What is causing these machining marks ?

[compact8]

I am getting this irrespect of the material and depth of cut. In the photo ( picture 1 ) it's a piece of aluminium ( not sure what type but softer than 6061 ). The tool is a 10 mm carbide end mill and conventional cut was used. The feeding was done manually and on the slow side. It's purely an aesthetical issue but I would like to know the reason. There was no chatter. Is it due to spindle runout ? or poor rigidity ? or other things ?

Update :

I subsequently did a cutting test under different settings and found that the relatively poor finish occurs only if the cutting is done along the Y axis. The only reason I can think of is the poorer rigidity of the head which is expected to flex / oscillate more along the X axis .

Details :

machine : Emco FB2 bench mill, weight about 300 lbs
workpiece material : 6061 aluminium
tool : Carbide end mill 10 mm diameter, run out measured next to the collet face = 0.01 mm TIR
spindle speed : 2000 rpm
feed speed : 65mm / min power feed ( along the X axis ) , about 80 mm / min manual feed ( along the Y axis )
depth of cut : 0.1 mm ( finishing )
length of cut : 9 mm
conventional cut
all axes with no motions including the quill locked
cutting fluid used ( Rocol )
set up shown in picture 2
surface finish comparison shown in picture 3.

 

[T Bredehoft]

Is this cut done with the side of the cutter? (as opposed to the end?) What was the RPM of the cutter?

 

[compact8]

Is this cut done with the side of the cutter? (as opposed to the end?) What was the RPM of the cutter?

Yes, it was done with the side of the tool. The RPM was 2000 which is the max the machine can do.

 

[T Bredehoft]

I'd guess your tool was bouncing, dunno what to suggest .I'd use a heavier tool for that.

Was the spindle clamped? (Vertical Milling machine?)

 

[JimDawson]

Hard to say what is happening, but it looks like chatter. I would try increasing the feed speed.

 

[higgite]

I'd guess your tool was bouncing, dunno what to suggest .I'd use a heavier tool for that.

Was the spindle clamped? (Vertical Milling machine?)

And were the 2 axes that weren't in use for that cut locked?

Tom

 

[macardoso]

How securely was the part clamped? was it hanging off the end of the vise a ways?

 

[keeena]

Certainly looks like chatter. What size is that piece? I assume it wasn't hanging out too far from the vise? A pic of the setup might help.

What was the WoC? Do you have a powerfeed option? Hard to quantify "slow" as far as hand-feeding.

Do you have an HSS EM you could try? Seems carbide wouldn't be the right choice here...

 

[markba633csi]

I think the problem is all in the cutting tool. Try a sharp HSS endmill and I bet your problem will disappear
-M

 

[compact8]

Thanks for all the replies. I will try again and report back with photos and other details mentioned.