facet cutting speed

[hinksgf3]

Hi looking to purchase a new motor and speed controller for my gf3 faceting machine looking at a 120 watt 240 volt one but top rpm's are 1350 my question is this a fast enough speed for cutting?.I also have the option of a 120 watt 12 volt dc 3000rpm one buy then have to source a converter to run on 240 volts any help on whether 1350 rpms's is fast enough for cutting or not would greatly be appreciated. 

[MakkyBrown]

What pulleys has the machine got, if it is stepping down you may need more rpm. At 1:1 it might do. 
A slightly more powerful motor might be good aswell as my machine with a stardard 120watt 240v motor is underpowered imo.Lots of motors on ebay/aliexpress.
Cheers MB

[Bucket]

Not sure if you'd need a more powerful motor than the 120 watt one. I suppose it depends on what your cutting and how fast you want to cut. I notice that in the latest 'Facet talk',  Horst Ricker is quoted as replacing a motor in a Hall 2000 with a 120 watt 12 volt motor. Horst as you know is a gun with this sort of thing and if it's good enough for him, I would suggest that it should be OK. As far as the speed goes, I would suggest that the slower one should be OK. Gemcuts in NSW are apparently converting GF4 and GF5s to 12 volt, might be worth giving them a ring to find out what RPM they are using.

[Dihusky]

A point that has not been mentioned, the 12v motors DC so are variable speed and reversible which is a massive advantage.

[FlashGP]

12v power supplies range in price.  A conventional transformer based power supply to drive a 120w 12v motor  can cost more than $500 for parts and an electrician to build ut.  The big cost is in the transformer which is big and heavy.  But they are robust.

As a rule of thumb, you need about twice the wattage in your power supply as in the motor.  E.g . 120w motor needs a 240w supply.  At 12v that is 20 amps.

This is because at low speeds the motor impedance is lower so it draws more current.

BUT you can buy a Chinese 25Amp (300W) switched mode 12v supply for about $35 from Banggood if you don't mind waiting 6 weeks for it to arrive.  Aussie electronics suppliers have them as well but a little bit dearer.  If you blow a couple, it us still cheaper than a traditional supply.

 You should keep them under a little load for a longer life.  I use a 10w 22 ohm load resister across the 12v rails.  It dissapates 6w.  But a 33 ir 47 ohm resistor would be better, it wouldn't get as warm.

A 40amp reversable pulse width modulator (speed controller) costs abt $15 from banggood.

All up my power supply for my concave machine cost me about $100 to build, including a housing (half the price) and terminals and fuses (I put fuses on both speed controllers as I only have 10 amp wiring as my concave machine has 2 motors, both less than 60w.  My 2nd speed controller was a single direction 10 amp pwm costing abt $4.  It regulates oscillation speed.  You don't need it for a faceting machine.

I over rated the supply as a 25amp supply is only a few dollars dearer than a 10amp supply, and if I needed a bigger motor, I don't need a new supply.

I also have a 150w 12v motor as a spare for when my faceting machine motor blows.

Regards
Flash

[Dihusky]

Get hold of the guys at Motion Dynamics, they're enormously helpful and have all the gear you'll need.

[FlashGP]

I sourced my 150w 12v dc motor from them.