[cncfun1]

Hi All, I am not sure if this topic has been covered already, but i have a issue with a cnc milling machine we are building. It uses a JianKen Spindle JGL-80/1.5R24, which has a max rpm of 24000 and ISO20 taper

We are very happy with the performance of the spindle and are able to run up-to 3Cubic Inch MRR. typical cuts are
DOC = 5mm
WOC=3.2
feed rate is 3000mm/min

We are mostly cutting aluminium T6061 and using 9 and 10mm cutters, at between 19000 and 22000 rpm.
As I said the spindle performs as expected, However we are having an issue with fretting in the spindle taper.
We can see signs of fretting after only 4-5 hours of use at these typical loads, has anybody else experience issues like this?

I have attached images of the tool-holder fretting but similar marks can be seen on the spindle taper. Also this has happened on a few spindles so its not a one off.

any feedback would be greatly appreciated.

[mactec54]

Hi All, I am not sure if this topic has been covered already, but i have a issue with a cnc milling machine we are building. It uses a JianKen Spindle JGL-80/1.5R24, which has a max rpm of 24000 and ISO20 taper

We are very happy with the performance of the spindle and are able to run up-to 3Cubic Inch MRR. typical cuts are
DOC = 5mm
WOC=3.2
feed rate is 3000mm/min

We are mostly cutting aluminium T6061 and using 9 and 10mm cutters, at between 19000 and 22000 rpm.
As I said the spindle performs as expected, However we are having an issue with fretting in the spindle taper.
We can see signs of fretting after only 4-5 hours of use at these typical loads, has anybody else experience issues like this?

I have attached images of the tool-holder fretting but similar marks can be seen on the spindle taper. Also this has happened on a few spindles so its not a one off.

any feedback would be greatly appreciated.

Fretting can be more than one thing.

Bad fitting tools.

Not enough pull to hold the tool in the spindle.

Dirty Tools or Spindle.

Out of Balance Tools.

Too much cutting force / load.

Incorrect cutters for the job.

[cncfun1]

Hi Mactec54, thanks for getting back to me. I will try to address each of your points

1) Bad Fitting tools: I assume you are referring to the tool holder spindle fit, Note that the spindle and tool holder are practically new with very little run time, The tool holder is a good quality and made by Regofix, the accuracy of the spindle taper is unknown, we tried the bluing test and it appears to be OK, but I would not have allot of experience looking at these results.
2) Not enough pull to hold the tool in the spindle: The pull force was was increased to approx 900N, the spindle manufacture says that if we go any higher they are concerned about tool holder mechanism not functioning properly, do you think this is high enough pull force?
3) Dirty Tools or Spindle: We where very carefully in cleaning the tapers on the tool holder and spindle.
4) Out of Balance Tools: we don't really have a way to check this, do you know anyway of checking this?
5) Too much cutting force / load: This could be problem, we could try lowering MRR and see if that reduces the fretting. Also do you know if having a different ratio for DOC to WOC would make a difference, for example the cuts we where doing where DOC=5mm, WOC=3mm if we changed it to DOC=10mm and WOC=1.5mm, would that help?
6) Incorrect cutters for the job: The tools selected where specially designed for Aluminium so i think we are OK in that department.

Since the spindle quality is unknown we where wondering if the hardness of the taper might be an issue. Do you think that could cause an issue?

[mactec54]

Hi Mactec54, thanks for getting back to me. I will try to address each of your points

1) Bad Fitting tools: I assume you are referring to the tool holder spindle fit, Note that the spindle and tool holder are practically new with very little run time, The tool holder is a good quality and made by Regofix, the accuracy of the spindle taper is unknown, we tried the bluing test and it appears to be OK, but I would not have allot of experience looking at these results.
2) Not enough pull to hold the tool in the spindle: The pull force was was increased to approx 900N, the spindle manufacture says that if we go any higher they are concerned about tool holder mechanism not functioning properly, do you think this is high enough pull force?
3) Dirty Tools or Spindle: We where very carefully in cleaning the tapers on the tool holder and spindle.
4) Out of Balance Tools: we don't really have a way to check this, do you know anyway of checking this?
5) Too much cutting force / load: This could be problem, we could try lowering MRR and see if that reduces the fretting. Also do you know if having a different ratio for DOC to WOC would make a difference, for example the cuts we where doing where DOC=5mm, WOC=3mm if we changed it to DOC=10mm and WOC=1.5mm, would that help?
6) Incorrect cutters for the job: The tools selected where specially designed for Aluminium so i think we are OK in that department.

Since the spindle quality is unknown we where wondering if the hardness of the taper might be an issue. Do you think that could cause an issue?

What happens with tool holders is, when you torque the Pull Stud it swells the taper at the top end of the tool holder, it's not by much but enough to allow the taper to be tight at the top and not at the bottom, this can be what causes most of the fretting.

Balance, every Tool Holder has a Balance rating from the manufacture, G2.5 is good up to 25,000 RPM make sure what you have are in the speed range you are using.

[cncfun1]

Hi Mactec54 thanks for the feedback. Note that i have noticed that only about 75% of the tool holder taper is in contact with the spindle taper, due to the design of the spindle. I wonder if this is typical of an ISO20 taper or something unique to this spindle.see the image the light blue area is in contact with the spindle taper.

[mactec54]

Hi Mactec54 thanks for the feedback. Note that i have noticed that only about 75% of the tool holder taper is in contact with the spindle taper, due to the design of the spindle. I wonder if this is typical of an ISO20 taper or something unique to this spindle.see the image the light blue area is in contact with the spindle taper.

Did not attach you may have to resize the photo

[cncfun1]

Hi Mactec54, I am able to see the image and i had some other people check and they can as well, are you still not able to see the image?

[mactec54]

Hi Mactec54, I am able to see the image and i had some other people check and they can as well, are you still not able to see the image?

Thats strange I normally don't have a problem, but there is nothing that I can open or see, how did you attach it.

[dazp1976]

Thats strange I normally don't have a problem, but there is nothing that I can open or see, how did you attach it.

Same here.
If I really zoom in on it I see what looks like a white apple symbol. Very small one.

[cncfun1]

Hi guys here is the original image

[ger21]

No images attached.

[ihavenofish]

Is there a picture restriction for new users?

Without seeing the fretting or blue out, can only make some guesses.

1 is the taper is bad, obviously. jianken is high quality so, not likely, but mistakes happen.
2 is the tool is bad, but regofix is the best of the best, so seems very unlikely unless maybe it is fake?
3 the drawbar force is too low, causing the holder to be able to rock and spin. This is where id put my money.

[cncfun1]

thanks ihavenofish, i will try and measure the pull force