Would someone give us a hint? We are experiencing 40% yield when tempering 5mm glass, with 25mm bevel, and with 2mm glass remain. We have lower the quench pressure to 50%, normally run about 70 to 85, and there are still breakage. We have set up many parameters to improve it but the result is the same.
Could someone help us with with the following :
1) top temp
2) bottom temp
3) Power setting
4) heating time
5) Quench frequency
Many thanks
I also agree with Mr. Jonathan Brarr. My solution is first check whether the 5 mm is actually 5 mm or 4.8 mm second thing is to change the angle on the beveling to achieve the 25 mm with a higher thickness at the remaining edge. next is to make a pencil grinding edge finish after the beveling before tempering. The breakage should reduce drastically. This is all assuming that the water flow in the cooling spray on grinding wheels (while beveling) is sufficient.
Hi Mr Luu,
Your problem is that at the edge of the bevel you are only leaving 2mm, and you cannot temper 2mm glass with an air quench. So the 2mm thickness is not tempered and is very weak.
Your only solution is to reduce the amount of the bevel. If you leave a final thickness of around 3.8mm to 4mm the optical effect of the bevel will still be there, and there will be sufficient thickness in the glass to be reasonably tempered right to the edge if you use quench air somewhere between 4mm and 5mm settings.
Regards,
Jonathan Barr