front of the tank. It worked, but seemed not to have enough pressure available to overcome backpressure if the aeration tube had partly filled with etchant.  Fitting it involved a few peculiarities, though.
 +
* There is a clamp on a branch of the tube near the pump, which can be used to restrict a controlled pressure relief and hence the vigor of the bubbles.
 +
* The pump is no longer fitted to the tank, but instead rests in the cabinet
 +
* It is still possible to remove the tank for maintenance: the cable and pipe connecting to the pump are very long but if they need to be detached the cable can be unplugged from the back of the pump and the pipe unplugged from the pump.
 +
* There is now a one-way valve between the pump and the antisyphon trap to reduce the possibility of etchant flowing into the pump.
 +
* The power connection to the pump has no earth wire connected and apparently swaps black/white colour coding. This is not just carelessness : the original black/white wiring apparently had black as neutral, white as live to the fish tank pump. The IEC lead to the new pump uses conventional euro colours : black is live. So black and white swap at the join. It's not very important as the pump doesn't have a preferred live connection.
 +
* The earth pin in the cable to the pump is not connected at the pump end (it's a 2-pin connector) so there was no point connecting it at the tank end.
  
−
'''Developer rinse'''. Spray button activates spray bar. Not yet available as it requires plumbing in.
+
The piping requires some care. Because of the increased pressure available from the pump, if the bubbler is blocked it's possible for the pump to blow the pipe off the bubbler. This can then lead to etchant leak.
  
−
'''Etch'''. Heat button and 'heater active' light. Set to about 48C.  Takes about 15-20 minutes to get hot.
+
At present, there are cable ties around the most important joints but NOT where it links to the pump. This tends to result in that joint breaking rather than any other, which is good because it's easily accessible and doesn't cause leaks. If there are problems with it blowing off too regularly, look into the cause : just fitting it more solidly is likely to lead to etchant leaks.
−
Air bubbler button. Only active when heating is also on.
 
  
−
'''Etch rinse'''. Spray button activates spray bar. Not yet available as it requires plumbing in.
+
Originally, I restricted the airflow into the tank (to avoid excessively vigorous bubbles) by pinching the air tube with a clamp. This often caused the pump connector to come off, prompting the use of cable ties. When the bubble tube silted up, it was that joint that came undone instead of the pump joint. This was a bad thing.
−
 
−
'''Photoresist stripper'''. Heat button and 'heater active' light. Set to about 50C. Optional.
 
  
−
'''Stripper rinse'''. Spray button activates spray bar. Not yet available as it requires plumbing in.
+
A new configuration places a T joint near the pump with the clamp fitted to the additional open outlet. The idea is to make a controlled leak so that excess pressure is bled off rather than overpressurising the joints. It's likely that this will need to be adjusted as the bubbler silts up.
  
−
'''Tinning'''. Heat button and 'heater active' light. Set to about 50C.  Optional.
+
The low-volume pump used for aeration is now teed into the bubbler pipe, so it will either bubble slowly from that or fast from the big pump. I had to add another non-return valve so the aerator air didn't all leak out the restricted leak. { diagram needed }
  
 
==Instructions==
 
==Instructions==
Line 76: Line 135:
 
The tank was previously in a school and there is a laminated sheet with usage instructions. It may not be applicable to our use but is worth looking at.
 
The tank was previously in a school and there is a laminated sheet with usage instructions. It may not be applicable to our use but is worth looking at.
  
−
[http://www.megauk.com/datasheets/5285_Data_Sheet_PB_BENCH_Line_and_PCB_Labstation_instructions.pdf Manufacturer's instructions]
+
* [[PCB etching instructions]] - '''This is the canonical guide to etching PCBs at LHS!!'''
  
−
[http://www.megauk.com/datasheets/5320_Data_Sheet_Fitting_Instructions_for_Heater_and_Bubble_Bar.pdf Heater and bubble bar Maintenance] - also see Mike's posting on mailing list.
+
== Extra references ==
  
−
[http://www.megauk.com/datasheets/5120_Data_Sheet_Ferric_Chloride_Etching_Solution_(600-015_600-016).pdf Ferric Chloride]
+
* [http://www.megauk.com/datasheets/5285_Data_Sheet_PB_BENCH_Line_and_PCB_Labstation_instructions.pdf Manufacturer's instructions] ([[Media:PB BENCH Line and PCB Labstation instructions.pdf|local copy]])
 +
* [http://www.electricstuff.co.uk/pcbs.html Electric suff PCB etching guide]
  
−
[http://www.megauk.com/datasheets/5125_Data_Sheet_Ferric_Chloride_Stain_Remover_(600-039).pdf Stain remover]
+
=== Spares and Repairs ===
 +
* [http://www.megauk.com/datasheets/5320_Data_Sheet_Fitting_Instructions_for_Heater_and_Bubble_Bar.pdf Heater and bubble bar Maintenance] - also see Mike's posting on mailing list.
  
