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  #1  
Old Tue 20 April 2010, 09:57
javeria
Just call me: Irfan #33
 
Bangalore
India
Z dropping suddenly - computer response is slower

Hi All,

since yesterday , my Z axis has dropped twice while cutting - this once has spoil a work piece and once killed a 8mm endmill

off late I have observed that the computer is responding slowly- may be a virus or may be overheating- but well this is a atom based board and I don't feel so much heat is generated in that

now folks can you all let me know if you faced this droping Z axis - and the reasons and solution if you had cleared them- the Mach DRO does not change values.

RGDS
Irfan
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  #2  
Old Tue 20 April 2010, 10:21
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Dropping Z axes well known on ShopBots. The typical advice over there is:
- check that bit is not sliding out of collet
- check grounding/earthing (we had Z problems and cured this way then)

It was primarily because of the SB z-drop experience that our MMs got shielded/screened cables from day one.
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  #3  
Old Tue 20 April 2010, 11:30
hennie
Just call me: Hennie #23
 
Roodepoort JHB
South Africa
Irfan, myne dropped due to a Gecko that died.
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  #4  
Old Tue 20 April 2010, 23:59
javeria
Just call me: Irfan #33
 
Bangalore
India
I just finished a job which ran for 10 hrs and there was no Z drop- I think it is the 8mm collet which is giving up! and letting the endmill slip!
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  #5  
Old Wed 21 April 2010, 02:08
Kobus_Joubert
Just call me: Kobus #6
 
Riversdale Western Cape
South Africa
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I had a endmill GROWING longer if I cut to hard...looks like the extra friction causes the collet to slip on the shaft.
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  #6  
Old Wed 21 April 2010, 03:00
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
An up-cutting bit is pulled down by the cutting forces.
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  #7  
Old Wed 21 April 2010, 07:04
digger
Just call me: Milosh #113
 
Toronto
Canada
Quote:
Originally Posted by javeria View Post
I just finished a job which ran for 10 hrs and there was no Z drop- I think it is the 8mm collet which is giving up! and letting the endmill slip!
Irfan,

it happened to me, at the begining with my handheld router. I googled and found that collet has to be kept clean, and when you put your bit into the collet, don't put it to the end but about 1/8 of the end of the collet. After applying this technique, no problem.

Also, could be, as you said, that collet is giving up.
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  #8  
Old Wed 21 April 2010, 09:07
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
I have had different collets on my router that would just not hold the bit reliably. Find one that works and stay with it. All are not made the same as I found out.
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  #9  
Old Wed 21 April 2010, 15:18
Travish
Just call me: Travis #75
 
Wa
United States of America
Also look for any heavy cuts or full cutter width's with chatter. This can draw the cutter out of the holder as well. Over torquing of the collet nut will distort the holder, collet and taper of your holder or spindle, causing problems later on...... for a ER 16 collet nut you want to have 45-50 ft/lbs of torque. ER 20 collet nut you want to have 67-75ft/lbs of torque. Hope this may help.

Travis
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  #10  
Old Thu 22 April 2010, 04:47
javeria
Just call me: Irfan #33
 
Bangalore
India
The endmill I used is a 4 flute one with slippery shank- may be thats the reason for it to slip. need to be careful while doing this.
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  #11  
Old Thu 22 April 2010, 05:33
hennie
Just call me: Hennie #23
 
Roodepoort JHB
South Africa
Irfan where was the collets manufactured
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  #12  
Old Thu 22 April 2010, 10:57
KenC
Just call me: Ken
 
Klang
Malaysia
Irfan, what spindle speed & feed rate are you used with 4 flute end mill? I has great success in burning up carbide 4 flute end milling bits 10 minutes into machining...
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  #13  
Old Thu 22 April 2010, 13:22
digger
Just call me: Milosh #113
 
Toronto
Canada
Ken,

I remember reading from somewhere that if you have four flute cutter, your spindle RPM must be two times lower - you have two more cutters. I forgot about feed rate.
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  #14  
Old Thu 22 April 2010, 14:05
Kobus_Joubert
Just call me: Kobus #6
 
Riversdale Western Cape
South Africa
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Me too.... burning some end-mills on first try, that is why I cut with my cheap Pro-Tech cutters.
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  #15  
Old Fri 23 April 2010, 12:12
javeria
Just call me: Irfan #33
 
Bangalore
India
Well

you folks can just say that Irfan was in a hurry!
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