Aluminium Sand Casting with 3D Printed Molds

“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.”

In order to replace the water manifold on a 1913 Dennis Fire Engine, Raise3D Forum user Caxton3D created cad models and molds for sand casting an aluminum part for an otherwise irreplaceable engine part.

With the difficulty in welding aluminum 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 molds for hollow castings. To properly achieve the final results, the Raise3D N2 Plus is used as an integral part of this skilled casting process

Casted water manifold on a 1913 Dennis Fire Engine and 3D printed prototype model

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 mold models.

Before including 3D printing, the industry’s traditional methods included:

1. Labor intensive hand carved wood models for impressions
2. Varying inaccuracies due to hand-made parts
3. Multiple castings to create positive and negative models

By applying 3D printing, the casting process experiences

1. Reduced costs with prototyping and test models
2. Reduced labor with automated printing process
3. Increased accuracy with precision digital models

Company: Raise3D forum user caxton3D

Industry​ ​or​ ​Trade: Aluminum Sand Casting

Raise3D​ ​system​ ​being​ ​used: Raise3D N2 Plus

Process:

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.

Solidworks model replicated with gathered measurements

Printed prototype attached to cylinder head for fit testing. 

Now that manifold has been designed, caxton3d will use the model to create a positive and a negative that can be molded from.

A ‘core’ is added which will will be used to prevent metal from flowing; creating a hollowed part. This modified model is designed with both the manifold face and the core. The extrusions from the core will be used to rest the separately-molded sand core within the mold.

Modified model with positive manifold half and core

Completed print of positive mold model

To create the sand core, a negative of the model are printed as a two-part mold. 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.

1 half of the sand core mold

Sliced model of the core mold.  Each half will be printed in 2 parts to allow printable size.

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 molded sand core that is removed from the two-part mold will be enclosed within the two sand halves. Metal is poured,and the final aluminum piece is removed.

3D model with part (silver) and core mold (Black).  Cross section of sand mold and sand core (red). Final aluminium casts.