Rapid Moves in MC vs at the Machine

[Jobnt]

We keep finding random gouges on new programs. Turns out they are coming from the rapid travel moves. 

MC plots both axes moving the rapid moves in a straight line but the machine moves both axes at 45° until it hits a position in one axis then straight lines the remainder. 

Is there a way to get MC to simulate a machine's actual rapid move instead of what we get here? 

[cam-eleon]

I feel your frustration. The problem is a plot issue and more importantly the posted code. Your machine moves 45 deg. I don't know if you can change parameters to have the machine rapid different. The sure way is to have the post set to fast feed (ex G01 F400ipm) for rapid motion. Not what you want to hear. I think todays machines move axis at different feeds  while in rapid to create a straight line as opposed to old time dog leg fashion.

 

[#Rekd™]

Check your control definition settings.

 

 

[gcode]

This is not a Mastercam issue, it is a programming issue

You have Mastercam set to rapid in a straight line and  apparently, your machine dogleg rapids.

If you set your machine definition per Rekd's instructions, Verify will dogleg and show you the gouges.

When you are running dynamic mill toolpaths, or optitough surfacing paths on a machine that

doglegs, make sure you set your rapid motion to G01 F (whatever your machine can handle).

Then the machine will travel in as straight line when you are down in a pocket  or dynamically milling a part.

 

[cncappsjames]

Orrrrrrrrrrr

FANUC Parameter #1401.1 =1 No dogleg rapid (LRP) if it's a FANUC 16, 18, 21, 30, 31, 32, or 0i...

 

[CEMENTHEAD]

Learned a long time ago to never rapid around inside a part.

[Jobnt]

Can't watch the video but found the setting. As this is a network install where others use the same control def I will have to verify I can change this without affecting anything else.

These are 5 axis Brother machines and there's some really wonky moves in there, apparently to make sure Simulate works correctly. 

Thanks for the heads up. 

[gcode]

44 minutes ago, Jobnt said:

I will have to verify I can change this without affecting anything else.

This setting will not change posted code.

It just changes rapid moves in Verify and Machin Sim backplot

Classic backplot  can not accurately simulate dogleg rapids

 

[Chally72]

Keep in mind that even the behavior change this shows in Verify/Simulation is still just a guess. Doglegs exist because the machine is allowed to move each linear axis independently, at its maximum acceleration/speed, to achieve that component of the positioning request. So, the motion of the dogleg is highly dependent on the individual acceleration rates of your machine axes. Have 500lbs of parts and fixture on the table? The acceleration of the X axis might be slower now, and your dogleg rapid move changes shape because the X axis completes its component of the G0 much later than it did with an empty table. These are things that can never be properly simulated because the machine position is inherently uncontrolled during the move.

 

CNCAppsJames mentioned the ultimate way to fix this if its possible for you- don't allow dogleg motion to exist at the machine. 

From a programming perspective, anytime you see yellow rapid moves and they are at or below the highest point on your part or fixturing, your antennae should be going up and you should be examining these moves to ensure there's no chance that the volume the tool is traveling through can hit anything if it does indeed dogleg.

 

 

[Jobnt]

25 minutes ago, gcode said:

It just changes rapid moves in Verify and Machin Sim backplot

1 hour ago, Jobnt said:

there's some really wonky moves in there, apparently to make sure Simulate works correctly. 

Will need to check out what this does to our verify. The wonky moves I mentioned above are to make sim work correctly. 

 

[Aaron Eberhard]

7 hours ago, cncappsjames said:

Orrrrrrrrrrr

FANUC Parameter #1401.1 =1 No dogleg rapid (LRP) if it's a FANUC 16, 18, 21, 30, 31, 32, or 0i...

 

...Writing this down and wandering out to the ol' Robodrill...

 

Also, another vote for NEVER allowing G0 motion, especially on a 5 axis machine.  My preference is to have the post automatically convert them to feed moves at your max rate, then it's always controlled.  It seems like there's always some weird edge case that will bite you in 3 years after you've gotten totally comfortable with how the machine's going to react, but on this new part you have to do...  

On machines that don't allow doglegs, you'll still often get weird jerky motions in G0 5 axis mode, whereas if you do it a G1, it'll be a lot smoother.

[#Rekd™]

28 minutes ago, Aaron Eberhard said:

Also, another vote for NEVER allowing G0 motion, especially on a 5 axis machine.  My preference is to have the post automatically convert them to feed moves at your max rate, then it's always controlled.  It seems like there's always some weird edge case that will bite you in 3 years after you've gotten totally comfortable with how the machine's going to react, but on this new part you have to do...  

On machines that don't allow doglegs, you'll still often get weird jerky motions in G0 5 axis mode, whereas if you do it a G1, it'll be a lot smoother.

