Poor tool life in Al?

I’m getting some quick tool wear and I’m wondering if it’s normal or not.

I’ve got about 3-4 hours on this tool and here’s what it looks like now vs a new tool (left is unused, right is used). Any tips on increasing the life? The tool on the right is done right? It got stuck in my work piece and started skipping steps, so I assume that’s a sign it’s not sharp enough.

I’m using the 45degree zrn coated 1/8" end mills from kodiak in 6061 (-t6 i think). 10krpm 15mil DOC 0.056in stepover 25ipm feed rate. I’m manually dropping on lube when convenient.

How are you clearing chips?

very occasional puffs from an air can :sweat:

I had a plan to hook building air, but didn’t follow through yet… Maybe I should.

“There’s yer problem”

You need to be continuously on the chips. Recutting the chips is terrible on the cutter. A brush isn’t good enough. Careful with compressed air. I’ve always been told never to use compressed air around machine tools. That said…I do so, at low pressure, and am careful not to blow chips toward anything (bearings, slides, etc). It’s still wrong, and would make my high school shop teacher (do they still have those?) chase me with a hammer…

1 Like

Interesting. Could you elaborate on why no compressed air? I could try to plumb up the shopvac but it’ll be a tougher job.

It’s quite straight-forward to add a vacuum / dust shoe: http://www.shapeoko.com/forum/viewtopic.php?f=8&t=3658

More at: http://www.shapeoko.com/wiki/index.php/Spindle_Options

I’m using a Nomad. Mbellon et al also have dust shoes though that look quite nice. I’m trying to avoid building a new larger enclosure though.

Looks like imp (http://community.carbide3d.com/t/nomad-883-pro-dust-head/1418/19) managed to cram a shopvac hose into the stock enclosure there though.

Why no compressed air? I would think it’s because you don’t want little bits of metal flying around in the machine where they could wind up in places they don’t belong (like bearings, threads, electronic components). Less problematic, I assume, if they’re carefully blown OUT of the enclosure rather than just off the work surface.

I was told it was because it keeps chips from getting pushed into gibs/ways (lathes) and into bearings and bushings. A scratch can rapidly damage any of those, and a scratch is not terribly far away with a chip of the wrong stuff in the wrong place. I don’t know how common that actually is, but I learned it from some old school machinists (and a crotchety old shop teacher) that were pretty adamant about it. Sort of makes sense. @mbellon has a lot to say on the matter. There are some great discussions here in the forums about dust shoes and how to fit them into the standard enclosure.

and so forth…

The primary reason for not using compressed air - usually 100 PSI in shops (but it can be higher) - for clean up (in metal machining) is that the air blast sends razor sharp swarf all over the place - into spindles, gears, bearings, belts, and rods. But this a factor when machining all substances.

This is VERY unhealthy to a mill; in the old days we were taught to sweep up first, then vacuum. Most of time, a vacuum was unnecessary. The swarf could also damage the vacuum as much or more than the mill.

Trying to blow things in a safe direction is practically impossible. It is just not done in practice.

Don’t forget that particles can get into lubricants too, decreasing their effectiveness.

Things become more complex - and dangerous - when friable (“easily crumbled”) materials (e.g. wood, MDF, FR4, Garolite, fiberglass, carbon composite) are machined. Now there is a host of particles generated, many in the range that are EXTREMELY damaging to the lungs and immune system. The last thing we want is to loft these particles unnecessarily. There are also issues of carcinogens, teratogens, toxics, and viruses - wood is the main culprit. Plants generate defenses to insects and have a mixture of chemicals and other things that can be pretty nasty.

Although not as “tough” as metal swarf, wood, plastic, and other particles getting thrown around can also land up in spindles, gears, rods, bearings, and so forth… not good for the overall life of a machine and possibly affecting the accuracy and precision of the machine.

A dust head brings a vacuum near the work and has an excellent chance of confining the swarf to within the dust head (it doesn’t get all over the price) and it can remove the smaller particles that are so health damaging BEFORE they accumulate (as they are generated).

It is true that compressed air can be used as a lubricant - look up a vortex tube - but this requires very critical positioning of the air stream. This is also generally done (only) with metals and by set up - the air isn’t blown UP - the air is blown TO THE SIDE.

