Diecastings – Surface Finishing Options

Diecasting 3

There are a number of ways diecast manufacturers can choose to go when looking to deburr and finish large numbers of components.

Here we look at the options of vibratory vs blast processing and bring to your attention a few facts and choices you should consider.

 

Raw castings frequently require a surface preparation or finishing process such as deburring, edge breaking and the metal casting industry employs a number of various technologies to manufacture millions of component parts, in a cost-effective manner.

New alloys, re-defined casting methods and additive manufacturing spurn new process applications.

Another important finishing process is the general cleaning and aesthetic finishing of the cast components and at the same time to remove any remaining mould release agent.

The finishes required range from component aesthetics, keying the surface for adhesion before applying paint, coating or a glue, to achieving a fine ‘pre-plate’ finish.
All metals and most composites including light alloys, non-ferrous metals, grey iron, steel and stainless steel castings are most likely to require and undergo a surface preparation and/or finishing process.

Fast deburring with subsequent edge breaking

Smaller aluminium, magnesium and zinc diecastings are usually finished in continuous vibratory systems.  This is a wet process and depending on the subsequent operation may require a rinse and/or drying process. The removal of flash and the breaking of sharp edges can be achieved within a processing time from as little as 5 minutes.

The majority of residual burrs caused by complex split mould tools can be removed, provided they can be reached by the grinding media.

Continuous vibratory systems are available as linear or circular – long radius systems.  These surface preparations and finishing systems can easily be linked with the actual die casting process and clipping cell, allowing a fully automatic and highly cost- effective finishing process.

Recycling of the process liquid

Vibratory finishing requires the use of water and compounds.

Besides deburring and edge breaking the process offers a washing and cleaning effect.  Modern recycling systems allow the re-use of the water/compound mix.   This reduces the water and compound consumption to a minimum and with the addition of a waste water centrifuge the compound and water can be used over and over again, before final discharge.

This saves the user considerable cost for water and compound.  Last but not least, it helps to keep our environment clean and helps permit a consent to discharge by local authority.

Additional applications

Other applications are the smoothing and polishing of parts such as bathroom, kitchen and plumbing fittings made from brass and stainless steel, or handles for doors and windows.

Frequently, in such cases the mass finishing process is preceded by an auto clipping machine or belt grinding operation to remove any heavy split line, metal sprue or runner.

The ultimate subsequent finishing process can achieve close to mirror image polished surfaces with values of less than Ra 0.02µm.

Depending on geometry, size and surface condition of the castAluminium Casting component, a selection of surface preparation and finishing process methods such as a circular or tub vibrator, a high energy centrifugal disk system, a “drag” plunge or “surf” finishing process can be considered and employed.

Depending on the component or part size and machine process type, hundreds or even thousands of parts can be processed simultaneously. Automation reduces idle times for parts loading and unloading to an absolute minimum or even eliminates it!

Alternative, surface preparation processes and finishing technologies to consider!

Deburring and the removal of sharp edges, with relatively short processing times represents only a small part of the overall range of surface preparation and finishing technologies.

Dry processes such as a fine abrasive blast, delivered by either a turbine or compressed air should also be placed into the equation, however it should be noted that a dry blast process cannot achieve a polished finish.

The advantage of a dry blast system is that it provides a very economic commercial process. The components remain dry, do not readily surface oxidise and have no surface water marks.

Smaller to medium sized components may be cascaded whilst medium to larger components can be placed in linear fashion or even hung.

Diecasting 2Small batch barrels, small continuous linear through barrels to larger sized machine capacities remain the commercial favourites.  Whilst more sensitive components may be processed on a wire mesh continuous blast machine with process speeds of 500mm to above 6 metres/minute.

Of special interest, diecastings of mainly flatwork and with a thin profile can be processed with the right application.

These three dry process methods and handling of the component parts account for more than 50% of the volume of all diecastings.  These diecastings are commercially processed to standards within the automotive, plumbing, valve, electronics, nuclear, toy, white goods and other manufacturing industries.

How to surface prepare and/or finish large components?

Surface preparation and/or finishing is not limited to the processing of smaller and medium sized component parts.

It can also be utilised, for example, for the surface finishing of engine casings for aircraft turbines and structural airframe parts with a length of more than 6,000 mm.

Even today many parts are still manually deburred after a machining process. This requires highly skilled and dedicated personnel to prevent damage of the usually high cost components.

  • Standard surface preparation and finishing technologies can offer 100% repeatability.
  • Additional or alternative solutions can be tailor-made for every conceivable application.

An example of special equipment is the centreless vibrator which allows the deburring and surface finishing of round components with a diameter of up to 2,000 mm.

Today, automation of any process equipment is now an economic factor, including process control, handling, quality, inspection, repeatability and reliability in integrated turnkey solutions. Stand alone single machines still have their place.

Special surface finishing solutions required?

Special surface preparation and finishing technologies offer solutions for any modern foundry operation and assistance can be found by developing such solutions in a reputable test centre.

 Click here to discuss which process is for you?

 

Haydn Kitchen New APost written by
Haydn Kitchen
Shot Blasting Technical Manager

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