CNC mill spindle up grade

[Jasonb]

I did not have too much of a problem getting the engrave to work. You need to extrude the writing so it has a flat bottom and then when doing the CAM select the edge of the letter not the bottom surface and then F360 will run the cutter up into the corners giving a nice engraved look and will automatically adjust the depth depending on the width of the letter.

I've been having a play and "peeling" at 1000m/min, video later

[Jasonb]

Well with all this talk of High Speed machining I thought I would sacrifice a bit of 6082 to see how quickly I could convert it into a pile of chips.

As I have mentioned I tend to use 3-flute cutters most of the time so this was no exception and I chose an Aluminium specific one from APT with a 55degree Helix that had had some but not too much use. https://www.shop-apt.co.uk/end-mills-for-aluminium-standard-length-3-flute-55-helix-uncoated-carbide/end-mill-for-aluminium-6mm-diameter-3-flute-un-coated-micro-grain-carbide.html

They give some suggested parameters for side cutting of 13,000rpm and 1,500mm/min feed so working that back to my maximum spindle speed of 5000rpm gives a feed of 577mm/min. They don't give how large the side cut can be but most other makers seem to suggest an Ae (sideways feed) of 0.1 D so I went with this making each pass 0.6mm. Ap (vertical Depth) of side cutting seem to either be given at 1D or 1.5D so I went half way with 1.25D which equates to 7.5mm. I drew up a simple block 2" (51mm) wide with a 0.6 x 7.5mm rebate in it and produced the code to cut that at various Fz (chip load) values and simply altered my Y axis zero by 0.6mm each time to compensate for the previous cut. Once I got to 500mm/min I just used the override to increase in steps of 20% eg 100mm/min.

For the first few cuts I just dabbed on a bit of paraffin but for the 800m/min and above also turned on the air as I was having problems getting the fluid to flow with the air. and being an external cut the chips were doing a reasonable job of staying away from the cutter anyway.

At no time did the machine seem to be under any strain, there was a bit of vibration on the 450mm/min pass but that was from the chip guard rather than the cutter. I stopped at 1000mm/min as I did not want to push too much and risk metal welding to the cutter or worse. Even at the highest feed the finish was quite good for what is a roughing cut with a fine series of vertical lines that could be seen when held to the light but not felt with a finger nail.

I'm not sure how often I will run at 1000mm/min as it will depend on the job as to any increases in cutter engagement or getting the chips out if a small pocket is being cut but it is nice to know what the machine can handle.

I put video and an image of the cut surface together with the feed rate son a video, couple are not the best for focus and I also mucked up the 600 & 700 videos but there was nothing exciting to see there anyway.

[Vixen]

Some very impressive feed rates there Jason. Boy do those chips fly   

There seems to be no limit to how high you can raise the feed rate with a straight cut.

As I said earlier, after I did my 0.1D Ae (sideways feed) by 1.4D Ap (vertical depth) internal pocket, something magical happens with very low Ae values with carbide tooling. The cutter finds a sweet spot, when it peels off a fine wafer of material due to the chip thinning effect, rather than cutting a chip. It feels as though you can keep increasing the feed rate higher and higher. However, I was not to brave as you, and never reached the high a feed rates you have achieved. Perhaps next time.

Chip removal is so much better with an external cut than when the chips are constrained in a deep pocket. Even with an air blast, it is difficult to clear a narrow, deep pocket adequately, so reducing the feed rate gives more time to clear the chips from the cutting area. When the pocket opens up, chip clearance improves and the feed rate can be increased back to the higher rate.

I am working to improve chip clearance on my machine using a link-lock air jet, fed from a airbrush compressor. I am also working on adding some coolant/lube mist, fed from a small variable speed, peristaltic pump. I will let you know how that dosing pump works out. Not sure what fluid to use. The Jokish Solis Varo fluid that Sebastian End recommends is a bit difficult to obtain in the UK, likwise KoolMist from the States, are there any other good alternatves?

Mike

[fumopuc]

I did not have too much of a problem getting the engrave to work. You need to extrude the writing so it has a flat bottom and then when doing the CAM select the edge of the letter not the bottom surface and then F360 will run the cutter up into the corners giving a nice engraved look and will automatically adjust the depth depending on the width of the letter.

I've been having a play and "peeling" at 1000m/min, video later

Hi Jason, as I mentioned before, this is the perfect tool for the guys which are deeply involved in wood carving.
All these nice wooden name plates at your local pubs.
The font/letter is always like a box and the material will be removed inside it, between the lines.
For a simple "marking" or "labelling" of a part I do prefer the one line xxx.shx fonts in Fusion, which can be selected at the sketch menu already.
So no extrusion is necessary and a one line text will be visible in the model only, to be selected than by the 2D trace command.
A German idiom translated would say: Many streets will lead to Rom.
In your country the people would say: There is more than one way to skin a cat,  or similar if I am right.
   

[fumopuc]

First of all thanks to Jason for his experiment with the high speed milling and the video documentation.
Really nice to the chips flying.

For my further spindle test I have put the 4th axis on the table against.
A piece of the AW 2007 Aluminium bar, d=45 mm, was also still available.
The raw part size/lengths  has been a bit increased to get a safer position against the chuck.

For the roughing out I have selected the 6 mm HSS Co8 cutter again, as used in spring already.
Not as much as Mike and Jason did, but my Ap was also increased and Ae decreased.
With my HSS cutter here I donīt want to go a full risk.
Cutting parameter for this job now:
N= 14.000 U/min
Vc= 264 m/min
Vf= 1.000 mm/min
Fz= 0,238 mm
Ap= 3 mm
Ae= 1,5 mm
The 3D adaptive cleaning strategy in Fusion does make first an Ap step by 3 mm and than the cutter will be lifted up again by 0,2 mm and remove the material between the last pass and the shape of the part. This will be repeated so long until it will reach the level of the 3 mm Ap pass before.
Hopefully the picture below will make it clear.
So the Ap/Ae story is relevant here for the big 3 mm steps here only.
The roughing out toke something about 3 hours.
Much more quicker than in first time in spring.
I have never had the feeling that the mill is doing real work.
The spindle is so silent, your hear nearly the cutting noise only and this is a kind of smooth also.
The chips looking more like needles.
I have done some minor experiments with the finishing process but nothing spectacular.
By hand and with the Dremel it was a bit polishing at the end.

So I will order some VHM/Carbide  end mill  cutters next week and than start to be more encouraged for milling with 1D or bigger values for Ap if possible and reasonable for a part. 

Thanks for the journey so far.
Mike, Jason, a very interesting learning curve supported by both of you.
Back to model engines now.

[Jasonb]

I will have to take a look in Alibre to see if they have those single line fonts which would be easier for basic engraving. Even if not I could still add the text in Fusion onto the imported part.

Figures look good and so do the chips

I have some 20mm thick steel to profile soon so will do some test cuts on that as well though I don't think I will be attempting the full 20mm depth, at least not for the adaptive cuts.

[Dave Otto]

You can download some basic single line fronts from the CamBam site. Once saved to the Windows font directory they can be access by any program. I have used the a number of times over the years.

Dave

[Jasonb]

Thanks Dave, I'll bear that in mind if there is nothing in Alibre