445nm laser CNC help - Mega 2560

Hey All,

This is my first post here, as I am pretty sure that going with RepRap is what I want to do for my project. Here is the project:

Create an inexpensive CNC low power laser cutter that competes with Cricut machines (up to $300 !!) that can cut paper and burn wood and etch plastic DIY style.

I have a 1 watt 445 nm blue laser mounted and cooled, the x and y axis mechanically sound using salvaged printer steppers and Sparkfun 4.3 stepper controllers hooked up and controllable via any of my Arduinos (Mega 2560 or Duemilanove).

The part that I need some help with, and the reason for this post, is getting from a .dxf file to controlled motion.

Can I install and use my Mega 2560 or Duemilanove with RepRap software to accomplish 2 axis motion control? If so, can you point me to any tutorials that might be helpful.

Thanks!

Hi 445Builder,

... all reprap-firmwares handles 3 steppers and temperature controlling, so you can't use them directly ... but with some programming skills you can tweak them for 2D only without temp. control ...

I'm busy with laserdiodes too - 405nm/200mW, 445nm/1W ... fibercoupled 808nm/25W and 975nm/5W.

But i use them in a CNC-controller setup where i run my normal CNC-software and switch them ON/OFF with my 'coolant' output.

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Hey Viktor,

Thanks for the quick reply. I have been reading a lot of your posts and it seems like you are the laser master!

How would you suggest I go about achieving my motion control? I have moderate skills when it comes to coding, as a mechanical engineer it is not my first language.

Do you use RepRap to do your motion control?

Thanks,
445Builder

... actually i'm using an Isel-CNC-mill with some tweaking regarding the outputs and sometimes an Atmega168 for laserbeam-shaping, but the next weeks i'll build a 'RepStrap-conversion-kit' for replacing the Isel-interface by a RepRap-motherboard or an ArduinoMega with the FiveD_on_Arduino-firmware.

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Very interesting, please keep me posted on the FiveD_on_Arduino process. I read through the description and it looks like something that I could handle.

I might go home and download that tonight to see what it is all about.

445Builder

445Builder,

What are you building? A gantry-type machine out of extruded aluminum?

Do you want to do it up in the wiki?

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

Hey Sebastien,

I am unsure of the technical term for what I am building, but if by gantry you mean, a fixed base with mobile axis then yes. Think of any CNC plasma machine, but out of old printer parts. For now I don't have any extruded aluminum but I will go that route once I get the proof of concept up and going.

I would not mind making a wiki, but I am stuck at the controlled motion part of my build. If I can get some help making this a complete project that I would be more than happy to share via a wiki.

445

So,

a bit like the new project:
http://reprap.org/wiki/WatBot

Do you have a working name for your machine?

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

... look at the atached images in this post - maybe you can build a similar setup with your salvaged printer-parts.

It's a plotter-design rigid enough, so the manufacturer offers the options to convert the base in a millbit- or laser- engraver

Most common plotter-designs drives only one side of the arm and let the other run passive, so you can't apply higher loads or forces than needen for the pen-head. With synchrone driving on both sides you'll have enough stability for load, but you need a good feeding in X and Y for avoiding mechanical oszillation of the toolhead ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Sebastien and Viktor,

The WatBot looks exactly like what I would like to build as a finished product. I currently have something resembling that built but out of my printer parts. Sorry for the poor quality images, they are from my cell phone.

I have a video that I can upload to youtube later tonight showing my "control" of one of the axis and the laser on and burning a line in my desk.

So, I can currently place a piece of paper in the machine and burn a line in it at whatever specifications I set the stepper to operate at, then I can tell the Y stepper to move in the Y direction and proceed to burn another line.

I just can't seem to figure out how to make the steppers work together to get any meaningful output.

I do not have a name for this build, any suggestions?

445

Edited 1 time(s). Last edit at 11/04/2010 10:13AM by 445Builder.

... you need a software, that controls all the steppers synchrone what's made with the firmware for 3 steppers, the extruder and temp-control.

As you have only two motors, you can try to use the Arduino with modified RepRap-firmware where you deactivate the temp-controlling.

The Z-coordinates can simply be ignored ... or maybe you can embedd laser-ON/OFF in the code with Z-coordinate set to 1 for laser on an 0 for laser off - then the dir-pin of the Z-axis can be used for switching your laser.

