Irreplaceable Parts? Replicate with Low-Cost 3D Printed Molds

Mar 18, 2018

“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 to create an aluminum part for an otherwise irreplaceable engine part.

With the difficulty in welding aluminum of this age, sand casting becomes the only solution for repairing this type of part. the sand casting aluminum process 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 3D printed molds as an integral part of this skilled casting process.

3D Printing Saves Cost in Sand Casting

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, 3D printed prototypes and negative mold models.

Before including 3D printing, the industry’s traditional methods consisted of:
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 3D printing molds for casting, the process has:
1. Reduced costs with prototyping and test models
2. Reduced labor with automated printing processes
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

3D Printing Molds for Casting

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.

Now that the manifold has been designed, Caxton3D will use the model to create a positive and a negative to create the mold.

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

To create the sand core, a negative of the model is 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.

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.

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