CNC metal machinists (for Stax amp cases) unite?

[jamesmking]

I could not help but notice that the dead tree carcass machinists have a thread on wood machining. But dead trees do not make the best cases for stax amplifiers. So i'm a little surprised that there is no thread dedicated to CNC machining metal. The motivation for this thread was that I turned 50 years old a few weeks ago and for my birthday I decided to buy myself a CNC machine so that I could make my own cases for my stax builds. I decided to buy the foxalien Vasto, https://www.foxalien.com/products/cnc-router-machine-vasto?sca_ref=725103.t6qfXeHAnx based on not much more than I needed to machine 400mm by 400mm and the reviews on youtube are very positive. I'm waiting for delivery so I can't comment on if it is any good and I am a complete CNC newbie so I'm hoping this thread might become popular and eventually contain some advice for people who want to build cases for their amps. 

regards and best wishes

james

 

Edited June 12 by jamesmking

[Kerry]

Agreed

The foxalien machine looks decent with linear rails which are needed for rigidity when machining metal.  You'll definitely need a real spindle.  I noticed they include a 65mm support, but you really should look for one that supports 80mm and an ER16 collet.  

If you want to get fancy like @naamanf you could get one with an auto tool changer.

Have fun!

[jamesmking]

6 hours ago, Kerry said:

Agreed

The foxalien machine looks decent with linear rails which are needed for rigidity when machining metal.  You'll definitely need a real spindle.  I noticed they include a 65mm support, but you really should look for one that supports 80mm and an ER16 collet.  

If you want to get fancy like @naamanf you could get one with an auto tool changer.

Have fun!

Thank you Kerry. My plan, to begin with, is to modify existing hifi2000 cases and just cut holes for connectors and valve bases, do some engraving and more ventilation slots etc.. . I can't see myself scratch building a case any time soon, but I agree if I go down that route I will need more power and bigger tools. One thing that I am a little concerned about is the lack of software spindle speed control and I don't think there is a tachometer to tell you what the spindle speed actually is. But I guess I could get a hand held tach.

I notice that most high power motors are water cooled. I wonder if I could use my pcs 480mm r(4x 120mm fans and 80mm thick) radiator 🙂

 

Edited June 13 by jamesmking

[jamesmking]

A few useful basic CNC beginners videos I have found.

 

calibrating axis

setting up a spoil board.

problem solving issues

guide to bits

some speeds and feeds for aluminium and steel - starting at 20min 20secs

 

Edited June 14 by jamesmking

[jamesmking]

this stuff looks interesting  Cermark Spray for making labels on steel, unfortunately does not work on aluminium- Starts at  25:32.

marking aluminium with a lesser 

 

Edited Thursday at 10:41 AM by jamesmking

[jamesmking]

a speed and feed calculator.

https://fswizard.com/

 

[jamesmking]

Well I'm no longer a cnc virgin finished building the machine yesterday. Broke my first end mill today. 2mm carbide endmill trying to mill 27mm long ventilation slots in 3mm thick aluminium... first two slots went ok taking tiny nibbles at 0.2mm depth of cut and a feed slow increasing from between 10mm to 100mm per min.  Then I got a little too ambitious with the feeds going for 200mm feed and 0.4 and then 0.6mm depth of cut. Instant SNAP I guess this is to be expected.... I did hear the sound of the cutting change a little before hand but did not react in time...Post mortem on the end mill shows it got clogged up... guess I need cutting fluid a single flute end mill and more experimentation... I literally had to use plyers to extract the broken end from the aluminium it got welded in.

well just broke a second bit... 100mm feed 0.3 depth of cut is too much for the cheap chinesium 2mm endmill again the end mill bound and clogged up....

need to wait for some (hopefully better) single flute 2mm to arrive....

 

Edited Saturday at 05:44 PM by jamesmking

[Kerry]

Congrats  

It's been a long while since I've had any lollipops on my endmills.

I just looked at some of my typical settings.  I'm using 1/8" bits, < .039" (.99mm) depth of cut with a speed of 15" (381mm) / minute for most general cutting.  For a 2mm bit with longer cuts I might dial back the depth to .03" (.75mm) or possibly a bit less (not a typical operation for me).  I run the spindle at 14400 RPM for most milling operations.  Drilling and thread milling is slower (5K - 12K RPM).  YMMV

I have a mister with air, but I typically only use air.

