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CNC

Last update: 31/07/2015

accuratezza pcb

We cannot understimate the accuracy of a cnc machine when used to realize pcbs. If a machine is well done, without any backlash, the accuracy of the milling process can be really astonishing.



On the image on the left you can see a small test, in millimeters, of a milled pcb. As you can see even a 0.25mm tracks can be really well clean-cut.
 

The small test has been realized using a micro-ball (0.15), showing a few tracks in ascending order.

accuratezza pcb

 

Consider that it is really difficult to find on the market economic micro 2 flutes end mills but it is quite easy to find (chinese origin) economic micro-ball end mills or vgrove end mills. Very probably these end mills are created for low-end jewelry but they respond to our needs even if such mills need to work at low speeds.

Naturally there are end mills just created to realize pcb: 

 frese pcb

In the picture three different end mill are shown:

  • a 0.6 mm drill bit;
  • a single flute Vgrove for scoring (0.2mm);
  • a Vgrove single flute end mill:
  • a 2 mm double flute for pcb cutting

 

These are particular, but still cheap, end mills easy to be found on many shops, even online.


Molte volte riceviamo domande riguardo le frese, fresatrici, punte per forare ecc. al fine di creare circuiti stampati con il processo della fresatura. Il mondo delle 'frese', in tutta sincerità, è un vero e proprio universo e non è facile rispondere correttamente e concretamente. Sul mercato si trovano migliaia di frese diverse, buone, non buone, economiche, costose ma cio' che si deve sottolineare, almeno per quanto riguarda la creazione di circuiti stampati, è che non è assolutamente necessario l'acquisto di costose particolari frese per raggiungere lo scopo. Una semplice punta di trapano, molata, con la punta divisa a meta' ha svolto egregiamente il proprio lavoro nella fresatura di un circuito stampato.

 

bulini

On the market is quite easy to purchase 'bulins', or 'vgrove' mills. Such a kind of mills are really interesting to realize pcb. It is important to find an area oin the cnc machine characterized by a good coplanarity because even a difference of only 0.1mm of coplanarity could represent a  problem for the final result.

Such a mills are really cheap but they have a short life and must be changed (or resharped) quite often. Such a mills are really interesting because they can be purchased to realize very small groves (even 0.1mm) for the tracks.

Unfortunately very small double flute end mills (0.2-0.3 mm.) are too expensive (60-150 euro) therefore are not used in an hobbystic environment. The breakage of an end mill can be considered normal during a routing process therefore, in our humble opinion, it is better the purchase of 50, short lasting, end mills than only one high quality end mill (the numbers have a real proportion). 

Such a mills are really interesting because they can be purchased to realize very small groves (even 0.1mm) for the tracks, even if they must be resharped quite often and suffer from a short working life.


Unfortunately very small double flute end mills (0.2-0.3 mm.) are too expensive (60-150 euro) therefore are not used in an hobbystic environment. The breakage of an end mill can be considered normal during a routing process therefore, in our humble opinion, it is better the purchase of 50, short lasting, end mills than only one high quality end mill (the numbers have a real proportion).

 

When we have to purchase end mills, we have to know exactly which will be the material we have to mill, and accordingly to the material and the power of the electrical apparate used we have to choose the right bit.
 
Even in this case the experience will help a lot but  it is a must to read the data-sheet of the end-mill itself.
 
Every 'serious' manufacturer publish end-mill data sheets suggesting speeds, deep of the cut, material, number of turns etc.
Following the manufacturer suggestions will extend the life of the end-mill and will allow to have a perfect cut. It is necessary, therefore, be really careful when we buy an end mill because a lot of work and material can be thrown away just because we have chosen the wrong mill. 
A quick test on a piece of material before to start the real milling process will help to understand the 'reaction' of the material. Remember that it is better a double pass with half of a deep that a single pass at a full deep cut, the life of the end mill will be longer.
 

frese

Router bits, in the picture, are absolutely perfect to cut even in only one pass pcb boards and light material (light wood, balsa,  carbon or glass plates etc.).

They are very cheap and can be bought (reshaped too) in many on line shops in a large number.
In my opinion the most difficult materials to mill are aluminum and plastics. These material normally have a bad 'behavior' fusing  themselves around the head of the end mill and prevent to obtain a good result.

The solution to this problem consists in the use use of the right end-mill. A single flute end-mill will give to the burr enough time to escape from its site, preventing the kneading of the material around the cutting head of the end mill.

preparazione pcb

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