@Aaron Eberhard Can you do this just in the Control Definition by checking the "Covert rapid to maximum feedrate" in the Feed area? Then set the max feedrate in the Machine Definition. Or does it need to be done in the post?

[Aaron Eberhard]

1 hour ago, #Rekd™ said:

@Aaron Eberhard Can you do this just in the Control Definition by checking the "Covert rapid to maximum feedrate" in the Feed area? Then set the max feedrate in the Machine Definition. Or does it need to be done in the post?

Depends on whether you're using a modern post or not.  Older posts pretty much ignore the control def, but if you're using a newer post you should be fine in the control def.   Sorry if I wasn't clear

[#Rekd™]

2 minutes ago, Aaron Eberhard said:

  Sorry if I wasn't clear

You were clear, just wanted some expert advise on it!!!!!!

[Newbeeee™]

Change ALL machine parameters to be identical. Remove doglegs from them all.

NOTHING is worse, than one machine (or when a new machine lands) and it's configured differently to the rest.

On 3/14/2023 at 12:47 PM, CEMENTHEAD said:

Learned a long time ago to never rapid around inside a part.

As for this comment (and I see someone LoL's at it) - IMHO, this is very true.

I got bit by one of my new (at the  time) Feeler drill/taps with 60m rapids. Fanuc Alpha pack model D.

Electrical enclosure that would fit in my hand with straight sidewalls and profiled internal tapped lugs and bosses - ran 1st part 25% rapid and got first off.

Ran second part at 50% while on another machine and heard a "ding" resonate for a split second. Didn't notice anything on the part.

Ran third part at 100% and there was a very loud "ding".

What happened was the rapid retract was well below the top surface of the component, and the tool simultaneously retracted up moving to the start position of the next feature - clipped a lug, putting a 1mm x 45degreeish gouge at 100% and scrapping the part.

The 50% would buff out (0.2x 45degree deburr LoL) and the 25% was only just visible. 

Long short the machine at those rapid rates/acc/dec had a LOT of following error, and there is/was no parameter to change to keep rapid following a more accurate path. This was in G05.1 lookahead.

So yes - from that day forth....I always rapided (rapidid?) (rabid ) to a clearance above the top of the part.

 

Back to the OP....Brother could be the same. Rapido rapids and the following error might be biting you too? 

[Jobnt]

Not sure how the Brothers do in slower rapid speeds, but will find out. Yeah, I'm rapiding to a better clearance plane now too.

 

[David Colin]

Another thing to pay attention if you are using the new 'fit rapid radius' in linking page: It is worth checking in the control definition and/or post that rapid motions X/Y/Z are not broken...
I almost been bitten, hopefully Vericut saved my arse. 

 

[JoshC]

On 3/14/2023 at 12:12 PM, Aaron Eberhard said:

...Writing this down and wandering out to the ol' Robodrill...

 

Also, another vote for NEVER allowing G0 motion, especially on a 5 axis machine.  My preference is to have the post automatically convert them to feed moves at your max rate, then it's always controlled.  It seems like there's always some weird edge case that will bite you in 3 years after you've gotten totally comfortable with how the machine's going to react, but on this new part you have to do...  

On machines that don't allow doglegs, you'll still often get weird jerky motions in G0 5 axis mode, whereas if you do it a G1, it'll be a lot smoother.

great info, the only sucky part about this that i can think of is then the operator cant use the Rapid override button to only effect those moves, like dropping rapid to 5% for example for the first run, if all rapids are converted to feed rates then the override feed rate button will effect those movements too.  

but i agree this would pretty much fix any possibly dogleg issue, everything would be nice and interpolated moves

[Aaron Eberhard]

3 hours ago, JoshC said:

great info, the only sucky part about this that i can think of is then the operator cant use the Rapid override button to only effect those moves, like dropping rapid to 5% for example for the first run, if all rapids are converted to feed rates then the override feed rate button will effect those movements too.  

but i agree this would pretty much fix any possibly dogleg issue, everything would be nice and interpolated moves

Yep, that is the downside

[Newbeeee™]

11 hours ago, Aaron Eberhard said:

Yep, that is the downside

What I did with my Robos, and all my Fanuc machines:-
Parameter 1401:- change bit Rapid linear/Rapid non linear
Also changed the bit so when the Feed override knob is "0", the rapid does not move when the rapid knob is "0".
Default, all my machines would creep, when Rapid was "0" (so "0", wasn't "0").
Then parameter 1421:- changed this to be 400 (mm/min)
So when proving a part, with rapid override at "0", the axes still move when rapid is commanded and the feed override is above zero.
Then to stop the rapid, wind the feed override to "0".

I chose 400mm/min as that was a suitably low rate that my reflexes would be able to react to if something didn't look right