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Subtractive sand mould production as a cost effective alternative to sand printing

An efficient, cost-effective solution for moving into a patternless mould making system, is how  Omega Sinto describes its Robotic Sand Milling Cell (RSM).The system offers an alternative to both traditional moulding methods and printed sand moulds.

The system utilises the flexibility of a high-accuracy 6-axis robot, combined with proprietary software designed from the ground up with foundry mould milling as its focus. The company says this enables a combination of design flexibility, cost savings and speed not seen in previous moulding methods.

 

Benefits over traditional moulding methods

The RSM package shares many of the same benefits as other patternless moulding methods when compared to traditional pattern-based moulding:

  • More flexibility/less limitations with geometry
  • No requirement for tapered sides.
  • Can easily mill undercuts.
  • Can quickly adapt to design changes
  • CAD/CAM based programming means modifications to mould design can be implemented immediately.
  • Moulds can be easily customised/switched for different variations

 

Benefits over printed sand moulds

In addition to the benefits over traditional moulding methods, the RSM package also has a number of benefits that can make it a more cost effective and efficient process when compared to other patternless moulding systems such as printing:

  • Works with any type of resin or sand system.
  • Not locked into a single resin system.
  • Milling cutters don’t care if they are cutting silica, chromite, zircon, olivine etc.
  • Customers can use existing equipment/technology for blank mould making.
  • Pairs well with continuous mixers.
  • A milled sand mould will typically cost a quarter to half that of a printed mould.
  • Approximately five times faster for large moulds (geometry dependent, assuming six hours milling for a 2m x 2m x 1m mould and a printer working at 100 L/Hr).
  • The cost of an RSM cell is less than half the projected price of the upcoming Omega Sinto 3DSP sand printer, which is already drastically less than other printers in the marketplace.

Additional benefits are that moulds can be re-machined/milled multiple times. Users can start with a basic cavity in the mould and add features. It reduces waste material and milling time. The RSM is also a fully automatic operation – once the mould is located in the cell, the system can run hands off from start to finish. It can be set up and left to run overnight, providing a finished mould in the morning.

 

System Operation

The RSM cell has been designed to be an intuitive, straight forward system for producing patternless moulds and tooling. With offline programming and fully automatic tool changing, operators can run hands off and lights out to truly get the most productivity out of the cell as possible.

 

Toothpath programming

Operators get to utilise a full 5-Axis suite of MasterCAM for programming toolpaths, giving a direct line from CAD model to CAM program. After loading the 3D model of the desired mould, a large array of toolpath types and methods can be used to ensure the cutting is done exactly as it needs to be. Users can also review the programmed paths inside the software, watching stock being removed in real time to help optimise operations.

Once the toolpaths are finalised in MasterCAM, the operators transfer the mould program into Robotmaster with the click of a single button. Inside Robotmaster, the motion of the robot can be observed and adjusted as it moves along the toolpaths. This is a critical ability for avoiding issues such as singularities, joint limits as well as general collisions inside the cell. Robotmaster clearly defines any such issues and offers easy to use tools to find solutions. Users can also take benefit from the automatic path optimisation, which can be geared toward smoothness, error avoidance or any combination of the two.

 

Call setup and preparation

To prepare the cell for machining, the mould is set into place on the clamping table. Once secured, the operator can locate the mould using a simple three-point touch off via the robot controller. This calibration ensures the robot and path program know the exact location of the mould. It also allows the mould to be removed from the cell and placed back in for more machining if the need arises.

Next the operator measures the length of the tooling that will be used. Once the lengths are known, they load the cutters into the tool changer, and record the positions in the cell control software. It will keep track of total milling time with each cutter, as well as automatically measure the wear if combined with the tool inspection option of the cell. With the mould located and the tool lengths measured, the operator can update these values in MasterCAM (tool length) and RobotMaster (mould position). The final program(s) can then be exported and loaded onto the robot controller for execution.

 

Mould milling

The last step is to select the desired toolpaths to run from the cell control software, and pair a tool/spindle speed to each path. Once the operator confirms that the execution screen is set up correctly, they hit execute and walk away while the cell runs through all the toolpaths start to finish.

 

System Components

The RSM system includes six core components. As the backbone of the system, these components ensure a seamless operation and turnkey integration for automatic mould milling. If further capabilities are required customers can specify an optional tool inspection system, 7th axis horizontal gantry, multiple milling stations per cell, and even multiple robot cells tied to the cell control software. These options give even more adaptability and efficiency to the system.

For more information contact: Omega Sinto Foundry Machinery, Tel: +44 (0) 1733 232231, email: [email protected] web: www.ofml.net