retract

[DavidB]

I have two qustions,when using an incremental retract height on a multi surface 3d toothpath is the processing time greater than if you were to us an absolute retract heieght?It say's in the help file that when you use an incremental retract height mc looks at all selected surfaces so as to miss in motion from one erea to another.If you use an absolute retract mc doesn't have to think about the retract height so i quesss that means less processing time.

 

I do muold work and my z0 is always top of job so i have used an absolute retract,but in cavity work there can be a lot of lifting to my absolute retract of say z3mm.Today i used an incremental retract,and had great results.not so much lifting

but my heart did stop a few times when retracting over ereas of the job and just missing.

 

I was also wondering with any one has had any crashes with using an incremental retract height?

 

Mastercam i love it.

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Mastercam i love it.

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I love it too!

 

I think that it is far more safer to use absolute retract and incremental feed rate and you will never have :

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but my heart did stop a few times when retracting over ereas of the job and just missing.

 

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and the machine time will be low

[Rick Damiani]

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Today i used an incremental retract,and had great results.not so much lifting

but my heart did stop a few times when retracting over ereas of the job and just missing.

 

I was also wondering with any one has had any crashes with using an incremental retract height?

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The only gotcha waiting for you on incremental retract is the direction that traverse moves take. MasterCAM displays and verifies rapid traverse moves as if they were interpolated. Most CNCs don't actually rapid that way, so a crash is a real possibility.

 

Suggusitons:

 

1) Invenst in good g-code verification software that will show the 'real' traverse path and use it to check and/or fix your code. This is probably your best long-term solution, especially if the g-code software can be configured to run as your default editor.

 

2) Look for rapids that are not aligned with the X or Y axis. On those toolpaths, set the retract height to a 'safe' abs height that is higher than the tallest thing you are traversing over, bearing in mind the actual path rapids will take on your CNC. This gives you another thing to think about while you are programming though, and introduces another opprotunity for error. I prefer to eliminate as many possibilities for error as I can, as I find that when I allow myself an extra opportunity to make a mistake, eventualy I make that mistake.

 

3) Modify your post to replace 'G00' with 'G01' and set the feed rate to the rapid rate you want to use. This will make your code essentally uneditable in the control, which may or may not be a problem for you. If you take this route, you'll have to make sure that your feed moves re-set the feed rate you want to use. Might make your operators a little nervous if you don't have any rapids though.

[DavidB]

I have made mod's to my post so there are no rapid moves(G00).I found out the hard way that the spindle load monitoring does not work while in G00 mode so my rapid moves are G01 F10000.

 

Rick

[Rick Damiani]

Ah. You should be golden then.

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DavidB!

You still have a risk of crash in case of clamps or some possible MC bug !

It is far better to use absolute retract higher then your highest surface and clamps and incremental feed rate .

And many modern machines have much faster rapid than 10000.

My g1 and g0 is 30000 max .

So it is much faster and safer to use g0 in the manner I mentioned before .

Personally If I would be your operator :

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Might make your operators a little nervous if you don't have any rapids though.

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I am afraid that it will be YOU a bit nervous seeing me running after you with a hammer and throwing at you all the things I can get on my way .

 

[ 05-12-2003, 05:16 AM: Message edited by: plasttav ]

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I found out the hard way that the spindle load monitoring does not work while in G00

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Why do you need to see it while in g0 ?

 

A spindle problem ?

[DavidB]

I program and run the nc machines at work so i wont be throwing anything at myself.My machine also rapids at 30 meters.I can set the spindle load for each tool and if the load goes over the set value the machine will stop,but only in G01 mode.The load monitoring doesn't work in G00 mode.

So say the tool feeds into or takes to a big cut the load monitoring will trip out but if i rapid into the job the machine wont trip out until the servo's overload by this stage the high speed spindle could be rat sh*t.I agree absolute height is safer.The main reason for my incremental ? was because the boss bought Power Mill and he is on my back to use it more and more but i like mc.Power Mill you can skim the job with increamental retracts and it is gough free.