Casting Defect Troubleshooting Checklist (Free)

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9 critical items still open - these are the highest-risk gaps.

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Gas porosity and pinholes

Check mold and core moisture and binder gas generation against limitsCRITICALConfirm core vents are open and core prints are sealed to the moldCheck mold permeability and venting at the last place to fillCheck metal hydrogen level, degassing time and dross removal (aluminium)CRITICALCheck pouring temperature is not too high and metal was not held too longInspect chills and chaplets for rust or moistureReview charge material for oil, water, rust and coatings

Shrinkage and feeding

Locate the defect at a hot spot, thick junction or last-to-freeze regionCheck riser size, neck size and feeding distance against the casting modulusCRITICALCheck riser height and whether riser sleeves or topping compound were usedReview pouring temperature, since high temperature increases liquid contractionCheck chill placement and whether it was in position at pourCheck mold wall movement from soft ramming or low mold hardnessFor ductile iron, check carbon equivalent and inoculation practiceCRITICAL

Inclusions, slag and dross

Check ladle skimming, slag removal and clean pour lipCRITICALConfirm gating includes a choke, a runner extension or filter where designedCheck filter size, placement and preheatReview magnesium treatment fade and slag carryover for nodular ironCheck for oxide films from turbulent filling or high ingate velocityCheck refractory lining and ladle condition for erosion

Sand and mold defects

Check green strength, compactibility, moisture and permeability at the mullerCRITICALCheck for sand wash or erosion at ingates and sharp cornersLook for scabs and buckles; check clay, sand expansion and mold coatingCheck for burn-on and penetration; verify coating, grain fineness and pouring temperatureCheck mold closing, cope drop, crush or mismatch at the parting lineConfirm core setting, core print fit and core shiftCheck mold hardness and ramming consistency

Cracks, tears and distortion

Distinguish hot tears (oxidised, jagged) from cold cracks (clean, straight)CRITICALCheck for abrupt section changes and missing radii or filletsCheck mold and core collapsibility, since hard cores restrain contractionCheck shakeout time and cooling rate before knock-outReview heat treatment or straightening steps after castingCheck for cold shuts and misruns from low pouring temperature or slow pour

Dimensions and records

Check the pattern against the drawing and the shrink allowance usedCheck pattern wear, loose parts and rapping allowanceRecord the heat number, pour time, pour temperature and mold number of the faulty castingsCRITICALRetain samples and photographs for the root cause fileOpen a nonconformance and containment for suspect lotsCRITICALUpdate scrap codes so defects are counted consistently

Tick each check you have completed. Start with the group matching the defect appearance, then review records. The list does not replace metallurgical examination, radiography or sectioning when the cause is not clear.

Scrap reason codes and trends

Optional: a review of how scrap and defect data is recorded in your ERP or MES.

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How to use the checklist

Start by naming the defect from its appearance and location. A rounded smooth cavity is usually gas, a rough dendritic cavity at a hot spot is usually shrinkage, and a spongy area at the surface may be sand or core gas. Go to the matching group and tick off each check. Items marked critical are the ones most often found to be the cause. Record findings with the heat, mold and time so you can find a pattern across shifts.

Gas or shrinkage

Confusing gas porosity with shrinkage leads to the wrong fix. Gas defects are usually spherical, smooth and often near the surface or under cores, and respond to venting, drier sand and degassing. Shrinkage is angular or dendritic and sits at heavy sections away from risers, and responds to better feeding, chills and pouring temperature control. Increasing riser size to fix gas defects wastes metal, and degassing more will not cure shrinkage.

Smooth round cavity: suspect gas
Rough interior, dendrites: suspect shrinkage
Surface slag or dross stringers: suspect inclusions
Cavity under a core: check core gas and venting

Closing the loop

A defect fix is only proven when scrap falls over many molds, not after one good shot. Change one variable at a time and note it in the process log. Monitor the scrap code for at least a week. Use sectioning, X-ray or dye penetrant testing on sample castings to confirm the defect type before spending on tooling changes. For safety-critical or customer-reported failures, run a formal 8D or corrective action report.

Common mistakes and ERP notes

Most foundries lose time because scrap is coded loosely, such as a single 'defective' reason. Use specific reason codes so Pareto charts mean something. In the ERP or MES, tie scrap and rework quantities to the heat, mold line and pattern so trends can be seen. Without heat and mold traceability the checklist yields opinions rather than evidence.

Frequently Asked Questions

How do I tell gas porosity from shrinkage porosity?

Gas porosity tends to be smooth, round and sometimes shiny, while shrinkage is rough, angular or dendritic and appears at the last-to-freeze section. Sectioning the casting and examining the cavity wall usually settles it.

What causes hot tears in castings?

Hot tears form while the casting is still weak and is restrained from contracting, often at sharp section changes or where cores and mold resist movement. Better radii, more collapsible cores and controlled pour temperature help.

Should I change the riser or the pouring temperature first?

Confirm the defect type first. Shrinkage points to feeding and temperature; gas points to venting, moisture and metal quality. Change one variable at a time and track scrap over many molds.

Does this checklist cover die casting?

It is written mainly for sand casting. Many ideas, such as gas, shrinkage and inclusions, carry across, but die casting adds shot profile, die temperature and lubricant factors that need their own list.

If scrap reasons and heat numbers are not captured consistently in your ERP, we can help set up the codes and reports that make defect trends visible.

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Casting Defect Troubleshooting Checklist: Porosity, Shrinkage, Sand and Metal Faults