Is this facing finish normal?

[plastikdreams]

When I finish face I go one way the back the other without stepping over. It takes a little extra time but yields good results.

 

[MiniMillMachinist]

When I finish face I go one way the back the other without stepping over. It takes a little extra time but yields good results.

I’ll give that a try, thanks!

 

[Ox]

Funnily enough if I push the cutter harder with a deeper cut the spindle tilt from the cut is enough to knock out the trailing edge of the face mill from the cut, I then don’t get the cross hatched lines and nor do I get the pattern.

That's to be expected, and the bigger D the face mill, the quicker that will happen.
Tool pressure has to go somewhere.
That's nothing to worry about.


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Think Snow Eh!
Ox

 

[MiniMillMachinist]

I see a light/dark pattern that's probably about 6mm pitch. My guess is even doing a long surface finish measurement, any error you'd see is well within any spec for the machine. Machines aren't perfect, not even a Haas. If you want to machine mirror finishes you need a different tool. OTOH, you can probably hide that stuff by using inserts with the right radius and possibly choosing material with different something. I don't know what that something is because I don't know what the material is. Looks kinda gold- is it brass or bronze?

Thanks Conrad, yes it’s brass. I am thinking a wiper may help the finish, but not sure!

 

[Milland]

If you place your indicator in the spindle, and rest the contact on a smooth ground surface in the vise, then forcefully push down and up on the spindle (without touching the indicator or rotating the spindle), how much deviation do you see on the indicator, and does the reading return to origin when force is removed?

 

[CarbideBob]

Thanks Conrad, yes it’s brass. I am thinking a wiper may help the finish, but not sure!

As a very general thing brass does not like wipers.

 

[Ox]

As a very general thing brass does not like wipers.

Well that's an interesting statement?

360 works well with form/shave tools / step drills.
Why would a wiper be any different?

I have not milled much 360 ever that I can think of.


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Think Snow Eh!
Ox

 

[rons]

When I finish face I go one way the back the other without stepping over. It takes a little extra time but yields good results.

Years ago somebody said that a better finish is obtained by titling the head and going in only one direction.
I found that to be true.

 

[CarbideBob]

Well that's an interesting statement?

360 works well with form/shave tools / step drills.
Why would a wiper be any different?

I have not milled much 360 ever that I can think of.


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Think Snow Eh!
Ox

Too much talk I guess.
I will do

 

[Ox]

That was a real question, not a challenge.


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Think Snow Eh!
Ox

 

[MiniMillMachinist]

Side note, but does anyone have experience with the Sandvik R590 face mills? Tempted to try one out with a wiper but they are a small fortune.

 

[Milland]

Side note, but does anyone have experience with the Sandvik R590 face mills? Tempted to try one out with a wiper but they are a small fortune.

No interest in trying this to see if there's issues with the spindle bearings? It could be other things, but it gets you started if there's looseness in Z.

"If you place your indicator in the spindle, and rest the contact on a smooth ground surface in the vise, then forcefully push down and up on the spindle (without touching the indicator or rotating the spindle), how much deviation do you see on the indicator, and does the reading return to origin when force is removed?"

 

[MiniMillMachinist]

No interest in trying this to see if there's issues with the spindle bearings? It could be other things, but it gets you started if there's looseness in Z.

"If you place your indicator in the spindle, and rest the contact on a smooth ground surface in the vise, then forcefully push down and up on the spindle (without touching the indicator or rotating the spindle), how much deviation do you see on the indicator, and does the reading return to origin when force is removed?"

Hi Milland, sorry, I missed your comment - I haven't done this yet but I will. Remember around 6 months ago you commented in my thread where I was having issues with my spindle? This was replaced and sorted out my issues at that time. The fact that no matter how fast I run the spindle, or how fast I feed the lines are evident at the exact same pitch as the ballscrew says to me it's more likely related to feed or physical motion via the ballscrew though. Bear in mind these lines are absolutely microscopic and can't be measured with a 2 micron indicator, it's just the way the light is bouncing off the cut. Thoughts?

