[BNX]

Hi. I've been trying to complete my first part but everytime I get to the edges (waterline, SprutCAM) of my engine bracket the end mill keeps breaking. I started with a Variable 4 Flute End Mills 1/4 from Maritool. It cuts great at DOC .03 but broke probably due to my work piece clamp a little lose. I went around town and found sonme 4 flute square end mill. I bought 6 more and broke 3 more I'm running 2560 rpm, DOC .02, feed 7.2 (can't remember, sprutCAM Trial ended midnioght yesterday). The last one I broke was on the 8th round of the edge (1.88 thick) and it broke. Should I be using a different tool, work on my speed, try a differnt approch besides waterline on sprutCAM? My next approch is to use a 3/8 end mill for more strength. Sorry for the noob question but I am assuring myself I am picking up pretty fast. I broke the tip of my Haimer Zero after trying to zero my next work piece and quitted. Got to order a new one.



Thank you.

[mike sr1]

If its steel youre cutting, try dropping the rpm to about 1500, feedrate should be OK, I dont see any traces of coolant on the part, I would use it, also check the mills that are broken to see if they are dull, if they are you have the rpm too high or no coolant.
You didnt mention HSS or carbide mills, the carbide will take more rpm.

A bit more information and a higher quality picture would help determine whats going on.

[tbaker2500]

I don't have GWizard in front of me, but a couple of initial thoughts. Use a 2-flute EM to help clear the chips. It's very easy for a 4-flute to get clogged when slotting like that. If the end mill is HSS, you really need to look at tool deflection. GWizard is great at that. If you're bending your bit, it's going to break sooner or later.
If the part is aluminum, make sure you're running coolant or fog buster. Aluminum will get gummy and stick the the cutting edge, making it dull. This breaks bits real quick.

If you haven't already, I highly recommend reading the feeds and speeds article at cnccookbook.com
CNC Feeds and Speeds Cookbook and Tutorial

[SCzEngrgGroup]

Aluminum will get gummy and stick the the cutting edge, making it dull.

That is, most often, not true. How "gummy" it is, is a function of the specific alloy. 6061 is not bad at all, and can be cut very well with no coolant. The "gumminess" many people blame on the aluminum is, rather, due to incorrect feeds and speeds. In particular, too high RPM, or too low feedrate. Both of these result in a low chipload, which causes heating of the cutting edges, softening the aluminum, causing it to weld to the tool. With a higher chipload (reduced RPM, and/or increased feedrate), the heat will be carried away very effectively by the chips, and the tool remains cool, even with little or no coolant. If the chips are not coming off HOT and the tool remaining COOL, you're doing something wrong. The normal reaction of most people to cutting problems is to "back off" by reducing feedrate, or increasing RPM, which is, more often than not, exactly the WRONG thing to do. If you're getting chips sticking to the tool, you need to REDUCE RPM, or INCREASE FEEDRATE. Reduce DOC if necessary to keep from over-loading the spindle, but keep the chip load as high as the tool will tolerate, and you'll not only get your job done quicker, but your tools will also last MUCH longer.

Regards,
Ray L.

[mike sr1]

6061 will get gummy and stick to the tool usually when the work starts to heat up, keep it cool or cold and its not a problem at all.

All bars of 6061 do not machine exactly the same either.

Most of my work with it was on the lathe cutting dry, I havent had a problem with it using coolant on the Tormach.

[BNX]

I was cutting 1018 steel.

I will order some 2 flute HSS and test it out. I will try coolant but I've been blowing chips with an air gun. Coolant looks messy.

[mike sr1]

I was cutting 1018 steel.

I will order some 2 flute HSS and test it out. I will try coolant but I've been blowing chips with an air gun. Coolant looks messy.

Coolant can be a bit messy but it takes the heat out of the part and cutter, the biggest killer is too much rpm, which generates heat, use coolant and you can run higher speeds and feeds

The cut doesnt look as smooth as it should to me as if the cutter is dull, which in turn will break it eventually as the load goes up as the edge on the cutter gets dull.

[BNX]

I see some Roughers at maritool, is it worth a try?

[BNX]

Here is some better pic. I am using some carbide .25 4 flute found locally. 2560rpm, DOC .02, feed 7 something.


This is a pic of a 1/4 variable 4 flute 2560rpm, DOC.03, feed 7 something. I think it's a cleaner cut.



I think I am going to stick to these variable flute from maritool. If my work piece didn't slip I think it would had turned out nice. Too bad I only order one to try out. I'll try out some 2 and 3 flute also.

[mike sr1]

I havent used roughers, I have a few but never used them.

