Aluminium Sand Casting with 3D Printed Molds
In order to replace the water manifold on a 1913 Dennis Fire Engine, Raise3D Forum user Caxton3D created cad models and moulds for sand casting an aluminium part for an otherwise irreplaceable engine part.
“I hope that there will be more interest in the future for printing for ‘real world’ tasks. Pattern making is one of the most obvious applications. Most patterns today are still hand produced from wood.”
Caxton3D, Raise3D Community Member
With the difficulty in welding aluminium of this age, casting becomes the only solution for repairing this type of part. The casting process itself brings a number of variables that must be considered such as the contraction of metal parts during cooling and core moulds for hollow castings. To properly achieve the final results, the Raise3D N2 Plus is used as an integral part of this skilled casting process
Without the aid of templates or factory drawings, the casting of replacement parts required a high level of trial and error with handmade wooden models. With the aid of 3D printing, digital models can be easily adjusted and used to create low-cost prototypes and negative mould models.
Before including 3D printing, the industry’s traditional methods included:
- Labor intensive hand carved wood models for impressions
- Varying inaccuracies due to hand-made parts
- Multiple castings to create positive and negative models
- By applying 3D printing, the casting process experiences
- Reduced costs with prototyping and test models
- Reduced labour with an automated printing process
- Increased accuracy with precision digital models
To begin a cast, caxton3d first creates a digital replica of the manifold using Solidworks.
For parts of this age, factory drawings are not readily available, so dimensions are taken from the original piece and translated into a CAD model. This design is printed as a prototype and installed onto the original hardware to measure fit and tolerances. Taking into consideration the amount of shrinkage that the metal will experience with cooling, the necessary changes are made in the model until the desired outcome is met.
To create the sand core, a negative of the model are printed as a two-part mould. When creating a part like this, which is much larger than the bed of the printer, each half will be split into two parts and joined together to create the mirrored halves. To ensure alignment caxton3d added registration marks for bolts that will create a continuous core box. To complete the cast, the modified positive is used to create the initial impression into the sand. This will be made in two halves. One of these two halves will be given a trough for metal to be poured in to. The moulded sand core that is removed from the two-part mould will be enclosed within the two sand halves. Metal is poured, and the final aluminium piece is removed.