I'm using these carbide single flute upcut bits:

Kyocera - 1/8" Single Flute

Kyocera - 2mm Single Flute

Onsrud - 1/4" Single Flute

They say for plastics, but someone had recommended them to me years ago and I haven't had issues since.

Good luck!

[jamesmking]

19 hours ago, Kerry said:

Congrats  

It's been a long while since I've had any lollipops on my endmills.

I just looked at some of my typical settings.  I'm using 1/8" bits, < .039" (.99mm) depth of cut with a speed of 15" (381mm) / minute for most general cutting.  For a 2mm bit with longer cuts I might dial back the depth to .03" (.75mm) or possibly a bit less (not a typical operation for me).  I run the spindle at 14400 RPM for most milling operations.  Drilling and thread milling is slower (5K - 12K RPM).  YMMV

I have a mister with air, but I typically only use air.

I'm using these carbide single flute upcut bits:

Kyocera - 1/8" Single Flute

Kyocera - 2mm Single Flute

Onsrud - 1/4" Single Flute

They say for plastics, but someone had recommended them to me years ago and I haven't had issues since.

Good luck!

Thank you for the advice and support Kerry,

I suspect the chineseium 2mm end mill is the problem.... rather than single flute it has lots of little burs on it and was garbage at clearing chips and sounded like shit at 10mm min cutting speed. I'm hoping single flute will be better. I have some single flute chinesium 3mm end mills and 6mm but I have not been brave enough to try them yet. Once I have got some experience I will get some good quality mills.

I tried some engraving with a 30degree 0.2mm chinesium engraving bit and this worked much better no breakages and a lot nicer cutting sounds. I did some rate tests and got up to 160mm 0.022mm depth of cut without breaking anything. I found the line quality slightly degrades as the cutting speed goes up so I settled on 100mm min. I have not tramed the mill yet or made a spoil board or levelled it so I was not expecting perfect results but the engraving is not bad.  The lines are a little thick for my liking (I made them 0.4mm wide in the cad) but I managed to cut through the anodizing without an issue at 100mm per min and 0.022mm depth of cut. Part of the e is missing in the volume text, but the text is quite small (which I knew would happen from the cutting simulation. I need a smaller angle engraving tool for the fine detail on the e, so I have ordered some 10degree 0.1mm engraving tools which the simulation shows will fill out the entire e). (sorry its slightly blurry just used my cheap phone could not be bothered to go slr and tripod)

For software I tried fusion360 - gui and user experience is diabolical as a lecturer I can get it for free  but I hated it. I settled on paying for vcarve desktop - it does what I want, is easy to use - I just wish it had adaptive tool paths. For sender software i'm using candle although I will probably go universal gcode sender.

 

I just tried 3.175mm single flute end mill and got chatter and lots of vibration of the aluminium I was cutting when going above 0.1mm DOC at 250mm/min. I suspect this is because:

1. I have not levelled the supplied spoil board,

2 I only used 4 hold cheap down clamps (material 430mm long, 90mm deep and 10mm thick) and I think painters tape + superglue might be better,

3 my machine is missing half the bolts. (carton containing all the bolts and washers split open in shipping and about half of everything must have fallen out of the box on route) 😞

On the other hand I did not break the tool  🙂

So I'm pausing experimentation until the rest of the bolts and a thicker spoil board arrive, then I can level and make more meaningful experiments... 

 

Edited yesterday at 11:04 AM by jamesmking

[n_maher]

1. Don't mess around with work holding.  Either get it clamped right or do an adhesive method.  You do not want to experience the carnage of a workpiece coming free.  

2. Similar to #1, I fully support the pause until the machine is built right.  It's kind of insane to be running it otherwise but maybe the missing bolts aren't in key places? (fingers crossed)

3. For anodized aluminum marking you should look at a laser.  I saw the one you posted above but didn't watch the video.  There are lots of them and used in conjunction with your CNC would likely but far better than an engraving bit in terms of speed and flexibility.  The other thing to consider would be a diamond drag bit, but those are very slow.  Some cool possibilities but mega machine time required. 

4. My personal approach is to not push feeds and speeds.  Just about any mistake/error with a CNC is catastrophic to either the material, tool, or worse.  Why risk it to save minutes?  It's not like you're trying to maximize a production rate in a shop.  Attempt patience.  Caveat - I lose mine all the time, YMMV, etc.