English: Zirconium 702 Pump Wear Plate CNC Tooling Case: Kidney Ports and Seal Grooves
The useful answer for a Zirconium 702 chemical-pump wear plate is to select tools from the sealing geometry outward. The two 18 mm-deep kidney ports need a sharp, open-flute rougher; the 2.2 mm-wide shallow seal grooves need a dedicated short slot tool; and the dowel bores need drilling followed by fine boring so port position is tied to the functional datum frame. This hypothetical case shows that tool map and the process decisions behind it.
Reading the drawing before selecting cutters
Face A is the pump-side sealing plane. Dowel bores B and C clock the plate, while the center bore is a clearance feature rather than a locating datum. The kidney-port profile is 0.04 mm to A-B-C, the grooves are 0.45 ±0.03 mm deep, the dowels are Ø8 H7, and A requires 0.025 mm flatness with Ra 0.8 µm. A 0.10 mm maximum edge break protects the elastomer without widening the sealing land. Because Zirconium 702 conducts heat poorly and fresh fine chips can be reactive, chip evacuation and edge sharpness are part of the tooling decision, not housekeeping after the cut.
Feature-to-tool selection table
| Drawing feature | Selected carbide tool and holder | Why it wins / rejected alternative |
|---|---|---|
| Datum face A | Ø50 positive-rake face mill, polished uncoated fine-grain carbide inserts, light edge hone, balanced arbor | Low cutting force limits heat and smearing. A negative steel face mill is rejected because it raises pressure at the sealing land. |
| Kidney-port volume | Ø12, 3-flute sharp uncoated micrograin carbide, 35° helix, short flute, hydraulic holder with through coolant | Large gullets clear ductile chips. A 5-flute coated rougher offers too little chip space and can rub when zirconium springs back. |
| Port wall and inside radii | Ø6, 4-flute unequal-pitch polished carbide, 0.2 mm corner radius, reduced neck, 24 mm reach, shrink holder | The corner radius protects the edge during finishing. A long ball nose would leave scallops and unnecessary axial force. |
| 2.2 mm seal groove | Ø2.0, 2-flute polished solid-carbide slot mill, 5 mm flute length, precision collet | A short dedicated tool controls width and floor. Interpolating with the Ø6 cutter cannot reach the drawing radius or groove width. |
| Ø8 H7 dowels | Ø7.5 through-coolant carbide drill followed by a small fine-boring head with positive carbide tip | Fine boring corrects location and size. A reamer is rejected because it follows a misplaced or bell-mouthed pre-hole. |
| Edge break | Ø6, 90° polished two-flute carbide chamfer mill, minimum projection | Programs a measured 0.08 mm break. Manual deburring risks touching the seal land. |
Fixture, roughing, finishing and tool-life logic
Operation one faces A and establishes B-C pilot geometry on a vacuum-assisted plate fixture with three hardened rest pads and perimeter clamps outside the seal zone. Operation two locates on A-B-C with relieved buttons under the ports. Kidney ports are opened by helical entry into sacrificial stock and high-efficiency paths at low radial engagement; 0.30 mm radial and 0.15 mm floor stock remain. Semifinishing uses the Ø6 tool to equalize wall stock before a climb-only contour. The seal grooves are cut last with two depth passes and a full circular exit so the tool never dwells at a corner.
Flood coolant remains continuous, and the enclosure is cleared of unrelated magnesium or steel fines. Collection and removal follow the material-specific procedure below; machining coolant does not by itself establish safe storage. A rising spindle load, shiny smeared wall or fuzzy exit burr triggers inspection of edge radius and flute packing. Tools are retired before polishing dullness appears: rubbing can create more heat than a productive cut.
Separate seal-groove width correction from depth acceptance
The 2.2 mm groove and 0.45 ±0.03 mm depth remain the hypothetical drawing values in this case. With a nominal Ø2.0 mm cutter, a straight groove needs cutter-center finish tracks nominally 0.10 mm to either side of its centerline. That is a geometry calculation, not a proven wear offset: substitute measured cutting diameter and check runout, deflection and the curved-path envelope before release.
| Check at the sealing feature | Tool or setup decision | Measure before correcting |
|---|---|---|
| Width drifts while floor is acceptable | Keep the short two-flute Ø2 tool; adjust lateral tracks only after inspecting adhesion | Width at straight and curved portions; effective cutter diameter |
| Depth changes around the plate | Recheck datum A, seating and tool length before changing Z | Groove floor relative to nearby A, not only fixture zero |
| Seal-land edge is rolled or smeared | Inspect the sharp groove edge and dedicated chamfer tool | Edge break and remaining land; do not hand-blend away the symptom |
After port roughing and semifinishing, clean and reseat without trapping a chip under A. Confirm free-state flatness separately from the clamped groove-depth reading. Use an optical method or suitably sized contact method that actually resolves the narrow floor; a stylus resting on the groove shoulders does not measure its depth. Record the same inspection locations before and after compensation so an apparent width improvement cannot hide a deeper floor.
See the cutting-parameter hub for a recorded trial calculation and the pocket access and residual-stock guide for the preceding port operation. These are separate decisions from acceptance of the finished seal.
Can the groove be accepted from cutter size alone?
No. A nominal Ø2 tool does not prove groove width, depth or land condition. The drawing’s actual width tolerance, measurement capability and in-process results must close that decision.
Separate machining coolant from chip-storage safety
Machining coolant and chip storage are different controls. Follow the material supplier’s current safety sheet and the facility’s approved zirconium procedure for collection, moisture condition, containers and removal. Damp fines can still present fire or explosion hazards; do not interpret ‘wet’ as automatically safe. If chips ignite, evacuate and follow the trained emergency response, not routine coolant or water application.
Alleima — zirconium safety information
Inspection plan and practical FAQ
After thermal stabilization, a CMM constructs A-B-C, scans both kidney profiles at the top, mid-depth and floor, and checks groove center paths. A fine-bore gauge confirms Ø8 H7 after CMM position verification. An optical comparator measures groove width and the programmed edge break; a profilometer records Ra across A without crossing a port. Flatness is checked in a free, unclamped state.
Should Zirconium 702 be machined with coated or uncoated carbide?
For this interrupted plate geometry, sharp polished uncoated fine-grain carbide reduces rubbing and built-up edge. A coating is not selected merely for heat resistance when it rounds the edge.
Why use a separate 2 mm tool for a 2.2 mm seal groove?
It leaves controlled side stock for a compensated finish orbit and keeps the groove floor independent of kidney-port tool wear.
How are reactive zirconium chips controlled?
Use continuous chip evacuation and the approved material-specific collection and emergency procedure below; do not assume a damp chip pile is safe.
Related process comparisons: sanitary seal-face datum planning and slot burr and datum recovery.
