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Messages - chad

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251
General Mach Discussion / Re: Spindle orientation
« on: September 18, 2006, 05:56:59 PM »
I am sure, this is a lathe without a turret. Just has a quick change post.

Chad

Pretty cool machine..

http://haasportal.net/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/DS_TLseries_US.pdf

252
General Mach Discussion / Re: Spindle orientation
« on: September 18, 2006, 05:42:10 PM »
Not an expert here but.. I don't think you can.
I had my head in the control cabinet of a Haas tl1 recently and it has 3 ac servo drives with encoder feedback. one for x, one for z , and one for spindle.  So what this is telling me is the spindle is treated just like an axis drive. Just a BIG ac servo motor with an encoder. With an index pulse you won't have the resolution to to be able to reliably position the spindle.. 

?

Chad

253
BUMP

Brian, or anyone any words of wisdom?

thanks,

Chad

254
Mach3 and G-Rex / G100 jog problems-ART
« on: September 18, 2006, 12:17:25 PM »
Hi Art, I have been having problems with jogging on my knee mill.

I have ac servos and the machine is tuned down to about 150 ipm. When I am slow jogging say 10% things are fine. If I shift- jog things are fine.
If I slow JOG then immediately do a Shift jog my table will lunge a little and fault the servo drive. Happens on all axis.

What I think is happening in on the fast transition from a slow jog to a Shift jog mach is not using the acceleration. It is like the grex is emptying the buffer from the slow jog then going from zero to 150 ipm. 

If I wait for the machine to come to a complete halt after a slow jog then do a rapid jog everything is fine. I don't think it is a servo tuning thing because I have never had this problem while running gcode and I have had the machine jogging just fine (but scary) around at 300 ipm.

BTW i have been following the g100 just stop problem. I have had it happen several times. At the time I was using a laptop wirelessly to control the mill (Iknow not a good idea) I have sense built a dedicated mach computer and haven't seen the problem but i have not done much cutting. I am going to be doing a bunch of work on it this week and I will let you know.

Chad



255
Show"N"Tell ( Your Machines) / Re: Chads new machine
« on: September 18, 2006, 01:57:51 AM »
I will be cutting some stuff this week.  I will bring the cam down and try to get some pictures.

Chad

256
Hey Brian, I am about to purchase the wizard set. I have found the free wizard is a little buggy.

Any how I am now confused. And probably missing something but i need to find a better way to prep stock. It is taking me longer to make my stock blocks than it does to cut a complicated 6 sided part.

Here is what I am doing now.  I know it is NOT the correct way but I don' t know a better way.

1. Using my miter box with a non Ferris cutting blade roughing the cube to +- .1 . This makes a pretty square -+ .02 or so block.

2. put it in the mill vice and and do a manual face with the jog keys to get a flat surface.

3. flip the part and do the same thing again.

4. jog the tool out of the way try to get in with calipers to measure the top of the stock to the bottom of the vice.

5. set the z dro to whatever is the measured value, mdi to the desired value and do another manual jog to face the final thickness.

6 Repeat this 2 more times for the other sides.  Yuck.

I only have a cheap 1.25 inch fly cutter that cuts like crap so i have been using a nice 3/4 roughing end mill for the surfacing.

So i was thinking about it tonight and it occurred to me that i could use a 2" gauge block to set the tool height.  This would give me an absolute reference height above the vice bottom, of witch the stock block is resting on. So i went to demo the surfacing wizard and entered 2" for the material surface and 1.85 for the depth. No deal. The wizard generated a preview that if i were able to post code to would surely have been the destruction of something.  I guess i don't understand why there is an option of entering a stock height. I would assume that this was always going to be 0. and the depth would be a -number.

I guess what i can't get my head around is what is your reference to the tool height, be it table top, mill vice bottom, parallels  or is it just whatever you are measuring.

I guess the way i would like it to work is:

1. Use a gauge block and set the tool height above the vice bottom, say 2"

2. now that I have an absolute reference above a surface go into the surfacing wizard and enter 2" for the stock height and 1.85 for the depth.  set the cut depth Etc..

3 Press cycle start.

4. Profit !

I know the danger with this is a goto 0. That could cause all kinds of catastrophe. But no more risky than using a machine that you aren't turning wheels on.

What am I not getting?

Plz Help!

Chad








257
General Mach Discussion / Re: New user has question about Mach3 setup
« on: September 16, 2006, 09:58:46 PM »
Hmmm , Maybe i should have asked more questions before stating the price.

OK the bipolar thing is going to be a problem. I can't find or think of any cheap bipolar drives..

The driver I used when I did my little mill and lathe:
http://www.hobbycnc.com/

This is a kit, for unipolar steppers (what I had laying around) and I  am pretty handy with a soldering iron.

Of course this would mean that you would have to buy new steppers. They also sell unipolar steppers at a pretty good price. This part always sucks

The Gecko drives are VERY nice and would work great. They are however $115 each axis. 

What kind of mill are you making?

258
General Mach Discussion / Re: New user has question about Mach3 setup
« on: September 16, 2006, 03:05:51 PM »
Steppers run hot. To hot to touch,hot.  They are made to run at these temperatures.

Now that being said if they are REALLY cooking, if you spit on it and it sizzles, you need to make sure that the driver your using doesn't need current limiting resistors in series with the steppers.

You really don't want to de energize the stepper, the only thing keeping your machine from loosing position is that energized coil. You can add some heatsink to the steppers, make sure you don't need resistors, and if all else fails you can find a nice 'chopping' or current limiting 3 axis stepper board for around $115.

Chad

259
Third party software and hardware support forums. / Re: Linear Encoder HELP
« on: September 14, 2006, 06:02:02 PM »
Quote
If the motor got a command to move .3" and the encoder moved .2" wouldn't the software issue additional pulses to the motor?

No.

(Servo- closed loop)
What we are talking about is a servo loop. Servo means the drive or amplifier knows the position of the motor and will correct the position if it isn't at the predicted position. All this is handled in the servo drive not inside of mach. if mach sends out pulses to go to .3 and the servo drive realizes it has only gone .2 the drive will all by it's self move to the .3 . Mach just assumes that that the position is correct. It can't look and say I am not there I need to go further. Mach lets the servo driver deal with that.

(Stepper- open loop)
Stepper motors 99% of the time don't have any sort of encoder on the shaft. Mach sends go one step, the driver sends one step to the motor, the motor goes one step. As far as mach is concerned it is where it should be. If you grab the shaft on the stepper and turn it mach will have know idea that the shaft has been turned and continue sending places out assuming it is in the right place.


I guess to summarize:
Stepper can loose position and there isn't anything you can do about (as far as mach is concerned)
Servos Rarely loose position because the servo driver is keeping track of the position and if it gets off by an encoder count it will correct for it on the fly.

In a servo system you want the encoder on the motor. If you put the encoder on the mechanics of the machine if there is ANY back lash or slop in the ball screw or the gear reduction/belt the servo drive will "hunt" and usually burn out your motor. 

Chad


260
Third party software and hardware support forums. / Re: Linear Encoder HELP
« on: September 14, 2006, 01:51:44 PM »
Mach won't close the position loop. You can hook the encoders to mach and view their position however if you do have some failure on the servo end mach will still send pulses out the port and not know that there was a problem.

The encoders are for reference only and won't affect the output of the software.
The best way to ensure it is where it is supposed to be is by using servos. If your hardware is well built a good servo will guarantee it is where it is supposed to be. Steppers can loose position, by definition servos won't. 

Chad

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