Mini mill vibrates a lot

[Ken from ontario]

Thank you so much for your answers and help.



I was triyin 3 mm because I have read you should use up to the half of the end mill OD, but now reading you I now I was wrong. This calculations must be for bigger and more quality machines.

And yes, I removed, cleaned and oiled all the gibs.

It takes a while to find what works best with these small mini mills, to figure out feed , speed, and depth of cut with these machines is something you need to also feel and hear, I am still learning everyday especially with new tools or different materials.

 

[Eyerelief]

I started out many years back with a small mill like that. I had much better success with four flute cutters, even in aluminum. Carbide for steel, HSS for everything else.

 

[homebrewed]

I have an SX2 mini mill and my typical depth of cut is around .01" for steel. More than that and the vibration gets pretty bad. DOCs can be greater for softer materials. I have a few 2-flute end mills and they are much more vibration-prone than the 4-flute ones. I have a 1/2" roughing mill that allows me to go to somewhat greater DOCs but it's not a huge improvement, maybe 2-3X is all.

These small DOCs can make some jobs take awhile so when I have have to remove a large amount of material I look for alternate ways to remove the bulk of it. As part of that I graduated from hack saw to portable bandsaw and eneded up with a 4x6 bandsaw. Just going from a hack saw to the portable bandsaw was a significant time saver. Not to mention arm saver Sometimes I end up with small but usable pieces for something else. The HF portable I use is pretty noisy so I wear ear protection when I use it.

I also got a few slitting saws and an R8 arbor for them, pretty much for the same reason. I also have to cut pretty slow with them but, again, they can release a larger chunk that would otherwise be turned into swarf (lots of swarf = lots of tme spent). And they leave a pretty nice surface behind.

 

[Shotgun]

Have you tried packing the column and base? I have an RF-30, a bit larger than yours, but still had a lot of vibration. I packed the column and base with a portland cement and granite gravel mixture. Didn't turn it into a Bridgeport, but did improve the vibration quite a bit.

 

[Alberto-sp]

Thank you so much again for all your help.

Ok first idea, I overstimated my machine. Second, 2 flutes sucks haha.

Well this is about the journey, not the destination and I have to learn that I´m going to make some mistakes and trow away some money. But now I feel comfortable knowing that the machine is not broken. I almost buy another model, a little more expensive but it wheights double, but size and weight is a concern in my house. I have the shop in the rooftop over the bedroom (This is why I can´t pack with concrete the mill)

So it´s OK, need to be patient and less RPM and DOC.

Nevertheless, next week I have some free time and with a dial indicator I´ll check all the measurementes you told me.

Thank you

 

[Road_Clam]

Couple setup questions. First is how is your mill bolted to your table , and what material is the table made of ? With a mini mill wood is your friend. Wood offers a robust table surface, AND helps to deaden harmonic vibrations. Second is how are you holding your endmill ? You always want to keep unncecssary protrusion length to an absolute minimum. Looks like you have your mill sticking out pretty long. This festers vibration. Lastly is rpm's in certain circumstances you want to slow down your rpm's and increase your feedrate.

 

[Alberto-sp]

Hello. I have been taking measures and trying to align the mill. At the beginning I thought tath I got it but not.

I have been taking the measurements in this way

Clamping the square firmly (It suposed to be a good square, chinese but not cheap) in diferent positions. But the measurementss change in each place of the table. For examenple, in the left side, in 150mm of path, the deviation is only 0,01mm, but in the right side is 0,3mm.

Even in the same place, if I flip the square, like in those pictures, I have diferents measurements. In the right one is almost perfect. 0,01mm in 130mm, but in the left one 0,12mm in the same path.

Every time I clamp the square I clean the base of the square and the table very well, and there is no visible dents. And I put it in the exact same position but flipped. How can it be possible? Y used only one clamp in these pictures but I use 2, the results are the same.

If I can´t trust the square, aling that milling machine is going to be complicated.

Nevertheless, what tolerances are OK for tath machine? How many 0,01mm per 100mm are tolerable? Because, I can try to get better align, but the more acurate I want to be, the bigger dificult it is, so I´d like to know how much I need to archieve

Road_Clam​

The table is made of steel, and there is 20mm hard rubber betwenn the table and the mill. And yes, I use to golde the end mill the shortest posibble, but I forgot about that in the video.

 

[Shotgun]

Attach your indicator to the quill and drop it to the table. Run the table back and forth underneath it, writing the measurement down every few inches (cm for you . I bet your table is wavy. My RF-30 table (much larger) was.

And I have serious doubts that having the indicator out on the end of that flat bar is doing you any favors. It's going to introduce all sorts of inconsistencies. Again, attach the indicator to the quill.

 

[Alberto-sp]

Thanks for your answer. Ok, I have attached the indicator to the quill, and the arm is very tight. I have repeated all the measurements to check that they are consistent.

In the first test I have attached the indicator to the quill and in each "way" , using the left side as reference "0" i have move the table until the indicator probe reach the other side, not really side to side, but 300mm. The + mean the table goes up.

In the second test, I have attached the indicator to the quill and took the lower way as reference 0. Move the table until the indicator probe reach the upper way.

The red numbers indicate that in each test I have moved the indicator, while the black numbers indicate that I have to move the indicator and the table

What do you think about that results?

Thank you

 

[Shotgun]

For my reference 0,04mm is about 0.0015"

So the table is off by a couple thou at most, but I'm bothered by the "moved the indicator". I don't know how you're going to get a repeatable measurement if you move the indicator. I'd lock the indicator to the quill, move the quill down to engage the indicator, then lock the quill. The only thing that moves is the table. Use a ruler to lift the probe when crossing from one way to the next. Drag the probe down every way. Write the measurement directly on the table with a sharpie (alcohol or any other solvent will take it off later). Measure at both the front and back of the ways. For extra credit, connect similar measurements with a line to get a topographical map of the table.

You'll find that the table has dips and rises that are impossible to see. When you clamp your square to the table, did you clamp a corner that was sitting in a valley? Maybe one side was on an incline? Measuring accurately at this level is a whole new world that I know barely enough about to speak to. But, I mounted a cup style grinding wheel in a collet, and was able to grind off the high spots from my table. My RF-30 had peaks as high at 0.006" (0,15mm)