first pass way too deep

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first pass way too deep

Postby shelkol » Sat Jul 13, 2019 6:45 pm

Hi,
I trying to cut a simple bracket out of aluminum. I am using a shapeoko 3 with the carbide motion and a .25" end mill. Since the first pass broke my end mill, I've been trying to go slow :)

The pass depth is set to 0.010. In the simulation it does a fine job. When I make the gcode file and put it on my router, the first pass is 0.250" deep. I zero'd it manually and also used the fancy probe. I made a new file from scratch and it did the same thing. I made other files (simpler) and they behaved as I expected. I am confused> can someone please tell me what I am doing wrong.

Thanks

P.S. Can someone recommend a good gcode reference book? I've programmed in ASM, C and C++ for decades, so would just to like decode the gcode.

Thanks
Sheldon
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Re: first pass way too deep

Postby Rcnewcomb » Sat Jul 13, 2019 7:13 pm

I zero'd it manually and also used the fancy probe

Are you setting your Z-Zero to the TOP of the material? That is how your job is set up.

When I make the gcode file and put it on my router, the first pass is 0.250" deep.

How are you determining that it is 0.25" deep?

Can someone recommend a good gcode reference book?

G-Gode Reference on wikipedia

I'd also recommend select ramps to your toolpaths.
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Re: first pass way too deep

Postby ger21 » Sat Jul 13, 2019 7:34 pm

This is the g-code bible.
https://www.amazon.com/Programming-Hand ... 0831133473

But G-Code is incredibly simple.
If you see a line of code like this.

G1 Z-0.5

It means move the Z axis at the commanded feedrate to -0.5.

G-code is basically just a list of coordinates that the machine moves to, using some basic commands.
G0 - Rapid move
G01 - Feedrate Move
G02 - CW arc
G03 - CCW arc
F## - set feedrate
S## - set spindle speed
M3 Start Spindle
M5 - Stop Spindle
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Re: first pass way too deep

Postby shelkol » Sat Jul 13, 2019 8:11 pm

rcnewcomb,

Yes I have the reference set to the top of my material and I have the material thickness set to 0.125. I am just trying to cut one side of aluminum angle, so setting it on a 2x4.

I am measuring the depth with a caliper. Been using 2x4 for samples - use fewer waist boards :)
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Re: first pass way too deep

Postby Adrian » Sat Jul 13, 2019 9:03 pm

Are you sure you aren't mixing up metric/inches on your control software? With the settings you have the first pass would be 0.244mm which would equate to 0.244 inches if something is out of whack units wise.
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Re: first pass way too deep

Postby shelkol » Sat Jul 13, 2019 10:14 pm

Adrian,
If I did set something to mm, I can't find it. Plus if the first pass was set to 0.010 mm, that would be about 0.004"

I guess I will have to experiment with the gcode and see where it goes haywire.

Thanks
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Re: first pass way too deep

Postby Adrian » Sat Jul 13, 2019 10:33 pm

No, what I am saying is that if you exported the g-code from VCarve in metric and then loaded it into your control software that was expecting inches then that would account for the first pass being 0.25".

You're doing 13 passes to makes 0.125" which gives 0.0096" per pass. That equates to 0.244mm. If you saved the g-code using a metric rather than inches post processor it would write the first pass as a Z movement of -0.244 which your control software may be seeing as an inch movement.

I can't think of any other way you would be seeing a first pass of 0.25" otherwise.
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Re: first pass way too deep

Postby garylmast » Sat Jul 13, 2019 11:16 pm

Make sure the mill isn't slipping out of the collet. Possible problems could be bad or worn out collet, or too big of collet for the mill. It could also be a bad nut...the snap ring holding the collet got hot and not clamping the collet tight enough. Easy to check. See where it zeros out after the pass. If it's lower than what was originally set, that's the problem.

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Re: first pass way too deep

Postby shelkol » Sat Jul 13, 2019 11:25 pm

Garylmast: Yeah, I checked the zero after I did it and it was still fine. In fact I have just been routing the same block, so it really isn't cutting anything.

Adrian: I did another project with the same software and it worked correctly.

So what I think I will do is edit the gcode and see if I can determine which line is causing it to go that extra 1/4 inch.

Thanks
Sheldon
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Re: first pass way too deep

Postby TReischl » Sun Jul 14, 2019 1:57 am

Adrian wrote:No, what I am saying is that if you exported the g-code from VCarve in metric and then loaded it into your control software that was expecting inches then that would account for the first pass being 0.25".

You're doing 13 passes to makes 0.125" which gives 0.0096" per pass. That equates to 0.244mm. If you saved the g-code using a metric rather than inches post processor it would write the first pass as a Z movement of -0.244 which your control software may be seeing as an inch movement.

I can't think of any other way you would be seeing a first pass of 0.25" otherwise.


Don't most of the posts output the proper g code to put the machine into metric if a metric post is selected? Pretty sure the mach3 posts do that but I am too lazy to head out to the shop to look.
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Re: first pass way too deep

Postby Adrian » Sun Jul 14, 2019 8:53 am

TReischl wrote:
Don't most of the posts output the proper g code to put the machine into metric if a metric post is selected? Pretty sure the mach3 posts do that but I am too lazy to head out to the shop to look.

Some do some don't.

Just seems to much of a coincidence to me that the two measurements are near enough identical. I don't get why some projects would work and some wouldn't though.
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Re: first pass way too deep

Postby TReischl » Sun Jul 14, 2019 1:00 pm

Adrian wrote:Some do some don't.

Just seems to much of a coincidence to me that the two measurements are near enough identical. I don't get why some projects would work and some wouldn't though.


Gotta agree with you there, very suspect.

It just amazes me how many times these sort of problems appear and I have yet to see one where the software output the wrong code. One of the great things about Vectric software is that it goes through a thorough debugging process. When I have a problem I check the code first because that is the easiest thing to do but I always know it is not the issue.
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Re: first pass way too deep

Postby Leo » Sun Jul 14, 2019 8:25 pm

Can you post the problem VCarve file?
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Re: first pass way too deep

Postby Rcnewcomb » Sun Jul 14, 2019 8:28 pm

Can you post the problem VCarve file?

It is in the first post.
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Re: first pass way too deep

Postby Leo » Sun Jul 14, 2019 10:32 pm

Missed that - thank you


As to the G-Code --- when I post in mach3 - which is pretty generic - the depth of pass looks like it is posting precisely what you want it to do. .010 per pass - I don't see anything even close to .25 depth anywhere.

Look at the "Z" axis commands. Anything positive is ABOVE the material surface and anything minus is cutting in the material.

The issue you are having is not in the programming, therefore is must be in setup or in machine or machine control. The other thing, is in the posting of the g-code - like others have said, mixing inches with mm.

So, can you post YOUR g-code that you are having trouble with.
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