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My DIY Laser CNC build...

rusirius

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Take this with a grain of salt since I don't claim to be an expert by any means, but the ttl driver should have some specs about what clock it can support. I've seen some in the past that should be more than capable of handling it. The reason I chose to go with analog modulation over pwm is just because it makes me nervous having the diode get blasted like that. From one extreme to the other so quickly. Don't get me wrong, I have driven leds like this a lot in the past with no noticeable ill effects, and it really shouldn't be a problem but for some reason when I think about an expensive diode versus a few pennies for an led it just gives me pause. The other advantage that made me decide on analog modulation was that the driver I'm using has a zero adjust, so you can set the lowest modulation to bring the diode just a hair below lasing. That way you have the largest range of power yet the diode is always powered and ready to go.

As for ramps, does it only support 3 axis? The reason I ask is because the setup I'm going to use will allow the laser power to be controlled just as if it were a stepper on another axis. So using the B axis for example, stepping in a positive direction increases power while negative reduces it. If ramps won't handle another axis, then perhaps the mechanical method I described could be used?
 

rusirius

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Ok, here's a quick update. I'm going full scale now. I've decided to use the OpenBuilds "V Slot" extruded aluminium for the build. In the mean time the project has grown considerably. I've now decided to make this a multi-purpose machine. It will have swapable heads. The first will obviously be the laser, but once it's working I'll also be fitting it with a spindle for routing/milling and follow that with an extruder to be able to do 3D printing as well. I haven't actually calculated the build area yet, but rough estimates it should be approximately 24"W x 20"D x 12"H. I've ordered the parts to build the frame, so I'll update with some pics hopefully soon! For now he's the CAD model I've done.



 
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Wow, 24x20? That's a huge build plate, pretty much double what I'm working with now. That could almost be too big, as far as 3d printing goes. It might be difficult to source a surface flat enough for a reasonable price. Of course, you could always have a smaller, and removable, surface just for printing, it be easier to heat this way, too. Good luck with your build! And since you're getting the stuff from OpenBuilds, why not post a build log there, too? You know, for fun. :whistle:
 

rusirius

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Wow, 24x20? That's a huge build plate, pretty much double what I'm working with now. That could almost be too big, as far as 3d printing goes. It might be difficult to source a surface flat enough for a reasonable price. Of course, you could always have a smaller, and removable, surface just for printing, it be easier to heat this way, too. Good luck with your build! And since you're getting the stuff from OpenBuilds, why not post a build log there, too? You know, for fun. :whistle:
That's exactly what I planned on doing. A 3D print even close to that large would be pretty crazy. I plan (when I get to the 3D printer part) to have a large glass pane that will hopefully be close to the full size of the table, just so i could print something that had a wide width or long length when using PLA. For ABS I'll just have a small glass pane with heatbed under it.

The size of the machine was really more about the laser/routing portion of it.

And I did actually. I just haven't updated it yet, hopefully today or tomorrow. I now have the frame fully constructed and motors tested and working. Next step is to get the laser set up. I'm currently waiting for my driver which has shipped from Russia. Just not sure how long it'll take to get here. :)

I also constructed an RC low pass for use with the driver once it arrives. (Fourier translation equations make my head hurt. LOL) It looks good on the scope, but I want to see the output of the driver itself with it as the input to make sure it looks good there too. Right now it's got very little ripple (a few millivolts) with a response time from 0 to 90% of less than 1ms. Given the engraving speed that should be WAY more than adequate. I calculated with a pretty high feed rate anything less than 5ms should make it very happy, and most pixels won't go full swing from one end to the other anyway.
 

rusirius

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So I got some building done over the holiday. Still a ways to go but it's getting closer. The motors are installed and linear motion is working great. I've got a couple of small issues to work out but I'll be working on getting the laser and electronics set up and mounted soon!

 

rusirius

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Got a few more things done tonight. Mostly bracing. Also got the diode in the module and the module installed in the heat sink I made last night.


 

LaserCo

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rusirius this is very cool! I like the idea of it being a 3d printer, laser printer or mill. how much money did this batch of aluminum to build this cost ?

+r thanks for sharing
 

rusirius

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LaserCo,
I need to do a count of the parts I used. I ordered a bunch of stuff just to have in case of design changes, etc... Which I'm glad I did as it morphed a couple of times. I'll get a parts list here soon and get some exact figures, but right now I'd estimate with everything (driver, frame, diode, electronics, etc) I probably have about $500-$600 in it. That's just a guess though.

On a side note... I managed to destroy my diode (and laseorb along with it). I was modifying the driver circuit to have a "low power" and "high power" switchable mode. So for cutting, etc it can be switched to high power and the 256 steps of resolution on power go from 150mA to 1.8A... In the low power mode the 256 steps cover from about 150mA to 500mA. Because for burning gray scale images you need the lower end of the power range, but want all 256 steps for more accurate reproduction. Unfortunately at one point in testing a combination of "3am should have went to bed" errors bit me. Between misreading the color codes on a resistor and turning the trim pot all the way up thinking I had turned it all the way down I blew the diode and laseorb big time. Now I'm waiting for my replacement to test further. Initial testing looked really awesome though!

Here's a rough schematic of my control boards and control panel. I'll post additional pics later of the actual unit.

 

Joelaw

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ruSirus,

which linear rails and rollers are you using. It doesn't look like the rails supplied from OpenRail. I was looking at IGUS rails but they come out to be pretty expensive even for the cheap ones.

The rails and rollers seem to be about the most expensive parts for this kind of project. Someone must make reasonably priced parts.

Thanks for posting your project. Much inspiration for others.

By the way, I live in Maryland and probably not too far from you. Maybe get together sometime in the future.

Joe L.
 

rusirius

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Joe,
I'm not using open rails, or rails at all for that matter. I'm using the open builds v slot. I'll post up some closer pics probably tomorrow, but it's really nice and really cheap compared to using rails.

You might get a better idea from some of these additional pics, but I'll get better ones for you soon.

click to my openbuilds page

Basically the slot in the aluminium is beveled instead of square like normal t slot. That let's delrin rollers mesh up and roll perfectly on them. Even using the belt and pinion style system there's no slop or play and no detectable backlash.
 
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ideas

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*subscribed*

congratz on ur build so far (I just finished my small CNC with one sled and one mini stepper from a 1985 HDD drive :) ) I'm finetuning the settings and software now (gbrl through arduino).
 

LaserCo

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very cool, I checked out the other page you have going on this also.
for an open source driver you might want to keep an eye on a recently re-opened (OLD) thread on the StanWax Driver over at PL, it is being redone and at least even the circuit boards will be available.

You need to get that lasorb as close to the diode as possible, straight across the leads even, for them to do what they are supposed to do requires "0" resistance as there is a high current surge and having it wired as you do will not be very effective.

I await the stage where it becomes a mill, hopefully before the 3D printing tests.
 

rusirius

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very cool, I checked out the other page you have going on this also.
for an open source driver you might want to keep an eye on a recently re-opened (OLD) thread on the StanWax Driver over at PL, it is being redone and at least even the circuit boards will be available.

You need to get that lasorb as close to the diode as possible, straight across the leads even, for them to do what they are supposed to do requires "0" resistance as there is a high current surge and having it wired as you do will not be very effective.

I await the stage where it becomes a mill, hopefully before the 3D printing tests.
It's about as close as I can get it. There certainly isn't any room in the module as it's mostly a solid slug, and behind it in the heat sink I don't think is large enough. As it is there is only about 3.5" of wire between it and the diode. I just don't think I can do any better than that. I'll do some examinations and see if I can possibly get it closer.
 




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