Tiếng Việt
Quick answer: Scanning cast parts for inspection means using a 3D scanner to capture the full shape of an aluminum casting, iron casting or injection-molded plastic part, then comparing it with CAD to quantify warpage, shrinkage, short fills and machining allowance. CT3D uses this method to evaluate molds and approve first articles (FAI) for factories.
Cast parts have one trait that makes traditional measurement difficult: most of the surfaces are raw, with draft angles, fillets, ribs and pockets that constantly change. Calipers have almost no reference surface to rest on, and a CMM takes many hours of programming for a single gearbox housing. Yet these raw surfaces are exactly what determine machining allowance, wall thickness and fit. 3D scanning solves the problem by capturing the part “as cast”.
Key points
- Scanning cast parts shows all post-casting distortion, not just a few hand-measured dimensions.
- Each casting process has its own typical deviations: aluminum die castings tend to warp in thin walls, sand-cast iron has core shift, and injection-molded plastic shrinks and warps along the flow direction.
- Scan data helps you decide whether to adjust the mold, change process parameters or adjust machining allowance.
- At the first article (FAI) stage, 3D scanning shortens approval time and creates clear evidence between the foundry and the customer.
Why should cast parts be inspected with 3D scanning?
Cast parts should be 3D scanned because their deviations are spread across the whole surface, not limited to a few dimensions. Solidification and cooling create stress, and metal or plastic shrinks unevenly depending on wall thickness. So a part can have correct overall dimensions and still be warped, have core shift or have locally thin walls.
Information 3D scanning provides that is hard to get by hand measurement:
- A wall thickness map (for parts that can be scanned inside and out).
- The actual machining allowance on each face to be milled or turned.
- The overall warpage shape and direction.
- Mismatch between the two mold halves (parting line shift) and sand core shift.
- Short fills, large flash, and distortion from ejection.
Typical deviations by type of cast part
Each forming process has its own deviation “fingerprint”. Knowing it in advance helps you place the right cross sections and measurement points during inspection.
| Part type | Common deviations | Common causes | Areas to check closely |
|---|---|---|---|
| Aluminum die casting | Thin-wall warpage, distortion when trimming gates, shifted pin holes | Uneven cooling, ejection, deburring | Mating faces, long ribs, screw hole clusters |
| Aluminum sand / gravity casting | Core shift, uneven wall thickness, rough surface | Sand core movement, shrinkage | Walls around cores, machining allowance |
| Iron casting (gray, ductile) | Parting line shift, mold swell, insufficient allowance | Weak sand molds, molten metal pressure | Parting line, machining datum surfaces |
| Injection-molded plastic | Shrinkage, warpage, sink marks, short shots | Flow direction, uneven thickness, cooling | Long walls, rib locations, screw bosses |
Mold inspection vs part inspection: which should you scan?
Scan both, but at different times and for different purposes. Scanning the mold cavity tells you whether the mold was machined correctly; scanning the part tells you what the casting or molding process produces. The difference between the two results is the effect of shrinkage and distortion.
| What to scan | When | Question it answers |
|---|---|---|
| Mold cavity, mold core | After mold machining, after weld repair, periodically as the mold wears | Does the mold match CAD (with the shrink factor applied)? Which areas are worn? |
| Mold trial parts (T0, T1…) | At every mold trial | Where is the part off? Is it caused by the mold or by the process settings? |
| First article (FAI) | Before mass production | Is it ready for approval? |
| Periodic production parts | According to the QC plan | Is the process drifting over time? |
An example: if the mold cavity matches CAD but the plastic part still warps 0.5 mm at both ends, correcting the mold geometry may not work. It’s better to review the cooling system, the gate location or apply warpage compensation in the mold design. On the other hand, if the part is off by exactly the amount the mold has worn, weld buildup and remachining of that area is enough.
Scanning cast parts at the first article (FAI) stage
FAI (First Article Inspection) is a complete inspection of the first part from a new mold or process before mass production, and 3D scanning makes FAI faster for parts with complex shapes. An FAI process using 3D scanning usually includes:
- Ballooning the dimensions on the drawing that need to be checked.
- Scanning the whole sample part and aligning it to the drawing datums.
- Measuring the dimensions and GD&T for each balloon number; very tight tolerances are added using a CMM or dedicated gauges.
- Producing an overall color map with a pass/fail results table.
- Saving the scan file as a “fingerprint” to compare with later batches.
The biggest benefit is not speed but the archived data: when the tenth batch has a problem, you can compare it directly with the first article scan to see where the mold has changed.
