This chamber component began as a cast aluminum alloy blank from an external casting supplier. Jinhua carried out the subsequent key CNC machining: turning followed by two separate 4-axis machining stages.
The engineering story is the relationship between those stages: establishing locating references on an irregular casting, transferring them between setups, and reaching internal, side and angular features without treating each feature as an isolated machining task.
Real component photo, approved for anonymous case use. Appearance alone is not evidence of a machining method or inspection result.
01 · The machining problem
Why This Casting Was Difficult to Machine
The challenge in complex aluminum casting machining was not simply removing excess stock. The casting combined a large internal opening, stepped and side bores, external profiles, a lug, threaded features and angled local surfaces. These features had to be addressed from different directions while preserving their reference relationships.
Locate before cutting
An irregular casting needs a defined starting location. The turning instruction specifies how the blank is gripped and supported before new locating surfaces are created.
Relationships, not isolated dimensions
The retained requirements relate bores, faces and threads to other features. Multiple approach directions and angular relationships make setup planning central to this case.
02 · Casting to machining references
From Casting to Controlled Machining Datums
The route does not assume that every as-cast surface is a final precision datum. Initial gripping and support locate the blank for turning; the turned outside locating diameter and shoulder then provide defined physical references for the later machining fixtures.
In this case, the primary machined datum and secondary locating datum are described as physical locating surfaces, not as a substitute for the customer's formal GD&T datum labels. The later setup instructions also use the lug for angular reference. Keeping those three locating functions distinct makes the datum transfer story understandable without exposing the customer drawing.
A second real product view. Which casting surfaces remain unmachined requires the controlled feature map; this photo is not used to infer that map.
03 · Actual production route
Actual Manufacturing Route
The documented production route used the following three-operation sequence. The process cards supply the operation and setup detail; these records do not supply measured inspection results.
Blank supply: external aluminum casting/purchase. This is post-casting CNC machining, not a part machined from solid billet, and not a claim that Jinhua performed the casting.
OP-010 · CNC turning. Locate the casting, turn the end and shoulder surfaces, establish the outside locating diameter, and machine the central internal bore. The locating diameter and shoulder are carried into the downstream fixture instructions.
OP-020 · First 4-axis machining setup. Locate on the turned diameter and shoulder, orient using the lug, and address external profile/groove features together with the side and stepped bore group.
OP-030 · Second, independent 4-axis machining setup. Re-establish the specified locating and angular references for additional approach directions: local faces, the conical feature, threaded and associated bore features, and cross-hole/angular relationships.
Supporting instructions, not result claims: the retained cards specify sharp-edge deburring at multiple stages and blowing residual cutting fluid dry after turning. These instructions are not a signed completion record, a validated cleaning process or a final inspection release.
04 · Two setups, one reference strategy
Why Two 4-Axis Setups Were Needed
The side/stepped bore group and the additional lug, thread and angular features require different tool approach directions. The recorded route separates them into two machining operations, each with its own rotary-fixture alignment and locating instruction.
Four-axis indexing is the process strategy for presenting multi-side features to the tool rather than repeatedly treating each side as an unrelated locating job. It does not remove the need to check the next fixture or transfer the reference relationship. No reduction in setup time or measured positioning error is claimed here.
First setup: profile and side access
OP-020 brings external profile work and side/internal bore machining into a defined rotary-fixture location.
Second setup: remaining directions
OP-030 is a separate setup for local, threaded and angular features. The two operations are not described as all features completed in one clamping.
05 · Datum-controlled aluminum casting machining
Datum & Angular Control
Controlled datum transfer is the link between the operations: establish the primary machined datum and secondary locating datum in turning, use the specified physical location and angular reference in the first setup, then re-establish them for the second. Bore-related datum relationships and datum-related positional control remain requirements to inspect, not results inferred from the route.
Original abstract process/reference diagram. Not a customer part drawing, fixture design or measured GD&T result.
Angular feature relationship: the retained drawing and process documentation describe how the angular relationship informs machining and inspection planning. This is a requirement and planning discussion, not a measured inspection result.
Local conical surfaces are part of the documented machining plan. Their potential sealing-related function is not evidence of a leak test, pressure rating or verified sealing performance.
06 · Methods specified, results not supplied
Inspection Strategy
Inspection methods were specified for the critical features; this case page does not claim measured GD&T results that are not present in the retained evidence.
CMM
Specified for selected geometric and angular requirements, including the conical feature, related bores, faces and hole relationships.
Roughness measurement
A roughness instrument is specified for the local conical surface. Its required finish is not presented as an achieved measurement.
Thread gauges
Go/no-go thread gauges and thread-depth checking are specified for the threaded features. No completed gauge record is claimed.
Dimensional inspection
Micrometers, depth/caliper checks, bore comparison and profile checks appear in the retained plan. Nominal values and checking limits are not sample measurements.
The retained inspection forms have no populated result entries for these operations. Accordingly, this case reports an inspection strategy, not all-dimension acceptance, full-lot conformance or general tolerance capability.
07 · A bounded manufacturing case
What This Case Demonstrates
This case illustrates precision machining of aluminum castings through the integration of turning and two four-axis machining stages. Its strongest story is reference establishment on an irregular casting followed by multi-setup, multi-side and angular process planning.
It is a case-specific account of post-casting CNC machining. It does not establish a universal Jinhua material, dimensional, surface-finish or process-capability guarantee.
