The haulm topper sits at the front of a potato harvester and strips the green haulm before the lifting share enters the ridge. Its drive hub transmits belt or gearbox torque to the flail rotor shaft at high rotational speed, in a cloud of abrasive sandy soil, stones and plant sap. The hub is therefore both a power transmission part and a wear item: it must carry keyway or splined torque, survive stone strike shock loading, hold bearing and seal seats true, and resist the scouring action of silica-laden dust. Harvester OEMs and aftermarket programmes replace these hubs between seasons, which makes them an ideal repeat casting with amortised tooling.
Specifications
| Parameter | Value |
|---|---|
| Material | ductile iron |
| Casting process | Silica sol lost wax investment casting |
| Dimensional tolerance | ISO 8062-3 CT6 to CT7 |
| Machined tolerance | ISO IT7 |
| Surface treatment | Shot blast |
| Documentation | EN 10204 3.1 material certificate; PPAP / FAIR on request |
Material and process
EN-GJS-600-3 is a pearlitic ductile iron offering 600 MPa tensile strength, 370 MPa 0.2% proof strength and 3% minimum elongation, with Brinell hardness typically in the 200-270 HB range as cast and higher after normalising or induction hardening of the bearing seat. That hardness is what resists abrasive soil wear at the seal land and the shaft bore, while the graphite nodules give the hub enough toughness to survive impact from stones and rotor imbalance events. The hub is produced by silica sol lost wax investment casting to hold the spline or keyway profile close to net shape, then normalised or quenched and tempered to the specified hardness band.
Casting and CNC route
After tooling release and first-article approval, the route is wax injection, assembly, shell build, dewax, pour, knock-out, cut-off and shot blast, followed by heat treatment. CNC turning produces the bearing seat, seal land, bolt circle and the outer drive face in a single chucking to keep concentricity, and a machining centre or broach finishes the spline or keyway. Hubs are balanced as a rotor assembly at the customer, so bore concentricity to the bolt circle is the controlling dimension. Still, machining allowance is held on the hub faces only; the as-cast surfaces between webs are left for wear resistance.
Tolerances and inspection
Generally, we quote casting tolerance to ISO 8062-3 CT6 to CT7, with machined features to the drawing. The bearing seat is normally held to ISO IT7 with a runout control to the bolt circle datum, and the spline or keyway is checked with a go/no-go gauge or by CMM against the mating shaft specification. Hardness is verified on the bearing seat and on a representative as-cast surface, and the hardness band is reported per heat lot. We verify surface roughness at the seal land because it directly drives seal life in dusty service.
Quality & compliance
Every production hub is magnetic particle inspected on the webs, hub-to-rim transition radii and the keyway root, since those are the areas where cyclic torque and stone strike initiate cracks. Additionally, ultrasonic testing is available on the heavier hub boss where section thickness allows. EN 10204 3.1 certificates carry chemical analysis, tensile and hardness results and heat treatment records with furnace chart traceability. In general, nodularity and pearlite content are verified metallographically per heat. Also, PPAP or FAIR packages are available for OEM new part introduction.
Packaging and logistics
We pack hubs with the machined bore and seal land protected by caps or VCI wraps, separated by dividers in cartons, then palletised and shrink-wrapped for container load. Aftermarket programmes are typically shipped as mixed pallets covering several harvester models, and Ningbo Ruican holds agreed buffer stock so that in-season replacement orders can be dispatched quickly during the harvest window.
CTA
- 3D model and drawing with spline or keyway specification and mating shaft details
- Grade and hardness band: EN-GJS-600-3, target HB range, any local hardening
- Heat treatment requirement: normalised, or quenched and tempered
- Moreover, Bearing and seal seat tolerances, runout to bolt circle
- Annual volume split between OEM build and aftermarket
- NDT scope and acceptance criteria
- Certification: EN 10204 3.1, PPAP or FAIR
- Packaging and labelling for aftermarket distribution
- Contact Wendy She – sales@cnsandcasting.com – WhatsApp +86-13777124360
FAQ
Why EN-GJS-600-3 rather than a lower grade?
The pearlitic matrix gives the surface hardness needed against abrasive sandy soil, while the ductile graphite keeps impact toughness for stone strike.
Can the spline or keyway be cast to size?
Close to net shape yes, but the torque-carrying profile is finish machined or broached so that the fit to the flail shaft is repeatable.
Is local hardening available?
Yes. We can apply induction hardening of the bearing seat or seal land where the drawing calls for a harder wearing surface.
Do you hold stock for in-season replacement orders?
Yes. We hold agreed buffer stock against a rolling forecast so harvest-season orders ship without waiting for a production slot.
