Using 3D Printing for Molding and Casting in Manufacturing.

Published on March 22, 2017

Using 3D Printing for Molding and Casting in Manufacturing.

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  • As well as using 3D printed parts directly in your supply chain you can also use 3D printing for intermediates.
  • 3D printing has been used for a number of years for casting and molding applications.
  • The technology is versatile and at in many results in lower costs for the manufacturer.

3D printing is mainly used as a prototyping technology or for manufacturing end use parts for industry. A little publicized application for 3D printing is as an intermediate for use in casting and molding applications. Over the past decades a number of different 3D printing technologies have been commercialized for casting and molding. For many companies casting and molding applications using 3D printing are a cost effective solution. In this article we’ll look at the main 3D printing casting and molding applications used in industry today.

Voxeljet Foundry Sand 3D Printing

Voxeljet is a German company that specializes in industrial 3D printers for sand molds. The Voxeljet 3D printing process consists of sand being applied in 300 µm thick layers to a build platform. An inkjet head then selectively puts binder on the loose sand. The platform is lowered and another layer is applied. The resulting sand can then be used for steel casting. The 3D printed sand molds and cores can be cast in Magnesium, Aluminum, Iron and Brass and broken away afterward. Voxeljet has a range of 3D printers including one of the largest industrial machines the VX4000 which can 3D print  4,000 x 2,000 x 1,000 mm parts in sand. The resulting metal parts are mainly used for pumps in the oil and gas industry and other applications requiring large industrial parts. One of the advantages of the Voxeljet system is that their 3D printing service or machines are relatively easy to implement by a foundry because the output and workflow is similar but in many cases more cost effective.

ExOne

An alternative to Voxeljet is ExOne. The company uses the same technology as Voxeljet, binder jetting, and the materials are similar. As well as silica sand they also have cerabeads and Zircon. The 2,200 X 1,200 X 600 mm Exerial 3D printer is the largest unit that they sell. With increased build speeds and automation the Exerial and new machines are becoming a viable option for large scale metal parts for foundries and other industrial companies already using sand casting methods.

When to use Voxeljet and ExOne: These technologies are ideally suited for foundries and industrial users. Especially with time critical large (+1m) parts for the oil, gas and shipping industries they really come into their own.  

How to get Started with Voxeljet and ExOne:  Both companies have in house 3D printing services where you can order 3D printed parts from. This is a very low effort and fast way to determine the cost of parts and to see if typical parts for your application and workflow would work.

Considerations to take into account: These are large industrial systems and are meant to be deployed in an industrial environment. Power, space and the entire design of these systems are optimized for large scale industrial use. If that sounds like you then this would be a good technology to consider. On the other hand these systems would be difficult to implement in anything less than a fully fledged industrial set up.

SLA and DLP molds

Stereolithography is a technology whereby a laser hardens a layer of resin in a vat, it is also called SLA. DLP is another similar technology whereby a DMD chip (like the one found in your office’s projector) hardens a surface of a resin in a vat. The correct name for both technologies is vat polymerization (but no one uses this). SLA and DLP give one very smooth and highly detailed parts that are ideal for molding and casting. These parts have to be cured post 3D printing however and support structures have to be removed by hand. In terms of manual labor SLA/DLP can have some of the highest associated costs in terms of manpower. Additionally the resins themselves are very expensive ($300-$800 per liter) and this increases part cost. Parts are also not very strong when compared to other 3D printing technologies such as FDM. Depending on the individual part and application either SLA or DLP could be best. In deskside implementations whereby a small form factor machine prints in a semi-office environment typically DLP wins out. In more industrial settings or when large parts are needed SLA is more often the technology of choice.

SLA/DLP molds are used most often to cast urethane and silicone parts in small series. One of the largest implementations of the technology is Invisalign a market leading dental aligner technology. With unique parts or small series 3D printing the mold using these technologies has a decided cost advantage over other alternatives. In series from 50-500 these technologies are very good at producing end use urethane and silicone parts in a productive cost effective way.

