Messages

231

General Mach Discussion / Re: Wrapper and toolpath view

« on: March 09, 2009, 09:10:01 AM »

Thanks for all your help on this people. I think I'm finally getting the picture.

I hadn't noticed that setting the diameter in the settings page, in addition to making the toolpath display proper, does affect the feed rate for the A axis. Perhaps I didn't have all the settings applied at the same time in the various places.

I have only looked at the tool path display but the speed of  X and A now appear about the same. I'll have to see what it actually does on the machine.

So - I presume what Mach is doing when applying the diameter factor, is managing the feed of A by inches per minute based on calculating the circumference of the part in inches rather than applying the feedate number as the usual degrees per minute. Is that what's going on?? Seems so.

This looks more manageable by a single feed rate in the code.

I'll have to try it out on the machine later and see what the movements look like.

Sorry for being so dense on this issue. It was difficult to see how all the pieces fit together. 

Very cool !! 

Sage

232

General Mach Discussion / Re: Wrapper and toolpath view

« on: March 08, 2009, 02:30:40 PM »

PS> What is this "Use diameter" setting you are mentioning. I seeit in the settings and have it checked but where ids the diameter of anything entered in a mill program? SO what is Mach using to calculate anything referenced to diameter?

Maybe someone can explain what Mach is going to do with (or without) such information.


Sage

233

General Mach Discussion / Re: Wrapper and toolpath view

« on: March 08, 2009, 02:27:13 PM »

Mach is doing a good job slowing the X down to accommodate the slow A when X and A commands are on the same line. This is absolutley required since otherwise a proper diagonal would not be possible - so no I don't WANT (or need) different feed rates when moving in X and A together but I do NEED a different rate for the lines with separate X and A moves.
I'd still like to hear from someone with a similar setup (A axis 90:1) and what settings they have for A axis and the results they get running the sample program. I can't see there being a single feed rate that can possibly work for both X and A.
 As I mentioned before I have no problems with A the way it is. Until now I've never had a reason to move X  and A together in sync. I've cut gears before but that's only a position A and then cut X sort of function and it makes no difference how long A takes. Since the two commands are always on separate lines of code I can adjust the Feed rate for all A position commands.

Let's hear from others using rotary tables .


Sage

234

General Mach Discussion / Re: Wrapper and toolpath view

« on: March 08, 2009, 09:22:01 AM »

I didn't program the F60. Wrapper did.
You're missing the point. I guess I tend to provide more info than people care to read.
YES F60 IS excessive for X moves but it's also - at the same time - too slow for A moves given my current A configuration.
There is only one F speed code programmed in the code produce by the wrapper program.
For me, the speed resulting from G0 is closer to a desireable speed for A moves  and a 1/16 cutter (just bit fast).


I agree that it might be possible to modify my A configuration BUT as I already mentioned I went through the process of tuning it until it skips and backing off a bit. I doubt there is any all encompassing F speed that will satisfy my hardware arangement.
I haven't really st down and thought about it too much. I'm sort of busy right now. I'll have to ponder it more.

I'd like to hear from someone else using a 90:1 ratio rotory axis and what motors and setting they have.

Sage

235

General Mach Discussion / Re: Wrapper and toolpath view

« on: March 07, 2009, 02:27:42 PM »

I have no control, over the microstepping. The Gecko drivers are fixed at 10 microsteps per input step pulse. Likewise the pulse width makes no difference with a Gecko. It's an edge triggered device therefore pulse width will have no effect.

20,000 steps per inch is not unreasonable for X and Y.

I have 0.2" per revolution ball screws. So the math is.

200 step motors x 10 microsteps = 2000 steps per revolution.
1 revolution is 0.2" of table travel.
0.2" / 2000 = .0001 or 1 tenth thou per step (10 steps per thou). I wouldn't want a step any bigger.

The A axis is not being slowed by X. The contrary is true. In a combined instruction the X is slowed down considerably waiting for A.

Consider:

G0 X1 A1
where X is 1 inch and A is one degree. Being that the two are on the same line of code they must complete at the same time to form a diagonal, therefore the X has a whole inch to move and the A has only one degree. You can figure out the the linear distance of one degree on a 6" rotary table as 6 x 3.1415 = 18".   18/360 is only .05 inches.  X must be slowed down about 20x  to be linear with A. (1/.05)
This has been proven when I run the wrapper code. Combined lines wi X and A don't need modification, X-only lines need a big reduction in the feed rate and A only lines I can practically run at G0 speeds since My A is so slow.

Let me play around with it a bit when I get some time. Maybe I can improve the A performance.


Sage

236

General Mach Discussion / Re: Wrapper and toolpath view

« on: March 06, 2009, 10:39:28 AM »

Running in air might be fine.
How's the balance between X speed and A rotation  speed for you?
60ipm for X is crazy fast for a 1/16 cutter.
Put some metal under it and see what happens for you.

I tried faster A velocity when I first set it up but the motor was losing steps on start up on G0's. I could try tuning the acceleration a bit to compensate. I somehow doubt there is going to be a stepper speed that s going to suffice with the rotary motor working into a 90:1 gear ratio compared to the X and  which are just driving ball screws.

