Today has been probably the most frustrating day I've worked in the shop yet, I broke three semi-expensive endmills and had some weird luck.
There weren't very many features on the part, but the ones that they do have are tiny, going all the way down to a 0.008" groove to cut out. I programmed the part around those features and didn't worry about trying to clean up any of the larger faces (I'd get those when I send it through the final operation. So I would take the 1/2" endmill and clean up the areas around the features, then with the smaller tools come through and mill them out.
My troubles started when I ran a 1/32" (0.03125") square endmill to pocket out a small cavity and snapped the endmill. I didn't think my speeds and feeds were breakneck, and I was shocked that it caught so quickly, I used an adaptive cleaning operation and had its ramp down to its final height, then spiral out from the center. I asked my boss about it, and he pointed out that the height of the pocket was over 100% of the tool diameter, which I didn't realize until then that it was. I was trying to get the endmill to cut about 120% depth of cut with an 18% sideload at 12 inches a minute. The hole itself was about 0.023" deep (80% tool dia) and should easily be able to handle that; however, I forgot to take into account that I had stock to leave on the top face above it (10 thou) and so couldn't take that kind of stress. I ended up just leaving five thou on that top face (I would clean it up on the final operation) and receive ten thou step-downs.
After cleaning out that small pocket, I then used a trace toolpath to get the 1/32" endmill to follow a specific path around this button like feature. Unfortunately, I thought I could take the endmill deeper than it could go and snapped the second one of the day, at this point I was got frustrated and had to take things way down, I was very caught up in getting these parts done that I took things too fast to get lower run time, but what I didn't think about was the amount of time I was spending trying to save those few seconds and ended up wasting over an hour if I had just let it take its time. Thankfully everything went much smoother after this and got the rest of the toolpaths done without much hassle, except for breaking yet another 1/32" endmill when I forgot to adjust the speed on a different pocket (it didn't break the first time because I manually lowered the feedrate on the machine).
I also had a very small 0.008" feature to slot out so I used a 10 thou endmill (oversized is acceptable) and took 1 thou step-downs (4 in total) till I reached the bottom.
My boss noticed that something about the part was out of line and wanted me to check with a dial indicator along one of the flats of the parts to see if it was true. Something I didn't realize was that the locating pins didn't actually stick out far enough and the chamfers on both the holes and locating pins shifted the part ever so slightly; the weird thing was that by some stroke of luck, the fixture plate in the A-axis was perfectly level (within 0.0001"). So I somehow messed up getting it level, but since the part wasn't perfectly straight, it worked out to be almost dead accurate. Another stroke of luck (if you can call it that) was that most of the features on the part where about thou or two undersized, this confused and concerned me. Still, after going it over with Wayne, he explained that due to the runout on the machine, tool holder, and endmill, most manufacturing companies would make their endmills undersized to compensate for that. Still, he said that if everything were in perfect alignment, you would get the tool perfectly aligned and get a small part, which was the case for this.
Overall it took a stupid amount of time, and I ended up staying an extra hour to get the first batch of parts done on the 4th axis operation. Since I got most of the kinks out, the rest should be pretty much smooth sailing as I only need to copy and paste the toolpaths over and program the final operation.