Address:
Glafo, PG Vejdes väg 15,
SE-351 96 Växjö
SWEDEN

Visitor's address:
Vejdes plats 3

Tel: +46 10 516 63 50
E-mail: info@glafo.se

You find a map at the
"about Glafo" page.

Project leader: Christina Stålhandske
Project status: on-going project


POLISHING GLASS BY MEANS OF WATER CUTTING TECHNOLOGY – CROSS-DICIPLINARY COLLABORATION FOR SUSTAINABLE DEVELOPMENT


The aims are:
- to develop an environmentally friendly polishing technique that produces the same finish as an acid-polished finish; for flat surfaces, cuts and holes both in float glass and in crystal glass
- to create a network within this field
- to appoint a person in the area of water cutting
- to produce a prototype glass polishing installation


You can read the first report and the background of the project here.
You can read the second report here.
You can read the third report here.
You can read the fourth report here.
You can read the fifth report here.


Polishing of plane surfaces
We have now produced polished grooves that, under visual inspection has the same quality as the acid-polished surfaces, which means that we have achieved the surface smoothness that had been aimed at. However, the method is still quite slow, with the best results being achieved at a speed of 2 mm/second.

The maximum pressure that we can achieve with any of the pump that we have is 50 bar. With a higher pressure, we could polish more quickly. We have investigated the market to find a pump that can pump slurry containing a high concentration of polishing abrasive. The first potential supplier withdrew when he realised that our application was not what the pump was intended for. We will now try an alternative pumping technology, which will hopefully allow us to perform polishing trials at a higher pressure.

When the project started, we investigated various polishing abrasives, but had difficulty in interpreting the results as the glass was seriously affected by blasting. In the most recent trials, we have found that aluminium oxide is more effective than cerium oxide: see Figure 1. These trials have been carried out with various nozzles, but at essentially the same pressure.

Pressure and speed have shown themselves to be very important; more so than the effect of the nozzle. It can be seen from Figure 1 that there is a substantial difference between the quality of the surface polished with cerium oxide and that of the surface polished with aluminium oxide.

The results of visual assessment are rated on a scale of 0 to 5, with 0 indicating no visible change, and 5 equivalent to an acid-polished surface. In the picture below, the cerium oxide-polished surface has been rated at 3, and aluminium oxide-polished surface at 5. These ratings are in good accordance with what we see in the optical profilometer.

Figure 1. Left: a surface polished with a 0,5 mm nozzle, 48 bar pressure and 50 % cerium oxide slurry. Right: a surface polished with a 1,3 mm nozzle, 45 bar pressure and 50 % aluminium oxide slurry. Magnification: 2,7 times. Click on the picture to enlarge it.

Polishing holes and mechanical assessment of unpolished holes
The strength of unpolished drilled and water-cut holes has been investigated, finding that the drilled holes were stronger than the water-cut holes. Ultrasonic testing gave the same result. To be able to polish the 'interiors' of the holes, we need greater flexibility than we have in the prototype test rig, and so we shall mainly use an ordinary water cutting machine, as shown in Figure 2.

Figure 2. A five-axis water cutting machine.

Continued work
The pump will be moved close to the water cutting machine. A tray to collect the polishing slurry will be made and positioned on the water cutting table. When this has been done, we shall start polishing the holes and then examine them by ultrasonic inspection. Finally, the strength of the material will be determined.