Cut dimensions are wrong

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Cut dimensions are wrong

Postby BernieNUFC » Sun May 27, 2018 11:07 am

Hi
I am doing a makecnc model and cutting a job on 6mm ply and the drawing is scaled to that for the joint/pegs etc.
when i cut it out the general size of the pieces are exact i.e. a rectangular piece to be 22mm and it is 22mm but the little cut outs and inner circle holes are smaller therefore the joints do not match up.
I have no allowance offset and can see no reason for this issue.
Does anyone have any idea where i can start looking please?

thanks malc
VCarve Pro v9.012
High-Zs 720- Kress 1050 router ( CNC-Step DE version)
BernieNUFC
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Re: Cut dimensions are wrong

Postby AlanAndrews » Sun May 27, 2018 11:31 am

Could be any number of things including....cutting to wrong side with profile cut, tool incorrectly sized in settings, error with machine setup.

It is always a help if you can provide your vcarve file so that we can cast an independent eye over setup and vectors.
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Re: Cut dimensions are wrong

Postby BernieNUFC » Sun May 27, 2018 11:38 am

Hi Alan
I will see what i can do regarding the file.

So it cuts to the right side of the profile and its automatic where circles are inside the main piece so as far as i can work out its right there.
The size is right and if it was wrong then whole dimension for the piece would come out wrong i.e. > or< 22mm
I wonder about the machine setup but again if the pieces ae right how can the cutouts be wrong.
I am using the CNCRouterparts post processor but i barelt can scrath the surface with g code to find owt wrong

malc
VCarve Pro v9.012
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BernieNUFC
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Re: Cut dimensions are wrong

Postby BernieNUFC » Sun May 27, 2018 11:46 am

my file
I know the thickness is 6.5 on this one but it was 6 on the cut, i am altering it to try some more work on different ply
Attachments
Engine for forum.crv
(2.42 MiB) Downloaded 44 times
Last edited by BernieNUFC on Sun May 27, 2018 11:49 am, edited 1 time in total.
VCarve Pro v9.012
High-Zs 720- Kress 1050 router ( CNC-Step DE version)
BernieNUFC
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Posts: 109
Joined: Fri Apr 10, 2015 5:36 pm
Location: Haltwhistle, Northumberland, UK
Model of CNC Machine: CRP 2448, 2.2 w/c Spindle, HY VFD

Re: Cut dimensions are wrong

Postby cbr_speedster » Sun May 27, 2018 11:49 am

What's the dia. and length of the tool and what size holes are you cutting?
cbr_speedster
 

Re: Cut dimensions are wrong

Postby BernieNUFC » Sun May 27, 2018 12:09 pm

The tool is 3.15 dia and the cut flutes are 15mm
The circles are 21mm I think (out with dog)
The slots are 6mm wide but come out 4.5mm wide
Cheers malc
Last edited by BernieNUFC on Sun May 27, 2018 12:15 pm, edited 1 time in total.
VCarve Pro v9.012
High-Zs 720- Kress 1050 router ( CNC-Step DE version)
BernieNUFC
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Posts: 109
Joined: Fri Apr 10, 2015 5:36 pm
Location: Haltwhistle, Northumberland, UK
Model of CNC Machine: CRP 2448, 2.2 w/c Spindle, HY VFD

Re: Cut dimensions are wrong

Postby cbr_speedster » Sun May 27, 2018 12:14 pm

Did you try re-running the program? The small endmill at 10,000rpm and 90ipm could be flexing on the CCW inside cuts vs CW outside cuts. May need a spring pass to size the holes better.
cbr_speedster
 

Re: Cut dimensions are wrong

Postby BernieNUFC » Sun May 27, 2018 12:16 pm

I can certainly try that when I get home
Malc
VCarve Pro v9.012
High-Zs 720- Kress 1050 router ( CNC-Step DE version)
BernieNUFC
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Posts: 109
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Location: Haltwhistle, Northumberland, UK
Model of CNC Machine: CRP 2448, 2.2 w/c Spindle, HY VFD

