My first climb milling

[BobWarfield]

Remember the trammed cut was a much deeper cut, not a finishing cut. You can see the pass doesn't cover the entire width of the plate, and you can see along that edge the depth of cut is pretty heavy!

The other cut was done with a different flycutter:



It's the one on the left, but adjust to its widest extent. The longer arm makes it much more sensitive to tram.

With that said, many prefer not to see the double cut pattern because they feel the single cut looks better. Many professionals intentionally run slightly out of tram to deliver a better surface finish. A discussion of how much and the tradeoffs can be found here:

http://www.cnczone.com/vb...ight=face+tram

There are also some cuts done with a 7 insert face mill here for comparison:

http://www.cnccookbook.com/CCMillYMount.htm

The 0.006" cuts leave a nice finish. On the face mill, you can see an out of tram pattern that I think has more to do with one insert hanging low than tram.

The metal you saw the dovetail cutting is 6061 aluminum, but it cuts steel or cast iron just about as well. If you make one, be sure to read the notes on my page about using different inserts!

Cheers,

BW

[alexccmeister]

Hi Bob,

Great info. Appreciate it very much. Can I say to get a smoother finish, best to use a cutter with slight radius at the tip? I see your fly cutter on the left has a cutter with a slightly rounded tip.

Alex

[BobWarfield]

A radius is helpful.

Keep in mind that the flycutter is largely cutting "across" rather than plunging "down". The radius and cutter geometry must be considered in relation to that. I have an HSS steel flycutting tool given to me by someone on these boards (sorry, don't want to have him deluged with requests!) that delivers absolutely gorgeous surface finish because it has just the right radius, rake, and angle for what's really happening when flycutting. Standard lathe tools are not quite optimal, though they're what I currently use.

Eventually, I will get some time to learn how duplicate the shape of the special cutter and will publish the results to my blog.

I've also noted some wonderful surface finish on the lathe with a round insert tool. At some point I plan to try that on the flycutter. There are some companies that make flycutters that use these inserts that the guys on the PM board say are fantastic. One thing about a round insert is the geometry is simplified--its round no matter what direction you come at it!

It wouldn't be too hard to put such a holder in your flycutter if you were minded to try it.

Search "RCMT" on this page to see these round insert holders and the surface finish relative to CCMT:

http://www.cnccookbook.com/CCBlogJul2008.htm

I just bought an inexpensive round insert end mill, 1" diameter, from Shars to try out on the mill and see how the finish looks. If I like it, I may go to round inserts for the face mill.

Cheers,

BW

[alexccmeister]

Hi Bob,

Thanks, will try that. I did another flycutting last night. I think I may have another problem. When I cut a larger piece of aluminium, I wrote a Gcode to cut in 2 linear passes 15mm apart. The first pass looked ok but when the 2nd pass come, I notice the edge that was cut by the first pass is so deep that the 2nd pass can't seem to remove. I thought the next depth cut will remove this but then the first pass always cut into the work piece. I am beginning to think now that my dovetail or the spindle is not 90 degree to the table. More leaning to the front. I got my table trammed but now I have this leaning issue. What I did to remove this problem is adjust my flycutter out until the diameter it makes is slightly larger than the work piece.

I measured the thickness of the piece and found the difference in thickness on opposite side is 0.17mm or 0.006". Is that good enough? Obviously not truly parallel to each other.

Any thoughts Bob?

Alex

[SpeedsCustom]

.17 seems a little high to me.


You need to shim your z-axis.


-Jason

[alexccmeister]

Hi Jason,

Will do that. What sort of difference is good enough? Thanks.

Alex

[ImanCarrot]

Many professionals intentionally run slightly out of tram to deliver a better surface finish

I do that, mainly because if the tool is cutting on the "back" stroke it will rub and wreck the tool.

Another thing you could try is if you're cutting from right to left traverse and your back stroke is hitting then just cut left to right instead- that will elliminate the back cut- think about it- if the head is slightly angled this will work.

[LeeWay]

Good stuff in this thread. In my experience, limited at best, if the machine is out of tram in either X or Y, you can sometimes use different paths to get better results. Getting perfect tram in both directions on an X2 was a little difficult for me. It would just flex out if the cut was too deep.
It's easier on my cnc mill. I just got lucky and it was dead on in the Y direction and I never had to add any shims at all.

I added some adjusters to the sides to make it easier to do in the X axis. I get much better results now with both end mills and flycutters and face mills.

I think for a bench sized machine, the smaller the cutter you choose, the less error you are going to have. Especially true if tram isn't within acceptable limits.

Before I trammed my mill the last time, I used a two cutter face mill for roughing, then I pulled out one insert, sped it up some and took a shallower final pass. While I could see where the cutter had ran, I could not feel it. It was purty. This face mill, BTW, has rounded points on them. Very minimal, but not a sharp cutter.


Oh, one other thing. Some aluminum doesn't mill for me very well at all. 5000 series stuff seems exceptionally gummy. I won't be buying anymore of that stuff. I think the sheet and plate I had was 5052, which I think you can heat treat. If so, it sure needed it before milling. Nasty stuff.

[alexccmeister]

Ok, I unscrew the three column bolts and tried to put some shim under it. Anyway before I did that I checked the level with a dial gauge. Assuming the table itself is flat, there was a obviously a difference in level back and front.

So I shimmed it slightly and tightened the bolt. The difference in level got real close. But the thing is when I press down on the spindle head, I can see the dial move. Beign an X2, I am not surprise. So my next project will be to beef up the column with a rectangular section at the back.

After doing the tramming in the Y direction, it got me thinking. Is my table running parallel with the column or is it raked at an angle. Didn't get too far with that though. Haven't got the right fixture. Any advice on what is the best way to make sure the column is parallel with the table?

Alex

[LeeWay]

I think to check the table, you first have to have it trammed correctly. Once it's trammed in mid table, then you can run the extents and see how it lays.

If the table is off by very much front to back, it might make the whole process pretty difficult. The column on the X2 is far less than rigid. I think that is the right move, to beef that up. I have seen some pretty good solutions on here and the Yahoo site. Throwing some steel at it should help with the rigidity as well as tram retention over time.

[alexccmeister]

Hi Lee,

Tramming the X axis is easy enough. But problem is with tramming the y axis. I have to shim it as well as adjust the column so its trammed with the Y axis. I just need to get the right gauge holder before I can even check whether the X table is parallel with the column. Thanks.

Alex