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Author Topic: Mach 3 turn constant sfm?  (Read 29872 times)

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Offline DaOne

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Re: Mach 3 turn constant sfm?
« Reply #10 on: December 08, 2010, 09:41:53 PM »
When I use this code CSS works fine meaning as the diameter decreases spindle speed increases. What is not working is the G95 or constant mm/rev feed rate.  If I assign F=.2mm/rev this feed rate only takes place at the start of the cut when the RPM is still 1000RPM. As the RPM increases the feed rate in mm/rev decreases.  Has anyone had experience with this behavior? My observation is that RPM x F(mm/rev) remains a constant value which suggests to me that the feed  is remaing constant in mm/min and not in mm/rev as it should having set G95.

I ran into this a couple of days back. It seams as if mach had a mind of its own. The feeds were almost rapids. CSS still worked but the feeds were way off. It required restarting to solve the issue and then it did it again after a few passes. Good thing for me I was cutting air. I feel there is a bug. I haven't had any more time to test if it occurs only with CSS and feed per rev on the same program. Something tells me its gonna be a long time before it gets fixed if there is actually a bug.

Offline Dan13

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Re: Mach 3 turn constant sfm?
« Reply #11 on: December 09, 2010, 02:02:27 AM »
It is a known bug in Mach3 Turn. The combination of G95 and CSS doesn't work. G94 with CSS work fine.

Dan

Offline DaOne

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Re: Mach 3 turn constant sfm?
« Reply #12 on: December 09, 2010, 02:25:33 AM »
It is a known bug in Mach3 Turn. The combination of G95 and CSS doesn't work. G94 with CSS work fine.

Dan

Seams like I keep uncovering these nice little easter eggs. Is there a thread listing all these bugs? If not maybe there should be.

Offline Hood

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Re: Mach 3 turn constant sfm?
« Reply #13 on: December 09, 2010, 04:20:33 AM »
I know it doesnt work with the SmoothStepper and I have had various people saying it does work,as well as others saying it doesnt work, with the PP. What you are describing is exactly what I see with the SS so I am thinking it is indeed a Mach issue but it could well be a combination of Mach and SS as I am not sure if the SS controls CSS internally or not.

Turn needs a lot of work done on it and this is one area that will be looked at but when that will be I dont have a clue.
Hood
Re: Mach 3 turn constant sfm?
« Reply #14 on: December 09, 2010, 06:29:57 AM »
I think this is a serious limitation especially when profiling with a good surface finish requirement.  I would like to ask the VB script and Brain experts out there if they think it would be technically  possible to get around this problem with a Brain or adding a few lines to a MacroPump that would constantly update F as a function of RPM.
Re: Mach 3 turn constant sfm?
« Reply #15 on: December 09, 2010, 07:52:40 AM »
I have had problems with G95 only (no CSS) with PP and Vn 40.

First run would be fine, second would be stepper commands outputted at max computer speed (no reference to feedrate or max velocity at all) (10 mins file executed in 5 seconds)! Steppers screaming and massive lost steps. Next would be fine, next same as above.

Went back to version 22 which works fine except for long, deep threads and finished my work.

However, I had some time and went back to version 40 AFTER changing my parallel port in BIOS from ECP or EPP mode to "Bidirectional Parallel" (for other reasons) and I've not had that problem with version 40 since. All G95 code I've tried so far is fine and ran same piece 6 times with no issues. (Was it a corruped install or does the parallel port make a difference, I don't know.)

With Vn40, I also found the MDI would not accept inputs until G-Code was run. I found this was due to the initialising strings in the Config page being empty after upgrade.

I did a quick check with G95 and G96 and it seems OK. So, at the moment, happy with Vn 40...

However, as per my previous post, G95 does not respond to spindle speed changes. I'm sure it used to in previous (very early) Mach3 versions as I remember being a little impressed with it... Seems that is broken now unless I remember badly.

Woody.

Re: Mach 3 turn constant sfm?
« Reply #16 on: December 09, 2010, 10:50:53 AM »
Regarding CCS

I'm using a SS and i think what is happening is when the X tool comes out to take a new cut, its only then that the spindle wants to slow down.

So it gets the timings wrong, as it starts a new cut with the spindle too fast. I put a G04 pause to slow the spindle and it seems to work OK cutting air

I am looking to getting a braking resister for my VFD to slow it down a bit quicker.

Maybe you guys could test the theory out.

Brian are you looking  ;D ;D

Phil
The Good Thing About Mach3, Is It's very Configurable

The Bad Thing About Mach3, Is It's Too Configurable

Offline Hood

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Re: Mach 3 turn constant sfm?
« Reply #17 on: December 09, 2010, 10:57:26 AM »
Brian only looks when there is no mention of Turn ;0

I will just go and do another test on the lathe for CSS and I will write down what it does this time as I always forget exactly. I had a long chat with Greg about it a month or so ago and he knew got how it was meant to work and said he would work on it in the future but backlash comes first.

Hood
Re: Mach 3 turn constant sfm?
« Reply #18 on: December 09, 2010, 11:22:37 AM »
Brian only looks when there is no mention of Turn ;0
Hood


A pic of Brian
« Last Edit: December 09, 2010, 11:24:40 AM by M250cnc »
The Good Thing About Mach3, Is It's very Configurable

The Bad Thing About Mach3, Is It's Too Configurable

Offline Hood

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Re: Mach 3 turn constant sfm?
« Reply #19 on: December 09, 2010, 11:31:04 AM »
Yes that seems to be a good likeness ;D

Ok quick test, first thing was add a blended feed DRO to the screenset

MDI
G96S200
M48S1000
M3

Start at X10
G1X200F0.5

FPR starts at 0.5 and as spindle slows gets as high as 1.3
Blended starts at 490 and remains constant
Next

Start X200
G1X10F.5

FPR Starts at 0.5 and as spindle speeds up it goes as low as 0.16
Blended starts and maintains 155

In other words its well screwed up and would be good to know if others get the same results with the same inputs with SS and PP.

Hood