 

[Milland]

It does sound more likely a function of a slightly bent or "drunken thread" (where the thread is not on the same axis as the rotating axis of the ballscrew), but if you think you're sorted on the spindle then perhaps it's not worth taking time to check it further. Won't hurt though...

 

[MiniMillMachinist]

It does sound more likely a function of a slightly bent or "drunken thread" (where the thread is not on the same axis as the rotating axis of the ballscrew), but if you think you're sorted on the spindle then perhaps it's not worth taking time to check it further. Won't hurt though...

Interesting... would that affect the feedrate of the machine, or impart physical motion onto the table up/down/side to side within the tolerance of the linear bearings? Hope I'm making sense! This isn't a huge concern since I'm very happy with the parts coming off my machine now, and I've seen similar effects in face milling paths in other machines. Just a curiosity more than anything. I noticed the effect is less noticeable in the center of the table, where any bend in the ballscrew would have the least effect on the motion of the machine. The effect seems most visible at the extremes of X. Unfortunately for me, I'm running twin vices with double jaws, so most of my machining happens at the furthest points of X and Y.

 

[Conrad Hoffman]

IMO, it could be some subtle imperfection in the lead screw. Again, nothing is perfect. The error needed to cause a visual effect can be really small and below any numbers the manufacturer would be willing to guarantee.

 

[Milland]

Interesting... would that affect the feedrate of the machine, or impart physical motion onto the table up/down/side to side within the tolerance of the linear bearings? Hope I'm making sense! This isn't a huge concern since I'm very happy with the parts coming off my machine now, and I've seen similar effects in face milling paths in other machines. Just a curiosity more than anything. I noticed the effect is less noticeable in the center of the table, where any bend in the ballscrew would have the least effect on the motion of the machine. The effect seems most visible at the extremes of X. Unfortunately for me, I'm running twin vices with double jaws, so most of my machining happens at the furthest points of X and Y.

It does make it sound a little like ballscrew error, but whether it's worth pursuing I doubt. In theory the linear bearings should be stiff enough on their own to mask minor perturbations of the ballscrew, but as the saying goes, everything is rubber...

 

[ernieflash]

people strive to GET that finish !!!
nice work

 

[dcsipo]

Hi dcsipo, thanks for the reply — the inserts are all within a few microns according to the renishaw tool setter (I swapped them out and flipped them to get them all as close to perfect as I could). Appreciate the tip on the fly cutter — I’ll give that a go and see how she finishes. Sadly no, the frequency of the lines stays the same. I can only imagine it’s some trick of light due to some microscopic height difference due to the slightest misalignment of the ballscrew or a tiny bend. Can’t be much or I imagine the ball bar would have picked it up!

Funnily enough if I push the cutter harder with a deeper cut the spindle tilt from the cut is enough to knock out the trailing edge of the face mill from the cut, I then don’t get the cross hatched lines and nor do I get the pattern.

Are you getting the same pattern in steel with steel inserts, or is it just non-ferrous with non-ferrous inserts? (I assume that you are using the correct insert for the material ) It would be interesting to see if you get the same with a fly cutter on brass using hss and zero rake. That would tell you if it is tool pressure related. Some non-ferrous inserts tend to be a bit grabby in brass.

 

[michiganbuck]

I used to put a small flat on an end mill end outward place near the corner ( the distance of one feed per rev) to blend in that effect, a small radius can also help eliminate it, and a dulling tool that has suffered a small wear land helps eliminate it...
Not much way to get away from with not having a slight scalp cut in one pass travel to the next by deliberately setting a tad out of tram.
less end dish on an end mill end allows faster Beak-in making the slight wear land flat.

Very accurate end mill end sharpening (or setting inserts on a mill cutter) so one tooth is not high is another important thing to consider.