Technical considerations
Maybe you have experience in casting, or maybe this is the first time dipping your toes in. We want to help make this as easy as possible. Casting is not rocket science but there are a number of factors to be aware of and consider, some of which will make the outcome for you significantly better.
Size considerations
Minimum individual part size - 20mm cubed.
Maximum individual part size - 400mm in any axis. (larger pieces can be discussed)
As our casting trees and waxes are dipped by hand into our slurry tanks (giant tanks full of liquid ceramic that are turning 24 hours a day), works that fit within a 400mm envelope are ideal. Pieces that are greater in size can be accommodated, however these require more work and are more expensive to produce.
Works larger than this will be separated into multiple parts to be welded together post casting.
Rumble polishing capabilities
We have two torus shaped tumble polishing machines with two different media and compounds for mass finishing.
Maximum width 220mm x maximum length 400mm
Design considerations
Minimum wall thickness of 3mm. Edges can taper out and be thinner, however we recommend aiming for a minimum average thickness of 3mm. Any thinner and we cannot guarantee your casting will be successful.
Uniform wall thickness strongly preferred — abrupt changes cause hot spots, shrinkage, and cracking during solidification.
Variation in thickness is fine, ensure there is a gradual or stepped taper when the difference between thicknesses is greater than 1.8 times the smaller thickness. Steps greater than this may have sinkage marks or tears in the metal when cooling.
Eg 3mm to 5.4 is fine, 3mm to 8mm may have issues.
Thick sections (> 25 mm) accumulate heat and are prone to centreline shrinkage porosity; strategic placement of risers or chills on the shell exterior is required.
Ribs and gussets are an effective way to achieve stiffness without increasing wall mass; investment casting can reproduce fine ribs (down to ~1-2 mm wide).
Holes, through holes, blind holes and tapped holes.
For any hole under 5mm, please place a divot or indentation in the model. On your drawings please specify hole diameter.
Any hole deeper than 10mm should be replaced with a divot for drill point alignment.
Our preference is to post machine all holes, if it is critical, please undersize the hole so that it can be post machined.
One-off castings
If you are looking to create a one off piece, this can be achieved in one of three ways, supplying a physical version of what you would like in metal, supplying your piece in wax to be cast directly, or supplying a digital file.
When supplying a physical version to replicate, there will be shrinkage, this happens in two stages, first when the wax cools and shrinks in the silicone mold, and again when the metal cools in the casting.
When supplying a wax, please ensure it is red or green casting wax, if you are unsure, please give us a call.
When supplying a digital file, we can either 3d print this in PLA, which is great for prototyping and testing a form, or 3d print this in high detail resin and silicone mold the piece. The silicone mold is reusable and multiple pieces can be made from the one mold.
If you have designed your piece digitally, we can 3d print this and attach it to a casting tree. We have 3D printers in house to do this.
If you would like to print it yourself, that is completely fine, however we cannot guarantee the quality of the casting. To ensure the best possible outcome, please confirm with us beforehand and adhere to the following with printing.
Please print in white or clear PLA only.
Ensure a sparse infill density of 10-15%
Sparse infill pattern - Gyroid
Sanding is fine, but do not use paint, putty or fillers on your 3d print.
Unfortunately the use of wax like resin is not feasible for large scale investment casting. When the casting trees are put through our autoclave, the resin expands cracking the molds from the inside. This resin is ideal for jewellery casting where the piece is encased in plaster.
Repeat castings and production
We have a wax injection machine for repeat castings, this paired with machined aluminium tooling enables the casting of identical components with tooling lasting for thousands of cycles without impacting quality.
We recommend starting out with prototyping before investing in tooling as it can be quite expensive. Our team is happy to walk you through the options for this.
When designing pieces that will eventually become products, be it components for a power station, hardware or a light fitting, there are a few guidelines that will make it easier from the start.
Draft is the taper applied to faces parallel to the draw direction to allow the solidified wax to be extracted cleanly from the tooling.
Typical exterior draft: 0° – 1° per face.
Internal features and holes: 0.5° – 1° per side.
Sharp internal corners are stress concentrators and restrict metal flow, making them a source of cracks, cold shuts, and shrinkage defects.
Where possible, please apply a minimum radii of 0.5mm; with a preference of 1.0mm or greater for parts requiring load applications.
Drawings
Please outline any critical dimensions or faces that are visible. Each part needs to be attached to a casting tree with gates; cylindrical or square attachments that will enable the molten metal to flow into the part.
File preparation
If supplying digital files, our preference is step, x_y or iges files as we can fully dissect the model in Solidworks or Rhino. Stl and obj are fine, however we have reduced capabilities to adjust the model for casting.
If you would like us to model the parts, please supply as much information as possible. There is no such thing as too much information. Sketches, drawings, photos, please send it all.