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Author Topic: Vcarving to Letter Cutout  (Read 2539 times)

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Vcarving to Letter Cutout
« on: December 10, 2015, 07:10:02 AM »
Hi Everyone:

So for years I have been doing signs - all v carving stuff.  Now I'm doing some product testing where we are actually cutting letters out. 

All motion is smooth on the machine when doing a v carving tool path.  But yesterday when I went to cut out a few letters I had some very jerky movement.

Feed rate is set to 700ipm, so I thought maybe it was missing steps so I reprogrammed the file to run at 80 ipm which is waay slow if you ask me.
Still the jerky movement, but just slower jerks I guess.

I generated my vectors in CorelDraw and found out that the letter C had a zillion nodes so I was guessing that it was trying to cut a zillion line segments.

So I tested another font that seems to have less nodes.  So there was less jerking, but still jerking around the serifs on the letter.  Is there a way to set up the machine
so there is fluid movement all the way around the shape?  I have to believe that the people doing cutout stuff all day long don't deal with this.  But I'm at a loss.  Any help
is appreciated.

Thanks so much
Bill

Offline Tweakie.CNC

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Re: Vcarving to Letter Cutout
« Reply #1 on: December 10, 2015, 07:33:23 AM »
Hi Bill,

It has a lot to do with the post processor you use to create the Gcode from your CAD/CAM software.

For example...

Vectric has Mach3 post processors (which will create the Gcode to process circles as a series of straight lines) and Mach3 arcs post processors (which will create the Gcode to process circles as a series of arcs) - most CAD/CAM (that I have used) have similar options.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Vcarving to Letter Cutout
« Reply #2 on: December 10, 2015, 07:44:15 AM »
Or it could be that you have "Exact stop" selected in Mach3. Try changing to "CV" instead and see how you go.
Have a read of the first parragraph of this document.
http://www.machsupport.com/wp-content/uploads/2013/02/Mach3_CVSettings_v2.pdf
Re: Vcarving to Letter Cutout
« Reply #3 on: December 10, 2015, 08:30:53 AM »
Thanks so much for the replies, I really appreciate it.

The post processor I'm using is the EZ-Router/Mach3 PP in Vectric.

The arc/line segment thing makes a lot of sense to me.

I do have the machine in CV mode.

What I did do was change my look ahead from 20 lines to 30 lines and took my accel values down from 20 to 7.  Velocity is still set at 750.  Now running at 700 ipm this thing has almost no noticeable jerk movements.  But I do have a question about look ahead.  Is there a top value that I should avoid on look ahead so many lines?  Like 30 seems really good, but still just a tiny bit of jerking around serifs.  Just a tiny bit.  But, I'd like to be perfect on it with no jerking.  Any thoughts?

Would taking the feed rate to 600 ipm make a difference at all do you think?

Bill

Offline Tweakie.CNC

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Re: Vcarving to Letter Cutout
« Reply #4 on: December 10, 2015, 10:35:30 AM »
Quote
What I did do was change my look ahead from 20 lines to 30 lines and took my accel values down from 20 to 7.  Velocity is still set at 750.  Now running at 700 ipm this thing has almost no noticeable jerk movements.  But I do have a question about look ahead.  Is there a top value that I should avoid on look ahead so many lines?  Like 30 seems really good, but still just a tiny bit of jerking around serifs.  Just a tiny bit.  But, I'd like to be perfect on it with no jerking.  Any thoughts?

 Good question Bill, many use a look ahead of 200 so I guess it is a matter for experimentation.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Vcarving to Letter Cutout
« Reply #5 on: December 10, 2015, 01:17:13 PM »
As pertaining to CV mode and such, now I've done a simple shape cutout (a star like shape) that has 5 inside corners.  I'm using a 3/8" diameter cutting tool, so I know the inside will not be 100% sharp, but this thing seems like it's really rounding the inside corners so much so that the shape is not that close to my original drawing.  Is there some mode where mach is trying to round that inside corner too much??

Bill

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Re: Vcarving to Letter Cutout
« Reply #6 on: December 11, 2015, 01:27:50 AM »
Increasing the Acceleration settings ( in Motor Tuning ) will reduce the corner rounding.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline nobby

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Re: Vcarving to Letter Cutout
« Reply #7 on: December 15, 2015, 10:09:29 AM »
hello,
have you tried exporting your files as
PLT HPGL plotter files ?

have a play,
when the HPGL export dialogue box opens opens
2nd tab 'PEN select pen 1 black
in the 3rd tab 'advanced'
make sure the curve resolution is ZERO
IF you can see the nodes in vectric, have a play with the curve resolution,
 as it will ADD nodes if you do not enter zero!!! and do the jerky jerk





Re: Vcarving to Letter Cutout
« Reply #8 on: December 16, 2015, 06:19:37 AM »
That's an interesting idea.  So I can export from CorelDraw as a plt file, but when I try to import that file into Vectric VCarve 6.5 it says "Format not implemented."