▲ Riser / feed head
Riser / feed head · Fundición (ISO 10135) · ISO 1101
Example in plan
How to interpret it
On the drawing, “Top riser · remove and dress” states a riser / feed head requirement.
What controls
Reservoir of metal connected to the part that feeds the area that solidifies last, compensating for shrinkage and preventing a shrinkage cavity from forming inside the material. It must not remain on the finished part: it is cut off and dressed, leaving a mark where it was connected. The drawing shows it to indicate where that mark will be and where functional surfaces should not be placed.
How to verify
Visually check that the cut-off is complete and dressed within the permissible remnant, with a straightedge or dial indicator against the adjacent surface. The soundness of the material under the riser, which is the really important point, is verified with penetrant testing on the surface once machined, and with ultrasonic testing or radiography when the part requires it. Leak tightness, if it is a fluid part, is confirmed with a leak test.
Common mistakes when interpreting it
- Accepting the riser area because the cut-off came out clean: what matters is whether there is sound material underneath.
- Referencing the setup on the riser mark.
- Confusing the riser with the sprue or the runner: they feed at different times and leave different marks.
How to get it in the workshop / if it comes out of tolerance
The riser area is the one most at risk of porosity if feeding did not work: if you have to machine there, expect less sound material just underneath. The cut-off leaves an irregular and sometimes hard surface: take a roughing pass with margin before finishing. Do not use the riser mark as a locator or as a reference.
Recurring porosity under the riser mark: the riser is undersized or poorly placed, and that is corrected at the foundry. If the cut-off leaves a hard pad, dress it before the tool runs into it. If an internal shrinkage cavity appears during machining, do not try to cover it up: it is a soundness defect and must be evaluated against the part's acceptance criteria.
Related symbols
Other symbols in Foundry (ISO 10135)
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