I found this about lettering in my MJSA Journal magazine..
"Expansion comes into play with lettering. If you have a model with long, skinny letters measuring up to 2mm, its helpful to remember that just because you can grow, doesn't mean you can cast it.
When you start the burnout and that resin starts to expand, you have all these skinny bits of investment between these 2mm tall letters. The expanding resin can crush those small bits of investment. Even if they do survive burnout, they still have to face molten metal rushing into the mold cavity.
With tall, skinny lettering the mold cavity is going to look like a series of skyscrapers. Now picture the metal rushing. Those little skyscrapers are just going to get plowed down leaving you with lettering that looks like crap.
How can you avoid this? Create smaller lettering. You don't need more than a height of 0.6-0.5 mm on lettering to be able to see it. In addition to not creating tall letters. the designer should also add a draft angle to the letters, making the top of the letters as as needed but tapering the width toward the base. Instead of creating skyscrapers in the cavity, the model will now create little Incan pyramids, which are better suited to handle the resins expansion during burnout as well as the subsequent rush of molten metal."
Statistics: Posted by cerriousdesign — Thu Jul 09, 2015 10:22 pm