im currently running the fet 3 i m getting up to 48 imp but cut at 25 , or i loose steps , i am tossed up on what driver to buy , i like the idea of hobby cnc 4 axis is cheap , but it is unipolar which is what i am running now , what kind of gain will i get with running hobby cnc , i understand it will be faster but will i gain more torque out of the chopper drive , and would i get an even better gain to the hobby cnc by using a Xylotex driver instead

so to sum it up which driver is best and what improvements can i expect from what i am using now

thanks
curt

Hard to say. It depends on what voltage your'e currently using, what voltage you plan on using, what motors you're using....

The HobbyCNC can handle 3amps and up to 42V, while the Xylotex is 2.5A and really limited to about 28V (safely). So, with the right motors, you should be able to get a little more speed from the HobbyCNC if you use ~36V. If you're using 24V, they'll both be pretty similar. But it does depend on the motors you choose.

my power supply is 24 - 28v , motors are Vexta PH268M-E1.5B , from what i gather they are 120oz-in when run unipolar

I don't think you'll see much improvement using the same motors. What kind of machine? What screws are you using?

the router table is 48 x 24 , i m using 3/4 -6 acme screws
do you mean i will not see much improvement from what i have now , i thought that those drivers were much faster that the fet3

Imo, those motors are way too small for that size machine, and a 3/4" leadscrew. Actually, I'm surprised it goes as fast as it does.

In the past, I've heard of people roughly doubling their speed when switching to chopper type drive. But they were going much slower than you are.

Joe has a similar sized machine, running a HobbyCNC at 33 volts using their 200 oz motors and 1/2-10 acme, and can cut at 80ipm. http://www.cnczone.com/forums/showthread.php?t=15139

The drivers can only do so much, motor size and power supply are the biggest factors. It sounds like you are running a large machine, with havy coarse leadscrews on tiny steppers. I am surprised that you are getting the performance you are. If you want faster, you need more voltage and stronger steppers, and the appropriate drivers to run them.
I doubt you will see better performance just by changing drivers alone.
Colin

ya i ve been thinking about the motors , i think if i go bigger i ll gain the needed torque and gain some speed , as for the lead screws i use , to my surprise i lost very little torque when i changed over from the smaller screws i had , but the speed gain was doubled , with the steppers being .9 deg i didn t loose enough accuracy to worry about it , so maybe i should change the motors , the thing i liked about the fet3 is i can run up to 36 amp , so maybe i should take advantage of that

the thing i liked about the fet3 is i can run up to 36 amp , so maybe i should take advantage of that

You should only supply the motors their rated amps. Any more will just destroy the motors. The fact that the FET can supply 36 Amps isn't necessarily a benefit. A lot of that is wasted through resistors. A 3 amp/phase motor that would draw 6 amps with your FET, would probably run a lot better on a chopper drive and only draw 2 amps.

i agree , i use resistors but my point was that i can run large high amperage motors with this board, the other boards are limited pretty low
this is why i m asking questions , i m really not sure which way to go and at this point ,i really don t want to replace everything , because everything is new and i really would hate to waiste the money , so it is either motors or drivers , one has to go one has to stay

, so it is either motors or drivers , one has to go one has to stay

You could try to sell it all on Ebay, and replace it all. How much voltage can the FET handle? doubling the voltage might be the best bet, but you'll need bigger resistors.

50v max , resistors are cheap enough , i think for now i ll stick to bigger motors , probably be the best bet for now , i can always change boards later
www.kelinginc.net has some good looking motors for a good price

holy crap it was deffinitely the motors , got some vexta ph299 nema 34 motors off ebay got er moving at 180 in /min im gonna knock it back to rapid at 120 in /min and cut at 80 - 100 , finally in the ball park , ive read a number of posts slamming stepper world , but i m impressed , the only other thing i will change is the voltage , then that sucker will howl

ph299? I've had occasion in the past couple of days to go through the whole set of Vexta stepper catalogs and haven't seen that series designation. Could it be pk299?

I'm just curious if it's maybe a discontinued line, or if I managed to miss something in my reading.


Tiger

It's an older, discontinued motor.

Whew, thx ger. Thought I'd finally slipped over the hill and the mind was going ;)


Tiger

i can t find exact specs but from what i gather they are about 300 oz unipolar

sooooo


need to make a correction
, i at some point switched to half stepping so the software was picking up double the feed rate , i should have picked up on that right away , but i was so excited to connect the motors that i overlooked that or it was the glue fumes in my shop , either way i got a rapid from 80-100 but ill keep it at 60 to be safe
sorry for the confusion