Going off track

Credit to you JB for your perseverance - glass forming is a dark art - Many, many  years ago I worked for a laminated vehicle windscreen manufacture where windscreens were produced from 2 sheets of 2.2mm flat glass cut to size with the outer sheet being larger to account for the external screen curvature then placed to a jig frame before being run through a multiple staged kiln process (semi automatic) through pre heating followed by the forming (taking less than a few mins) then a staged cooling process - The 2 formed pieces of glass were then separated, cleaned and a plastic interlayer added between them - final process after being racked to stillages was for them to be autoclaved - Several critical areas in the preheat / forming / cooling process had to be adhered to otherwise very negative results occurred - This included incorrect curvatures, stress cracking, distorted vision etc - wastage was present but only in a very small % and the factory was producing units in the 1,000's weekly   

Thank you for the kind words

Yes. Along with the 4 sets of Panther stuff 🤣

So ,having looked at the failures a bit closer,it was evident two things were different. I already knew the second failure piece of glass was from a different pane and might not be the same glass as before. Further analysis showed that all the broken edges on both were fire polished. This means that the part must have broken when it was warming up, not when it was cooling down.

This piece is actually fused together again, confirming that it definitely was  broken during the heating cycle,and that it had a lower melting point than the previously used glass.

So I changed the program, lower slumping temperature, less slumping time and a much slower ramp up to temperature. So it should of sorted all the issues…but it didn’t 🤔 So I looked at the previous data log

I then looked at the infamous 300 c data log


The red circle highlighted something I hadn’t figured on. All the good parts made previously had been done by hot swapping blanks when the kiln was still above 50c

Changed the program that the initial ramp wouldn’t rapidly spike over 100c


And we were back to making good parts

With the glass blanks well under control again, I started making a tool to trim them to size. Would have been quicker to make in the Cnc lathe, but that was busy on three rotor parts.( Another thread I need to start 🤣)

Concave side done. Got some scrap silicon sprue from a customer to make the glass grip into the holder a bit better

Cut a piece to fit

Could then move onto the bottom piece

Looks great but, why the bearings? will it spin in the kiln?

Drew up a modification for a cheap angle grinder

Machined and bolted on a linear bearing

Turned a previously used lump of ally into a guard

Milled to shape
Assembled

Glass trimming with a diamond blade a success

Trimmed item

Trimming done, six finished, two still to sandblast

What they look like assembled,without the guard
Job done. Tired of glass,time for a new challenge

Very interesting, lots of learning on the job going on! hate to think of the hours that have gone into those!

That’s a wrap then. Ready to install. The black Bosch connector is where the gun plugs in. For the uninformed, the main gun on the Hetzer was electrically fired. Funnily enough, I’ve got four of those firing mechanisms to make next, along with all the gun parts and breech blocks. All suitably manufactured to go bang but without being able to propel projectiles any more. A much better option than chopping holes in barrels or welding holes up, easier just to leave certain holes out.