Contamination on an aluminum die-cast part adheres differently than a cooling lubricant — and what has to come out of the cavity sits in a geometry that was built for exactly that: to be inaccessible.
Cleaning aluminum die-cast parts and washing out salt cores
1 · The challenge
Why aluminum die-cast parts are difficult to clean
Contamination on an aluminum die-cast part adheres differently than a cooling lubricant from machining: casting residues, release agent and fine particles in rough surfaces. From the casting process, residues remain on the component that adhere differently than oil or emulsion — the most difficult case we know, and the only one in which we expressly clarify feasibility beforehand.
The inside of an aluminum die-cast part is not empty. Cavities are created via cores, and what remains in the component afterwards has to come out — out of geometries that were built for exactly that: to be inaccessible.
When washing out salt cores, what is added on the aluminum die-cast part is that material has to come out of the inside, not off the surface. Washing out is something other than cleaning — it needs volume and dwell time, not pressure on a surface. What is left behind is not dirt, but a remnant of the tool.
The same geometry makes cleaning the aluminum die-cast part difficult: spraying creates a spray shadow, and with complex geometries with many blind holes, immersion and flooding deliver the better results. The cavity from core making is only accessible if the process medium is guided into it.
And the aluminum die-cast part is still a raw part at this stage: it has not yet been machined, dimensional accuracy and surface are not yet final. Added to this are casting flash and metal fines — loose burr remnants that come loose and travel in the component. Where they fall is not decided by the design.
2 · Engineering considerations
What we base the system design on
- 01
Part geometry
Aluminum and aluminum die casting are the focus, not the limit: steel, stainless steel, brass, copper, zinc die casting and plastic we process just as well — there is no limit at the material. On the cast part, the material condition is added; which material and which material condition are present is one of the factors that determine the system design. Whether an individual part is processed or a batch of bulk parts stands at the same beginning. - 02
Internal geometry
On the aluminum die-cast part, the cavities from core making help decide the method: they are only accessible if the process medium is guided into them. Spraying creates a spray shadow, not every surface can be reached — the more complex the component and the more bores and blind holes, the sooner immersion or flooding instead of spraying. - 03
Workpiece fixture
On the aluminum die-cast part, the parts carrier is not an accessory but an essential part of the system concept: its design engineering helps determine where spray shadow arises and whether the nozzles reach the component — especially with residual contamination requirements it is a decisive factor. Whether the batch is rotated and tilted during the process depends on it as well. - 04
Type of contamination
Casting residues, release agent and fine particles in rough surfaces behave differently in the process than oil, emulsion, dust or chips — and the amount counts as much as the type. With baked-on contamination on the aluminum die-cast part, we clarify feasibility before you plan, not afterwards. - 05
Residual contamination requirement
What has to be verified on the aluminum die-cast part stands at the beginning of the system design, not at its end: the required residual contamination values act on the method, the filtration, the drying and the workpiece fixture at the same time. In the foundry, the requirement often does not come from the own quality department, but from the customer — whoever casts for the automotive industry or machinery manufacturing inherits their cleanliness requirement. - 06
Deburring requirement
Whether the aluminum die-cast part additionally has to be deburred is decided in the same technical clarification: where a burr is involved as well, water jet deburring is usually the better solution. With cast parts, the two tasks do not arise one after the other anyway, but intertwined — the casting flash is a form deviation as long as it sits, and residual contamination as soon as it comes loose. - 07
Water and process media
Especially with aluminum and with baked-on residues, the process chemistry helps decide the result — and likewise corrosion protection and passivation. We do not develop and produce cleaning chemicals of our own; we select the process media, coordinate them with established chemical manufacturers for your process and integrate them into the system. - 08
Downstream process
The required cleanliness of the aluminum die-cast part depends on the subsequent production process. In the foundry, that is mostly machining, behind it stand coating and assembly at the customer. Whether adhesive bonding, coating or painting follows the cleaning changes the requirement fundamentally — right down to the question of which water quality is needed.
