Hacking UM to cut stuff...

[SandervG 1,521]

What do you use underneath whatever you cut?

And wow, super cool!!

Edited December 9, 2015 by Guest

[rigs 735]

@didierklein next upgrade on your shop ?

@labern thanks ! It's perfect

[Labern 774]

Here is an example Cut. Its very fine and it cut out all the tiny squares which pushed out with ease.

[Labern 774]

What do you use underneath whatever you cut?

 

I replaced the glass with some custom wood. I did try on a piece of aluminium and it didn't effect it, so if it burns through it should be fine.

[foehnsturm 969]

@drayson, @Labern does the 455 nm laser have any impact on (well not blue) PLA?

PLA absorbs the near IR wavelength which is widely used for laser material processing (you cannot cut it because it melts first) and there seems to be absorption in the near UV.

[Labern 774]

@drayson, @Labern does the 455 nm laser have any impact on (well not blue) PLA?

PLA absorbs the near IR wavelength which is widely used for laser material processing (you cannot cut it because it melts first) and there seems to be absorption in the near UV.

 

I will try later. Not home at the moment.

[drayson 75]

hmmm... good question...

My shroud is the nearest PLA to the beam and up to now I have no bad experience.

[foehnsturm 969]

Well, actually I asked because I'd find it interesting if there was some impact Laser welding of PLA ...

[randyinla 14]

I see the most powerful one at J Tech Photonics is 3.8Watts. A buddy of mine has a Full Spectrum 20" x 12" laser cutter which has a sealed C02 laser tube @ 40W/45W/90W. Obviously, the 3.8W can't cut as deep/fast as those, but is there a similar kit to the J Tech Photonics that is closer to the wattage of the Full Spectrum? I have an U2 and an X-Carve and it would be awesome to have a single laser attachment I could use on both.

[foehnsturm 969]

Hi guys,

Quick question. Would a laser module somehow fit into a toolhead with the same width as the UM2 printhead but just 70% in depth?

[drayson 75]

My laser head is a clip-on part so the size of the head is´nt the issue...

[gr5 2,172]

 

@labern - did you set the laser to the max power with jumpers (where they say you can't run it for very long at all) and then control the pwm and mostly use it at lower power? If so what is your max fan-pwm setting for continuous use (out of 255)?

[Labern 774]

There are jumpers which you set to the max for your laser. Then there is a pot which you disconnect the laser and use a multi meter to measure the amperage. You can adjust the amperage using the pot to the max you want to use. I used the max for continuious use in this case. then use the PWM to controll it from there. So mine was on 255. You can use software to generate gcode that alters the PWM output to laser photos. I have other plans for mine though so didn't get into that.

Edited May 25, 2016 by Guest

[Wisar 86]

I have hacked my UM2+ to cut stuff and am pretty pleased with the result though I still have a couple things to iron out. I bought the JTechPhotonics 3.8W laser with their controller / power supply.

First a couple of learnings / questions. My first configuration was to use the fan PWM to drive the laser via the M106 command.

From a hardware perspective you need to do two things, first you need to get the 24V fan power down to close to the 5V PWM input. Jay, at JTechPhotonics, said the following: "For the voltage on the fans, yes it would be better if they were put down to 5V (or even 12V). The input is isolated, so it should work fine, but it was designed with 5V in mind. I think the high end of the design is rated at 24volts. If you have a way to get it to 5V then I would recommend it, but you probably are fine at 24V. " I did a voltage divider and took it down to close to 5V. Second, I installed a switch so that I could toggle between the fans working or the laser working.

There is a slight issue on the firmware side though. At least with my printer there is a spike of voltage when the fan circuit activates. I am assuming this is to help the blades of a fan spin up but have not dug into the code to see. You can see the spike using a meter or just by watching, with glasses of course, the laser turn on. Not at all optimal to have a litle black spot everywhere the laser activates! Is this on all machines?

With the above being the case I decided to go the LED PWM route. This is not as clean due to the normal state of the LED being on but I decided to try it anyway. I chose not to use a voltage driver as the supply for the LEDs is under 12V. Same comment about it needing to be switched but this time there are no spikes! There was another problem though. The LED PWM command, M42 S200, seems to get processed as soon as the firmware reads it without waiting for previous commands to be completed! You need to put an M400, wait for everything to be done, command just ahead of it (found that above in the comments on this thread).

The issue that I have now, and know this is probably mechanical, but I am getting two completely different cuts on the Y-axis versus the X-axis! I don't think that I am seeing this when I print though I will do some tests today to try and confirm this. I have a couple blog postings with pictures if you care to take a look. I guess the question for you is whether you have seen this before?

 

http://raspberrypirobot.blogspot.co.uk/2016/10/yet-more-laser-tuning.html

[gr5 2,172]

The fan-turn on command puts it at 100% briefly to get it to start spinning before starting the PWM phase. This is a flag in Configuarion.h which you can disable.

Regarding X versus Y directional cuts being different depths. It could be grain related but it could also be a focus issue where the point of light is focused (thinner) in one direction and blurrier (wider) in the other. Maybe? I don't know if that's a common problem with lasers. An astigmatism.

[gr5 2,172]

Oh - you could test the astigmatism versus grain issues by rotating the object you are cutting to see if it moves (then it's grain) or rotating the laser (then it's astigmatism if the problem moves).

[Wisar 86]

Oh - you could test the astigmatism versus grain issues by rotating the object you are cutting to see if it moves (then it's grain) or rotating the laser (then it's astigmatism if the problem moves).

 

Hey gr5, it is 'def not grain as I have done the rotation test with the same results...and it works the same with real wood and with MDF! I like the astigmatism though. I think the diode laser does cast a rectangular beam...and that could explain it. I was thinking something mechanical but the printer showed zero evidence when spitting out plastic.

On the fan...I suspected that might be the case but did not look at the source code as I really don't want to change anything that would alter printing operations as it is, after all, primarily a printer. It just dabbles in laser cutting (and some plotting). Now my challenge with the LED PWM is the need to preface the laser on and off commands with the M400. I am using a pre-processor though so it is not that hard.

Thanks, Will

[gr5 2,172]

As long as you never set the fan to below 30%, getting rid of this feature won't hurt.  Plus it doesn't work very well anyway.  If I don't set the fan to 100% until 5mm and is printing .1mm layers that is 50 layers so fan is 2%, then 4% then 6%, etc.  When it hits 2% it powers 100% for 200ms then to 2% and fan stops.  When it goes to 4% it is already on and it doesn't do the special "power on" code.  So the code is kind of useless.  It should do full power everytime power is increased - not every time fan is turned on.

In Configuration_adv.h just set the time to 0 or minpwm to 255:

 

// When first starting the main fan, run it at full speed for the// given number of milliseconds.  This gets the fan spinning reliably// before setting a PWM value. (Does not work with software PWM for fan on Sanguinololu)#define FAN_KICKSTART_TIME 200#define FAN_KICKSTART_MINPWM 20

 

Edited October 31, 2016 by Guest

[Wisar 86]

As long as you never set the fan to below 30%...

 

I am in the process of making this change to the firmware as I was not able to get the LCD PWM to work as easily as one would expect... It seems that PWM commands are executed by the firmware when ever it feels like it as opposed to in the order encountered. I guess this is part of the look ahead speed up logic but it adds some complexity. I tried using M400 to correct but things still did not seem to work as I expected so I gave up as I knew the fan PWM works but for the pulse. Anyway, thanks for the above pointer.