Milling Aluminium - too fast?

[KH0UJ]

Here`s the code Gary sorry for the long delay, been working offsite lately, install the 3mm tool bit first, position the spindle on the material, zero all axis with the tool bit tip slightly touching the material, make sure you jog all corners to make sure it fits on the material, load the 3mm program and start plunging the pilot holes, after the program it will return to zero, turn off the spindle and press Z upwards enough to install the 6.5mm tool bit, after installing zero the Z axis again on the material, use 2% jog mode so that it will go down slowly slightly touching the material, zero all axis using "ref all home", start the spindle @ full speed (24000 RPM) and load the 6.5mm program, it`ll take you a whooping one hour and 28 minute to complete the program @ 100% FRO, use 50-50 kerosene+cooking as your lubricant just like I did on the video or you can use whatever coolant / lubricant you want available in your area by the way you dont need to worry about the depth cut, it`s only 0.25mm so it`s not gonna touch the middle part of your tool bit, it`s just like scratching the aluminum in a thin foil degree that you can run it all day without worrying of your tool bit getting dull in the middle of the program, flush the chips using compressed air and squirt some lubricant on it after blowing the chips away. enjoy milling with your router





Sorry I forgot, after all is done, extract the machined material using a metal hacksaw blade, I put a 2mm tabs on it to hold it`s place while the router is still working, grind the tabs to the level of your material, drill the pilot holes using a drill press to make it through the other side. it`s faster to just drill it than include it to the program because I was worried of the total height (40mm) using a 1/8 tool bit to create a 40mm long hole is too risky, I also doubt there`s an available 1/8 dia. 50 mm long available (40mm+10mm for the chuck to hold), the last time I used to cut 60mm thick aluminum it was just a straight long bit custom sharpened into a single flute. and the hole I cut on the model is 60mm in diameter not 8mm.

[GaryWilliams]

Hi Khouj,

Thank you for all your efforts on my behalf. I now have the important information to sucessfully mill aluminium on my 6040Z! You have really sorted out how to mill inexpensively. I've been buying expensive super-duper end mills from Germany (and breaking them by milling too fast) and using aerosol cans of silicon lubricant. A simple router bit and a kerosene+cooking oil lubricant is an excellent replacement. The information you have give in this topic should be made a 'sticky' for noobie CNC users like me. I'll post some photos and videos of my first attempt.

Cheers

Gary

[RCaffin]

Hi Gary

Depending on the alloy,it might be worth your while looking at two other sorts of milling cutters:
* Aluminium-specific cutters - sharper angle on the cutting edge to slice into the aluminium better
* HRC 55 rated or even HRC 65 rated cutters from someone like CarbideChiu on ebay (HRC is a steel hardness rating)
Both may be a little more $$, but I have found them to be worth the money.

I use 3 parts kero to 1 part olive oil as a pulsed misting lubricant: works well.

Cheers
Roger

[GaryWilliams]

Hi Roger,

Thanks. I'll have a look at those cutters. I like the cheap lubricants you and Khouj use. I do have and air pump and valve/nozzle to create a mist and another 1" dia nozzle that I connect to my home vacuum system to suck up MDF and now, aluminium, chips. I really must make a decent bracket to hold these close to the cutting tool. Cable ties are a bit naff!

Cheers

Gary

[RCaffin]

Hi Gary

If it is a stupid idea but it works, then it is not a stupid idea.

Cheers
Roger

[GaryWilliams]

Hi Khouj & Roger,

I have been practicing with scrap blocks and plates of aluminium and I'm getting somewhere. Now I have the correct values for feed speed and step down, my 6040 sounds much happier. When I have milled my rocker box as nicely as Khoujs' part, I will post it here. Thanks for all your help. I wouldn't have got anywhere without it.

Cheers

Gary

[RCaffin]

Hi Gary

Take a brownie point as well: too many people ask for and then ignore advice - which is frustrating.
OK, no worries, and it would be nice to see the photo.

Cheers
Roger
PS: I have a lot of old scrap pine softwood ... and a lot of sawdust.

[GaryWilliams]

Hi Roger and Khouj,

I have been milling 2D shapes out of 2mm aluminium sheet. To protect the base of the CNC, I have a sheet of 10mm MDF fitted and clamp the aluminium sheet to this. To ensure I cut right through the aluminium, I add an extra 0.25mm to the depth of cut so only the bridges are left to prevent the cut shape from moving during the final pass. This means that on the final pass, my endmill is cutting MDF which I understand is not good for endmills used for milling aluminium. How do you solve this problem?

Cheers

Gary

[RCaffin]

Hi Gary

MDF is 'orrible stuff. It is little more than high-density cardboard.

I use soft pine or scrap HDPE. If I am using more robust CARBIDE cutters I may use (Australian) hardwood, but that is extremely hard stuff and probably not available in the UK.
I use some overshoot as well, but usually more like 0.1 mm - AFTER first surfacing the disposable substrate. That is usually enough.

A thought for you: my slabs of pine are sometimes 25 mm thick. I can recess the hold-down T-slot bolts and resurface the wood many times.

Cheers
Roger

[GaryWilliams]

Hi Roger,

I get it. Use a thick substrate, surfaced to ensure it is perpendicular to both axes. Allow a 0.1mm overshoot and re-surface as necessary. I noticed that is what the PCBcode does to a substrate before cutting the PCB tracks. In this case the milling is only 0.1mm across the whole PCB.

As 2mm MDF is cheaper than aluminium, I have been using it to prototype the 2D shapes before committing to the more expensive aluminium sheet. What do you use for prototyping?

