Wednesday, 18 January 2017

Assessing Pre-programmed Schedules

Many kiln manufacturers are shipping their kilns with a set of programs already entered and saved into the controllers. 

You might think that all these pre-set schedules would all be the same, as the range of glass to be considered is relatively small. Yet, the range of schedules for the same glass varies from one manufacturer to another.  Yes, you may respond, but every kiln is different.  Well, I’d say, the variation is within a product line as much as between kiln manufacturers.

Assessing the installed schedules

What this means is that you need to assess the schedules that come with your kiln, rather than simply accepting what has been placed there.  There are a few things that can be looked at to assess whether you wish to rely on these pre-set schedules or not.

Differences between fast and slow fuses. 
  • ·         What are the initial rates of advance, are they different?
  • ·         Where is the bubble squeeze, is there one?
  • ·         Are there different rates of advance from bubble squeeze to top temperature?
  • ·         If you can compare their larger and smaller kilns, is there a difference in schedules?

Differences between tack and full fuses
  • ·         Are the top temperatures different for tack and fuse?
  • ·         Is there more than one tack fuse temperature to allow for various levels of tack from lamination to fully rounded?
  • ·         Is there a difference in soak times at the target temperatures?

Differences in slump temperatures
  • ·         Are there low and high temperature slumps?
  • ·         Is there a difference in temperature or time between various slumps?
  • ·         Is there any allowance for span or size of mould?
  • ·         Does depth of the mould make any difference to the schedule?
  • ·         Is a difference for the depth of the mould offered?

Differences for different manufacturers’ glasses
  • ·         Are there different schedules for Spectrum, Wissmach, Bullseye, etc. fusing glasses?
  • ·         Are float glass schedules any different for rates, soak times, annealing points?

Printed schedules
  • ·         Are the schedules printed in the kiln handbook or manual?
  • ·         Are you given clear instruction on when to alter the programs?
  • ·         Are you given clear instruction on how to alter the programs?

The more “no” answers you get to these questions, the less you can rely on the installed schedules.