Tranchage de précision du verre optique avec fil diamanté en boucle: 30.5 Données de test de barres en mm

Abstrait: This application report covers a high-precision straight-slicing test on optical glass
supplied by a European customer. The workpiece was a rod of 30.5 mm diameter, cut into sections 15 mm long on an
ESO-GM gantry diamond wire loop cutting machine, with cutting oil as the cooling medium and a fully coated diamond
un fil. Measured results across three sections: variation d'épaisseur totale (TTV) 0.003-0.008 mm, tolérance d'épaisseur
±0.141 mm against a 15.000 mm nominal, surface roughness Ra 0.58-1.06 μm, and maximum edge chipping
4.9-6.2 μm. Matching machine structure, the oil cutting method, wire selection and process parameters to the
brittle behaviour of optical glass kept material removal stable and held section dimensional accuracy and cut-surface
quality inside a workable band.

Sample test for a European customer | Diamond wire loop cutting process

Overview of the Optical Glass Precision Slicing Test

This test was run on optical glass supplied by a European customer, with high-precision straight slicing as the
main requirement. Optical glass sits firmly in the hard, brittle family: la dureté est assez élevée, brittleness is
pronounced and fracture toughness is low. Once the diamond grains start abrading continuously, poor control of the
cutting load or of the temperature in the cutting zone concentrates stress inside the material, and that is where
les éclats, micro-fissures, end-face damage and section dimensional deviation come from. The work therefore went at
machine structure, cutting method, wire selection and process parameters as one set, so the slicing stayed stable and
section dimensions and cut-surface quality could be held to the tolerances required for
découpe optique du verre.

Because optical glass asks for dimensional accuracy, end-face quality and edge integrity at the same time, Ensoll
applied a diamond wire loop process matched to those characteristics. On the machine side the choice fell on a
dedicated gantry diamond wire loop cutting machine. Its rigidity and running stability give the workpiece a firm
clamping base and hold the wire on a steady path, which cuts down the effect of machine vibration and motion error on
the cutting trajectory and on section dimensions. On the consumable side, a diamond wire matched to optical glass
keeps the grains removing material at a steady rate, so a change in wire condition does not turn into a change in
section quality. For cooling and lubrication, cutting oil was used: it improves lubrication and heat dissipation at
the contact zone between wire and glass, réduit la friction et l'accumulation de chaleur lors de la coupe, and reduces what a local
temperature rise does to the cut face. On top of that, wire running speed and feed rate were set against the
properties of the material and the target section length, keeping the cutting load inside a suitable band and avoiding
the local overload and edge breakage that an aggressive feed produces. Machine, un fil, oil cutting and parameters
matched as one set kept the process stable and brought section dimensional accuracy, la constance de l'épaisseur,
cut-surface quality and edge integrity under control — a workable process basis for high-precision straight
slicing of optical glass. The same parameter logic applied to flat work is set out in our
BG38 glass sheet slicing test.

1. Test Object: Basic Information

• Material: verre optique
• Dureté: environ MH 6 À 7
• Dimensions de la pièce: diamètre 30.5 mm
• Cut dimensions: 15 mm (L) x 30.5 mm (φ)

2. Sélection de la machine et du fil

Machine type: ESO-GM. Given the brittle behaviour of optical glass and the high-precision straight
slicing requirement, Ensoll selected the ESO-GM diamond wire saw, the gantry machine built
for this class of work. It holds running stability and trajectory accuracy through the cut, reduces the effect of
machine vibration and load fluctuation on machining quality, limits the chipping, micro-cracking and dimensional
deviation that uneven loading would otherwise produce, et améliore ainsi la précision dimensionnelle, cut-surface quality and
edge integrity in optical glass sections.

• Type de liquide de refroidissement: cutting oil. L'huile de coupe est utilisée comme milieu de refroidissement et de lubrification. It improves
  lubrication and heat dissipation in the contact zone, réduit la friction et l'accumulation de chaleur lors de la coupe, and reduces
  the thermal and local stress variation the glass sees. Cela réduit le risque d'éclats, micro-cracks and end-face
  damage, ce qui aide à la stabilité dimensionnelle, la qualité de surface et l'intégrité des arêtes.
• Wire type: entièrement revêtue. A fully coated diamond wire raises the bond strength between grains and
  the steel core and keeps grain distribution even, so the wire removes material continuously and steadily through the
  cut. It reduces the effect of grain pull-out and wire wear on the cutting state, which limits dimensional variation
  and edge damage when slicing optical glass.

