Analysis of implementing additive manufacturing for the making of casting patterns

Abstract (Swedish)

I den här rapporten undersöks möjligheten för att tillverka och använda gjutmodeller tillverkade genom additiv tillverkning, i folkmun kallat 3D-printing. Först görs en grundläggande analys över hur modellerna tillverkas idag och vilka krav som ställs på modellen. Detta innefattar både rena material och hållfasthetskrav, men även mer svårdefinierade krav där man enbart kan resonera kring rimliga antaganden. Sedan undersöks de tillverkningsmetoder som kan vara av intresse för den här rapporten samt vilka material som isåfall skulle vara lämpliga.

Därefter kontaktas potentiella leverantörer för att undersöka den praktiska genomförbarheten och få in jämförande prisuppgifter. Som mål var också uppställt att genomföra ett praktiskt test som skulle utmynna i att en modell i full skala testades under verkliga förhållanden som en del av företagets produktion. Av tidsskäl så var den här rapporten, tyvärr, tvungen att färdigställas innan själva testet hann slutföras, men flera viktiga steg i tillverkningen hade genomförts och prognosen såg god ut.

I rapporten så presenteras också kostnads och miljöanalyser av den tänkta tillverkningen. Där additiv tillverkning jämförs med den traditionella modelltillverkningen i trä.
Slutligen sammanställs det som man har kommit fram till och rekomendationer inför framtiden ges till företaget.

Abstract

In this report the possibility for the manufacture and use of molding-patterns made through additive manufacturing methods, commonly called 3D-printing, is evaluated. First an analysis of how the patterns are currently being made and which demands that are put on them will be made. This includes more pure material and load demands, as well as more abstract and hard defined demands. After this the different possible manufacturing methods will be evaluated, as well as those materials that could be reasonable.

After this potential suppliers are contacted to evaluate the practical aspects of the project. Here comparative prices will also be gathered. The goal was set to complete a full scale test under real circumstances, as a part of the companies production line. Due to time constraints this report sadly had to be finished before those tests were completed, but several important steps had been made and everything were looking good.

In this report there are also some sections on the cost and environmental implications related to the planned production and use of a 3D-printed pattern. It will be compared to the conventional pattern-making in wood. Finally this is all compiled and recommendations for the future are made.

Popular Abstract

3D-printing large foundry patterns

3D-printing is a hot topic with new uses and possibilities popping up practically every day, but is it really the ``be-all, end-all" solution to industries demands? Sometimes going back to a more conventional process might be the right decision.


For a long time the pattern making process has been more or less standardized, with a pattern-maker making the pattern out of wood, often with traditional methods such as turning. Though this produces good results it is really dependent on the pattern-makers personal skills and precision, and though the turning itself does not take that long, building up large blanks before the turning even starts does. To work around these issues the idea of making the patterns with 3D-printing arose, what in the industry is called additive manufacturing.

With 3D-printing you don’t start with a solid object and then machine it down. Instead the machine build up the part layer by layer to achieve the desired three-dimensional shape. 3D-printing is today quite common, both in some industries but perhaps more noticeably as a hobby product. The prizes for 3D-printers have gone down drastically in the last ten years and as a result a lot of people find it both fun and useful to print their own parts from time to time. This could be either just for fun sakes or for printing more useful parts such as spare parts that are otherwise not available.

The problem for this project was then the size. Most hobby 3D-printers are quite small, few being able to print anything larger than a 300mm cube. For this project the base has to be at least 1.2m and the height is around 600mm. This leaves few options, which in turn sets limits to what techniques that are available. For this project it narrowed it down so that the only option was FDM, Fused Deposition Modeling. If you have ever seen a 3D-printer, it is likely that it was an FDM-printer. It is by far the most common printer and can be likened to a computer controlled hot glue gun that works its way up, layer by layer. It is a fast and cheap method, but comes with a crude surface finish.

The foundry patterns require a smooth surface to avoid the sand getting stuck to it when the pattern is removed, since this was unachievable with the 3D-printing alone the part will then also have to be machined down with a CNC-mill. One could say that this was the downfall of the project, adding another machine operation adds another level to the cost calculations, as well as delaying the finished product substantially. The cost difference to the conventional patternmaking was not that large and could have been outweighed by a shorter delivery time, but this was not the case. The project was definitely not complete failure, it showed that it is possible to make these patterns with 3D-printing and it might just be that the technology is not ready yet. There are other 3D-printing techniques that offer better surface quality that might be available in the right size in the future, only time will tell, but at the moment it might be best to stick with what is tried and true, gluing up large pieces of wood and spinning them around a central axis while you slowly remove the wood by bringing a sharp metal piece in contact with the spinning surface.


Author: Simon Håkansson
Full report: Håkansson, Analysis of implementing additive manufacturing for the making of casting patterns, 2022

• author: Håkansson, Simon
• supervisor: Christina Windmark
• organization: Production and Materials Engineering
• course: MMTM01 20212
• year: 2022
• type: H3 - Professional qualifications (4 Years - )
• subject: Technology and Engineering
• keywords: 3D-printing, additive, manufacturing, polymer, plastic, wood, pattern, casting, molding, vacuum, sand, ABS, milling, turning
• other publication id: CODEN:LUTMDN/(TMMV-5333)/1-84/2022
• language: English
• id: 9075002
• date added to LUP: 2022-02-10 11:52:31
• date last changed: 2022-02-10 11:52:31