3 · The system concepts
Which system concepts and methods come into question
Spray-immersion cleaning systems
APOLLOIf an aluminum die-cast part needs both — accessible outer surfaces and internal cavities — the spray-immersion cleaning system can make sense: both methods run in one hermetically sealed chamber, and the batch rotates and tilts in all axes while doing so.
Immersion cleaning systems
ZTWhere spraying on the aluminum die-cast part fails at the spray shadow, complete immersion can lead to the result: workpiece or bulk parts are brought entirely into the process medium so that it reliably reaches all areas.
Chamber cleaning systems
ZKIf the range of parts changes and several process steps on the aluminum die-cast part are to take place in one closed chamber, the chamber cleaning system can make sense — for bulk parts usually as flood washing within the chamber.
Flood washing
If a directed jet does not reach concealed surfaces and transitions on the aluminum die-cast part cleanly, without the complete immersion process being necessary right away, flooding comes into question: the process medium is guided over and around the workpiece at high volume. Flooding is primarily a process within a chamber cleaning system, not a machine type of its own.
Special-purpose systems
If washing out salt cores is pending on the aluminum die-cast part, no standard machine type carries the task: the system is created according to the geometry of the cavity, not according to a catalog. Systems for washing out salt cores we have built — for tasks that no standard machine type carries, we design the system around the task.
Robot cell with downstream continuous process
If the aluminum die-cast part has to be moved between several process steps and then processed further in a continuous flow, a robot cell with a downstream continuous process comes into question — the robot takes over the handling, the continuous process the cycle. Both then belong to one process chain, not to two separate systems.
Water jet deburring
If casting flash and metal fines sit on the aluminum die-cast part, water jet deburring comes into question in particular: the same jet removes the burr and at the same time carries it out of the component. A detached metal fine that stays in the cavity would only have shifted the problem.
The principle
Why several solutions are possible for the aluminum die-cast part
None of these assignments is a rule. Depending on production volume, cycle time, residual contamination requirement and material flow, the same aluminum die-cast part can be better placed in a different system — there is no rule “component X, machine Y”. Part geometry, type of contamination, residual contamination requirement, production volume, cycle time, production concept, degree of automation, workpiece fixture, future expandability and cost-effectiveness decide together. What you see here is the consideration, not its result.
4 · What else to consider
What else has to be clarified for the aluminum die-cast part beyond cleaning and deburring
- 01
Washing out is a production step, not a cleaning step
The salt core in the aluminum die-cast part has fulfilled its task as soon as the component has solidified — and afterwards has to come out of the cavity completely. What is left behind is not dirt, but a remnant of the tool. That is why washing out is not a cleaning step in the usual sense. - 02
It is two verifications, not one
The aluminum die-cast part is inspected twice: residual burr — is the burr gone? — and residual contamination — is the part clean? Both verifications run through one contact person, but not both through the same hands: the residual contamination analysis is carried out by an independent, accredited test laboratory, not by us. - 03
With baked-on contamination, we clarify feasibility beforehand
Baked-on residues on the aluminum die-cast part are no reason for exclusion, but the only case in which we expressly want to check feasibility beforehand. And where a residual contamination requirement is technically not achievable, we decline beforehand — before the quotation, not at acceptance. - 04
The cast part is a raw part, not a finished component
On the aluminum die-cast part, dimensional accuracy and surface are not yet final; it still has the first machining step ahead of it. What is created here as a raw part reappears later as a component to be machined — the same component, seen from the other side of the supply chain.
Questions and answers
Frequently asked questions about the aluminum die-cast part
Why are aluminum die-cast parts hard to clean?
Is washing out salt cores the same as cleaning?
Is baked-on contamination a reason for exclusion?
Where does the cleanliness requirement for a cast part come from?
Do you develop the cleaning chemistry yourselves?
Direct contact
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93186 Pettendorf
Pettendorf bei Regensburg
Fax +49 (0) 9409-777 3607
Technically responsible for this page: Günther Zippel — International Sales & Technical Consulting