Isn't a desire of my own, from pcb laminates datasheets you can read
recommended drill bit speeds.
It is about 100.000rpm for an 0.25mm to 10.000rpm for 4mm. To drill a
0.5mm drill hole on FR4 is recommended 60.000rpm with infeed of 37mm/s.
But this is just to give a longer live to the drill bits. Lower rpm just
need lower infeed ( i guess).
On westwind
http://www.westwind-airbearings.com/pcb/index.html you can
see 80.000 to 210.000rpm spindles (in a price range like cars i guess),
they have air bearings, water cool and need a lot of equipment to
operate. Also the cheapest (but still expensive pcb cnc's) use cheaper
spindles like
http://www.centerline-inc.com/partners/kavo/kavo_product_documents.php of 60.000rpm.
You are right when say i should look at tool cost more than just speed.
Making a speedy machine but with big run-out will result in damage tools
anyway. And more than a carbide bit price, is a good bearing, which
should also live longer.
My only wish is to run between 30.000rpm and 40.000rpm all tool bits
bellow 1mm. But never bellow 30.000rpm for these. And i hope to make a
machine capable of this.
Simao
lcdpublishing wrote:
>
> I can understand and appreciate your desire for speed, however, there
> are many drawbacks to this speed as well. Heat is going to be a
> problem - keeping the bearings from getting too hot will be a problem.
> Making sure that the spindle and tool all run perfectly true - within
> 1 to 2 microns at worst is key. Any run-out at the tool will
> eventually cause the bit to wobble and that leads to breakage. Power
> is generally not an issue with these small drill bits, but if you are
> overdriving, you have to account for that in your power requirements.
>
> I have probably drilled a couple thousand holes in PCB stock using a
> large woodworking drill press. I believe the speed I am running at is
> around 2500 RPM. The most common size drill I have been using is .75
> MM (.030") and I go up or down from there for various components.
> >From what I have observed over time, the drills don't break or dull
> due to slow spindle speed, they break due to operator error -
>
> feeding too fast
> not having the bit aligned on center of where to drill
> moving the part sideways while drilling or retracting
>
> Speed helps, but attention to method will save more bits in the long
> run.
>
> Chris
>