Cheers

Gary

[KH0UJ]

The last time I cut 3mm aluminum I only use a custom sharpened 1/8 carbide bit @ 24K RPM, I`ved cut all day on the motorcycle parts from a customer without sharpening, a 1/8 concrete nail will do but will get dull in 6-8 pieces of cutting, I only use a 1/2 thick plywood as my sacrificial bed.





A chinese carbide bits nowadays are more tougher than the U.S. carbide bits, on my experience, a U.S. carbide bit 1/8 dia. can only last 3-4 days on cutting hardwood, but on the chinese carbide bits it last 2 weeks before I resharpen, you can bench test it yourself and see the difference, I really had no idea why a cheap chinese carbide can outperform a U.S. made carbide.

[RCaffin]

Hi Gary

You got it.

What do you use for prototyping?

Well, for a FIRST check I rely on the screen display Mach3 provides. If it looks at all wrong ... it is.
Then I might cut air for a run - just have Z 50 mm up. Or I might cut some really cheap thin 3-ply. For solids I might use some scrap HDPE - I have a bit of that. Really soft pine or oregon is also forgiving.

I am intrigued by Khouj's comment about 'cheap Chinese carbide'. I have a few of those, and I sometimes use them for rough work or testing. Yeah - they do seem to last longer than I expected, as long as I don't use them on hard steel. Very tough stuff, but with a hardness limit.

Cheers
Roger

[GaryWilliams]

Hi Roger & Khouj,

[Roger] That is what I do - air cut and use 3mm MDF. My son goes nuts when he sees me milling MDF but I do have the CNC in an enclosure (made with 3mm MDF!) with dust extraction connected to my home vacuum cleaner. I must get the lid stays finished.

[Khouj] The custom sharpened 1/8 carbide bit. Is that the one in the photo? Do you sharpen them yourself? Looking at my router bit, they may be a bit tricky to re-sharpen as it is made as two blades set into a central boss. I'll look for some of your 'cheap chinese carbide' bits.

Cheers

Gary

[KH0UJ]

Hi Gary, yes I made it myself, there`s a grinding stone that can be bought to grind/resharpen carbide bits, >>> Link



Sharpening a 2 flute straight bit is a piece of cake compared to sharpening a regular drill bit by hand
the grinding stone is a bit pricey but it will save you tons of money in the long run, it`s like sharpening a piece of pencil, you can utilize the tool bit until you cannot hold it anymore on the collet hehe

Word of advice on your enclosure though, unless you install a powerful vacuum/suction machine to collect the chips or dust it`s all right, if not then if the X axis ball screw will get contaminated with the debris/chips, it will mess up your program code, sometimes it will get offset often times that will scrape your main aluminum table (stuck Z axis) most of the time the X axis will get stuck then routing your program code in a different position that will damage your material or the table itself. I used a 6040 machines on a daily basis, the last time I put it in an enclosure it cannot last 2-3 hours of cutting in a loop program without getting offset.

[A_Camera]

My son goes nuts when he sees me milling MDF but I do have the CNC in an enclosure (made with 3mm MDF!) with dust extraction connected to my home vacuum cleaner.

I'd also add a dust shoe if I were you. That is far more efficient then an enclosure.

[GaryWilliams]

Hi Khouj & A_Camera,

I see what you mean. I use the enclosure as the CNC is in a room in the house, rather than in a workshop/garage/shed. To get the dust out, I have a 25mm tube that (up to now) I have cable tied to the motor. That is what I connect to the vacuum cleaner. I removed it before I took the photo. I also have a lubricating/air blast nozzle with an air pump to cool the cutting tool and dislodge any chips for sucking up. I need to make a decent bracket to hold both of these.

I like the grinding stone. Just checked the UK eBay site, they are readily available. I must have a look at dust shoes again.

Cheers

Gary

[GaryWilliams]

Hi Khouj, A_Camera and Roger,

Success! Using your settings, I have successfully milled some 2D shapes out of 2mm aluminium and 1mm copper sheet. As I had to mill some 2mm wide slots, I purchased a 2mm, 2 flute end mill. By using this for all the milling, I have reduced the amount of chips produced. Whilst the cutting was in progress, I used a WD40 aerosol can to apply occasional squirts of lubricant. Not only did the milling proceed without any drama, but the spray also 'stuck' the chips to the excess metal of the workpiece. This meant that I did not have small metallic chips floating around. I'm now going to to fix up my lubricating/air blast nozzle (above) and use your lubricant mixture to provide a very fine mist onto the workpiece. Here is a photo of my milling. The three aluminium pieces create an oil anti-surge system for our Kart engines, (I might need a few more holes in the plates). The copper piece is a 1mm copper head gasket for our kart engines.

The next job is the 40mm thick rocker box and cover.

Many thanks for your advice. I would not have got this far without you

Cheers

Gary

[RCaffin]

Excellent!
Ah - if you made the copper 0.5 mm thick, would the kart go faster?

Cheers
Roger

[A_Camera]

I use the enclosure as the CNC is in a room in the house, rather than in a workshop/garage/shed. To get the dust out, I have a 25mm tube that (up to now) I have cable tied to the motor. That is what I connect to the vacuum cleaner. I removed it before I took the photo.

I thought I was the only one with a CNC in a room in the house... My "workshop" is far too small with all the other things in it, just bought a Bosch GTS 10 J table saw which is the last possible machine to fit in there, no more free space. I like the comfort of having the CNC in a hobby activity room. I can sit comfortably, close the door and nobody is bothered but me with the noise it makes. There isn't much floor space left though... Anyway, I also have an enclosure on five sides (not the top) and also use the dust shoe, but not using any lubricants, only dry milling.

[A_Camera]

Success!

Good news! Thanks for the feedback!