A high-purity quartz tube, nearly one meter long. A continuous hexagonal bore that has to run straight through the entire length. A material that chips and microcracks at the slightest mechanical stress.
At first glance this looks like a simple quartz tube. The hexagonal bore changes everything. Conventional internal grinding cannot reach deep into a long, brittle quartz tube without leaving chipped edges and microcracks — which is why this preform was given to diamond wire cutting instead.
The Application: Hexagonal Bores for Photonic Crystal Fiber Preforms
The workpiece is a long, high-purity quartz tube destined for use in specialty optical fibers, hollow-core fibers, and photonic crystal fibers (PCF). These advanced fibers depend on extremely precise internal geometry — air-hole arrays and structured cladding patterns that govern how light propagates through the fiber.
A clean, straight, continuous hexagonal internal profile lets the preform stack predictably during subsequent fiber drawing. The hexagonal geometry isn’t decorative — it’s there because six-fold symmetry is the natural packing structure for the air-hole arrays used in many PCF designs. Any variation in the hexagonal profile along the tube length translates into variation in the drawn fiber’s optical performance.
The cutting process has to deliver two things at once: uniform internal geometry そして mechanical integrity of a long, brittle workpiece. Both at the same time. Across nearly a meter of length. Most internal machining approaches cannot do both.
The Challenge: Deep Cavity + Brittle Material + Long Workpiece
The challenge here is not the quartz itself. Quartz cutting on diamond wire saws is well-developed — see our wire saw cutting overview for general material behavior across quartz, ceramics, and optical glass.
The challenge is the combination:
| Constraint | Why It’s Hard |
|---|---|
| Hexagonal bore (not round) | Cannot be produced by drilling or boring |
| ~1 meter length | Tool deflection accumulates with depth |
| Continuous through-bore | No restart points; profile must be consistent end to end |
| Brittle high-purity quartz | Microcracks initiate easily under lateral force |
| Dimensional accuracy required | Hex flat-to-flat tolerance directly affects fiber draw |
| Damage minimization | Subsurface damage degrades fiber transmission |
These constraints don’t fight each other — they multiply. A method that handles two of them well might still fail on the third.
Why Conventional Methods Hit Their Limits
Two common approaches are tried first, and both have known failure modes for this geometry:
Internal grinding and abrasive machining
For deep internal cavities, the grinding tool has to be small (to fit), long (to reach), and stiff (to avoid deflection) — three properties that fight each other. As cavity depth grows, the practical limits show up:
- Tool deflection — long, slender grinding tools flex under cutting force, drifting the hexagonal flats out of plane
- Limited machining depth — chip evacuation and coolant delivery break down beyond a certain depth
- Edge chipping at the hex corners where stress concentrates
- Microcrack formation from accumulated lateral force, which can propagate during subsequent fiber drawing
Alternative approaches using inserts or spacers
Some shops avoid the deep internal cut entirely by assembling the hexagonal profile from separate parts — inserts, spacers, segmented preforms. This solves the machining problem but creates new ones:
- Additional assembly complexity
- Potential dimensional variation at the joining interfaces
- Extra contamination risk for high-purity applications
- Variability introduced during subsequent fiber drawing
For high-end PCF preforms, neither path is ideal. The internal-grinding path is technically possible but yield-limited. The assembly path moves the variation problem from machining to drawing, which is the wrong place to put it.
The Approach: Precision Diamond Wire Cutting
VIMFUN cut this preform with a narrow-kerf, low-force diamond wire process.
Why diamond wire works here:
- The cutting tool is the wire itself, not a long rigid shaft — so length doesn’t compound deflection the way it does with grinding tools
- Cutting force is distributed along the wire contact, lower per-unit-area mechanical stress than abrasive machining
- A controlled, continuous wire path can trace the hexagonal profile without restart marks
- The same setup that handles round cuts can be configured for non-round geometries with the right fixturing
For full background on the cutting platform, see our pages on ダイヤモンドワイヤーソー構造 そして 電着ダイヤモンド・ワイヤー・ループ — the closed-loop wire architecture is what makes this kind of deep, continuous profile cut viable.