What to prepare when sending cast parts for inspection scanning
Good preparation makes scan results accurate and fit for purpose. CT3D usually asks customers to:
- Send the part CAD file (STEP/IGES), stating clearly whether it is the as-cast CAD or the machined CAD.
- Send the 2D drawing with datums and tolerances; mark the critical dimensions.
- Tell us the condition of the sample: whether gates have been trimmed, and whether it has been shot blasted or heat treated, since each step can distort the part further.
- For thin plastic parts, say whether they need to be scanned on a fixture that simulates the assembled state (flexible parts can sag under their own weight).
- The number of samples to scan to evaluate repeatability between cavities (multi-cavity molds).
For large molds or heavy castings that are hard to ship, CT3D can do on-site 3D scanning at your factory. If an old mold no longer has design files, the scan data can be used for reverse engineering to a CAD file to make a new mold.
Limits of 3D scanning for cast parts
3D scanning only measures visible surfaces, so it can’t detect internal defects. Gas porosity, shrinkage porosity, hot tears and slag inclusions in iron need non-destructive testing such as X-ray CT/NDT. Long bores and deep, narrow pockets can also limit the scanner’s line of sight. When advising you, CT3D will be clear about what 3D scanning can handle and what needs another method.
Frequently asked questions
Can raw cast surfaces be scanned accurately?
Yes. The rough surface of a sand casting is actually easier to scan than a shiny one. Accuracy then depends mainly on the equipment and alignment method; with industrial handheld scanners it is usually around a few tens of microns.
Should a cast part be compared with the as-cast CAD or the machined CAD?
To evaluate the casting mold and allowance, compare with the as-cast CAD. To inspect the part after machining, compare with the machined CAD. In many cases it’s worth doing both to see whether the allowance is sufficient.
Can 3D scanning find gas porosity in aluminum parts?
No, 3D scanning only captures the surface. Internal porosity needs X-ray or industrial CT; porosity exposed on the surface after machining can be captured by scanning.
Do all parts from a multi-cavity mold need to be scanned?
At the approval stage, scan at least one part from each cavity, because each cavity can shrink and warp differently.
Do thin, flexible plastic parts distort during scanning?
Optical scanners are non-contact, so they don’t cause distortion, but the part can sag under its own weight. In that case it should be scanned on a locating fixture that simulates the assembled state.
I’m in Binh Duong. Can I send cast samples to CT3D?
Yes. You can bring samples to our workshop in Ho Chi Minh City, send them by courier, or contact CT3D to scan on site if the parts are large.
Conclusion
For aluminum castings, iron castings and injection-molded plastic parts, inspecting with 3D scanning is the fastest way to see warpage and shrinkage clearly and tell whether a defect comes from the mold or the process settings. That data lets the foundry and the buyer speak the same language when approving first articles. Send your samples and drawings to CT3D via Zalo at 0985 936 728 for advice on an inspection plan.
Related articles on 3D inspection scanning
- 3D inspection scanning service: measuring dimensions, comparing with CAD and producing deviation reports
- On-site factory 3D scanning: how to coordinate with the QC department in Binh Duong, Dong Nai and Long An industrial parks
- What does 3D scanning cost depend on? How to choose affordable 3D scanning that still gets dimensions right
- What is 3D inspection? 3D measurement methods, benefits and when to use them
CT3D service ecosystem
- 3D scanning and inspection of cast parts
- CT3D mold and silicone mold services
- Rapid prototyping before making casting molds
- Metal 3D printing to replace low-volume castings
- CT3D Group
- CT3D company profile
- Contact us about cast part inspection scanning
About CT3D – a large-scale, multi-industry prototyping and manufacturing technology company
CT3D works with molds and cast parts every day, so it understands casting deviations from the point of view of both the inspector and the moldmaker. As a large-scale, multi-industry prototyping and manufacturing technology company, CT3D runs workshops in Ho Chi Minh City (Thu Duc, District 6) and Hai Phong and offers an end-to-end chain of services from 3D scanning, design, 3D printing and mold making to production and inspection. This means that after inspection scanning, customers can move on to reverse engineering, prototypes or new molds with the same team. CT3D serves companies nationwide. Contact 0975 008 728 – 0985 936 728 or contact@ct3dgroup.com.
Related services at CT3D Group
- 3D scanning service – high-accuracy 3D scanning
- 3D inspection service with 3D scanners
- Silicone molds and vacuum casting
- CT3D Group network: ct3dgroup.com · in3d.edu.vn – Hotline/Zalo 0975 008 728
