What is causing these machining marks ?

[Ken226]

The chatter marks shown in the photo is kind of misleading because I intentionally adjust the lighting to maximize their visibility. The depth of the marks is definitely not that much. I have tried to indicate the marks ( ball diameter of the indicator = 2 mm ), the TIR I get is about 0.003 mm or about one tenth.

Ok.

I'm assuming you've checked your spindle to make sure it's clean inside, no chips or burs, and tried different collets and different end Mills, just to factor out variables. Perhaps try without the collet chuck as well, with an R8/mt collet, or end mill holder, depending on your spindle.


Definitely ask on the model engineer forum. Guys with alot of experience on your specific machine would be a great source of info.

 

[mikey]

The chatter marks shown in the photo is kind of misleading because I intentionally adjust the lighting to maximize their visibility. The depth of the marks is definitely not that much. I have tried to indicate the marks ( ball diameter of the indicator = 2 mm ), the TIR I get is about 0.003 mm or about one tenth.

A carbide end mill spinning at 2,000 rpm should shear cut the material at light depths of cut. Too light and the end mill will deflect but if is deep enough to bite, a sharp end mill will cut shavings light enough to float in air and produce a nice finish. I cannot see how the head of the mill could be the cause of this. Something is loose somewhere.

Are you sure the is no slack in the Y-axis leadscrew?

 

[compact8]

Are you sure the is no slack in the Y-axis leadscrew?

There is definitely some backlash, about 0.04 mm which should be normal.

 

[mikey]

So, you're conventional milling this, right? That is, if the edge of the work is sticking out the right side of the vise, your end mill contacts the work piece at the front first as you pull the table towards you in Y.

 

[compact8]

So, you're conventional milling this, right? That is, if the edge of the work is sticking out the right side of the vise, your end mill contacts the work piece at the front first as you pull the table towards you in Y.

Yes. I know climb cut is not for machines with backlash

 

[mikey]

Okay, if the gibs are tight and there is no significant backlash and you're conventional cutting then I can't think of anything else.

Try asking Graham Meeks and let us know what he says.

 

[compact8]

Try asking Graham Meeks and let us know what he says.

Thanks for the referral. Graham Meeks replied to my post there and said that he also encountered the same problem on his Emco FB2. The problem can be alleviated / solved by changing the tool.

The thread :

404 | Model Engineer & Model Engineers Workshop

It looks like we've lost a piece!404: Page not found This page could not be found. Maybe try a search? If it's a forum topic you are looking for, ...

www.model-engineer.co.uk

 

[mikey]

Huh. One is again reminded of the folly of assumptions and/or shallow thinking. I should have caught that.

Did you change the tool? What happened?

For aluminum, high helix end mills work well. Niagara Cutter and Brubaker make good ones, as do others.

 

[compact8]

Did you change the tool? What happened?

I meant Graham Meeks replied that the problem was solved or alleviated by changing the tool to those with larger rake angle. I have ordered this one which is supposed to be optimized for cutting aluminium. Will see what happen.

 

[Ken226]

I meant Graham Meeks replied that the problem was solved or alleviated by changing the tool to those with larger rake angle. I have ordered this one which is supposed to be optimized for cutting aluminium. Will see what happen.

View attachment 391595 View attachment 391596

That looks like a Yg1 Alu-Power 3 flute? If not, it's pretty much identical.

I used them with excellent results in 6061. Be careful, the flutes will shave the hairs off your arm. I've cut myself a few times handling them.