Part: Battery Cover for the Yonezawa Talking Robot - a plastic component.
1 Get an original part and embed it in moulding clay. Put register holes around the edge to allow for keying two halves of the mould together. Place rods to leave holes down which the casting material can run, and out of which air can be released. Cover with plaster compound and leave to dry. Repeat operation for other half of mould.
2 Here are the two halves of the mould with the original part still in situ.
4 And the completed mould.
4 Fasten mould halves together and carefully fill with casting compound, ensuring all bubbles are removed and mould is fully filled. Leave to set.
5 Here's the completed repro part in the mould, with the pouring sprue and the vent sprue still attached. Carefully remove them and tidy up the part.