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Extremely fast rapid movement
« on: June 05, 2010, 07:13:52 PM »
Hi guys,

We have built a router at school and we're just now to the point that we can start using it  :)
However i have discovered one problem with it when running certain programs.

Example:
When i run a drilling cycle it will go down and drill just fine, but when the drilling is done it rapids up at an extremely high rapid feedrate. This causes the machine to loose all the steps in Z axis movement. This of course snapped the drill right off when the machine started moving in X-Y direction

Another example:
When running a circular pocket created on Mach3 wizards the machine goes down to the center of the pocket and starts plunging in to the material. When the machine then starts to move in X-Y direction the feed is extremely high and a few steps are lost until the diameter of movement is starting to get higher.

- Motor tuning is set and works fine (these rapid movements by far exceed both speed and acceleration i motor tuning).
- There are no rapid FRO active.
- FRO is 100 %
- Machine jogs fine.
- This does not happen on all rapid feeding, so far just the examples above.

Machine information:
GREX motion controller
Dual X-axis steppers (A-axis is slaved to X-axis). A-axis is set to not angular in general config.

Unfortunately i don't have the G-code programs now, but i could post it on Monday when I'm back at school.
However i don't really think the problem is in the program. This happens programs created by both the Mach3 wizard and on VcarvePro.

Offline ger21

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Re: Extremely fast rapid movement
« Reply #1 on: June 05, 2010, 07:45:10 PM »
Normally, I'd tell you that the values in the motor tuning will never be exceeded. However, you're using a G100, which controls the motion, so all bets are off. I'd guess that the G100 is the source of your problems.

Why are you using a G100? Most users have abandoned them, and Gecko stopped selling them to people for Mach3 use, as there are too many random problems.
Gerry

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Re: Extremely fast rapid movement
« Reply #2 on: June 05, 2010, 08:00:04 PM »
Last years students bought the G100 when it was still in normal sales from Geckodrive.
If I'd known what i know today i would have thrown it away and used another solution. However the control cabinet is finished and re-doing it for another motion controller would require a lot of work.
I think the G100 is actually a really nice concept, but as you say it has a whole lot of problems.

I have tried searching for other people having this problem on the G100 but I haven't really found anyone. It would be sad if this is a problem that can not be resolved.  :-\

Offline BR549

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Re: Extremely fast rapid movement
« Reply #3 on: June 05, 2010, 08:45:06 PM »
Where a G100 will fit the Smoothstepper will also fit.

AND if I remember correctly Gecko has offered to buy any OLD g100s back.

So It looks like a win win situation.

Just a thought,
Re: Extremely fast rapid movement
« Reply #4 on: June 07, 2010, 12:27:44 PM »
We have milled some more today and i have discovered where the problem occur.

In VcarvePro i have set plunge rate to 60mm/min and feed rate to 1630mm/min
The following example is a rectangular profile. The "very fast feed" occurs when the tool plunge down and start feeding in Y+.

As you can see (bold text) the tool plunge down 1mm at 60mm/min.
At the next line it does an arc move at 1630mm/min.

I have discovered that when a line with a feed rate change is followed by another line with a feed rate change  the G100 goes crazy.

Quote
(Rectangular profile)
()
G00X41.215Y40.556Z5.000
G00Z2.000
G1Z-1.000F60.0
G2X38.715Y43.056I0.000J2.500F1630.0
G1Y165.502

G2X41.215Y168.002I2.500J0.000
G1X290.384
G2X292.884Y165.502I0.000J-2.500
0G1Y43.056
G2X290.384Y40.556I-2.500J0.000
G1X41.215
%

However, if i put in a very small pause between the lines it all works fine, example

Quote
(Rectangular profile)
()
G00X41.215Y40.556Z5.000
G00Z2.000
G1Z-1.000F60.0

G04 P.001

G2X38.715Y43.056I0.000J2.500F1630.0
G1Y165.502

G2X41.215Y168.002I2.500J0.000
G1X290.384
G2X292.884Y165.502I0.000J-2.500
0G1Y43.056
G2X290.384Y40.556I-2.500J0.000
G1X41.215
%

If i set the plunge rate higher (ex. 110mm/min) the speed / accel is less extreme when the problem occurs. It may seem that it is the difference between the two feed rates, or the relatively low plunge rate, that causes the problem to occur.

All this i find very strange  :o

It seems weird no other G100 users (that i can find) have reported this problem?
Anybody have a smart solution to fool the G100 to work in this situation?

Offline Hood

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Re: Extremely fast rapid movement
« Reply #5 on: June 07, 2010, 01:58:12 PM »
Anybody have a smart solution to fool the G100 to work in this situation?

Yes, a 10lb hammer ;D

Seriously though I think you really need to load an old version of Mach if using the G100, go to the Yahoo group and give Mark Vaughn a shout as he uses the G100 and knows all its pitfalls so hopefully can give sound advice.
Hood