English: EN AC-42100 E-Motor End Shield CNC Tooling Case: Bearing Bore and Stator Pilot
For an EN AC-42100 cast-aluminum e-motor end shield, the decisive tooling choice is to finish the bearing bore and stator pilot in one datum-controlled setup. PCD handles the abrasive casting skin and maintains a stable bore edge, while short polished-carbide cutters machine coolant ports and thin ears without exciting the casting. This hypothetical case maps each drawing feature to the tool that protects coaxiality.
Datum chain and casting variability
The drawing defines rear mounting face A, bearing bore B and one dowel hole C. The Ø72 H6 bearing seat must be coaxial within 0.015 mm to the Ø184 g6 stator pilot, A is perpendicular to B within 0.02 mm, and the seal face requires Ra 1.6 µm. Four mounting ears are 7 mm thick after machining. Cast stock varies by 1.2 mm, so a probe first measures three pads, the raw bearing core and two ear tips. Toolpaths are shifted from the measured casting envelope rather than blindly centered on the outer skin.
Feature-to-tool selection table
| Feature | Selected tool and holder | Reason / rejected choice |
|---|---|---|
| Mounting face A and casting skin | Ø63 PCD face mill with positive axial rake and one wiper cartridge, short balanced arbor | PCD resists silicon abrasion and produces a continuous seal finish. A small end mill would leave stitch marks across A. |
| Ø72 bearing-seat roughing | Ø32 indexable boring bar, polished positive carbide inserts, hydraulic coupling | Adjustable stock removal tolerates core shift. A large inserted end mill risks a lobed interpolated bore in the thin shell. |
| Ø72 H6 finish | Fine-boring head with PCD-tipped cartridge, 0.4 mm nose radius, minimum projection | Micrometric diameter compensation and low wear. A reamer of this size cannot correct core position or coaxiality. |
| Ø184 g6 stator pilot | PCD finish-boring cartridge on a modular bridge, dynamically balanced | Uses the same spindle axis as B. Separate circular milling would add interpolation and thermal errors. |
| Coolant ports | Ø8 three-flute polished carbide drill mill with through coolant, hydraulic chuck | Helical entry opens interrupted cast surfaces and breaks chips; a long two-flute tool lacks radial support. |
| Thin mounting ears | Ø10 three-flute polished carbide, 38° helix, short flute, 0.2 mm corner radius | Low radial force with sufficient stiffness. A high-flute steel finisher can chatter and form built-up edge. |
| Edge sealing chamfer | Ø12 single-flute PCD chamfer tool at 90°, preset holder | Produces a clean controlled edge without hand-deburring the bearing mouth. |
Fixture and process plan
A nest supports three cast pads close to the bearing hub and uses swing clamps on thick ribs, not the ears. After probing, the PCD face mill establishes A. The bearing bore is rough-bored with two equal radial cuts, then the stator pilot is semifinished while the hub remains supported by internal webs. A temperature pause follows. The PCD fine-boring tools then finish B and the pilot from the same spindle orientation; no clamp is released between them.
Coolant ports are helixed from the open side and cross-drilled only after the bearing work, so interrupted chips cannot mark the finished seat. Ears are semifinished in an alternating 1-3-2-4 sequence, leaving 0.25 mm, then finish-contoured with constant engagement. A 0.15 mm programmed chamfer removes the exit feather. Cast-skin variation, silicon particles and embedded sand are the dominant tool-life risks. Spindle-load trend and bore surface reflection are checked after every defined tool-life interval; a wiper line or diameter taper triggers cartridge inspection rather than offset alone.
Inspection plan and FAQ
An air gauge measures the Ø72 H6 seat at two depths and two temperatures. A CMM builds A-B-C, then reports pilot coaxiality, face perpendicularity, ear-hole position and coolant-port breakout. A roundness trace distinguishes tool vibration from casting relaxation. Surface finish is measured on A and the bearing seat, and a functional master checks the stator pilot without forcing a warm casting.
Why finish the bearing bore and stator pilot in one setup?
Their coaxiality is more important than their relationship to the irregular outer casting; one spindle axis removes fixture-transfer error.
Is PCD necessary for EN AC-42100?
It is justified on high-value sealing and bore surfaces because silicon-rich cast aluminum is abrasive. Polished carbide remains economical for ports and interrupted ear contours.
How is casting core shift handled?
Probe the functional raw features, calculate a safe stock distribution and preserve minimum wall before roughing; do not simply offset the final bore.
Useful comparisons: bearing-axis datum control and aluminum port and seal-face finishing.