3. Méthode de découpe et avantages de la machine

Gantry cutting method. The gantry structure gives the machine high overall rigidity and running
la stabilité, and the top-down vertical feed helps keep the boucle de fil de diamant on a stable
path, reducing the effect of load variation on kerf position and dimensional accuracy in optical glass sections. Le
machine also carries a mist extraction system that clears the oil mist produced during cutting, keeping the work zone
clean and the cutting area in good condition for a stable run.

Système de contrôle intelligent de la tension. The system adjusts wire tension in real time according to the
machining state and supports both constant-tension and variable-tension modes, so the wire runs steadily through the
cut. Stable tension reduces trajectory drift and cuts the risk of wire breakage that tension variation brings, which
narrows the local load changes seen at the cut and helps control section dimensions and edge quality across the
batch.

Breakpoint resume. If the wire breaks or the machine stops abnormally, the system records the
current cutting position and the associated running state. After a wire change the cut resumes from that position,
which reduces the re-positioning error and repeat cutting that would otherwise affect cut position and quality, and it
keeps material loss down while the slicing run stays continuous.

High-rigidity one-piece cast iron frame. The one-piece cast iron frame raises overall stiffness and
vibration resistance, lowering the effect of structural vibration and deformation on the wire path. For a hard,
brittle material such as optical glass, that rigidity reduces load fluctuation during the cut and gives the dimensional
exactitude, cut-surface quality and edge integrity of precision slicing a reliable machine basis.

4. Paramètres et méthode de refroidissement

The parameter set below was used for the whole run, and the sections reported in section 5 all came off it. Fil
tension and wire speed are the two settings that carry most of the load control; the cutting load reading is what the
operator watches to keep the wire inside its working band.

Paramètre	Valeur
Diamètre du fil (mm)	0.35 x 1880
Vitesse de déplacement du fil (mm/min)	10
Largeur de coupe (mm)	30.5
Tension du fil de coupe (N)	140
Vitesse du fil (m/s)	24
Temps de flexion du fil (s)	60
Charge de coupe (N·m)	20

5. Efficacité et résultats de coupe

5.1 Données de test TTV (mm)

TTV (Variation totale de l’épaisseur) was measured with a nine-point grid, dual-probe thickness method on a vacuum-chuck
stage, applied to sections produced by diamond wire loop cutting. The sections measured 15 mm (L) x 30.5 mm (φ),
avec une épaisseur nominale de 15 mm. Before measurement the instrument was thermally stabilised and calibrated with a
standard thickness block to reduce zero drift and systematic error. Après un nettoyage sans poussière, each sample was centred
on the vacuum chuck and held by negative pressure, so that warping, tilt and position shift during measurement had
less effect on the thickness readings. Thickness data were then collected in sequence at the preset nine grid
positions, and the difference between the largest and the smallest reading across those points was taken as the TTV
of that sample, used to evaluate thickness uniformity and machining consistency. The procedure follows the method
explained in nine-point TTV measurement.

Échantillon	Nine-point thickness readings (mm)	Tmax	Tmin	TTV
S01	15.056, 15.057, 15.058 / 15.059, 15.060, 15.061 / 15.062, 15.058, 15.057	15.062	15.056	0.006
S02	15.112, 15.113, 15.114 / 15.115, 15.113, 15.114 / 15.113, 15.114, 15.115	15.115	15.112	0.003
S03	15.135, 15.137, 15.138 / 15.140, 15.141, 15.142 / 15.143, 15.138, 15.139	15.143	15.135	0.008

Évaluation: Looking at the nine-point readings for the three sections, S01 measured between 15.056
et 15.062 mm, S02 between 15.112 et 15.115 mm and S03 between 15.135 et 15.143 mm, giving TTV values of 0.006 mm,
0.003 mm et 0.008 mm respectively. S02 held the tightest thickness uniformity and S03 showed the widest spread, but
every section stayed inside 0.008 mm. Thickness variation across the measured areas is therefore small, which says the
wire ran steadily and the cutting state held through the run, and thickness consistency meets what high-precision
optical glass slicing asks for.

