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### Author Topic: Mill brake when micro machining PCB boards  (Read 3214 times)

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#### pedroesteves.biosurfit

• 8
##### Mill brake when micro machining PCB boards
« on: December 21, 2009, 08:56:12 AM »
Good afternoon,i have a question.

I´m micromachining a a PCB board(copper material) ,i´m using a 0.254mm mill with 15000 rpm,and a 81mm/min feedrate,and taking 0.100mm per passage,however,the mill brake after a little while.
i´m consulting inumerus books off cnc machining ,and the values i use,aren´t too far diferent from the values from the books.

Does anybody have a sugestion?

Thanks

#### pedroesteves.biosurfit

• 8
##### Re: Mill brake when micro machining PCB boards
« Reply #1 on: December 21, 2009, 10:10:19 AM »
Even when i put an higher rotacion(30000 rpm),and lower feedrate(31 mm/mm) and deepht of cute (0.100mm), the mill(0,254mm) still brake.

I´m using the formulas and data from Gurhring and sandvik catologs to get this values.

N = (1000x Vc) / p x 0.254    adicional information Pi= 3,14 , Vc(for copper)= 27

F= N x Fz x Z ,                    adicional information    Fz=0,0005 ,  Z =2

I will apreciate any kind of help.

Thanks

#### Graham Waterworth

• 2,557
• Yorkshire Dales, England
##### Re: Mill brake when micro machining PCB boards
« Reply #2 on: December 21, 2009, 10:32:04 AM »
Are you using HSS or Carbide mills, PCB board is very abrasive and needs very hard cutting tools.

Graham
Without engineers the world stops

#### pedroesteves.biosurfit

• 8
##### Re: Mill brake when micro machining PCB boards
« Reply #3 on: December 21, 2009, 10:52:46 AM »
I´m using a carbide Mill from PMT.

I´m using a  two flute micro/miniature endmills are designed for the machining of small electronic components and highly abrasive materials.

that information is in the personal page of PMT,the brand of my miils.

I think taking all the right steps.

Proper mill,proper machining condition,good fixation off the mill and the PCB board ,good refrigeration...................Missing something?

#### gd.marsh

• 50
##### Re: Mill brake when micro machining PCB boards
« Reply #4 on: January 22, 2010, 07:19:17 PM »
How much run-out in your spindle? .. Even the high quality micro mills get beat up pretty badly by spindle run-out.

#### pjcevallos@gmail.com

• 18
##### Re: Mill brake when micro machining PCB boards
« Reply #5 on: April 11, 2022, 05:51:29 AM »
Hi Pedro

Can I ask what micromachining spindle are you using?
I was going to buy a Nakanishi, but the lead time is 4 months and I need something faster.

Best Regards

Pablo

#### kf2qd

• 132
##### Re: Mill brake when micro machining PCB boards
« Reply #6 on: April 19, 2022, 07:44:14 PM »
Too high a feedrate.