My X and Y are set to 20000 steps per and a velocity of 50 ipmin. That gives me a G0 of about twice what I can turn the handle (mill drill) at which keeps me out of trouble.

As a test I purposly de-tuned my X axis to slow it down. That helped balance things for the wrapper code but obvioulsy that isn't a good solution. Or maybe it's all I can do to have a separate XML for this application.

What kind of rotary setup do you have??


You mention setting pulse width wider. Where is that done? I'm scheptical on that becuause I use Gecko drivers and their going to drive the motor how they see fit. I'm not losing any pulses from Mach to the drivers. That interface is solid.
I just think I'm driving the motor too fast for it's abilities to overcome the 90:1 ratio compared to the direct drive of the X axis.



Sage

237

General Mach Discussion / Re: Wrapper and toolpath view

« on: March 06, 2009, 08:27:31 AM »

Thanks everyone:

docltf:
 I set what you have stated and it looks fine now. Now all I have to do is remember the settings.
What else will the rotation diameter affect ?

The next question is:

My rotary axis work fine for other purposes so far - accurate and reliable. The parameters for it are:
300 oz/in NEMA 23 200 step motor with Gecko set for microsteps (2000 steps per rev of stepper). Fits on the table and still allows normal mounting of table to mill without motor interference.
The rotary table has 90:1 ratio
I calculated the following settings for motor tuning to balance missed steps on acceleration and enough power under load.
360deg / 90 = 4 degrees per rev
2000steps for 4 degrees means 2000/4 = 500 steps per degree therefore settings are:
Steps per = 500
Velocity = 669
Accel = 9 


For normal use the rotary table is fine although a bit slow on G0's but I find it missing steps under load if I speed it up. I'm not in a hurry. But maybe I've missed something here.

The problem is with the code from the wrapper program. It has only a fixed F60 which is rediculously fast for the X axis and too slow for the A axis. 60 for A is almost not moving.
For the lnes of code with X and A on the same line it actually results in a feed of about F2 for the two combined because the A movements are slowing down the X. F2 is about what I'd like to use for a 1/16 cutter.
 Editing the code to put different feeds for each line is the only solution but not reasonable. ( I tried it).

So the question is (after all that):
Is there something I've done wrong with the settings for A or is there something else that can be tweeked  to make the A axis work better for wrapper.

Sage

238

General Mach Discussion / Re: Wrapper and toolpath view

« on: March 05, 2009, 03:07:45 PM »

Hood:

Yes A-axis is set to angular.
One strange thing is I went back a few minutes ago to play abit more. I loaded the file again and it showed up fine as a curved surface in the small toolpath display and seems to rotate fine as I ran the code. Then because it was a bit small I went to the big toolpath diaplay and even after regenerating it there was no way to get it to show properly. I went back to the small display and now it too was screwed up. I shut Mach down, started it again and check all the settings and still I can't get it to show up properly again. Only that once it showed properly.

The file is attached. Maye someone else can comment. It is the letters TSME. It should show on the toolpath as a slightly curved toolpath so it may require some pushing around with the mouse to see it all properly.

Thanks

Sage

239

General Mach Discussion / Wrapper and toolpath view

« on: March 05, 2009, 11:34:58 AM »

I'm using the Wrapper sotware to machine some text onto a cylinder. Although I've set all the parameters in Mach according to the wrapper software HELP  I can't get the Mach toolpath display to show a cylinder with the text as it says it should in the wrapper help. The toolpath is  just some sort of flattened X,Y,Z display. No A axis shown. I think the machining is going to be correct judging by air cutting movement but it would be nice to see it properly in the toolpath.
Ive set Mach:
Config/toopath/ A-rotations checked and Axis of rotation X checked.
Confg/general config/ rotational - Rotate 360 rollover unchecked.

Anything I'm missing.

Sage

240

General Mach Discussion / Re: Connecting an MPG to Mach3

« on: January 05, 2009, 09:33:04 AM »

The transistor will work fine to change the levels to more solid values BUT (assuming I follow what you have done) the MPG signal has now been inverted using the transistor i.e. when the MPG gives a low the BOB is now seeing a high and vise versa. I'm not sure what Mach is doing with the signal but I'm surprised it isn't a bit confused. Perhaps it is looking at logic edges only and not the levels.
  Apparently it's not making any difference and if it works stick with it.
 As for your old single resistor arrangement, The 2.8v was a marginal high and it looks like the low did not suffer so you might have gotten away with just a lower resistor than 4k7 as a pull up - say 3k3 or 2k2. If you were buying resistors every time to try this then leave it like it is and see what happens. I have piles of components around to use to get it just right so I have an advantage there.

Also. I'm not sure what the MPG is using to drive it's output but it might be a bit easier on the transistor if you leave the 4k7 in the line going to the transistor base (B) to limit the current when it drives the transistor base low. Check the temperature of the transistor when it is supplying a high to the BOB. Probably won't be a problem.

Keep these comments in mind if you experience problems later but as I say if it works leave it alone. You'll be better off like it is now with the transistor if everyting is working.

 Good work.

Sage