Author Topic: Zero position and dimensions  (Read 1788 times)

n1te

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Zero position and dimensions
« on: April 27, 2016, 06:11:18 AM »
Hello again,
i'm trying to lear how to use the machine and I have a bunch of problems!  :)

I created a new project with inkscape set the document proprieties to 100x100mm and designed a shape inside, then i used the J Tech extension to export G-CODE file.
Then I imported the generated G-CODE file in GRBL,  I can see the shape in the visualizer like in the screenshot.

When i run the file the machine move to the corner and motors hit the end, it looks like the dimensions are much bigger  from what i've designed. What I'm doing wrong?
I'm also having difficulties to understand how to set a starting position (zero)

I attach a screenshot and the G-code file generated

The firmware loaded is  grbl 0.8c, for now I want to learn how to control the machine correctly then i will make the PWM mod!


Thank you so much.

n1te




kkberg

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Re: Zero position and dimensions
« Reply #1 on: April 27, 2016, 06:55:57 AM »
$100 and $101 are interesting to know. May be you have to calibrate steps/mm before you start.
If to much steps where sent, the laser head crashes to the end of the axis.
I take 240 steps/mm from $100 for X-axis (you have to use the value your controller is showing.
Draw a line 100mm length and measure how long it really is. If it's may be 120mm long you can
calculate (100mm * 240 steps/mm) / 120mm =200 steps/mm. After that you send via grbl controller $100=200 and verify
the length of the line again.
That should solve the problem.

Klaus
« Last Edit: April 27, 2016, 06:57:17 AM by kkberg »

Zax

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Re: Zero position and dimensions
« Reply #2 on: April 27, 2016, 06:57:08 AM »
G-Code doesn't have units, but what you saved is only 2.6 x 3.

It looks like you have a combination of mm and inches in your screenshot and nothing is aligned to 0,0.

I cannot tell since not all your Grbl parameters are shown, but the machine may be attempting to "home", if it is moving to the front / left? Of course that will fail since you likely don't have limit switches.

See attached examples of drawing a 100mm x 100mm box in Inkscape, using the G-Code tools to create a path and then the saved output.

If you haven't set the Grbl parameters correctly, you'll never get any good results.

Keep in mind Grbl 0.8 (or any master Grbl) does not currently support lasers so your results will always be limited. Points will get burned dark due to the pausing and you will not be able to do engraving / scanning.

- Zax



Zax

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Re: Zero position and dimensions
« Reply #3 on: April 27, 2016, 06:59:17 AM »
Klaus would be correct IF you were using Grbl 0.9, but as you are using 0.8 his instructions are not applicable.

$0 and $1 are the values for steps/mm.

https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.8

- Zax

n1te

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Re: Zero position and dimensions
« Reply #4 on: April 27, 2016, 08:45:34 AM »
Thank you all, please forgive me I'm totally new in this.

I've loaded the 0.9c firmware and set the jumper to 0.9c but when i click on the arrows i get an error: Undefined feed rate.

What I'm tryng to achieve is make a square 40x40mm and cut it with exact dimensions.

I will not use the machine to engrave anything but just cut simple shapes of paper!

my actual grbl setting are in the screenshot i haven't  changed anything yet.


Ty

Zax

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Re: Zero position and dimensions
« Reply #5 on: April 27, 2016, 08:52:53 AM »
The machine can't move until it knows what feed rate to use, so you would have to send it an F (feed) command prior to trying to jog, so something like F1000.

I also see your parameters are wrong if you have a standard machine.

You can change them by sending $xx=yyy where xx is the parameter and yyy is the new value. Since you have T2Laser trial installed you can cheat and use the parameter download feature to do them all at once.

- Zax

n1te

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Re: Zero position and dimensions
« Reply #6 on: April 27, 2016, 09:06:01 AM »
Thanks, I'm still fighting with clickonce so I cant use your software to download the correct settings.
Can you please post them so i can change manually?


n1te

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Re: Zero position and dimensions
« Reply #8 on: April 27, 2016, 10:16:19 AM »
Now it works  ;) Thanks Zax, finally I can test your software!


Zax

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Re: Zero position and dimensions
« Reply #9 on: April 27, 2016, 10:36:42 AM »
I think it will be easier for you, but perhaps the program from @Admin will be better since you only want vector.

- Zax

n1te

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Re: Zero position and dimensions
« Reply #10 on: April 27, 2016, 11:11:51 AM »
I can't understand why my machine act like this:
https://www.dropbox.com/s/b8a5ikwibu0zo25/VID_20160427_195733.mp4?dl=0

I draw a circle or any other shape in the center and it goes on side crashing the motors.

the firmware loaded is J Tech 0.9g

About Admin sofware I'm waiting for it to be released but i'm really new in this so at this time im just learning how to control the machine correctly.

Thanks (again) :)

Administrator

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Re: Zero position and dimensions
« Reply #11 on: April 27, 2016, 12:22:19 PM »
Believe me...I'm working very hard at getting the initial beta release pushed out...while the initial release won't have toolpaths or gcode job generation, it still has a very large 'support base' of code to support those two main features down the road. The initial release will still have a lot of features to play with and test.

n1te

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Re: Zero position and dimensions
« Reply #12 on: April 27, 2016, 12:54:26 PM »
Believe me...I'm working very hard at getting the initial beta release pushed out...while the initial release won't have toolpaths or gcode job generation, it still has a very large 'support base' of code to support those two main features down the road. The initial release will still have a lot of features to play with and test.

I believe you, I develop apps for Android and I know what hard work means!
relax and enjoy programming, I'm sure that your will achieve good results and it will be an extremely usefull tool for all of us ;)

n1te

Zax

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Re: Zero position and dimensions
« Reply #13 on: April 27, 2016, 02:34:11 PM »
@n1te

It looks like everything worked correctly, let me explain.

You opened a new drawing 220mm x 170mm (presumably the size of your machine).
You created an ellipse in the center or around 100mm from the 0,0 (origin).
You sent the G-Code to the machine, so it goes right and up to find the starting point for the ellipse.

Now, how to fix it.

Option #1:
First jog the head to the lower (front) left and right click the home button to set a new 0,0 (origin).
Then send the G-Code and it will put the Ellipse in the middle of your machine.

Option #2:
Put the ellipse at 0,0 in sketch (either draw it there or click it to highlight and then click/drag to the corner or click to select it and then press P and change the parameters)

Option #3:
Select the Center (Start Point) setting before creating the sketch.

- Zax

Note: I saw you also changed the manual laser power, which has no effect to the G-Code. You should adjust laser power before creating the G-Code, but can also use that control to manually override the G-Code if really needed.

n1te

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Re: Zero position and dimensions
« Reply #14 on: April 27, 2016, 10:17:17 PM »
It makes sense now ::)

ty