Making Skins #74 - Brisbane Australia

[bradm]

That's a lot of heat! Conventional wisdom would be that the feed is too slow and or the speed is too high; Are your chips coming off as spirals or flakes? Ideally, you want spirals, indicating that you are only cutting the material once. If you have flakes, particularly small ones, you are cutting the cut material, and recutting the sides of the cut, generating much more heat.

I always find this counterintuitive and scary, but you want to be very close to overfeeding to get the best cut and temperature control.

[danilom]

This is my first try with aluminium. I used 4mm Carbide TiAlN coated bit, spindle 12k rpm, feed 1200mm/min and 0.5mm stepdown.

It machines beautiful and the finish is extra smooth.




bit is from ebay : carbidechiu

[purpura]

Hi Roos, i thing yuo dont use coolin liquid http://www.limpieza-empresas.com/cat...na-blanca.html and is posible the tool is olso not de best for aluminium http://www.belintools.com/Catalog.pdf ....

[skillalot]

For aluminum it's best to use non coated tools. And try lubricating it a with a few drops of lampoil every now and then.

[Gerald D]

lampoil=kerosene=parafin

[danilom]

As you can read on wikipedia or any other search trough internet I found that TiAlN is ok for aluminium

Coatings: The right tool coatings can have a great influence on the cutting process by increasing cutting speed and tool life, and improving the surface finish. Polycrystalline Diamond (PCD) is an exceptionally hard coating used on cutters which must withstand high abrasive wear. A PCD coated tool may last up to 100 times longer than an uncoated tool. However the coating cannot be used at temperatures above 600 degrees C, or on ferrous metals. Tools for machining aluminium are sometimes given a coating of TiAlN. Aluminium is a relatively sticky metal, and can weld itself to the teeth of tools, causing them to appear blunt. However it tends not to stick to TiAlN, allowing the tool to be used for much longer in aluminium.

[Surfcnc]

Thanks everyone for your input.

Aluminium is type is unknown.
Cutter was a 3mm Carbide End Mill.
Pass Depth .3 mm and Stepover 1.25
12,000 RPM and 10mm/sec feedrate.
Feedrate was dropped by 50% after I saw the bit flex on contact.

The chips were flakes not spirals and towards the end (as the workpiece got hotter) they were obviously rewelding to the bit and the work.
With respect to the cutter size I have been considering using a larger end mill as 3mm is fairly weak even by comparison to a 4mm cutter that Danilo has used.

Cheers
Ross

[Surfcnc]

Better this time.

6mm Aluminium Test Piece.jpg

A video of part of the process - http://www.youtube.com/watch?v=qnMIMSP-LWc

Details...
6mm 2 flute HR45 Carbide End Mill at 1200RPM
0.3 mm Depth of Cut
20mm/Sec Feed Rate

I also periodically stopped and used some welding anti spatter grease on the bit if the aluminium was starting to stick to the bit (you can hear it when it is starting to go wrong).

Not perfect but better. Note I cleaned up the outside top edge with some 400 grit wet and dry.
Thanks everyone for your help.

Regards
Ross

[danilom]

Instead of simple plunge , do a ramping plunge, and you can go deeper than 0.3 with 6mm bit.

[Surfcnc]

Ahh of course, that makes perfect sense Danilo.

Ross

[AuS MaDDoG]

As usual, Nice work Ross!!

Cheers
Tony.

[ger21]

You should be able to increase your feedrate at least 50% with the same rpm.

[bradm]

I agree with Ger, you can keep upping the feedrate. Look for spirals!

[KenC]

Now I'm tempted to have a go....
Good job!

[Surfcnc]

Will definitely give the faster feed rate ago and watch for the spirals.
Can't help but thinking lots of coolant and lubricants will make cutting aluminium all that much easier.

Regards
Ross

[Kobus_Joubert]

I just don't like the BIG MESS that ALU leaves. Wood shavings are much more pleasant.

[Surfcnc]

Agreed Kobus, still finding metal everywhere.

