Final finish pass was with TiN coated 1" & 1/4" ball end mills running at 20ipm, 2500rpm at 2% stepover. It took nearly 48 hrs for the whole program to run but the end result was worth it.
The mold was then given some minor sanding to clear up some rough spots around the strap notches in the shoulders and then put into the former.
We did have some problems with warping after we took the mold off the mill. We started out with a 16" x 40" x 3" block and it must have had some internal stresses because the entire back section of the mold bowed when we unscrewed it from the jig. Luckily this didnt matter as the whole thing was then screwed to the cooling plate - 20" x 50" x 1/2", but it was interesting to see nevertheless. Some thought it was from heat buildup during machining but at those feed rates, under flood cooling the entire time, there was no heat buildup at all.
Fun Stuff. |