Educa's BigFoot

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Re: Educa's BigFoot

Postby educa » Thu Apr 26, 2012 2:27 pm

Looks nice,

I'm currently busy with mounting all parts so that will still take a considerable amount of time since all the special alu parts have to be milled individually.

Also looking now at a way to do limit/home switches using slotted optoswitches to eliminate mechanical contacts (+ they sound more sexy) :)
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Re: Educa's BigFoot

Postby educa » Fri May 04, 2012 12:23 pm

There is a reasonable big chance that I will try to power the complete machine with a beaglebone

For the people who don't know a beaglebone, it is a 720Mhz arm cortex board which runs linux, has 256Mb ram, SD, Ethernet and there is are 2 extra onboard controllers with each 200Mhz speed which can do very precize timings.

Currently learning a lot but this device looks like a very capable candidate to do very high speed signal processing for the laser, especially the speeds needed for raster engraving and PPI.

Image
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And we have liftoff

Postby educa » Fri Jun 15, 2012 7:11 pm

Hi guys,

The beaglebone adventure is going quite well and I have almost working code with full PPI support at steprates upto 60kHz

Today I did another test, since the Y axis is completely ready on my machine and so I decided to do a speed test.

The speed on video is 500mm/s . I was able to go upto 700mm/s before you clearly hear that the stepper would like to divorce from me :)

Anyway, I cannot imagine this axis ever to run at speeds above 200 or 300 mm/s , so the results are superb.

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Re: Educa's BigFoot

Postby evokanivo » Fri Jun 15, 2012 8:41 pm

Would you mind explaining what portion of the required processing the board is doing? I can't tell what software it's running or what it interfaces with. Are you building off the standard starting images?

I'm currently doing my own pulse generation and would like to get over 100kHz on bare metal, which is above the limits of my current dev board. So thanks for letting me know about the Beagleboard - it's cheaper and more powerful.
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Re: Educa's BigFoot

Postby educa » Fri Jun 15, 2012 9:49 pm

Actually I don't use beagleboard but beagleBONE. Ist of the same family.

The big problem with these kinds of boards is that the linux os isn't realtime, so you cannot get very accurate timings.

Fortunately the beaglebone also has some kind of mini CPU called PRUSS which runs on itself at 200mHz and can accept commands from the c code running on the beaglebone.


I cannot give a lot more information currently as I have to give credit to somebody else for the low level stuff.
A person from Holland is building a cape for beaglebone + the needed PRUSS driver.

Once that is ready this person is going to make the cape available commercially, but we are nog in betatest.


I just bought a beta board and am going to assist in the higher level code to run lasercutter. The lower level high frequency code is still his stuff.


So.. in future I will be able to tell more.


By the way, what you see on the movie is a testrun with EMC2 under linux, not yet the bone since EMC2 has such a nice testing routine that I didn't care to create it on the beaglebone just to be able to discover possible speeds and accelerations :)
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Re: Educa's BigFoot

Postby educa » Wed Jun 20, 2012 9:10 pm

While the Y axis was running smooth, it was time to start working on the X axis.

See how smooth this one will run

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Re: Educa's BigFoot

Postby educa » Mon Jul 09, 2012 9:35 pm

Time for a few updates.

The machine now works in all 3 axes.

Some videos I made since the working of the Y axis are the working of up-down table , the X axis + the alignment of mirrors while testing with a red laser pointer







I don't like the sound in the last movie. Its because my energy guiding chain makes this noise and I need it to guide the air tubing for the air assist. Maybe I should try to find much smaller energy chain for this...
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Re: Educa's BigFoot

Postby Techgraphix » Mon Jul 09, 2012 9:49 pm

educa wrote:I don't like the sound in the last movie. ...

Maybe it's gone when you put the airhose in it.. Maybe also a wire for the Z-autofocus-sensor and one for a Pilot-laser-light? In that case you shouldn't go to small..
But: it's not a musical instrument... some mechanical noises are considered normal..

Kees
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Re: Educa's BigFoot

Postby educa » Mon Jul 09, 2012 9:56 pm

Airhose is allready in it. Pilot laser is going to come through the mirrors as a drop in replacement when lasertube is off

The only thing which might interest me is autofocus, but I still don't know how on earth I would do that. Ideas ??? I though I was going to do that with a focus gauge, but autofocus is a lot nicer of course
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Re: Educa's BigFoot

Postby Enraged » Mon Jul 09, 2012 10:07 pm

can the autofocus be a subroutine you can run? if so, you could just use a microswitch on the laser head, and the have table rise up until it touches, and then back off a set distance to the focal length.
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