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Get to know the most common asked questions regarding rheocasting and you will , in no time, also understand the strengths and possibilies of the method.

It is not a new casting process, it is an melt preparation HPDC process

Frequently asked questions

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:

  • Remove the need of impregnation
  • High pressure applications that cannot be impregnated
  • In cases with extreme tool wear and die soldering
  • Allowing for heat treatment such as T6 treatment
  • Strength problems by using stronger alloys in combination with T6 treatment
  • Increase thermal conductivity in heat sinks
  • Removing the need of heat treatment for thermal transport reason (conducting heat in the as cast condition as conventionally processed material does after heat treatment)
  • When You are improving cooling/designing heat sinks
  • Weight saving by using thinner walls
  • Extreme heat sinks with very high aspect ratio fins
  • Avoid surface damage by using very high silicon content, like cavitation damages

And probably some more than above but as a summary: start with the parts that has high total cost.

There is an investment to be made why there is an effect on the part price with regards to as cast condition and it works as the table shows below in general:
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:

  • Heat sinks, automotive and telecom, from small to very large
  • Various housings that must be leak free
  • Coolers for power electronics for electrical busses
  • E-car components, often requiring weight reduction
  • Table arms for aviation seats and parts as such
  • Machine parts with high requirements
  • Radio filters for telecom
  • Total cost is lower for parts with problems
  • Thin walled parts are to the same price more or less
  • Thick walled parts are cheaper

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:

  • Telecom 5G
  • Electrical vehicles
  • Low emission vehicles

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:

  • IP rights for the world excluding China is Rheometal machinery AB
  • Sales of license to use the process and also the equipment is Rheometal machinery
  • Industrialization and services and know how is delivered by Comptech AB
  • Equipment is produced by Comptech

The major differences among the processes that are on the market are:

  • Cost of the process, in terms of investment and licenses
  • Homogeneity of the slurry, important to avoid metal meetings
  • Solid fraction of the slurry, to low fraction gives turbulent flow
  • In our opinion the extremes: very thin walls and very thick walls as well as all the parts that uses HPDC today.

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:

  • Slurry preparation station
  • Robot for melt handling
  • Small dozing system for EEM casting

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