When to use SLA or DLP for molds: When time critical small series are needed then this is a very good technology choice. Other molds however may give you longer life (in terms of both castings and the shelf life of the mold itself) and will let you cast a wider array of materials.

How to get started with SLA or DLP for molds: You can order 3D printed molds made with the right material for your application from 3D printing services such as Materialise. This will let you test out the workflow. We would recommend doing this before buying and evaluating a machine. If a company does few molds per year then investing in a machine will probably not make sense.    

Considerations to take into account: DLP and SLA resins have photoinitiators in them. These can be skin sensitisation agents and lead to long term contact allergy problems with your staff if they repeatedly come into contact with the uncured resin. Additional very serious health risks are present when coming into contact with uncured parts and the resin itself. Care must always be taken to avoid contact with the resins.

SLA, DLP and Solidscape Lost wax casting

One of the largest applications for 3D printing is the use of SLA, DLP and Solidscape in lost wax casting jewelry. Many individual high end jewelry pieces and series of rings, earrings and pendants are cast worldwide. The risks and considerations are the same as stated above for SLA and DLP. Solidscape is an ink jetting technology combined with a milling step. Generally the systems are seen as having less throughput and detail than SLA/DLP systems but are easier to implement in small foundries. The Solidscape systems also use wax or materials similar to wax. Compared to SLA/DLP the casting company will typically have to make less adjustments to its casting process to implement the technology.

These technologies all have in common that they save on labor. Even in low cost countries these 3D printing technologies have been widely adopted in the jewelry industry. Even with high resin cost parts are cheaper than making the wax pattern by hand.

When to use SLA, Solidscape or DLP for lost wax casting: When a jewelry company would like to save costs on the production of jewelry pieces.

How to get started: Vendors such as Envisiontec, Solidscape, Asiga and 3D Systems typically will make demo parts for you for you to test.

Considerations to take into account: When switching to 3D printing as a manufacturing technology lack of 3D modeling or CAD skills are often a key bottleneck. Especially in the lost wax casting applications companies will usually have to take care in hiring in house CAD staff to upgrade their workflow to a digital one.

FDM lost wax casting and molding.

A relatively new field is to use desktop or industrial 3D printers for lost wax casting or molding. Fused Deposition Modeling 3D printers use a filament made from an engineering plastic which is extruded and melted onto a build platform. The technology is colloquially referred to as FDM  and also called FFF. Typically surface roughness on FDM parts will be higher than SLA/DLP. FDM parts are faster however. The total time from idea to 3D printed part is shortest with FDM because there is little to no post processing required. For casting however parts will have to be smoothed in a tumbler, by machining or by vapor smoothing. Even with these steps included FDM parts that are 50mm to 300mm in size are able to be put to use significantly faster than with SLA/DLP. There is also a much wider variety of materials on offer in FDM. Many system vendors of desktop 3D printers are open. This means that the customer can put any material in their 3D printer from any vendor. The Nectar One is open as well. If you want, you can purchase materials directly from us. Our on board RFID system will recognize the material and make sure that you have the right settings on your printer. If however you’d like to use a material from another vendor you are free to do so. This means that the desktop 3D printing ecosystem using FDM as a technology is growing much faster and quicker than other technologies. With open 3D printers material vendors and specialist have been able to flourish and bring much more open R&D to 3D printing.

When to use FDM for lost wax casting and molding: Typically in parts that are larger than 50mm in diameter there are significant cost and time savings when using FDM in stead of other technologies. If you have a particular molding and casting application for which there is no suitable material in place it would be easiest to develop this material for FDM.

How to get started: You can order 3D printed parts from a 3D printing service. Or let us know what your requirements are and we’ll get you a sample part to test.  

Considerations to take into account: Surface roughness of the parts will need to be addressed. Depending on your part and the shape of your part FDM may be the best suited technology for you or another could be superior.