Hello guys, i'm new here. i'm looking for advice about core boxes design. I designed my own 50cc 2 stroke cylinder, and since i'm too poor to pay someone to study and manifacture all the necessary stuff for casting, i'm trying to model and create the core boxes by myself via 3d printing. I've already tried some prints and coated them with a special filler, and the results were good: optimal roughness, perfect alignment and coupling. The problem is that since this is my first experience with castings, i'm experiencing some difficulties at "reverse thinking" to obtain the right planes and angles and all. I'm a mechanical designer with skills on Creo 7, so the software part is not too much of a problem (even if i needed to learn some surfaces features i wasn't used to). I thought that maybe an expert eye can solve in 5 minutes what i'd need 5 days to understand. -First of all: i know that i usually need a min 2-3° draft angle to extract the cores, but can i just ignore that where i don't need a strict dimensional control? For example on the outside shell or in some liquid pattern surfaces? i don't care if the sand rubs on the walls a little. The local foundry man said that he's not using my boxes if they're at 90°... -there are some surfaces, especially those in the ducts, than i can't reshape to avoid a negative draft: how can i design the core boxes in these cases? (The green core) -any suggestion on how to divide the box for the fuchsia core? if i divide it in two halves i always have negative angles (see the yellow and orange models) thanks for your attention Andrea
Hey Andrea, it looks like you are using 3d printing to make patterns for green sand casting. Have you thought about making a positive model, scaling for shrinkage, and doing a lost-wax(lost-PLA) approach? You could shell coat the model+feeder system+risers and subsequently burn on the plastic while firing the shell. This would be more of a one-off approach but would give you more CAD freedom for proving concepts. Could also print in however many pieces. I bring this up because of some past successes and experiences this forum has had with shell casting. Locating a slurry may be difficult for your region. Maybe not? Nice work on the CAD by the way!
hello Batty, to be honest the lost foam/pla approach was the first that came to mind. The problem is that old foundry men around here aren't eager to just melt some aluminium in a plaster bucket filled at home by myself. They say it's not correct, they bring up the possibility of plaster breaking due to the temperature and all... and i can't build an home foundry as of now. Regarding the model obviusly it would be easier, if only i could find someone that can help me with plaster making, feeder size, equipped with an oven capable of melting the pla (or even to take the plaster mould at the right temperature before casting), and with all the stuff to melt alumium.. I also saw some guys on youtube using a sand bucket with a vibrating platform and a lost foam model, but i can't find anything similar on the market except for maybe some concrete dedicated machines. Anyway, at the moment i found someone providing sand cores printend directly in 3d, Voxeljet, and the costs looks promising (under 100€ for the entire core which is 130x104x86mm). If you order 10 pieces, the cost drops drastically (19€ a piece! that's low even for traditional core boxes sand), so i stopped the core developing a bit. We'll see!
Sounds like you are going for 10 prototype castings to me! Peanut butter and jealous sandwich over here. Looking forward to the pictures for sure.
Hi Gradella, I allso going to order Voxeljet printed Sand Cores for my Cylinder Project. Where you let print yours? Greetings from Tirol/Austria
