Introduction
The sintering process takes parts from a “green” state to their final, fully solid metal forms. Preparing parts to sit in the graphite retort properly for the 40+ hours that they will be in the furnace is important to achieving good parts without damaging the (very expensive) graphite retort.
Images by: Terrapin Works
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Before sintering, parts are in a "green" state and must be handled with care
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Parts would fuse to the graphite retort without a layer of separation
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Setter plates are made of ceramic and serve this purpose
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Always maintain a 5-10mm margin to the boundaries of plates to minimize risk
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All parts involved in this process are fragile, so take great care and patience
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Clear a decent area on a powder processing worktable
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Wipe down the area with DI water and dry thoroughly
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Connect and power on a parts scale
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Prepare to track object weights on a sticky note or similar
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Retrieve a graphite retort ring
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Inspect the retort ring for any solidified metals
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Carefully set in a graphite base plate:
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Place the retort ring over the edge of a table or tilt up the ring with one hand
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Set one edge of the graphite base plate into the ring
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While supporting the base plate, lower it into the ring gently
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Retrieve setter plates - 4 per base plate
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Setter plates are also fragile, handle with care
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Check setter plates for warping
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Setter plates can be reused but also can warp - these should not be used
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Place the plate on a flat, clean surface (ideally stone or resin)
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Using two fingers, alternatively tap each pair of diagonal corners
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Feel and listen for any up or down movement - any movement indicates that the plate should not be used
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Place 4 setter plates in the base plate
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Butt each plate right up to each other
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Center all setter plates on the base plate
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Tare the scale and ensure it is displaying in kg or grams
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Place a batch of parts on the scale
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Ideally, all parts in each ring should be weighed together to minimize mistakes
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The rings should each be as balanced as possible - evenly distribute large parts between each ring
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Take note of the weight and quantity of parts
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Parts that are weighed can be transferred from the scale to the prepared retort ring
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Place large parts towards the right side (when the retort is in the furnace)
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Large parts should only 'span' multiple setter plates if absolutely necessary, but be careful to ensure there is no gap
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Try not to place parts 'behind' each other
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Forming gas is flowing through the retort in this direction, so each part creates a gas 'shadow'
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Leave about 10 mm of space between larger parts - smaller parts can be slightly closer
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Leave about 10 mm of space from the parts to the edge of the setter plates
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Check to see if parts are taller than where the next base plate will sit
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If parts inside the ring are too tall to safely put a base plate on the next ring in the stack:
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Retrieve another graphite retort ring
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Slowly lower it on the prepared ring
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Ensure that the next ring and baseplate will be clear of the parts
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Follow the instructions (see separate guide) to place the prepared retort ring into the furnace
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Repeat the previous steps to build all rings
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There will be total of 6 rings and a maximum of 6 base plates
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EACH RING MUST go into the furnace, regardless of how many parts are inside
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Remember to weigh parts
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Avoid accidently reweighing parts that have already been tracked
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The retort layers will be loaded into the furnace following directions in this guide
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