For Letters and Logos on my lost foam castings I have used wax appliques. Works fine but kind of laborious for one copy because I need to make a master pattern, pull a silicone mold, and then cast and apply waxes. So I figured for one-offs, why not just CNC machine them? For my recent intake manifold project I wanted a part number and a name plate, so I machined it from foam with an .031" diameter bit. The font is Arial and is .31" tall. The line weight ranges from .025"-.035" and .035" deep. I bolded the part number but not the rest. I hot wired the part number to a thin thickness and attached it to the intake manifold pattern but I figured the name plate features were too small to successfully cast, so as an experiment, I just stuck it onto the sprue of another aluminum casting I did today and here's how it came out. I'm sort of surprised it came out as well as it did. It only had about 6" total of sprue head pressure. The foam pattern detail was pretty good. You can see the result is somewhat passable, but a number of the characters didnt fill to full depth. I suspect this may be surface tension problem and I may have had the same result using the shell or investment method without vacuum assist. I've had decent results with engraving the pattern and scrubbing in the coating. Best, Kelly
I have some 1/8" 15 degree Dremal bits I use in the CNC. Works well but I have trouble with the letters filling too. I use foam and sometimes a hard machine wax. The wax is hard enough to use as a pattern with Petro bond. Bold letters and wide spacing seems to work best.
Not sure whether that's for me or Jammer but in my case, no, not on this example, and for me in general, almost never. Best, Kelly
Sorry, I did mean to ask you Kelly, some vacuum would likely give good results with such fine detail. I'm guessing a layer of saran wrap or that thicker film used to wrap pallets of boxes on the top of the flask as a vacuum barrier. The pouring cup could be covered by the film as the hot metal would go straight through it, I think that's what's done commercially based on a foundry magazine article I read ages ago.
