It is not a new casting process, it is an melt preparation HPDC process
Rheocasting with a high solid fraction offers two main advantages: Reduces turbulence and reduce porosity as the flow in the die cavity turns more laminar in nature.
Laminar flow reduces the risk of air and gas bubbles and allows after feeding thus giving a part without or with strongly reduced porosity. In practical life this means impregnation free parts that are weldable with high quality weld seems.
Rheocasting also exhibits a thixotropic flow behavior meaning that it flows more easily as sections turns thinner and viscosity is reduced (Just like no drip painting). This allows casting a wider range of thicknesses in a casting and especially allows the casting of very thin fins.
Extended alloys range capability, meaning that alloys for strength, thermal conductivity etc. can be chosen. The alloys that does not work are the eutectic alloys used in HPDC, like 44300/43400 and 46000. In conclusion this means that engineers have a new set of tools to design more features or to increase functionality or to reduce weight of parts by using “better” alloys than the traditional HPDC alloys now used.
Rheocasting can be used to improve the following:
And probably some more than above but as a summary: start with the parts that has high total cost.
|Cost driver||Rheo vs HPDC||Remark|
|Locking force||Smaller machine needed||Thin wall +/-0 Thick walls larger difference|
|Cycle time||The same opr shorter as for HPDC||But You can cast parts that HPDC can not|
|Ingate removal||More costly with Rheo for pressure tight parts||Ingates are thicker and more massive to allow after feeding|
|Machining||The same “Due to approx. 100 degree lower filling temperature the tool can allow smaller features which otherwise might need machining”||No measurable difference|
|Surface treatment||Less costly||Due to lesser Q problems|
|Tool lifetime||Depending part but up to 4 times the tool-life compared to HPDC due to a reduction close half the thermal load on the tool||Same steel Quality|
The process is a melt conditioning process where the slurry is formed in the ladle before casting the shot. The process is based on the stirring of a piece of aluminum into a ladle filled with molten aluminum. By rotating the melt is sheared and a slurry is formed with a globular micro structure.
After the slurry making the slurry is poured into the casting machine and the rest looks very much as HPDC.
The part that are of interest from our customers are as example:
Everything except the ingate and overflow design is the same as for an HPDC tool. This means that also the cost and the lead time are the same.
Our market drivers are:
Our conclusion is that the applications above is stretching the requirements why traditional HPDC cannot fulfill them and 10 years ago designers were happy to use HPDC as it resulted in enough high characteristics. One other issue is the cost of changing the alloy often including a design verification. Our customers have not been willing to do this for old parts. Now we and our friends in the industry are developing parts from the design stage based on Rheocasting, so this has delayed the market break through with 2 years. Process stability and production cost was not enough in the beginning when Rheocasting was started in 2007. Since then it has been a constant development and since a few years we have developed and designed a stable process based on reliable equipment and with this the process has become more interesting.
Automotive, telecom and general industry
All alloys that are not eutectic, meaning that Silicon content between 9 to 11% is more or less impossible to use with Rheocasting, or any other semi solid process. N short, stay away from 44 300, 43 400 and 46 000.
The lead time from order to installation of a Rheocasting machine is 22 working weeks, depending also on the delivery schedule in general. Installation, education and start of production is approximately 5 weeks.
Comptech are offering a full range of services as simulations, alloy selection, test bars, CT-Scan reports, X-ray etc., needed for development projects.
For foundries starting the Rheocasting process we offer installation, training, SOP assistance and if needed material and information for customer communication.
1. Call Comptech (+46-(0) 370-66 50 66
2. Send Your NDA to safe guard Your info and IP
3. Send a 3D STEP file
4. Comptech makes a technical report in power point for your further consideration
Simulations are the first important step. This is to ensure after feeding and tool design. After the simulation the process is the same as for HPDC
We expect that the new generation of cars, public transportation and communication equipment will create a demand for a number of new and developed processes to be able to support new and higher requirements. Broken down to Rheocasting our projection is that the penetration will be 5-10% of the installed base of HPDC machines world wide
To make it simple:
The major differences among the processes that are on the market are:
Basically, You can do everything designed for HPDC and slightly better with Rheo as thinner sections can be casted as well as somewhat smaller draft angles.
Depending on what is found in the foundry one can re-use a lot of equipment. In a cell the following is needed:
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