CNC MACHINING

What is die casting factory cnc machining?

Die casting factory CNC processing, essentially is the die casting machine rapid prototyping of metal blanks, through the computer-controlled cutting machine tool for precision trimming, because die casting can only make the general outline of the parts and the basic shape, but can not guarantee that the mounting surface, screw holes, bearings, and other key positions of the ultra-high precision, and even more can not be directly excised into the mouth and burr, only through the CNC this road “Only through the CNC process, die-casting parts can be transformed from semi-finished products with residual material and rough tolerance into qualified parts with accurate dimensions that can be directly delivered to customers for assembly.

CNC Precision Machining of Aluminum Alloy Castings

Aluminum alloy blank parts produced by die casting, theirMounting surfaces, threaded holes, bearing housing bores, and sealing surfacesThe tolerances for critical parts such as these are typically greater than ±0.1 mm, which falls far short of assembly requirements. Hexin’s CNC machining process uses computer-numerically controlled (CNC) machine tools to perform secondary precision machining on the castings, controlling the hole diameter tolerance toIT7 grade (±0.015 mm), flatness controlled toWithin 0.05 mm...while simultaneously removing gate residue, flash, and excess material along the parting line, transforming the casting from a "raw" state into a qualified finished part ready for direct delivery to the assembly line.

Process Positioning:CNC machining is a precision post-processing step in the die-casting process; it does not involve shaping the blank but only makes precision adjustments. Hexin’s CNC machining center is located adjacent to the foundry, allowing castings to enter the machining process within two hours of coming off the production line, thereby reducing the risk of damage during intermediate transport.

CNC Machining Process Flow

Clamping and Positioning

Design specialized hydraulic or pneumatic fixtures based on the casting’s geometry, using the casting’s reference surface or machined surface as the positioning reference to ensure repeatable clamping and positioning accuracy of ≤0.02 mm, thereby preventing dimensional drift between batches caused by clamping errors.

Rough Machining

Use a carbide end mill or a modular face mill to remove excess material from the sprue, burrs along the parting line, and large machining allowances using a deep cut and moderate feed rate, leaving a finishing allowance of 0.3–0.5 mm while relieving internal stresses in the casting.

Finishing is complete

Switch to PCD or CBN cutting tools to perform boring of the bearing bore, milling of the sealing surfaces, and tapping of threads at high speed with a small cutting depth (0.05–0.15 mm), high spindle speeds to bore bearing holes, mill sealing surfaces, and tap threads, ensuring that critical dimensions meet the tolerance requirements specified in the drawings and achieving a surface roughness of Ra 0.8–1.6 μm.

Online Testing

After machining is complete, key dimensions are inspected online on the machine tool using a pneumatic gauge or electronic plug gauge. Sampled parts are transferred to the coordinate measuring machine (CMM) room to generate a full-dimension inspection report, and parts that pass inspection are sent to the cleaning and rust prevention process.

Machining Accuracy and Equipment Capabilities

IT7

Pore Size Tolerance Grade

Hole diameters ranging from Φ10 to Φ100 mm can be consistently controlled within ±0.015 mm.

0.05 mm

Flatness/Parallelism

Flatness within a 200 mm × 200 mm area: ≤0.05 mm

Ra 0.8

surface roughness

Sealing surfaces and bearing bores can be finished to a surface roughness of Ra 0.8 μm

Equipment Name	Quantity	Travel Range (X/Y/Z)	Spindle Speed	Typical Processing Capabilities
High-Speed, High-Precision CNC Machining Center	2 units	800 × 500 × 500 mm	12,000 rpm	Precision Machining of Small and Medium-Sized Housing and Bracket Castings
Electrical Discharge Machining (EDM) Machines	Several	-	-	Precision EDM Machining of Mold Cavities, Deep and Narrow Groove Machining
Auxiliary Processing Equipment	More than 10 units	-	-	Drilling, Tapping, Deburring, Surface Treatment

Typical Applications of CNC Machining

He Xin's CNC machining capabilities cover aluminum alloy castingsFlat milling, boring, drilling, tapping, reaming, and contour millingAll types of cutting processes, with typical workpieces including:

Engine Housing Components

Gear housing, oil pan, timing cover, etc.—pay particular attention to ensuring the flatness of mounting surfaces, the positional accuracy of locating pin holes, and the precision of threaded holes.