At the end of the job, one still have to clean up - brush and vacuum (if necessary).

I machine MANY JOBS with a dust head in place… even when no vacuum is being used. This confines the mess. The geometry of the job, and the fixtures determines when the dust head stays or goes. An air stream for metal machining WITH a dust head - even with no vacuum - works really well.

I’m not a big fan of the propellers attached to spindles because of the unnecessary lofting. The potential health issues are DEAD SERIOUS so I use a dust head and vacuum. With experience and simulation (before the job goes on the machine) there is little need to be able to see things (you get used to it). If there is any unbalancing, increased spindle wear is also possible (but this should be small).

Al alloy is notorious for being sensitive to chip clearance. One has to get the swarf out of the work area ASAP… but this is a general problem. All those little pieces slamming in the end mill is disastrous to the end mill and the stock. This is why many have seen the videos of high end mills practically bathing the stock in lubricant (which is mostly water by the way). This is primarily for swarf removal, not lubrication.

Here is a good article that should help:

http://www.cnccookbook.com/CCCNCMillFeedsSpeedsFloodCoolant.htm

Swarf (chip) clearance is more important than the lubricant issue.

Since lubricants are expensive and generally have to be recycled like car oil, the industry have been moving towards alternatives - micro drop, fog, cold air, etc. - even pure water!

mark

1 Like

Compressed air blowing + swarf = eye injury. Not a good practice.:cry:

1 Like

Compressed air blowing + swarf = eye injury. Not a good practice.:cry:

For sure! :ok_hand:

Of course, we all ALWAYS use eye and ear protection when we go near our machines as documented in the manual… :smiling_imp:

mark

1 Like

As usual great info Mark!

I aborted my compressed air plans and 3d printed a quick and dirty temporary vac setup until more hosing and those bristles come in. It’s collecting probably 80% of the chips as is, and once I refine I’m sure it’ll get better.

That said, I’m still getting aweful tool wear. :frowning: those tiny, thin corners just chip off after, apparently about an hour.

I kinda don’t blame them, they’re very small and very hard, i’m surprised they don’t chip off on the first cut.

Would roughing with a 1/8" bull nose and then finishing with the square end mill help? I figure the rounded corners on the bull nose would be more robust, but I don’t have any experience with them.

Also, for the record, i’m very conservative and always wear eye protection.

I aborted my compressed air plans and 3d printed a quick and dirty temporary vac setup until more hosing and those bristles come in. It’s collecting probably 80% of the chips as is, and once I refine I’m sure it’ll get better.

A good dust head will do wonders. When machining friable materials the dust head is an essential; with metal, it can contain the metal swarf, pick up quite a bit of the mess, and easily allow for careful compressed air.

That said, I’m still getting aweful tool wear. :frowning:

With a dust head in place, we can discuss you compressed air. As I pointed out - and many others did too - removing swarf is critical.

First off, the nozzle is the hardest part. It’s size must be balanced with the pressure to ensure a “just right” blow that clears the work area but doesn’t make too much of a mess - or blow things too fast. A “blast” isn’t necessary.

One of those flexible, multi-segmented tubes (e.g. Loc-Line) that holds its shape is perfect. Nozzle selection can be plastic or metal. It takes some experimentation to get it right… unless you go fancy and add a valve to control the air flow.

Ever hear of a koi pond? Look it up. They need a small air pump to keep them aerated. The pump must be designed to run for years. One needs a pump that is quiet too.


http://www.cnczone.com/forums/diy-cnc-router-table-machines/284588-air-blower-cutting.html

Something like this should be enough:

http://www.hakkoairpumps.com/prod32.html

Read up and think on it. We - and others - can discuss things. A good improvement will be valuable to EVERYONE.

those tiny, thin corners just chip off after, apparently about an hour.

The 25 IPM may be a bit fast for roughing. Try slowing it down 20 IPM and see if things change.

Would roughing with a 1/8" bull nose and then finishing with the square end mill help? I figure the rounded corners on the bull nose would be more robust, but I don’t have any experience with them.

Nope. One of the things a bull nose end mill is super for are jobs where one has right angles and a small “corner” must be left to ensure strength (e.g. letters on signs). They don’t clear swarf any better than other end mills.

Also, for the record, i’m very conservative and always wear eye protection.

:thumbsup:

mark