The CNC flame polishing machine is the core equipment for precision machining
of quartz glassware (laboratory vessels, optical components). It directly
determines the appearance quality and safety of the product through
high-temperature flame melting of the glass surface (requiring a polishing
surface glossiness of ≥ 95GU, no erosion or burrs on the edges). If there is
uneven gloss on the polished surface (gloss deviation exceeding 8GU) and edge
erosion (erosion width exceeding 0.5mm), it will cause the finished product
qualification rate to drop below 70%, significantly increasing rework costs.
Based on the high temperature resistance of quartz glass (melting point 1713 ℃)
but its tendency to react with oxygen at high temperatures, a three-step
troubleshooting method is summarized to quickly restore polishing
performance.
Step 1: Optimize flame parameters and spray gun configuration - the core heat
source determines the polishing effect
Improper flame temperature, shape, and spray gun adaptation are the main
causes of uneven gloss and erosion.
Imbalance of flame parameters: deviation of natural gas to oxygen ratio from
1:2.5, flame temperature below 1600 ℃, insufficient melting of glass surface,
poor glossiness; When the ratio exceeds 1:3 and the temperature exceeds 1800 ℃,
the edges are prone to excessive melting and erosion; The deviation of the flame
center from the glass surface exceeds 2mm, with uneven heating in some areas and
significant fluctuations in gloss. By accurately proportioning with a gas flow
controller, the natural gas flow rate is stable at 0.8-1.2m ³/h, and the oxygen
flow rate is 2.0-3.0m ³/h, ensuring a flame temperature of 1650-1750 ℃;
Calibrate the height of the spray gun, with the flame center 1-2mm away from the
surface, using the heating method of "external flame as the main, flame center
as the auxiliary".
Mismatched spray gun model or nozzle wear: using a regular direct spray spray
gun, uneven flame coverage range; The nozzle aperture wear exceeds 0.1mm, and
the flame shape is distorted (divergent); The swing frequency deviation of the
spray gun exceeds 1Hz, and the local heating time is too long. Replace the
quartz glass specialized fan-shaped spray gun (with adjustable flame width of
3-8mm), regularly inspect the nozzle, and replace it promptly if the wear
exceeds 0.05mm; Set the swing frequency of the spray gun to 3-5Hz, and the swing
amplitude should be adapted to the size of the workpiece to ensure uniform
surface heating.
Step 2: Calibrate motion trajectory and polishing parameters - precise
control to reduce defects
Improper CNC trajectory accuracy, polishing speed, and dwell time can
exacerbate the problem.
Trajectory deviation or uneven speed: The positioning accuracy of the CNC
system exceeds 0.1mm, the polishing path deviates, and there are local missed or
repeated polishing; When the moving speed is less than 5mm/s, the glass is prone
to erosion due to excessive heating; Above 15mm/s, insufficient surface melting
and low glossiness. Calibrate the CNC system with a laser locator, and control
the positioning accuracy within ± 0.05mm; Set the speed in sections according to
the complexity of the workpiece, with a plane area of 8-12mm/s and an edge area
of 5-8mm/s, to avoid excessive edge dwell time.
Unreasonable segmented polishing logic: The "rough polishing fine polishing"
segmented mode was not adopted, and the high temperature during rough polishing
directly led to ablation; Insufficient flame intensity during fine polishing,
unable to eliminate rough polishing marks. Optimize polishing process: During
the rough polishing stage, use a wide flame (6-8mm) and medium speed (8mm/s) to
quickly eliminate surface scratches; During the polishing stage, narrow flames
(3-5mm) and high speeds (12mm/s) are used to enhance glossiness; Set the "weak
flame+fast speed" parameter separately in the edge area to avoid erosion.
Step 3: Adapt glass characteristics and gas protection - avoid oxidation and
erosion at the source
Improper gas purity, protective measures, and workpiece pretreatment can
affect polishing stability.
Insufficient gas purity or lack of protection: natural gas with sulfur
content exceeding 50mg/m ³, combustion produces sulfide pollution on the
surface; Oxygen purity below 99.9%, containing impurities that cause flame
instability; Without protective gas, the glass surface oxidizes at high
temperatures, forming a misty layer. Select high-purity natural gas with a
sulfur content of ≤ 10mg/m ³ and 99.99% high-purity oxygen; Install an argon
protective cover in the polishing area, with an argon flow rate of 0.3-0.5m ³/h,
to isolate air and prevent oxidation.
Insufficient pre-treatment or surface contamination of the workpiece: The
surface of the workpiece has oil stains and dust (with an adhesion amount
exceeding 0.1g/m ²), which form spots after combustion; There are burrs on the
edges that have not been pre treated, and during polishing, the burrs melt
excessively, leading to erosion. Wipe the surface of the workpiece with
anhydrous ethanol before polishing, dry it before processing; For edges with
burrs, first use a diamond grinding wheel to slightly chamfer (chamfer radius
0.2-0.3mm), and then polish.
Daily maintenance should pay attention to: checking gas purity, flow rate,
and flame shape every day; Weekly calibration of CNC trajectory accuracy and
spray gun swing parameters; Clean the nozzle and replace the aging gas pipeline
every month; Check the uniformity of heating temperature every quarter. By
taking the above measures, the glossiness of the polished surface can be
stabilized at above 98GU, the edge erosion rate can be reduced to below 5%, and
the finished product qualification rate can be increased to 95%. If there are
still problems, it is recommended to contact the manufacturer to optimize the
flame control algorithm and match the polishing requirements of different
specifications of quartz glass.