Casting - Cores and Prints

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For most of the photos on this page, you can click the image for a larger picture.

	Casting in progress
	The casting after being broken out of the mould and before going into the machine shop at Bo'ness
	The blastpipe cap showing the purpose of a core
	Tony now needs to produce the cores for Hengist's cylinder pattern. To help him visualise what he has to produce, Keith has produced a 3 model in his CAD system showing the internal air spaces within the casting. All of these will need to be converted to cores of moulding sand. The 4 layers of the mould are shown. The black colours show the "prints" which will support the cores in the mould.
	Again to assist Tony in visualising the job, we've had this small model created by 3D printing.
	The core boxes need to produced in Tony's workshop. The first one to be tackled (only because it's the easiest) is a half core for the main motion cylinder which requires to be around 48" long and 20" in diameter. The accuracy of the cores are most important remembering that the main pattern is only the outside of the cylinder, and the solid core being produced is the 'hole' through it. Without cores the, the casting would be a solid lump of iron. Tony has decided to make it by creating 26 U shaped sections which will be glued together and fitted inside a box. The U shaped sections will formed initially by gluing timber sections together and then routing them to the final dimensions. This is the half core from Keith's model with the "print" extensions in black.
	A jig is required for routing the sections to the final shape. The jig will guide the router. A specialist company who can laser cut MDF board will be required so a drawing of the jig is prepared. Tony will create a draft drawing knowing the dimensions of his router. He has passed this to Keith who produces a CAD model which can sent to the laser cutting company.
	The jig has come back from the cutting company. It's made out of Medium Density Fibreboard.
	To prove that it is correct, Tony has used a hardboard offcut in the jig to produce a section that should be the correct profile. The ends of the core project out as "prints" which will rest in cutouts formed in the mould from the main pattern. The test piece fits nicely so we can move onto making the sections.
	Now Tony can start producing the timber sections. First job is to convert timber planks of Canadian Yellow Pine to the sections he needs. Canadian Yellow Pine is the choice timber for patternmaking offering great stability.

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