5.2 Données de tolérance d'épaisseur (mm)

Thickness tolerance was measured by the same nine-point grid method, avec 15.000 mm as the nominal thickness. Le
deviation of each measured point from nominal was calculated, et le maximum d'écart positif, maximum negative
deviation and overall thickness tolerance were collated, to assess dimensional accuracy and machining consistency of
the optical glass sections.

Échantillon	Épaisseur moyenne (mm)	Déviation d'épaisseur (mm)
S01	15.059	+0.059
S02	15.114	+0.114
S03	15.141	+0.141
Écart positif maximal	+0.141	+0.141
Écart négatif maximal	0	0
Tolérance d'épaisseur	±0.141	±0.141

Évaluation: Avec 15.000 mm as nominal, the three sections averaged 15.059, 15.114 et 15.141 mm,
corresponding to deviations of +0.059, +0.114 et +0.141 mm. All three sat on the positive side, the maximum positive
deviation was +0.141 mm and no negative deviation was recorded, so the overall thickness tolerance is quoted as
±0.141 mm. Average thickness also rises steadily with sample number, which shows the batch carried a small
systematic bias towards the thick side. The bias is regular rather than random, so it is a compensation matter rather
than a process-capability one.

5.3 Surface Roughness Ra Data (μm)

Rugosité de surface (Ra) was measured to ISO 4287 with a stylus profiler. Three representative positions were profiled
on the cut face of each section — centre, mid-left and mid-right — and Ra was calculated at each position
to assess the cut surface and machining quality.

Échantillon	Ra-1	Ra-2	Ra-3	Ra moyen
S01	1.02	1.08	1.07	1.06
S02	0.55	0.61	0.58	0.58
S03	0.82	0.91	0.88	0.87

Évaluation: Measured by the three-point method, average Ra came out at 1.06, 0.58 et 0.87 μm
for S01, S02 and S03, so the whole set falls in the 0.58-1.06 μm range. The difference between measuring
positions on a single section is small, which means the cut face is fairly even and the process holds surface quality
under control. S02, which also held the best TTV, returned the lowest Ra — the two indicators moved together on
this run.

5.4 Données sur l’ébréchure des bords (μm)

Chipping was measured by optical imaging on a toolmaker’s microscope to quantify edge defects on the sections, which
mesurés 15 mm (L) x 30.5 mm (φ) after cutting. Sample edges were cleaned before measurement, and the instrument
magnification and measuring scale were calibrated. The edge regions were then scanned under the microscope,
recognisable chips were located and measured, and the defect size at each point was recorded, giving an assessment of
edge quality and cutting performance.

Échantillon	Position 1	Position 2	Position 3	Position 4	Ébréchure maximale
S01	4.6	5.2	4.9	5.8	5.8
S02	3.8	4.5	4.1	4.9	4.9
S03	5.1	5.7	5.4	6.2	6.2

Évaluation: Inspected by the four-point method, the largest chip measured 4.9-6.2 μm across
the three sections, with the individual measurement points sitting close together. Defect sizes are small and the
difference between samples is limited, which indicates a stable cutting state through the run and good edge integrity
on the sections.

6. Conclusion

The optical glass in this run sliced well, and the result came mainly from matching a dedicated gantry machine, le
oil cutting method and the process parameters as one set. Optical glass is a classic hard, cassant: dureté
is fairly high, la fragilité est prononcée et la ténacité à la fracture est faible, and during diamond wire loop cutting the
continuous abrasion of the grains means that local cutting load and heat build-up easily concentrate stress, which
produces chipping, micro-fissures, an uneven cut face and section dimensional deviation. Aimed at the machining
behaviour of the material and the requirement for high-precision straight slicing, machine selection, cutting method
and parameters were all adjusted in a targeted way, holding section dimensional accuracy, thickness consistency and
cut-surface quality in check while the cutting process itself stayed stable.

