Terje's buildlog

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Terje's buildlog

Postby terjeio » Thu Nov 20, 2014 5:22 pm

Hi all,

I have started building two lasers, one based on the 2.x design and a smaller one for exposing photosenstive PCBs by utilizing a 405nm laser diode.
The 2.x frame is nearly complete, waiting for bits & pieces from China so I can proceed with construction.
So, for now I am working on the PCB exposer, this is based on a TI MSP430 controller, FTDI USB -> UART communication and Polulu drivers.
Toolchain is Visual Studio 2010 and C# for converting a 1200 dpi BMP file to a datastream for the controller which code is implemented
by using CCS and C as the programming language. So far so good, axes are now moving and a more or less harmless red laser diode is happily blinking.
I have got the 405nm diode already but I am not ready to fire that up yet - I guess it is best to wait until the safety goggles arrives.

The plan for this is to implement a printer driver that can drive the exposer directly, maybe a bit ambitious - we'll see what I am able to put together.

The fun thing about the exposer controller is that it may be used for the 2.x as well, my initial plan was to control it from Mach3 but a combo might be a better idea?
I want PPI control and I am thinking of implementing the counters for this, and selection logic for swiching controllers, in a TTL-tolerant CPLD, again hopefylly within my abilities.

Prototyping for the PCB exposer:

Image
Image

Terje
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Re: Terje's buildlog

Postby sshwarts » Thu Nov 20, 2014 6:51 pm

Very cool.
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2.x frame coming together

Postby terjeio » Sun Dec 14, 2014 11:51 am

Most of the mechanical parts completed now. I have decided to bolt the frame together for two reasons, corner brackets are insanely expensive here and I think they do not provide the same stiffness as bolting does. Lots of tapping to be done, but that is part of the fun making stuff. X-axis rail is a real beauty, not much frcition to overcome - bougth SH from US-based eBayer. Laser head I got is wrong way around, so had to make a fancy mounting bracket for it.
Attachments
20141214_112057.jpg
The homemade CNC-mill used for creating the parts
20141214_112234.jpg
Fixed mirror assembly, tapped and bolted joints
20141214_112214.jpg
Moving mirror assembly (prototype)
20141214_112115.jpg
Frame
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Re: Terje's buildlog

Postby terjeio » Thu Dec 25, 2014 4:58 pm

PCB exposer: after being forced to design my own diode driver due to the Chinese driver being totally useless I am now ready to move the electronics from a breadboard to some real PCBs. Hopefully I will then be able to get rid of some artefacts which I suspect is due to noise in the current setup...
Attachments
1225-5.jpg
Detail of first succesful exposure, looks promising.
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Re: Terje's buildlog

Postby terjeio » Fri Dec 26, 2014 2:13 pm

PCB Exposer: problem solved, artefacts were a combination of buggy program, bad focus, laser power and noise. I am using Dupont dry film photoresist,
it is very sensitive and I have to run the diode just above its lasing threshold in order to avoid fogging around the tracks.
Attachments
1226-15.jpg
SOT23 footprint, 0.5 & 0.3mm track widths - from final driver board
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Re: Terje's buildlog

Postby cvoinescu » Fri Dec 26, 2014 4:18 pm

That is a very nice result!
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Re: Terje's buildlog

Postby terjeio » Sun Jan 11, 2015 9:51 pm

PCB Exposer: nearly completed, no endstop switches and Z-axis control (for focus) implemented - not sure they are really needed. The laser sled is cannibalized from a 3.5" Sony floppy drive - from the days when these drives were high quality stuff. Controller is a MSP340 in companion with a FTDI 232 chip and Polulu drivers, amazing what can be done with only 512 bytes of RAM - code is just over 3k! Laser power is controlled via a DA converter, so I will look into using the controller for my 2.x for greyscale engraving. The data stream from the controlling PC is packed as 7 pixels per byte and transferred at 38 kbaud, for the 2.x this can be extended to 1 pixel per byte due to the 2.x beeing a lot slower (10-30 times) than the exposer.

2.x: got the axes moving today - soon time to order the laser tube :)

IMG_7185.JPG
Front view, some finished PCBs to the left.


IMG_7186.JPG
Controller board, made by the exposer for itself. Microcontroller and FTDI chip surface mounted on the copper side.


exposer.png
Exposer application
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Re: Terje's buildlog

Postby terjeio » Fri Mar 27, 2015 8:23 pm

After my 24V PSU literally blew up, I have been a bit slow on starting my 2.x build again. Luckily my drivers survived even as the PSU voltage surged to nearly 60V...
Yesterday I finally powered up the laser tube so I am now ready to move on. Today I have modified my PCB Exposer software to match the CO2 tube and the initial results looks promising.
Having been spoiled by the resolution of the 405nm laser it is quite a change to work with the CO2, I have started out with 3ms/pixel which seems to be a bit on the fast side. Maybe my tube/laser PSU combo is a bit slow to react, when I increase power to get single pixels to show up continuous pixels (> 10) gets too much power. Maybe this can be solved by implementing PPI?
Anyway, I think I'll stick to my plan to use my own software for engraving and Mach 3 for cutting for now.
Attachments
IMG_7355.JPG
From my initital attemps at engraving, image is 90mmx90mm @ 300dpi on some scrap cardboard. Artefacts are from me moving the cardboard while engraving.
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Re: Terje's buildlog

Postby terjeio » Wed Apr 08, 2015 3:32 pm

My prototype controller is now working as it should so I have spent a few days designing a PCB for it. It will piggy-back onto a chinese breakout board to factilitate a clean interface to Mach 3. I have to submit it to fabrication as I am not able to make it myself, too many vias for that - I will not try plating it myself. The whole design is broken down into separate subsystems and I am using i2c for communation. The setup consists of no less than five MSP430 microcontrollers and two CPLDs... MSP430 are only a few euros each so cost is no issue. The separate processors are tasked with power control, input switch handling, relay control (fans, pump & air assist) & cooolant flow monitoring, PPI handling for Mach 3 and motor/laser control for bitmap rendering. The CPLDs are for the stepper pulse counters used for PPI, 24-bit each with latching since the counters are read a byte at a time. Laser power is controlled by a 12-bit DAC, maybe this will come in handy if I want to try grayscale engraving?
Attachments
IMG_7367.JPG
Closed loop cooling, air intake is only ø 50mm - enough?
IMG_7365.JPG
Brushed aluminium skin, PCBs for power control & switches behind panels. I am abit old fashioned so no LCD-display, 7-segment leds for power level
IMG_7363.JPG
Coolant reservoir in electronics bay - maybe a bit dangerous?
IMG_7362.JPG
Closed electronics bay, air intake inside - hopefully it will work...
IMG_7359.JPG
Second mirror mount
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Re: Terje's buildlog

Postby sshwarts » Wed Apr 08, 2015 5:34 pm

You do beautiful work! Very impressive.

Scott
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