Copper plating on gravure cylinders Q&A's Problems & Solutions

A. Dear Komal,

Each microstructural change caused by improper process parameters will immediately also change your engraving properties, which means shorter life-time of diamonds and bad shaped cells. Many providers in the rotogravure industry offers courses in electroplating for the rotogravure industry which, I am absolutely sure, won't leave any questions open ... anyhow, some answers to your questions:

Too low in Copper sulphate: Lower efficiency, bad distribution of copper deposition over the whole cylinder, burning on cylinder radius

Too high in Copper sulphate: Roughness, Brittle deposits, Crystallization

Too low Sulphuric Acid: Bad conductivity, low hardness, low ductility

Too high Sulphuric Acid: Higher hardness of deposits, brittle deposits, lower ductility

Additives in use are grain refiners. Hardness can be well adjusted, maintained and controlled over the dosage of these additives via Amp-hour dosing.

A. Sir,
Something is not clear. Copper sulfate baths have an efficiency close to 100%. If your efficiency was very low the copper concentration should not be OK but rising. Perhaps you mean speed of deposition. In that case, carefully raise temperature and current and observe results.

A. Hello Komal,

Copper electrolytes, as mentioned by my mexican colleague, work with almost 100% efficiency.

Some hints:
- If your thickness over the cylinder is uneven, then you might have a problem with the level of amount copper nuggets in your cylinders plating tank. Archived distance between cylinder and copper anode should be around 30-50 mm.
- Do not raise temperature above 32 °C since this will cause a higher consumption of you hardness additive.
- Check you voltage at working current.
- Are you sure you are working with effective 25 A/dm2? If you are not sure, then I recommend a measurement on your rectifier shunt during copper plating. Measure the mV-Signal and re-calculate the real current.
- Are all contacts in order? Check carbon brushes on each side, or in case you have a cylinder plating tank with pinholes, then check the pinholes are not damaged and providing a good current flow.

Regards,

A. Hello Komal,

you are fine with 6 Volts at working current. Higher Voltage will increase temperature of your electrolyte and, if chilling system at your company doesn't work properly, will negatively affect your hardening additive and therefore the microcrystaline structure of the deposited copper. Try to keep your sulfuric acid at an concentration between 62 and 65 g/l. Copper sulfate better on 210-230 g/l.

Greetings,

A. Probably because of the temperature rise. Sulfuric is very exothermic.

A. Hello Komal,

the drop of the hardness is, as mentioned by James, caused by the heat generated by adding the sulfuric acid. Obviously, depends on the amount of sulfuric acid which is added.

Regards,
Dominik

A. Hi Komal.
In my previous posts I have already written to you what can cause the hardness drop/increase. Therefore I recommend to you the following:

- Make small additions of sulfuric acid.
- Re-adjust your electrolyte temperature from 28 to 30°C.
- Re-adjust your dosing amount of hardness additive.
- Since it costs you quite lot of money re-doing the cylinders due of low hardness I recommend to you to automate as much as possible your dosings.
- I expect that you use DI-Water with a conductivity of less then 10 microSiemens.

Good Luck

That sounded like a "goodbye" to this thread from Dominik, but I wanted to compliment and thank him for his patient and informative answers! Answering an initial question, then patiently following up 5 more times is yeoman work :-)

Regards,

A. It is because of copper additive , because earlier i am also facing the same problem but since i replaced old powder type additive with liquid type high speed copper additive; working condition @ CD 30 to 40 amp/dm2 temp 35 to 45 degree, this problem eliminated. Good surface & ductile deposition also reduce stylus consumption (1 stylus 280 Cyl) and printing issues like roughness, tail lines & lose of dots.

A. Hi Ravi, Set your dosing pump somewhere @ 7 Ah, 4 Second. Measure the additive quantity by removing hardener pipe from tank, connecting to beaker [affil link], checking the volume. It should be 1000 Amp-hour consumes 150 ml to 190 ml (100Ah: 16 to 18 ml)