Re: Cut dimensions are wrong

Postby BernieNUFC » Sun May 27, 2018 1:32 pm

I tried 18000 rpm and slower feed but still the same
VCarve Pro v9.012
High-Zs 720- Kress 1050 router ( CNC-Step DE version)
BernieNUFC
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Posts: 109
Joined: Fri Apr 10, 2015 5:36 pm
Location: Haltwhistle, Northumberland, UK
Model of CNC Machine: CRP 2448, 2.2 w/c Spindle, HY VFD

Re: Cut dimensions are wrong

Postby cbr_speedster » Sun May 27, 2018 4:02 pm

How much undersize are you talking? Did you add a separate last pass to make up the difference? If the hole is .020 under, make the last cleanup pass .010 then re cut the inside holes...
cbr_speedster
 

Re: Cut dimensions are wrong

Postby Adrian » Sun May 27, 2018 10:01 pm

Very much doubt it's a software issue. It's going to be bit deflection, machine movement etc.

Look at the generated code and it should be simple to work out what dimensions the slots are being cut too which will eliminate the post processor and VCarve as the issue.
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Re: Cut dimensions are wrong

Postby AlanAndrews » Sun May 27, 2018 10:13 pm

Yes, i'm in agreement with Adrian on this.

Can you provide a copy of your gcode file please?

This will allow us to confirm the correct cut dimensions are being used. If the cutter is 3.15 dia then this is relatively easy to diagnose.
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Re: Cut dimensions are wrong

Postby cbr_speedster » Mon May 28, 2018 12:10 am

Have you looked at the code? You'll notice the circle geometry is made up of small line segments and 10,000 lines of code... I prefer cutting small holes with small cutters using the helical command. Plus, if the circle was a complete circle instead of line segments the code would be much more manageable. Here's the code to helical interpolate a small hole. I don't like plunge cutting with small bits that can deflect...

N23 X22.033 Y14.0937
N24 X22.043 Z0.1 F60.0
N25 Z0.0
N26 G03 Z-0.07 I-0.1715 J0.0
N27 G03 Z-0.14 I-0.1715 J0.0
N28 G03 Z-0.21 I-0.1715 J0.0
N29 G03 Z-0.256 I-0.1715 J0.0
N30 G03 I-0.1715 J0.0
N31 G01 Z0.1 F30.0
N32 X22.033 Y14.0937
N33 G00 Z3.0
N34 M05
N35 M30
Attachments
Helical.JPG
cbr_speedster
 

Re: Cut dimensions are wrong

Postby BernieNUFC » Mon May 28, 2018 9:13 am

Thanks all for replies.
I could not work out really if there was an error in the g code as when i look at the numbers together they blend as 1, i can work out m codes but that's about it at the mo.
So here is the G Code for a sample cut i made to test it without a full cut :-)

Cheers Malc
Attachments
Profile 1.txt
(19.92 KiB) Downloaded 42 times
VCarve Pro v9.012
High-Zs 720- Kress 1050 router ( CNC-Step DE version)
BernieNUFC
Vectric Craftsman
 
Posts: 109
Joined: Fri Apr 10, 2015 5:36 pm
Location: Haltwhistle, Northumberland, UK
Model of CNC Machine: CRP 2448, 2.2 w/c Spindle, HY VFD

Re: Cut dimensions are wrong

Postby BernieNUFC » Mon May 28, 2018 9:54 am

Further to my post above, i have now tried it on other software same file speed and feed and cutter etc and it came out perfect.

I (as a novice) can only come to the assumption it is the post, it does not mean it invalidates the comments above because i intent to learn form them and when i get a min i will try them out to compare.

thanks malc
VCarve Pro v9.012
High-Zs 720- Kress 1050 router ( CNC-Step DE version)
BernieNUFC
Vectric Craftsman
 
Posts: 109
Joined: Fri Apr 10, 2015 5:36 pm
Location: Haltwhistle, Northumberland, UK
Model of CNC Machine: CRP 2448, 2.2 w/c Spindle, HY VFD

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