[Noisebridge-discuss] Moar Laser Cutter Infos

[Zach R]

Wow, that's some super useful info Danukeru!  Good thing we discussed this on this list so you came across the thread.

Mitch, if you are going to China why not just ask about the parts we need from the company based there?  Their website is actually printed on the PCBs inside the Laser Cutter: http://www.jnmydy.com/

http://s18.photobucket.com/user/Segasonicfan/media/NB%20Hardware%20Class/20151015_225704_zps2heogqs2.jpg.html?sort=3&o=1

If you get the PCBs direct from them I bet it will be much, much cheaper.  I sent them an email in English (on their English website version) but received no reply yet.  Perhaps someone can translate?

and again, let me try and fix the main power PCB before we make any decisions on buying a new one (unless someone has money to burn!).  It would be a super huge waste and would be like replacing an entire car when you just need a new battery and wheels.

-Zach


________________________________
From: noisebridge-discuss-bounces at lists.noisebridge.net <noisebridge-discuss-bounces at lists.noisebridge.net> on behalf of Danukeru <danukasan+nb at gmail.com>
Sent: Thursday, November 12, 2015 12:53 AM
To: Zachary Morriss
Cc: noisebridge-discuss
Subject: Re: [Noisebridge-discuss] Moar Laser Cutter Infos

Reading the manual for the laser cutter reveals that we could already drive the laser cutter now with a copy of EMC2.

We have a custom toolchain built around EMC2 for our hobby CNC at foulab, so I can tell you pretty certainly that your standard LPT-USB board/cable will not work due to buffering of the pin state that their controller board most certainly does.

EMC2 is a GCODE interpreter that drives an analog controller over LPT directly.

EMC2 takes advantage of the LPT port to make sure that the timing is as accurate as possible because there is very little feedback from the steppers themselves. You generally need a real-time linux kernel for the best results for this reason. Our CNC runs on an old ubuntu with such a kernel.

Due to USB being much faster, packetizatioin, driving voltage levels, no guarantee on command order, etc, there is no assurances on timing on the LPT pins with a cheap adapter.  You'll most likely have cumulative errors/jumps/ etc on actual long runs .

The LPT board in the cutter itself is very dumb and relies entirely on what is driving it. It's literally a bunch of shift registers bitbanged over the LPT by either EMC2 or the USB controller in this case.

As such this is where the buffering comes in on that small board. Proper timing and command queuing.

ie. Why Henner's BUMPS cape for the BBB uses the A8s specific programmeable PRU for real time control of the pins.



On Wed, Nov 11, 2015 at 9:00 PM, Zachary Morriss <zmorriss at gmail.com<mailto:zmorriss at gmail.com>> wrote:
I don't want to distract this perfectly excellent hack in progress, but being that the laser is EOL, it might be time to invest in some new jank:
http://www.amazon.com/Engraving-Cutting-Engraver-Parallel-Winsealxp/dp/B00C9UZCOS/ref=sr_1_1?ie=UTF8&qid=1447304268&sr=8-1&keywords=40+watt+laser

Price goes up and down and can be had cheaper on ebay.

Or even better, something with a DSP controller, z adjust, air assist, and a little moar power:
http://www.aliexpress.com/item/Free-ship-Best-price-rayjet-laser-engraver-3040-co2-laser-cutting-machine-50W-with-rotary/32247621015.html?spm=2114.01010108.3.48.cC334H&ws_ab_test=searchweb201556_1_71_72_73_74_75,searchweb0_0,searchweb201560_9

Just stirring the pot,
Zach


On Wed, Nov 11, 2015 at 8:22 PM, Brian Klug <brian.klug at gmail.com<mailto:brian.klug at gmail.com>> wrote:
> USB to DB25 Adapter Uses GRBL For Parallel Port CNC ...

The following USB <-> GRBL interface might help..?

http://www.esreality.com/files/placeimages/2013/93363-gerbil.gif

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