CNC machining
Procedures
At CE Glass, the glass is drilled using diamond-crowned drill bits that are positioned opposite each other. The lower knife drills halfway through the glass, while the upper knife finishes the drilling from the other side and removes the little glass disc. The pipe knives are cooled with water. The operation is carried out with vertical automatic drilling machines.
Size tolerances:
- for holes 3-20mm in diameter ±1 mm,
- for holes 20-80 mm in diameter ±2 mm.
Tolerance on hole location:
- For glass with a maximum side length of 2000 mm ±2.5 mm,
- Max. For glass with a side length of 3000 mm ±3 mm,
- For glass with side lengths of 3000 mm or more ± 4 mm.
- Above 12 mm glass thickness, the above tolerances are increased by an additional 1 mm.
Further machining can be carried out on the inner arches of the holes, depending on whether the target tool will fit into the hole.
Certain machining operations can only be carried out on larger holes treated as cut-outs.
- Holes below Ø60 mm are treated as drilled holes.
- Holes over Ø60 mm are treated as cut-outs.
Important rules:
- The diameter of the hole must be at least the thickness of the glass.
- The shorter side of the drilled glass must not be less than eight times the glass thickness.
- The distance between the holes and the distance from the edge of the glass must not be less than twice the glass thickness.
- In the case of a sharp corner, the minimum distance between the tip of the corner and the edge of the hole shall be six times the thickness of the glass.
- In the case of rounded glass corners, the minimum distance between the tip of the rounded corner and the edge of the hole shall be four times the glass thickness.
- If the hole is closer to the edge of the glass, the "opening up" of the hole may be used, provided that the notch joining the edge of the hole to the edge of the glass is not less than 5 mm and not more than twice the thickness of the glass.
Cut out:
A hole drilled in glass above ø60 is considered a cutout, which is called a "Fan Cutout". Not only circular but also other shaped cut-outs are possible. Depending on their location and size, the cut-outs can be made during the glass cutting process or by milling with a CNC machine's milling tool. In both cases, the edges of the cut-out are finished with a peeling tool. Cuts can be located on the surface (inner), edge (edge) or corner (corner) of the glass sheet.
Internal cut-outs:
For internal cut-outs, holes are first created and then shaped with a milling tool. These cut-outs are usually made to allow the glass sheet to pass through, e.g. for locks, sockets, cat flaps.
Restrictions:
- Size: not to exceed 1/3 of the width or length of the glass sheet.
- Spacing: the edge of the cut-out must be at least half the side length of the cut-out away from the edge of the glass.
- Corner radius: min. r=6mm.
Size tolerances:
- Cutout dimensions: ±3mm.
- Positioning:
- Glass sheet up to 2000mm: ±2.5mm.
- Glass sheet up to 3000mm: ±3mm.
- Above 3000mm: ±4mm.
- Glass over 12mm thick: +1mm tolerance.
Edge finishing: Cut edges can be polished using the P-FMF (Fine Polished Machining) method if the ø65 polishing tool fits. Otherwise they remain with M-FMF (Fine Matte Machining) profile.
Edge cuttings:
They are made using milling tools and are mainly used to grip the glass sheet or to locate items such as hinges and handles to be fitted to the edge of the glass.
Restrictions:
- Size: up to 1/3 of the width or length of the glass sheet.
- Distance: the edge of the cut-out must be at least half the width of the cut-out, but at least 100mm from the edge of the glass.
- Corner radius: minimum r=6mm.
- Distance between cut-outs: at least half the width of the larger of the two cut-outs.
Size tolerances:
- Cut-out size: ±3mm.
- Positioning:
- Up to 2000mm: ±2,5mm.
- Up to 3000mm: ±3mm.
- Above 3000mm: ±4mm.
- Glass thicker than 12mm: +1mm tolerance.
Corner cut-outs:
Corner cuts are made on a tailor's table or with milling tools, depending on their size. They are made using cutting tools or bench cutters.
Limitations:
- Size: maximum 1/3 of the width or length of the glass sheet.
- Corner radius: minimum r=6mm.
Size tolerances:
- Cutout size: ±3mm.
- Positioning:
- Up to 2000mm: ±2.5mm.
- Up to 3000mm: ±3mm.
- Above 3000mm: ±4mm.
- Glass thicker than 12mm: +1mm tolerance.
Edge machining: cut-out edges are ground using the P-FMF (Fine Polished Machining) method or remain machined using the M-FMF (Fine Matte Machining) profile. Tempering of the glass is recommended to reduce the risk of breakage.
Grinding
Types:
- Live grinding, Counting
- Polishing edge-to-edge sanding
- Faceting (angle grinding of the straight sides of glass, from 5 mm to 50 mm in width, from 4 to 25 degrees, this can be either straight or curved.)
- Corner rounding
- Corner bevelling, stuccoing
- Sanding (angle grinding)
Aesthetic grinding can be made in matt or polished finish.
Grinding is the next process after cutting, which results in the elimination of sharp edges and is aesthetic. Grinding is an essential part of the tempering process and is necessary because it is after the edges have been polished that the glass is stress relieved.
In most cases, grinding is done on architectural glass for safety reasons, as it is used to de-stress the glass on larger surfaces. For glass up to 6 mm thick, a smooth edge grinding is used, for glass 8 mm thick or more, a peening is used, which grinds the upper part of the thickness in addition to the edge of the glass.
Aesthetic grinding is mostly used in interior architecture, the idea being that visible edges can also serve as decoration.