You can create a gcode-file for testing your system manually by writing the lines in a text-file - the specific g-codes are documented somewhere in the wiki ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Thanks Viktor,

Exactly what I was looking for. I will try my hand at modifying some rep-rap software this weekend. I'll keep the forum posted on my progress.


445

445builder, have you looked a EMC2 as the control software? I have not used it myself, but it is geared more towards many forms of CNC, and might even have a mode for laser cutting already defined. It only runs on full size laptop or desktop computers, but can probably be configured to send commands to a microcontroller running you X-Y stage stepper motors.

Mike

Mike,

I have looked at EMC2 and my main sticking point is that I no longer own a single computer that has a parallel port on it. I know it's sad, but people on Craigslist want ~ $75 for some old machine.

My goal was to use what I had (arduino) and to learn about to motion control in the process. I am documenting my build so that I can make a wiki and share everything from the mechanical and electrical to software configuration for a laser build. I looked around and could not find something low cost like that already in existence.

If I can not make RepRap work, I will break down and buy a hunk of junk and switch to EMC2. Thanks for the suggestion.

445

That makes sense. Then you best bet is the modified code for your arduino.

Mike

I envisage you could trivially use a photodiode feedback as a "temperature" and the laser itself as a "heater", leveraging the firmware's existing capabilities to precisely control laser brightness.

Alternatively, you could connect the laser to the extruder step output, thereby "extruding" groups of photons.

Both of these possibilities should be possible with any of the reprap firmwares. You just need to work out how to convert dxf into suitable gcode.. extrude to 1 layer thickness in blender, or pester enrique to add dxf input to skeinforge perhaps.

Leave Z unconnected, although you may need to figure out what to do with the opto endstop input.

Ultimately, you may find that you need more laser-oriented intelligence, or you may not. keep us posted

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Wooden Mendel
Teacup Firmware

Triffiid,

Thanks for the advice. Where do you think the photo diode should be placed? I was thinking that it would have to be place so as to collect the reflected light and if that was the case it would have to be adjusted for the emissivity of the material every time the material changed.

Since I plan on using this for vector only (as I think it would be really hard to get RepRap to support a raster output, EMC2 would be better for this) I am planning on having a simple on/off trigger and am leaning toward going off of the Z height as suggested by Viktor.

A little update: I tried to get some RepRap code up and going on my Mega 2560 last night and although it compiled and got sent without error, I could not get any movement out of my stepper that I had hooked up via a Spark Fun V4.3 Stepper controller. I tested the stepper controller and it works on the Mega with previously used code.

I was using the "nudge" function in the RepRap interface to do the test on the X step and direction pins. Is there another way that I can test to make sure that there is communication between the interface and the Mega? I was thinking of something simple like making an LED blink.

445

Hey All,

I attempted to take apart the code tonight and did not get too far. Any one who has a Mega and want to help with some coding, please PM me.

I am trying to distance myself from the temperature and extruder control and my hack and slash method of "fixing" the code has not gone very well.

445

Hi 445,

... i have an Arduino Mega and plans to rewrite the firmware for 2D+diodelaser, as i have a plotter perfect suitable for this and some other 2.5D applications too - but this will take some time, as i'm busy now with some more urgent tasks ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Viktor,

Good to hear. I'll keep you posted on my progress, but it will be slow at best. Good luck on your current project.

445

445Builder,

I am developing this electronics for RepRap [reprap.org] and I am planning to have a module for laser cutter/engraver.

Right now I bought the 1W 808nm diode + housing + protection goggles. I would love to make the same as here, but with laser controlling from board<-software: [wiki.makerbot.com]

Hey, I am sure you can use the straight RepRap firmware for what you are looking for!!

For example, Skeinforge generates GCode for laser and not just for plastic extrusion...

And you can always remove from the GCode files the M commands that deals with extrusion temperature. For example, you can try to make a 3D file from 2D SVG files, then put skeinforge generating just the 1st layer (2D) and disable the output of M codes for extruder temperature. You would ended up with movement on X, Y , Z and E axis, and you can disable the electronic connections of Z and E and then you have just a X and Y movement as you need ;-)
(see here the examples for plotting: [reprap.org])

Edited 1 time(s). Last edit at 11/25/2010 06:05AM by casainho.

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