Messages

3791

Mach3 under Vista / Re: laptop to parallel

« on: February 18, 2011, 07:03:10 AM »

At our end we have probably tried 10 laptops. I personally have use an old dead dog NEC which had a PP port and it worked perfectly fine. 
All the Dell laptops  ( about 5 or so ) didn't work well . The Tashiba one was junk fro CNC. A friend uses a Dell laptop and it works fine but he also made a circuit to refine the pulse from the PC. So you just don't know.
I use a dedicated PC for CNC and it is not a laptop.
The SS sits on the shelf gathering dust ( no backlash and there probably never will be in my opinion).
RICH

3792

General Mach Discussion / Re: Hesitation between Lines of G-code

« on: February 18, 2011, 06:49:53 AM »

Dan,
Mach is computing X & Y velocities  / change in Y with respect to x  and as you aproach 0-90-180-360 one axis velocity is realy slowed down
to maintain position. So there seems like a pause and in CV mode it is transparent. Since there is a change in time at those points the tool
dwells there slightly longer and with tool runout you will get marking. Depending on axis resolution, accuracy of the axis, and spindle run out  you won't get any flat spots.
RICH

3793

Video P*r*o*b*i*n*g / Re: What do i need to video probe and is it comparable to using a probe?

« on: February 17, 2011, 06:30:16 PM »

I would suggest you have a look at the manual for CopyCat in Members Docs as it is all about using a web cam to probe and other things.
I would think that a regular probe would be more accurate.
RICH

3794

Show"N"Tell ( What you have made with your CNC machine.) / Re: Gertrude Gets Some!

« on: February 17, 2011, 06:44:08 AM »

Hey Chris,
That snake bangle ring is eye catching, but, as you said  the modeling would seem to be a challenge. Some how believe your up to it from the work
you have done and posted. Give it a try and remark about the tech difficulties in doing it. As always enjoy your posts.
RICH

3795

General Mach Discussion / Re: Long Taper groove (thread) Can it be done?

« on: February 16, 2011, 07:17:24 PM »

I know that the threading wizard has a taper option but i'm not sure exactly how to use it.

The threasding wizard  will cut a tappered thread. One of the important inputs is the taper. The taper is defined as 1/2 of the total taper on the end of the piece.
You need to be carefull because the axis movement is along the taper and as such the initial movement ie; say 3 to 5 diameters to allow for acceleration will be along the taper and can be negative / cross the x=0.

I get a chance i will do a little write up on taper threading and put in the members docs. I was waiting for a friends backplotter to be refined to show the pathing of the code generated by the threading wizard.
No that i have that i can see what is really happening with the generated code.

Till Then,
RICH

3796

General Mach Discussion / Re: Hesitation between Lines of G-code

« on: February 16, 2011, 06:57:32 PM »

Keith,
Try 7 for accel value for X & Y, and 3 for the Z.
RICH

3797

General Mach Discussion / Re: If I don't have a none integrated graphics board what happens?

« on: February 16, 2011, 06:48:48 PM »

Ray,
I am assuming that you mean you have on-board graphics on the motherboard. It may or may not affect your pulse quality and thus steppers don't work too well.
Some pc's allow ou to turn off the on-board graphiccs and install a card. To do that you may need to set a jumper on the motherboard. Only way to know is try it.
RICH

3798

LazyCam (Beta) / Re: MultiPass Cuts

« on: February 16, 2011, 06:37:16 AM »

Nicolas,
Two completely different programs even though they do a similar task. Can't really compare the two.
RICH

3799

General Mach Discussion / Re: Problems with axis accuracy - MachTurn

« on: February 15, 2011, 06:44:17 AM »

John,
I fogot to mention that I have a Sherline lathe and it has a threaded screw. I was impressed when i checked the screw in that it was quite accurate in lead going both directions. The problem tough was backlash, even though i had the anti backlash attachment for it.
You could only get so much of the backlash out and then it had to be re-adjusted if used frequently. I will also remark that my tool makers microscope has threaded screws along with an anti-backlash setup and it is extremely accurate. Manny movement tables
use screws, but those devices don't see the wear that a running machine machine will produce. Thus a step up would be ball screws and provide for longevity. Since your interested in accuracy, then each component of the mechanical system needs corresponding attention to selection. You ge a lot for your money but pay more as the accuracy of component is upgraded....ball screws are a good example. Try to make your axis have no backalsh or absolutey minimise it along with a nice balll screw and i think for prcatical use you will be happy with your machine.
RICH

3800

General Mach Discussion / Re: Problems with axis accuracy - MachTurn

« on: February 14, 2011, 09:40:58 PM »

If turning down to a specified diameter using the wizard, what is a reasonable accuracy to expect?

Actual turned down diameter will only be as accurate as your lathes "complete system" and additionaly accuracy can be related to surface finish when measurements
are taken on the diameter of the piece. Depends on spindle runout, surface finish, etc.
You have what you have.....!

Moving the slide repeatedly backwards and forwards to the same nominal position, what repeatability can be expected?

Depends on the motors / electonics / drives but also on the mechanics of the system ( backlash / ball screw accuracy).
On my converted lathe repeatable backlash is like  .0004 on the Z and even better on the X. The x axis ball screw is a high end ground ball screw.
So in testing using a .0001" indicator or opticaly compared  it's on as compared to Mach's DRO.

but I was wondering about just how repeatable microstepping is

Well, for my engraving machine i could not measure it ie; didn't have enough light at 400x to read the calibrated glass scale with a microscope.
 I have found different steppers will microstep better than others....Russ gave an example from Geco for the reason.
I can however easily split .001 into 10 parts by jogging in .0001" steps. Now remember that my steps per unit is 253000, thus resolution is
.000004" but practicaly the screws ware only calibrated / certified to .000040" acuuracy over the total movement. As noted by others you will find that
there will be no movement and then the stepper will jump to the next postion and the number of steps can vary over one revolution of the motor. Change the motor and
 you will see a difference if you graphed and compared the movements to steps. So not all motors are created equaly.
 Now if you had a pulse counter you may also find out that even the tension of a timing belt can influence your readings as even though the motor turned from a pulse there was no
mechanical movement due to the belt tension. We did some testing and found that Mach / the PC provided the pulses but the drives, belting, motor, etc didn't mecessarily react to them all.
Things are just not perfect......!

And what is people's experience of the accuracy achievable with Mach?

Mach is more accurate than your ability to  measure the movement..........!
If you have a quality system then you will have accuracy.

RICH