−
[http://www.megauk.com/datasheets/5135_Data_Sheet_Fine_Etch_Crystals_(600-014_-_5_Ltr).pdf Fine etch crystals] - we don't use this at present but it's been suggested.
+
* [http://www.megauk.com/datasheets/5125_Data_Sheet_Ferric_Chloride_Stain_Remover_(600-039).pdf Stain remover]
 +
* <del>[http://www.megauk.com/datasheets/5135_Data_Sheet_Fine_Etch_Crystals_(600-014_-_5_Ltr).pdf Fine etch crystals] - we don't use this at present but it's been suggested.</del> we use Cupric Chloride currently ...
  
−
[http://www.megauk.com/datasheets/5290_Data_Sheet_Photoresist_Stripper_PC155_(600-019).pdf Photoresist stripper]
+
* [http://www.megauk.com/datasheets/5290_Data_Sheet_Photoresist_Stripper_PC155_(600-019).pdf Photoresist stripper]
 +
* [http://www.megauk.com/datasheets/5185_Data_Sheet_Immerse_Tin_(600-020-021).pdf Tin plating] - We have a small tub of this, possibly unusably old.
 +
* [http://www.megauk.com/cgi-bin/mega/datasheets.pl All Mega MSDS and data sheets]
 +
* [http://rdchem.com/chemical-milling.html Maintaining ferric chloride etchant]
  
−
[http://www.megauk.com/datasheets/5185_Data_Sheet_Immerse_Tin_(600-020-021).pdf Tin plating] - We have a small tub of this, possibly unusably old.
 
  
−
[http://www.megauk.com/cgi-bin/mega/datasheets.pl All Mega MSDS and data sheets]
+
[[Category:PCB making]]

Latest revision as of 18:59, 30 May 2019

PCB etching station
PCB710S.jpg
Model PCB710S
Sub-category Fabrication
Status Good working order
Consumables Cupric Chloride, Developer
Accessories Pump
Training requirement no
Training link Etching instructions
ACnode no
Owner Artag
Origin Pledge
Location Ground Floor, Murder Kitchen
Maintainers Artag, Mentar, Liam

We have a Mega Electronics PB710S PCB Production line etching station, obtained by a Pledge

Note : see Pcb for other references

Important Warnings

  • CLEAN UP AFTERWARDS
  • Do not run any heater unless the tank is full of liquid. It should blow a thermal fuse before melting the tank, but that may involve replacing the heater. Keep unused heated tanks full of plain water or disable the heaters by unplugging the associated connector inside the cupboard door.
  • Do not etch anything except copper (other metals will pollute the etchant).
  • Do not drink the contents, even when there's no beer.
  • Do not allow children or drunken hackers to play with the tanks.
  • Check the power has been turned off after use.
  • Do not dip a basket soaked in one chemical into the tank of another chemical.
  • Read the instructions (pdf)
  • CLEAN UP AFTERWARDS

Less important warnings

  • You normally place boards to be etched in the plastic basket under a tank lid, then dip it into the tank. If the PCB is too close to the open end, it will fall out. You may have to drain the tank to retrieve it. You don't want to do this, so put the pcb well into the opening and don't tip it forwards as you remove the basket from the tank.
  • Very small PCBs may fall through the holes. A possible solution is to put them in fine-mesh envelopes before putting them in the basket. Finding a suitable envelope is left as an exercise for the user (hint - look on the Mega website).

Model

The PCB station

Manual: File:PB BENCH Line and PCB Labstation instructions.pdf

Controls

Controls for the PCB station

The leftmost button on the control panel is mains power. If you see it lit up when no-one is using the tank, please turn it off (but if someone _might_ be waiting for it to warm up, please check first!). Probably a good idea to switch off at the mains as well.

Each tank and rinser then has a control section. Working from left to right, these are:

  • Developer - Heat button and 'heater active' light. Set to about 28°C. Heating not normally required.
  • Developer rinse - Spray button activates spray bar.
  • Etch - Heat button and 'heater active' light. Set to about 48°C. Takes about 15-20 minutes to get hot.
    • Air bubbler button - only active when heating is also on.
  • Etch rinse - Spray button activates spray bar.
  • Photoresist stripper - Heat button and 'heater active' light. Set to about 50°C. Optional.
  • Stripper rinse - Spray button activates spray bar.
  • Tinning - Heat button and 'heater active' light. Set to about 50°C. Optional.

The spray bars work best if only one is on at a time (and unless you're making a lot of boards at once, you probably only need one).

Status

1st Tank - Developer

Working SENO4006 (concentrate, fresh as of 20-FEB-2016) Resupply with:

2nd Tank - Etchant

Now contains CuCl2 etchant at ~3M strength. Ready to use. (Heater does not seem to shut down by itself so make sure not to overheat the solution, being worked on)

Resupply: instructions below! Required materials are:

  • HCl
  • Copper
  • NaOH (for checking concentration)

DO NOT put Ferric Chloride in this tank !!! In fact, please don't use ferric chloride at all - it silts up the tank and is really difficult to clean up. If there is some reason why we wish to use it again, it may be possible to use the 4th tank for it.

