First CNC fart

[wildcat]

Today was the first time that I ran an Al part on a newly converted IH mill. The part is a small flywheel drawn up in a CAD package and has a diameter of 3in. A four flute 1/4in end mill was used - if you look closely you can see see the tip of the endmill - hence first CNC fart. The chips got packed in the flutes and something had to give. I am really happy with the finish considering I have not even trammed or squared the head yet. Feed was only 3ipm at 1800rpm at .3in depth. This was a cheap end mill from Enco (from the pack of twenty box). The speed/feed equation would seem suggest that I should be able to go a lot faster than 3ipm. What do you think? What is the best way to avoid the packing and breaking of the end mill? Thanks!

[widgitmaster]

Nice!
I would suggest you use a 2-flute end mill in aluminum, NOT 4-flutes!
The 4-Flutes do not have enough chip clearance and build up between flutes!
Also, you did not mention the use of coolant, I hope you use a spray mister or flood coolant at that feedrate!

2-Flutes and feed much faster and deeper when flooded!

Eric

[wildcat]

I don't have an automatic coolent system yet. I really don't want to go the flood coolent route unless absolutely necessary and instead was going to get a Trico Micro Drop system. Think this will be fine? For this part I brushed a little CoolTool on it but that's it. The part was 120 deg. F at the time the end mill snapped. Is 3ipm a fast feedrate? I checked a couple of books and it seems pretty slows compared to what is suggested by the feed equation. I should probably not have gone so deep at once and perhaps also made multiple passes on the outer diameter to provide additional clearance. Thanks

[ViperTX]

It's not that the feed rate is too fast....it's that the chips are not clearing the mill.....don't you see chips wrapped around the mill??

[drwc]

I think your spindle speed was too slow, should have been up in the 4000 range for a 1/4 in mill bit.
Coolant will definitely make a big difference, and hard to do without for long cnc runs.

I agree that that was a pretty aggressive depth of cut as well.I in my short experience find 1/3 diameter is max practical z feed on slotting style cut.

[BobWarfield]

Wildcat, I'd even try a steady stream of air blowing in if you can't get flood. You have to clear those chips. Widgit is also of course correct in suggesting a 2 flute mill will have an easier time in aluminum.

I find when milling aluminum I can't go fast enough on the spindle so I crank the feed rate. It's a good argument to go to the bigger motor on the IH so you can get to 3200 rpm if you're going to do a lot of aluminum.

Here's another tip that works well if you can't get flood. WD-40 really seems to eliminate chips welding to the cutter with aluminum. Give the thing a healthy dose on the cutter and the workpiece before starting your cycle, and zap it a few more times along the way.

BTW, thanks for showing your part, even though incomplete. Show us some sequences once you got it working good so we can see how it comes out.

Best,

BW

[Blaster33442]

Welcome to the world of cnc that most likely wont be the only endmill you break But it shure is fun lol

[wildcat]

Thanks for the help everyone. I rigged up a mounted air stream to blow the chips out until I have a coolant system. Had no more 3/16 end mills so used a 1/4 which pretty much removed all the thin features, but it was a 2-flute variety. Also, instead of plunging to the target depth I redid the program to make several passes when pocketing. The total time did not increase much becase I could increase feed a little. The chips were like confetti instead of like hair before.

For the time being I have been mounting atop a piece of 2x8 until my limit switches arrive. The 2x8 has saved me big once already when an unexpected G28 sent the head striaght down to the table. Luckily the endmill was short and the table was not damaged. Anyway, looking foward to being able to use a vice again soon.

[philbur]

Should make home on the Z up not down. Then an unexpected G28 doesn't do any damage. I've had a few when using CAD/CAM software.

Regards
Phil

Originally Posted by wildcat Thanks for the help everyone. I rigged up a mounted air stream to blow the chips out until I have a coolant system. Had no more 3/16 end mills so used a 1/4 which pretty much removed all the thin features, but it was a 2-flute variety. Also, instead of plunging to the target depth I redid the program to make several passes when pocketing. The total time did not increase much becase I could increase feed a little. The chips were like confetti instead of like hair before. For the time being I have been mounting atop a piece of 2x8 until my limit switches arrive. The 2x8 has saved me big once already when an unexpected G28 sent the head striaght down to the table. Luckily the endmill was short and the table was not damaged. Anyway, looking foward to being able to use a vice again soon.

[wildcat]

Phil - is "making home up" a function of Mach or something else? At the moment increasing values on Z-axis raise the head. This seemed more intuitive to me but I had to swap the motor and encoder wires on the Gecko to have this behavior.

[Walt@SGS.Inc]

One way to remember Z
Axis directions is remember,
+ adds material
- removes materilal.
Minus should move Z axis down or
into the work.
See if that works for your machine.
Plus and minus can be wired either
way you want to wire them.
Rots o Ruck
Walt.

[wildcat]

Walt - thanks for affirming the standard approach, that's how Z is wired now. Just seems more intuitive. Perhaps something was getting crossed in the breakout board? Works great now though.