[AchillesGr]

hi guys,
the last days i am trying to understand why i have bad surface when miling 7075 aluminium.
i am new without experience in these machines and i am searching to find the cause of all this.i measure my spindle runout at the er25 collet body and there is a 0.01mm runout per revolution.if i remove the er 25 holder and measure it at the spindle inself there is a runout of 0.006 mm .

my question is if this is normal and causes any kind of problems. as the endmil rotates i hear the sound changes in every recolution .
is this amount of runout normal?

my machine:
optimum bf20 vario
mt2 drawbar 10mm

no cooling
aluminium 7075

i have this machine not long time and one time i jamed the cuter so badly that the whole head rotated a bit and i forced to realighn the head.is it posible to bent the spindle and now have this runnout?

thanks

[underthetire]

Well, i had to convert , .0004" isnt too bad for an endmill. You need to start pushing on the spindle with an indicator, see how much it moves, and does it return to the same value. Are you using long or short holders, hows the belts in the head, is this thing stepper or servo, hows the lubrication on the machine? Box way or guides or ?? Coolant for the part? RPM and feed rates? Lots and lots of variables for a bad finish.

[mc_n_g]

Endmill sticking out too far from holder. Too deep of a cut. Play in the leadscrew. Crappy endmills. Wrong type of endmill. Wrong spindle RPM.
The list goes on and on. A picture would help showing what 'bad' is.
You talk about how bad the finish is but not one measurement or categorization of the the actual finish.

[AchillesGr]

hi,
thanks for the reply.
the endmill is a chinese 4flute plunge type.
i also tried endmils from 1/4 to1/2" chinnese too .
also tried cuting too much per pass and cutting too litle just to shape the finish.
still i get the wavy effect .
first i thought that the collet are faulty so i remove the holder and took measurement directly to the spindle.

i post some pictures to see the machine a have, the setup i did for spindle runout and the wavy finish. the last picture not showing too much since it was taken from my cell pfone and i thought it could do better than that. anyway, please take a look if you can understand what i am talkig about.
it seems to me that it is some kind of resonation but here i need your experience.

the cuting is made without any liquids and also with some wd40 that helped a litle.

if i push the spinle by hand i do not have relative movment to the head but i noticed if i push hard the head itself a have a movemend and flexibility relative to the table.

am i expecting too much from this machine?
they sell and advertice this machine for cnc conversion and the brand( OPTIMUM) is a very reputable in Europe. i cannot think that a company like that sells a machine 1800$ and another 10004 for cnc conversion that produces poor items.

Mc, what measurements and categorization do you need and how i do that?
thanks again!

[AchillesGr]

please note that i tried cuting with the side of the endmil and the bottom.the aluminium plate clamped in vice at the third photo have a slightly beter finish than the cut at the second picture that was made using the side of the endmill.

[mc_n_g]

First you should have the HSS endmill running with high RPM.
Aluminum should normally be cut with 2 or 3 flutes for chip clearance. The side cut like in photo 2 is ok with 4 flutes to keep more flutes engaged in the cut.

The endmill holder extends far out from the spindle. You will have some flex there when cutting. The endmill should be as far up in the holder to reduce that distance. The shorter the distance the less chance of flex.

You should not be climb cutting with a manual mill, you should be using a conventional type cutting style. Milling cutter - Wikipedia, the free encyclopedia

Once you start on a cut in a set direction you should lock the table ways so the table cannot move in the other direction. This should help remove play in the ways and a leadscrew on that axis.

You should take the indicator you have, mount it in the spindle (not turning) and measure the 'wave' height from the cuts. It may be a lot less than you think. Conventional cutting should take care of some of that. I am guessing you are seeing a combination of things: flex in the endmill holder, table moving because it is not locked, and possible not enough RPM.

There is also a possibility that the endmills you have are just crap. The endmills should not have any coatings (TiN, 'gold coloring' etc) and the flutes and bottom should be razor sharp. If they are not get new end mills. If the endmill has any built up aluminum on the cutting edge it will affect the cutting conditions.

Milling (like in photo 3) allows the part to flex a lot.
I also do not know if that is a proper milling vise or not. It looks like a drill press vise and that will not have the strength to hold well.