CuCl2 Etchant

The bath for Cupric Chloride etch was prepared using the slow method : leave some copper in acid, allow corrosion to occur generating some oxides, add further copper and acid as required. Water, acid, copper and hydrogen peroxide (if used) should be noted as it's easy to over-dilute if you just add stuff randomly.

The preparation so far contains 540g copper, 2900ml 38% HCl, 1750ml water. SG is 1260. This is ready for use - air has been bubbled through it and it has reached the bright green colour indicating it has converted copper to cupric chloride. The acid concentration appears to be correct and I have reconnected the heater. If the etchant is not bright green, please leave the small fishtank bubbler running. The bubbles will regenerate the etchant.

DO NOT ETCH ANYTHING EXCEPT COPPER IN THIS TANK

See File:CuCl.pdf for maintenance instructions. These are basically : Check colour. Bubble if dark. Titrate against 1 molar NaOH to check acid concentration (this only requires a check for precipitate, no need for acid indicator). Add HCl if necessary.

If you use it, don't rely on the small bubbler to provide agitation - keep it moving the whole time (and be careful your board doesn't walk out the end of the basket when you do that). The small bubbler is really only there to re-aerate the solution after use, as it's quiet enough to leave on.

3rd Tank - (water) stripper

Currently contains clean water (mainly to protect the heater if accidentally switched on

Stripper can be resupplied with:

4th Tank - (Water)

Currently contains clean water (mainly to protect the heater if accidentally switched on

Planned changes

  • Use Cupric chloride in the etch tank rather than Ferric chloride, which is messier, requires frequent replacement and silts up the bubbler. Has been done
  • Replace the bubbler in the bottom of the tank with a bar suspended from the basket, so that it's easier to clean.
  • Link both the large air pump and the small one into the same air supply so the cupric chloride can easily be regenerated (requires long slow bubbling rather than short fast bubbling)
  • It would be nice to have power without using the extension lead. The existing ring main might be extended fairly easily to put sockets on the wall near the sink.

Notes

The pump was replaced with a heavier duty medical unit mostly because it was cheap & available. The original was a fishtank pump and is still mounted on the front of the tank. It worked, but seemed not to have enough pressure available to overcome backpressure if the aeration tube had partly filled with etchant. Fitting it involved a few peculiarities, though.

  • There is a clamp on a branch of the tube near the pump, which can be used to restrict a controlled pressure relief and hence the vigor of the bubbles.
  • The pump is no longer fitted to the tank, but instead rests in the cabinet
  • It is still possible to remove the tank for maintenance: the cable and pipe connecting to the pump are very long but if they need to be detached the cable can be unplugged from the back of the pump and the pipe unplugged from the pump.
  • There is now a one-way valve between the pump and the antisyphon trap to reduce the possibility of etchant flowing into the pump.
  • The power connection to the pump has no earth wire connected and apparently swaps black/white colour coding. This is not just carelessness : the original black/white wiring apparently had black as neutral, white as live to the fish tank pump. The IEC lead to the new pump uses conventional euro colours : black is live. So black and white swap at the join. It's not very important as the pump doesn't have a preferred live connection.
  • The earth pin in the cable to the pump is not connected at the pump end (it's a 2-pin connector) so there was no point connecting it at the tank end.

The piping requires some care. Because of the increased pressure available from the pump, if the bubbler is blocked it's possible for the pump to blow the pipe off the bubbler. This can then lead to etchant leak.

At present, there are cable ties around the most important joints but NOT where it links to the pump. This tends to result in that joint breaking rather than any other, which is good because it's easily accessible and doesn't cause leaks. If there are problems with it blowing off too regularly, look into the cause : just fitting it more solidly is likely to lead to etchant leaks.

Originally, I restricted the airflow into the tank (to avoid excessively vigorous bubbles) by pinching the air tube with a clamp. This often caused the pump connector to come off, prompting the use of cable ties. When the bubble tube silted up, it was that joint that came undone instead of the pump joint. This was a bad thing.

A new configuration places a T joint near the pump with the clamp fitted to the additional open outlet. The idea is to make a controlled leak so that excess pressure is bled off rather than overpressurising the joints. It's likely that this will need to be adjusted as the bubbler silts up.

The low-volume pump used for aeration is now teed into the bubbler pipe, so it will either bubble slowly from that or fast from the big pump. I had to add another non-return valve so the aerator air didn't all leak out the restricted leak. { diagram needed }

Instructions

The tank was previously in a school and there is a laminated sheet with usage instructions. It may not be applicable to our use but is worth looking at.

Extra references

Spares and Repairs

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