Pump and Valve Body Components

For components such as the oil pump housing, hydraulic valve body, and water pump housing, requirements include the coaxiality of oil passage bores, the surface roughness of sealing surfaces, and thread strength.

Bracket Connector

Engine mounts, shock absorber brackets, mirror brackets, etc.—ensure that mounting hole spacing tolerances and structural strength are met, and remove all sharp edges and burrs.

New Energy Components

Precision machining must be performed on thin-walled castings—such as electrical control box housings, battery pack brackets, and radiator housings—to control deformation.

Manufacturing Quality Control System

✓

First-Piece Inspection System

After each batch change or tool change, a full-dimension inspection of the first piece is performed. An inspection report is generated using a coordinate measuring machine (CMM), and batch production may only continue after the piece has been confirmed as合格.

✓

Tool Life Management

Establish a tool life database and set mandatory replacement intervals based on the number of parts machined or cutting time to prevent dimensional deviations and deterioration in surface quality caused by tool wear.

✓

In-Process Sampling and Inspection Control

During mass production, key dimensions are randomly inspected at regular intervals using in-line inspection tools such as pneumatic gauges and roughness meters; any abnormal data immediately triggers a production halt for troubleshooting.

✓

Centralized Management of Cutting Fluids

Use only water-soluble cutting fluid specifically designed for aluminum alloys, and regularly test its concentration, pH level, and bacterial content to ensure consistent cooling and lubrication and prevent corrosion on workpiece surfaces.

A CNC machining center performs precision boring on aluminum alloy die-cast parts to remove excess material from the gate and burrs along the parting line, ensuring dimensional accuracy of the mating surfaces.

CNC machining centers perform precision machining on aluminum alloy castings, transforming raw castings into high-precision finished parts.

Common Technical Issues in CNC Machining

Q: Why must die-cast parts undergo CNC machining before they can be shipped?

The cavity accuracy of die-casting molds is affected by factors such as thermal expansion and contraction, draft angles, and mold wear; as a result, the dimensional tolerances of critical mating surfaces on castings are typically only ±0.1–0.3 mm after molding, whereas engineering drawings specify tolerances for bearing bores and locating pin holes in the range of ±0.015–0.03 mm. In addition, the excess material resulting from the gate, sprue, and parting line must be removed via CNC machining. Therefore, CNC machining is not an optional process, but rather a necessary finishing step in transforming die-cast parts from rough castings into qualified components.

Q: What kinds of problems commonly arise during CNC machining of aluminum alloy castings?

Common issues include: ① Surface scratches caused by built-up edge on the cutting edge—resolved by selecting cutting tools specifically designed for aluminum alloys and using sufficient coolant; ② Deformation during machining of thin-walled parts—resolved by optimizing the clamping method, reducing the cutting depth, and using symmetrical machining paths; ③ Internal porosity in castings becoming exposed after machining—control casting process parameters at the source to reduce subsurface porosity; ④ Tap breakage during threading—use helical-fluted taps and a rigid tapping cycle, and strictly control the pilot hole diameter.

Q: What is the minimum order quantity for CNC machining at Hexin?

He Xin supports flexible manufacturing models ranging from small-batch prototyping (10–50 units) to high-volume mass production (tens of thousands of units). For small batches, quick-change fixtures are used to enable rapid production without the need for custom tooling; for large-volume production, dedicated hydraulic multi-station fixtures are designed in conjunction with automated loading and unloading solutions to improve cycle time efficiency. The prototype production cycle typically takes 3–5 business days.

Q: What post-processing steps are required for castings after CNC machining?

After machining is complete, perform the following steps in order: ① High-pressure washing to remove chips and cutting fluid residue; ② Blow-drying with compressed air; ③ Spraying with a water-soluble rust inhibitor (for storage periods ≤ 6 months) or rust-preventive oil (for storage periods > 6 months); ④ Perform surface treatment as required by the customer (e.g., anodizing, sandblasting, electroplating, etc.). A dimensional inspection report for each batch is included with the shipment.

Do you have aluminum alloy castings that require precision CNC machining?

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