Bale Wrapper Film Pre-Stretcher Carriage Frame Body

The pre-stretcher carriage carries the film roll and the pair of pre-stretch rollers that elongate stretch film before it is laid onto a round or square bale. Still, the frame body is the structural spine of that carriage: it locates both roller bearings, the brake arm pivot, the film roll mandrel and the guide roller, and it reacts the film tension load that runs through the carriage on every wrapper revolution. Field loads are modest in magnitude but highly cyclic, and the frame also sees impact when a roll is dropped into the cradle or when the carriage hits its end stop at speed on a wrapping table. Frames are consumed in volume: wrapper OEMs build for a narrow spring and early summer window, so castings must be on the shelf before line start-up rather than in transit.

Specifications

Material and process

Also, we specify EN-GJS-500-7 ductile iron for its combination of 500 MPa tensile strength, 320 MPa 0.2% proof strength and 7% minimum elongation, which gives the frame enough ductility to survive impact and bearing press-fit operations without cracking. The ferritic-pearlitic matrix machines cleanly and holds a good surface finish at the bearing seats. Generally, castings are produced by silica sol lost wax investment casting for the finer geometry – roller slots, brake arm lugs and lightening pockets – which removes most of the weld-and-fabricate work from the buyer’s assembly. In general, where section sizes are heavier, water glass lost wax is offered as a cost-down route. Castings are stress-relief annealed or normalised before machining. Hot-dip galvanising, zinc flake coating or a two-pack epoxy system can be applied to the finished part for fertilizer and silage effluent exposure.

Casting and CNC route

Overall, we build tooling to the customer’s 3D model with shrinkage and machining allowance applied to the agreed datum scheme. Shell building, dewax and pouring are followed by cut-off, shot blast and gate grind. First parts go through a dimensional study before the route is frozen. CNC work is typically a 4-axis machining centre for the roller-slot faces and bearing bores in one setup, then a second operation for cross-drilled grease ports, the brake pivot bore and the mandrel seat. We use turning for round features such as the roller trunnion seats. Because the tooling is a repeat asset, annual call-offs of a wear-item frame run on tooling that is already amortised, so unit price does not carry new tool cost in year two and beyond.

Tolerances and inspection

Additionally, we quote general casting tolerances to ISO 8062-3, typically CT6 to CT7 for silica sol route, with machining allowance agreed at the datum faces. Still, we hold machined bearing bores to the drawing tolerance, commonly ISO IT7 to IT8, with geometric controls on the parallelism of the two roller axes and on the perpendicularity of the mounting face to those axes – the parameters that determine film tracking. Inspection uses CMM for the datum and bore relationships, bore gauges and height gauges for in-process checks, and surface roughness verification at sealing and bearing seats. Overall, first-piece and last-piece checks are recorded against the drawing balloon list.

Quality & compliance

Surface crack detection by magnetic particle inspection is applied to high-stress areas such as the roller slot radii and the brake arm lug roots; dye penetrant inspection is used on as-cast surfaces where MPI is impractical. At the same time, we offer ultrasonic testing on heavier boss sections on request. Material certificates to EN 10204 3.1 are issued with chemical analysis, tensile results and hardness, and nodularity and matrix verification are reported from the cast-on test block or separately poured test lugs. Moreover, PPAP or FAIR documentation is available on request for new part introduction. Also, inspection and NDT are performed to the buyer’s specified standard, not to any third-party approval scheme.

Packaging and logistics

Parts are degreased, dried, individually bagged or wrapped in VCI paper with edge protectors on machined faces, then packed in plywood or heat-treated timber crates on ISPM 15 compliant pallets. Generally, we strap crates and stretch-wrapped for container shipment. For seasonal programmes Ningbo Ruican can build and hold agreed safety stock so that pre-season call-offs ship inside a short lead time, and mixed containers of several frame variants are consolidated for the same assembly plant.

CTA

• 3D model (STEP or Parasolid) plus 2D drawing with datums and geometric tolerances
• Grade confirmation: EN-GJS-500-7, required mechanical properties, hardness range
• Annual volume, call-off pattern and first-article deadline relative to the build season
• Machining scope: which faces, bores and threads are machined by Ningbo Ruican
• Coating: galvanised, zinc flake, epoxy or primer only
• NDT scope (MPI / PT / UT) and acceptance criteria
• Certificate requirement: EN 10204 3.1, PPAP or FAIR level
• Packaging, labelling and pallet specification
• Send the package to Wendy She – sales@cnsandcasting.com – WhatsApp +86-13777124360

FAQ

Can the pre-stretcher frame replace a welded fabrication?

Yes. Investment casting consolidates the roller slots, brake lugs and lightening pockets into one part, removes weld distortion and gives consistent bearing alignment from part to part.

What is the typical lead time for first articles?

Still, tooling and sample parts are typically released inside a few weeks of drawing freeze, with production call-offs scheduled to the customer’s build season.

Do you supply the frame galvanised or coated?

Yes. Hot-dip galvanising, zinc flake and two-pack epoxy are all offered, with coating thickness recorded on the inspection report.

How is repeat volume priced?

Tooling is amortised on the first production release; repeat annual call-offs run on existing tooling, so no new tool charge is carried into the unit price.