Messages

21

General Mach Discussion / Re: servo selection.......

« on: October 01, 2008, 07:21:10 PM »

Original poster is obviously not going to use the machine in a commercial
environment.  If he was a good used VMC would be a much better
 than an "old knee mill"

He can get about 220 ipm rapids with the PP and a divide by 4 on the drive.
This would take the table 18" in 4.9 seconds. 
Are his ballscrews designed for that kind of rotational inertia?
Does he even have ballscrews?  Was his machine designed
to take high speed rapids?

Speed is nice to oooh and ahhh the bystanders but how much time does
it really save?  Very little unless you are making parts day-in and day-out.

I set my BOSS to 80 IPM rapids and I program so I spend my time cutting
parts and not rapiding.

A router, plasma, etc would be a different story as you are moving a
lower mass and usually moving it a much larger distance.

Scott

22

General Mach Discussion / Re: servo selection.......

« on: October 01, 2008, 06:24:46 PM »

Go with the minimum encoder count available.
Use a servo drive that has "electronic gearing" such as the
G340.  (Not the best, -but the best bang for the dollar)
Save your money and don't bother with a smooth stepper.
Get a 1.8 Ghz or better computer running XP or XP pro.
Use the parallel port to drive the servos (through a break out board)
and you will get all the rapid speed a knee mill can handle.
Forget the G100.....99.5% of all mach users use the parallel port. 
I just picked up a P4 at 1.8 ghz and 512mb ram with 40 Gb hard drive
for $199.
I use a similar machine on my BP series 1 with no issue. 

Scott

23

General Mach Discussion / Re: Proper way to pause program for tool change

« on: November 13, 2007, 04:23:27 PM »

Thank You,
I appreciate your response.


Scott

24

General Mach Discussion / Proper way to pause program for tool change

« on: November 13, 2007, 11:39:52 AM »

I have no automatic changer on my BOSS.
I tried M6 in the program, but the program just runs right past it.
M0 works, but I don't think this is the right way. 

What is the proper way to suspend program execution so I can
change tools?

Thank You,
Scott

25

Show"N"Tell ( Your Machines) / Re: My Self Built Router

« on: July 19, 2007, 06:30:04 PM »

Very, Very nice. 
Thanks for sharing.
Someday I would like to build a router like that.


Scott

26

Show"N"Tell ( Your Machines) / Re: Help! Hardinge CHNC Retrofit

« on: July 12, 2007, 06:46:09 AM »

I don't have the encoders on my ballscrews right now.  I use 1000 CPR
encoders on my motors.  I am just warning that if you have some backlash
in your system,  having the encoders on the screws can cause serious
dithering problems.  The system has to be tight.  Some used machines can
get a bit sloppy.

Having your encoder on the ballscrew will help you with the 128 count problem
that the Gecko drives have.  The 4:1 reduction you have between the motors
and the encoders will actually cause the system to see the encoders as 250
line units which is more ideal for Gecko's. 

Just the inertia can cause these drives to trip if accelerated too high. 
Once the commanded position is 128 counts out of sync with the encoder
position, the drive will trip.  I can trip my drives by just spinning the motor
too fast. (over 2200 rpm or so).

Dennis,  I looked into the Viper drives and was not really impressed with their
construction.  I would like to hear some feedback from someone who owns one.


Good luck.

27

Show"N"Tell ( Your Machines) / Re: Help! Hardinge CHNC Retrofit

« on: July 11, 2007, 07:05:23 PM »

I don't think you want to mount the encoders onto the ballscrews.
Your servos have a 4:1 reduction and the ballscrews are 5 TPI.
The system may break out into oscillation because of the backlash
between your reduction/ballscrews/motor. 
Your following error will be way more than the Gecko's can handle.
They are great drives but sadly they have one shortcoming, and it
is a big one.   The following error is permanently set at 128 encoder
counts.  Not good. 
There is not a single servo drive currently on the market that takes
step and direction and is capable of driving large servos reliably.  Rutex and
CNC Teknix are both having serious troubles with their drives and are
in the redesign process.
Gecko has the short coming I mention above. 
I am using small 12.5 in-lb Baldor servos with 1000 line encoders
driving a series 1 BP mill with 4:1 reduction between motor and
ballscrew.  I am using Gecko drives and they are probably the best
currently out their until CNC Teknix and Rutex get their drives
redesigned.  I have constant problems with my drives going into
error state due to the small following error.   The only solution is
to keep my drive rates low.  I use 80 IPM rapids when my motor is
perfectly capable of driving my table at almost 200 IPM.
Granite devices is the best drive available if you can deal with a
12.5A peak current for your motor.  http://www.granitedevices.fi/
Most of us need 20A or better for our larger machine tools.

Best luck,
Scott

28

Competitions / Re: ******Guess and win a G100 Grex******

« on: May 22, 2007, 06:35:56 PM »

Did you count them all Brett?

How about 2,100,000

Scott

29

General Mach Discussion / Re: Can use both LTP Port

« on: April 22, 2007, 09:01:09 PM »

I want use both LTP 1 and LTP 2, because i want use encoder for xyz axis. Need too much input, 1 LTP just have 5 input. If i use LTP 2 port I have more than 17 input. That right? 

Yeap. See picture

Scott

30

General Mach Discussion / Re: 2000 line encoder mach3

« on: April 12, 2007, 02:02:29 PM »

I'm running 1000 line encoders on my servos which are geared down
4:1 driving a 5TPI ballscrew.  I am using gecko drives with the step
multiplier set at x5.  I should be able to run 168 IPM with this setup
but my Gecko's fall apart at anything over 120 IPM.  They just can't
handle the fast count rate that the encoders put out. 

Scott