Wednesday, 7 August 2013

3D Printed Parts Cast for the First Time in Aluminium - Part Four

The Journey to Find Cost Efficient Aluminium Rapid Parts Continued.

Hi all, just for a quick recap, in the last blog I prepared the CAD for our part to be cast.  I ran through the design and looked at how the molten aluminium will flow through the mould, checked to make sure there is the correct draft angles on faces and finally scaled the CAD to take into account shrinkage.
Below shows the CAD model.

I checked the measurements of the rapid prototyped part (remembering that its 3% larger than the desired size) and it was accurate within approximately 0.25mm, well within our requirements.  Following the measurement check, I very lightly sanded the top layer of the part, just to remove the subtle steps between the build layers of the part. 

With the part ready to cast, I went over to our local foundry.  I took my tablet with edrawings as well so they could see the 3D CAD just to make sure I did not miss anything.

The sand casting foundry has been in operation for over 50 years, and the owner took over from his father, so has decades of experience in casting. Our rapid prototyped master was the first one he had seen, and he was impressed with the overall finish.

He commented that for simple parts, with basic geometry, he could probably manufacture a master pattern at a lower cost than printing, however, for parts with unusual geometry (such as this part with its sweeping radii) the printed parts could well be a much lower cost and quicker option.

Two days later the part was ready for collection.

Driving back over to the foundry I was keen to see exactly how the part had come out, if it was "in tolerance" and also if there were any issues during the casting process.

Below is the finished aluminium part

The foundry owner seemed very pleased as he presented the part to me, and said it was really easy to cast, with no issues.

He commented that all they needed to do was add the sprue and riser to the plastic part, and cover it in release agent.

There were no issues with the flow through the mould, and also looking at the part closely, there were no visual distortion from shrinkage or uneven cooling.

I asked him if there was anything that could make the process easier next time, and all he commented on was taking into consideration the split line on the part and in the mould, if the parts were more complicated in the future.  I will go into more detail about split lines in future blogs, but for now, he said with such a simple part, there were no issues, and that he was very pleased with the part.

I have only just got the part back but wanted to put this blog up to let you know how things are going.  Over the next week I will carefully measure the part and compare it to the original CAD to see if there have been any issues that were not apparent by a visual check.

If the part is indeed accurate, we have quite a few other aluminium parts that need to be made, so fingers crossed that this part is good and will work for us. So far so good!

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