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.


Polishing of flat surfaces
We are no longer having problems with blasting, and have started to get really interesting results from polishing. We have started making measurements using our optical profilometer, which therefore enables us to investigate both the appearance and the surface smoothness parameters of surfaces. By using narrow nozzles, we have managed to get the pressure up to almost 50 bar.
Figure 1 shows an example of such a polished groove. It can also be seen how we have removed material from the surface, removing almost 9 µm and leaving only faint traces of the grinding scratches.

Figure 1. Polishing using a 0,5 mm nozzle and pressure of 43 bar, with 40 two-way passes across the surface. The upper picture shows the general layout, with the blue area indicating the polished surface, while the lower picture shows the profile through the same area. Magnification 2,7 times.

Figure 2 shows the same area, but at higher magnification. The surface has been polished down to only small surface variations. The structure differs quite considerably from an acid-polished surface, but working mechanisms are completely different. The important thing is to get rid of the scratches from grinding and to even out any high or low spots.

Figure 2. The bottom of a polished groove, seen with 10 times magnification.

Mechanical evaluation of polished holes
If we are to be able to polish a surface more effectively, we need higher pressures and wide nozzles. This requires a larger pump, and we shall very soon be ordering a proportioning pump. However, delivery time is long, and so while we are waiting for the new pump we shall start trying to polish holes. To increase the strength around holes, it is important to round off the bottom of any cracks, as they otherwise act as stress raisers, with high stresses over a small area and very considerable risk of the crack propagating.

We are going to compare the strength of drilled and water-cut holes, with and without polishing. Testing of the unpolished holes will start in the spring. The first question to answer is whether there is any significant difference between a drilled hole and a water-cut hole. The first test will also show the spread of results between the samples, and indicate how many holes we need to test and polish in order to obtain a significant result.

Polishing of cuts
Polishing cuts differs less from polishing flat surfaces than it does from polishing holes. We have performed the first very simple tests, which show that once we can polish flat surfaces to the desired surface finish, not much additional development will be required in order to be able to use the method on cuts. Polishing of cuts will therefore not start before the autumn.