Process Parameters (Case-Specific)
| パラメータ | 価値 |
|---|---|
| Workpiece | High-purity quartz tube, ~1000 mm length |
| Outer diameter | Customer specification |
| Hex flat-to-flat dimension | Customer specification |
| ダイヤモンドワイヤー径 | 0.55–0.8 mm |
| ワイヤータイプ | 電着ダイヤモンド・ワイヤー・ループ |
| ワイヤーテンション | 150–200 N |
| ワイヤースピード | 30～60m/s |
| 送り速度 | 2–10 mm/min (low end of range) |
| 冷却水 | ホワイトミネラルオイル |
| Machine platform | Horizontal rotary (SH150-R / SH300-R for full-meter workpieces) |
Values shown represent VIMFUN’s standard process envelope for high-purity quartz, validated across multiple production runs. For this preform the feed rate sat at the lower end of the range — a deliberate trade for stability over the deep cavity. See wire speed, tension and feed rate そして ワイヤー張力校正 for how these parameters interact.
The Result: Profile Consistency Over the Full Length
The diamond wire approach delivered the two properties the application needs simultaneously:
- Profile consistency along the full ~1 meter length — the hexagonal flats stay in plane from end to end
- 材料へのダメージは最小限 — reduced chipping at the hex corners, suppressed microcrack initiation, lower subsurface damage compared to abrasive deep-cavity machining
- No assembly seams — the bore is produced as a single continuous geometry, not stacked from segments
For PCF preform production, those three properties translate directly to more predictable fiber draw behavior and lower variation in the finished fiber’s optical performance. The customer no longer carries the assembly-step variation into the drawing furnace.
Why Diamond Wire Works for Deep Internal Profiles
It comes down to how force is applied to the workpiece. Abrasive grinding concentrates force at a small tool footprint. Diamond wire distributes force along a flexible cutting element. For brittle material in a deep cavity, that single difference is what separates microcracks from clean profiles.
A few other things have to be right:
- Cooling and chip evacuation — proper 冷却と潤滑 keeps the cut zone temperature stable over the full meter, preventing thermal-stress-induced cracking
- ワイヤー張力安定性 — uniform tension across a long cut path is what keeps the hex flats from drifting out of plane
- Controlled feed rate — low feed rate trades cycle time for stability; for brittle materials and deep profiles, that’s the correct trade
This also works for ceramics, advanced optical glass, and single crystals — anywhere force distribution matters more than tool stiffness. Parameter envelopes differ. The underlying mechanics don’t.
産業と用途
Diamond wire cutting for deep internal profiles serves manufacturers in:
- Photonics — PCF, hollow-core fiber, specialty fiber preforms
- Optical fiber production — preform shaping and dimensional control
- 半導体材料 — quartz fixtures and components for wafer processing
- Advanced research — custom geometries for laser systems and beam delivery
If you have a quartz, ceramic, or optical glass workpiece with internal geometry that conventional machining cannot reach cleanly, the same approach applies. For a related case in ceramics with tight dimensional constraints, see our alumina ceramic ring cutting case study.
Can We Do This for Your Application?
If any of these match your application, send us your part drawing:
- Long workpieces (> 500 mm) with internal profiles
- Brittle materials (quartz, advanced ceramics, optical glass) requiring deep internal cuts
- Non-circular internal geometries (hexagonal, square, custom shapes)
- Photonic, semiconductor, or advanced material applications where subsurface damage is a constraint
Send us your workpiece drawing — including material, length, target internal profile, and tolerance requirements — and we will return a process feasibility assessment within 3 business days. Where the geometry is within our envelope, we can typically run a sample piece for verification before committing to production tooling.
VIMFUN continues to support manufacturers in photonics, optical fiber production, semiconductor materials, and other advanced technology industries with high-precision cutting solutions.