Ross

[KenC]

Even the dust foot didn't help ro contain the metal chips?

[javeria]

Ken that is the reason they use flood coolant while milling most metals - except for some

[Surfcnc]

Hi Ken
I was not using it as it prevented me using the spatter grease on the work and cutter every now and then.

Infran
You got that right, with a coolant system in place cutting metals would be significantly easier.

Regards
Ross

[Surfcnc]

Demonstrating how the CNC machine works is so much better than just telling esp when it comes to the kids.
A visiting 10 year old future engineer got his name cut out and was very happy with his new possession.
The timber was reclaimed from a broken piece of furniture and the capital letter "A" is around 100mm high x 10mm thick.

Angus cropped.jpg

Regards
Ross

[Surfcnc]

Greetings All

Recently it has all been about tidying up my work spaces and getting my older tools back into shape.
Dare I say it but I killed my favourite 1100 Watt grinder last week, something not to be taken lightly on the MM forum as we all know !!

The welding skills I learned building the Mechmate have come in handy as my ageing box trailer had finally passed the 50 percent mark - that is 50% steel and 50% rust.
The ladder section base and the A frame have now been nicely re-fabricated so it rolls on for a few more years yet.

As part of getting some sanding drums chucked up into my drill press I thought it might benefit from a retrofit with some of those crazy looking but very effective Power Twist belts from Fenner.
As promised the belts reduce vibration a treat and have eliminated a harmonic at low speed (160 RPM) and smoothed out the 3000 RPM performance.
Fenner belts are appearing on anything that turns in my place after they turned my beast of a table saw into a purring pussycat.
Fenner Power Twist Belts in a Drill Press.jpg

Once my restructuring and repair of all the support gear is over it will be back to the Mechmate and hopefully a few new and interesting projects.

Some of the newer builds on the forum are speeding along and I am totally impressed with the support some of the senior members continue to give.

Regards
Ross

[Kobus_Joubert]

I lke those Fenner belts as well but they are VERY expensive here.

[jehayes]

They are very expensive here as well!

[Surfcnc]

Expensive everywhere !!

Here in Australia they are wickedly expensive.
From the USA the belt is 7 USD a foot plus 14 USD for the initial postage so buying a bit makes it cheaper if their is such a thing.
As usual Ebay is your friend.

My tidy up continues - today I reclaimed some bench space by making a mobile sanding station for my disk sander.
My neighbours entertainment unit is reborn !!
No back or doors as the day ran out but should be finished tomorrow.

Mobile Sanding Station.gif

Regards
Ross

[Surfcnc]

I know I run off the rails every now and then... it's to be expected!
BUT when the Mechmate gantry runs off the rails that will never do.

My machine developed a very bad habit of crawling up off the rails and it was just so annoying.

Anyway after a good look, either the LHS motor swing plate bolt had come loose or I had not tightened it properly after some fiddling with the LHS rail.
Realistically probably the latter.
Just a few simple turns to snug up the plate pivot point turned the MM from a out of control beast to a well behaved machine.
Though I might leave a record of the symptom and the fix on the forum for others to stumble across.

Stefan MM #73 is doing some nice stuff and Kobus is also knocking out some great creations on his thread.

Also whoever "stole" my 4mm collet better fess up soon.
I mean there is no way "I" could have lost it is there???

Regards
Ross

[Red_boards]

Thanks for posting the off the rails tip. I was wondering what conditions might lead to it.
The person that got your 4mm collet is probably the same one who needed my 8mm one for their set. Definitely time to get the shed in shape!

[Surfcnc]

Thanks to Kobus and his post on using the Mechmate as a plug cutter.
I used my Mechmate to cut a few timber plugs for a friend who is building a recycled timber table (complete with pre-existing bolt holes).

Plugs2.jpg

Regards
Ross

[Kobus_Joubert]

I am a great FOLLOWER.....the original idea came from Hennie. Nice to see it is used by others.

[Surfcnc]

Hi Kobus

Thanks for the attribution to Hennie - now we got a conga line.