Première, machine selection. Given what optical glass slicing demands in motion stability, machine
rigidity and cutting accuracy, a dedicated gantry diamond wire loop cutting machine was selected. The gantry structure
provides good overall rigidity and running stability, which gives the workpiece firm clamping and the wire a reliable
mechanical basis for steady running, and reduces the effect of machine vibration, motion error and wire running
fluctuation on the cutting trajectory. Stable feed and motion control also narrow the cutting-load variation, so wire
and glass stay in a comparatively steady relative motion, which lowers the risk of dimensional deviation and local
chipping and gives high-precision slicing a stable machine basis.

Deuxièmement, cutting method. Optical glass is markedly brittle and sensitive to thermal effects during
découpage, so oil cutting was used, with cutting oil as the cooling and lubricating medium. Cutting oil improves
lubrication and heat dissipation in the contact zone between wire and glass, lowering friction and heat build-up and
reducing the effect of local temperature rise and thermal stress on the material. Steady cooling and lubrication also
help hold the cutting zone in a consistent state and reduce the cutting fluctuation that friction or concentrated heat
would cause, so chipping, micro-cracks and end-face damage become less likely and the cut surface and edge integrity
improve.

Third, paramètres du processus. Against the material properties and the target section size, un fil
running speed and feed rate were matched accordingly. Parameters were set to keep the wire running stably and material
removal even, avoiding a feed rate so high that the cutting load climbs, and avoiding a combination that produces
local heating, stress concentration and brittle fracture. The targeted adjustment kept material removal comparatively
steady and, while still meeting machining efficiency, reduced impact and load fluctuation through the cut, which
improved thickness consistency, cut-surface quality and edge integrity.

Taken together, the results for section dimensional accuracy, tolérance d'épaisseur, Rugosité (Ra) et
cut-edge quality show that, with a dedicated gantry cutting machine, oil cutting and suitable parameters working
together, diamond wire loop cutting meets the requirements of high-precision straight slicing for optical glass. Le
samples performed steadily in dimensional accuracy, la constance de l'épaisseur, cut-surface quality and edge integrity,
which indicates that matching machine structure, cooling and lubrication method and process parameters to the
properties of the material improves the removal state and process stability, and offers a process reference for
high-precision straight slicing of optical glass.

Questions fréquemment posées

Can a diamond wire loop slice a 30.5 mm optical glass rod into 15 mm sections?

Oui. In this test a rod of 30.5 mm diameter was cut into sections 15 mm long on an ESO-GM gantry machine, avec
cutting oil and a fully coated 0.35 x 1880 mm wire running at 10 mm/min travel, 140 N tension and 24 m/s wire speed.
Measured TTV was 0.003-0.008 mm, thickness tolerance ±0.141 mm, average Ra 0.58-1.06 μm and maximum
les éclats 4.9-6.2 μm.

What TTV can be held when slicing optical glass with a diamond wire loop?

In this run TTV was 0.006 mm, 0.003 mm et 0.008 mm across three sections, measured by the nine-point grid method
on a vacuum chuck against a 15 épaisseur nominale en mm. All three sat inside 0.008 mm, which is the sort of uniformity a
precision slicing process needs before any lapping or polishing step.

Why use cutting oil instead of a water-based coolant for optical glass?

Cutting oil lubricates and cools the contact zone between wire and glass. Here it improved heat dissipation in the
cutting zone and lowered friction and heat build-up, which cut the thermal and local stress variation the glass sees
and lowered the risk of chipping, micro-cracks and end-face damage. The machine carries a mist extraction system to
clear the oil mist produced during the cut.

How much edge chipping should be expected on sliced optical glass?

In this test maximum chipping came to 4.9-6.2 μm measured by optical microscopy, with four positions checked
per section. Individual measurements were tightly grouped, so the chip size is small and consistent rather than
occasional deep damage — an edge condition that normally cleans up in a light finishing pass.

Why did all three optical glass sections come out thicker than nominal?

Against a 15.000 mm nominal, the sections averaged 15.059, 15.114 et 15.141 mm, so every one ran on the plus side
par 0.059 À 0.141 mm. Because the deviation moves steadily with sample number it is a systematic offset, not random
scatter, and the practical fix is dimensional compensation on the next run rather than a change to the cutting
parameters.

Technical content reviewed by the Ensoll engineering team – a diamond wire loop manufacturer with 10+ des années d'expérience en production.