The Importance of Jigging in the Anodising Process
Jigging is a crucial step in the anodising process, as it ensures proper electrical contact and uniform coating. However, jigging also leaves visible marks on the aluminium, which need to be considered when designing aluminium parts which are to be anodised.
What is Jigging?
Jigging refers to the process of securely mounting and holding metal parts (usually aluminium) on a jig or rack before anodising. This ensures:
Good electrical conductivity (necessary for anodisation).
Proper immersion in the electrolyte bath.
Consistent and uniform coating thickness.
Preventing parts from floating or touching each other.
Steps in the Jigging Process
Selection of Jig Material
Jigs are usually made from titanium or aluminium because they resist anodising and maintain good electrical contact.
Titanium is preferred for longevity, while aluminium is sometimes used for cost-effectiveness.
Arranging the Parts
The parts are positioned to maximise electrolyte exposure.
Adequate spacing is maintained to prevent shadowing (uneven coating due to overlapping parts).
Ensuring Firm Electrical Contact
The parts must have a solid mechanical connection to the jig.
Clips, clamps, or hooks are used to hold the parts.
Contact points should be minimised but firmly secured to ensure good conductivity.
Jigging Marks on Aluminium
Since the jig must make direct electrical contact with the aluminium, the points where the part is held do not anodise.
This leaves visible marks (often small bare metal spots).
The location of these marks is carefully chosen to be in less visible or non-critical areas.
In some cases, post-processing (such as dyeing or touch-up coatings) can help reduce the visibility of jigging marks.
Masking (If Needed)
If certain areas of the part should not be anodised, a masking agent (like lacquer, tape, or plugs) is applied.
Testing for Conductivity
Before anodising, a conductivity test is sometimes performed to ensure all parts are properly connected.
Immersion into the Anodising Bath
The jig, along with the parts, is immersed in the electrolytic bath where the anodising process takes place.
Why is Jigging Important?
Ensures uniform anodising: Proper positioning prevents defects.
Prevents arcing or burning: Poor contact can cause sparks and damage.
Optimises efficiency: Good jigging improves throughput in mass production.
Minimises reject rates: Ensures better quality and fewer failed parts.
How to Minimise Jigging Marks?
Strategic placement: Holding points are positioned in less visible areas.
Rotating contact points: If possible, multiple jigging setups can be used to spread marks.
Post-processing: Marks can sometimes be reduced by blending, polishing, or touch-up coatings.
Alternative fixing methods: Using conductive clips or specialised racks can sometimes help reduce visible marks.