Lower rpm with no coolant
higher rpm with coolant or oil. coolant is the best for heat disapation.
If the chips are blue slow down as the tool wont last long at that point.
10 ipm is OK for a starting point.
I like to put the spindle in manual and adjust as its running if the rpm is something you are unsure about.
The cut should be smooth and shiny, if its ragged and rough, and a burr on the edge of the cut, the cutter is dull.

A cutter should last several small jobs at least.

maybe some of this will help you out.

[BNX]

I havent used roughers, I have a few but never used them.

Lower rpm with no coolant
higher rpm with coolant or oil. coolant is the best for heat disapation.
If the chips are blue slow down as the tool wont last long at that point.
10 ipm is OK for a starting point.
I like to put the spindle in manual and adjust as its running if the rpm is something you are unsure about.
The cut should be smooth and shiny, if its ragged and rough, and a burr on the edge of the cut, the cutter is dull.

A cutter should last several small jobs at least.

maybe some of this will help you out.

It helps a lot. I appreciate it. I'm planning to add coolant on my next run when I get more end mill and tip for the haimer. Learning as I go

[mike sr1]

The last pics look much better.......Machining is not a really clean process, oil or coolant is necessary if you want long tool life and a good finish especially on steel.

[SCzEngrgGroup]

Either cut your RPM in half, or double your feedrate. For steel, you're running a very high SFPM and low chipload, which is very hard on the tool, as you're not so much cutting as rubbing. With steel, you pretty much NEED some kind of coolant or at least lubricant. Just spraying occasionally with WD40 will help a lot. For slotting like that, you might have better luck with a 2-flute.

Regards,
Ray L.

[BNX]

Either cut your RPM in half, or double your feedrate. For steel, you're running a very high SFPM and low chipload, which is very hard on the tool, as you're not so much cutting as rubbing. With steel, you pretty much NEED some kind of coolant or at least lubricant. Just spraying occasionally with WD40 will help a lot. For slotting like that, you might have better luck with a 2-flute.

Regards,
Ray L.

Yeah I plan to go as advise and hoping for better results

[David Bord]

That is, most often, not true. How "gummy" it is, is a function of the specific alloy. 6061 is not bad at all, and can be cut very well with no coolant. The "gumminess" many people blame on the aluminum is, rather, due to incorrect feeds and speeds. In particular, too high RPM, or too low feedrate. Both of these result in a low chipload, which causes heating of the cutting edges, softening the aluminum, causing it to weld to the tool. With a higher chipload (reduced RPM, and/or increased feedrate), the heat will be carried away very effectively by the chips, and the tool remains cool, even with little or no coolant. If the chips are not coming off HOT and the tool remaining COOL, you're doing something wrong. The normal reaction of most people to cutting problems is to "back off" by reducing feedrate, or increasing RPM, which is, more often than not, exactly the WRONG thing to do. If you're getting chips sticking to the tool, you need to REDUCE RPM, or INCREASE FEEDRATE. Reduce DOC if necessary to keep from over-loading the spindle, but keep the chip load as high as the tool will tolerate, and you'll not only get your job done quicker, but your tools will also last MUCH longer.

Regards,
Ray L.

That's my exact experience as well... I had little experience machining when I got my tormach 5+ years ago. It wasn't till I got G-Wizard and listened to guys like Ray that things started to click.

I must have rubbed 100s of EM to death

David

[kevinro]

That's my exact experience as well... I had little experience machining when I got my tormach 5+ years ago. It wasn't till I got G-Wizard and listened to guys like Ray that things started to click.

I must have rubbed 100s of EM to death

David

I have a drawer full of end mills I used on my manual mill that are all dull as can be because I was turning WAY to slowly. G-Wizard completely change the quality of work I can do since I now know how fast to feed things. The money spend on GWizard has likely saved me a thousand bucks in two years by not killing my tooling.

[BNX]

Well I tired Gwizard and it's great. I got the 2 flute from Maritool and it was carbide. Had to double check but I couldn't find any HSS so I guess my order was correct. I went start with the calculator and it gave me. With 4800rpm, 2.668 inch per min, .062 DOC, I had my mouse on the emergency stop in case. I've hadn't broke a tool unless it was my mistake (override feed).

[tbaker2500]

Nice. Amazing how much better life becomes, ins't it?

[Peter Neill]

Relax, at that speed and feed rate you won't break then anymore, you'll just rub them to death instead.
IMO that feed rate is around 3.5 times slower than it should be.

[BNX]

Relax, at that speed and feed rate you won't break then anymore, you'll just rub them to death instead.
IMO that feed rate is around 3.5 times slower than it should be.

Thats what I thought. I'm going to play with it more.