Sterling Dump

[will916691]

for a .015 endmill you want to try and stay around .0075 depth of cut a good rule is half the dia of you endmill smaller depth of cut will be less stress on the endmill what did you work out with your speed and feeds?

[ddc333]

The finished product looks outstanding

[Heavy Metal]

Thanks all for comments. Looking forward to doing some more work on this but will be another week or two before I have any more to show...business travel coming up right thru weekend. At least I'm headed to Orlando where it's a bit warmer!

Originally Posted by will916691

for a .015 endmill you want to try and stay around .0075 depth of cut a good rule is half the dia of you endmill smaller depth of cut will be less stress on the endmill what did you work out with your speed and feeds?

Will - Thanks. I did finally find a good source for these calculations and that's pretty much what I learned...no more than 1/2 endmill width for DOC. For the bottom grill plate with STERLING letters I had no problems. I used a .037 2 flute endmill w/ .01 DOC at 3IPM w/ 10,500 RPM spindle. I have since read that I should have been running about 10 IPM to keep from burning up the bit. I was hesitant to run that fast for fear of bit snapping. ?? On S relief pocket for the main grill I was going with the .015 endmill and went for same .01 DOC and the bit snapped almost immediately. Having not learned my lesson I loaded a .025 EM (not what the CAM file called for but figured it would be fine for test) and...same thing. Wha?? I ended resetting the Z axis height and cutting the S relief with the broken .025. LOL. As it turns out I had accidentally ordered standard length mini bits instead of stub. I think stub might have handled the .01 DOC but I'm staying under 1/2 endmill width for DOC from now on!! The correct miniature stub endmills have been ordered so I have high hopes for next set of parts.

Any thoughts on this next issue would be appreciated as well. I also had problems with slightly bigger end mills (more rookie stuff). Cutting the slots for the main grill with a .0625 2 flute EM (still at 10,500) w/ DOC .03 and Feed at 3IPM things looked real nice for about two or three slots then started looking rough...then real rough, then SNAP. I actually did the same thing with a .125 EM the night before cutting profiles out. After digging in to some metal cutting reading I'm pretty sure the issue was that I was actually running too slow on feed rate and overheated the bit causing it to clog w/ melted chips...calculations I have since found say at least 10 to 15 IPM at these spindle RPMs to keep from overheating or dulling. I kept slowing the feed rates down when I had problems and I think that was opposite of what I should have been doing. Looking forward to testing this theory and will probably slow the spindle down for .0625 and larger endmills. Thoughts?

Joe

[ihbuilder]

Joe , I got better results slowing the spindle down and a light spray of wd-40 . I know your doing it by way of cnc and I'm in the cave yet by hand but I think the principle would be the same . no ? my issue is getting my big mill going so I can play with it and see how it works with my amateur programing skills BTW , from where I'm sitting , the grill look great

IHSteve

[will916691]

running at 10,500 rpm that endmill is going to heat up fast you really need some coolant the math for speeds and feeds is tricky it may look good on paper but not work so well in the real world I would try and cut your spindle down and your feed down as well and see what that does for you also some oil to keep your work cool would sure help also how well is you part clamped down? if you tap on it in the center does it sound hollow? did the sound of the cutting change before it snaped? just want to make sure its not a issue with chatter

Will