Exploroatory laser build questions

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Exploroatory laser build questions

Postby Phil B » Tue May 08, 2012 6:42 pm

I’m considering adding a laser to my arsenal of tools. I’ve built a decent cnc router before so building a laser seems doable as well. However I still don’t understand much so I have a few basic questions if you don’t mind:


1. Realistically, can a diy laser hold it’s own with regards to speed, accuracy, and reliability compared to a decent commercial machine?
2. I’m used to the ease of use of vertic s/w on my router, is there some similar cam s/w for lasers or is a print driver the best way to go?
3. What the effective cutting speed for 0.25” veneer plywood with a 40w / 60w / 80w laser?
4. When you go up in power is there some loss of detail capability?
5. How does one focus the laser for a particular job? Does the head adjust or is it all done with the table. Is there some way this can be done automatically as it is done with a router?
6. I used cnc router parts stuff on my router and like them. If I build a laser using these components as opposed to the v-bearing setup in the drawings would I run into problems associated with the increased weight?

http://www.cncrouterparts.com/linear-ca ... l?cPath=21


PMB
http://benchmark.20m.com
Phil B
 
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Re: Exploroatory laser build questions

Postby TLHarrell » Tue May 08, 2012 11:32 pm

1. Absolutely, and more. You are free to add or remove components and features at will.
2. I'm kind of partial toward FSE's software, but I'm biased. Others here would better answer based on your specific setup.
3. Depends on the material, material supplier and batch. Some cuts like butter. Some you can't get past the first glue layer.
4. Yes, and no. Higher power laser minimum firing current will be at higher power than a 40w. People here are setting up PPI which adds additional pulsing profile to the laser beam, and they are seeing good effect.
5. Depends on your particular machine. There are adjustable heads, and there are adjustable tables. In reality, automatic adjustment isn't necessary. It's added cost, setup and complexity. For the adjustable head, turn a thumbscrew and drop it on an indexing block. For the table, same idea but turn a wheel to lift/lower it. Mine's a manual adjust table. I usually run similar material, so rarely have to adjust it more than once every few parts runs and it only takes a few seconds.
6. The lighter your optics head is, the faster it can accel/decel. Very high rates are desirable for raster engraving on a laser. Feel free to use any type of linear motion system you care to use. Some (like threaded lead screws) are not well suited to very high speeds. The benefits of Makerslide are cost, simplicity and reduction of parts. If I were building a machine with no cost worries, I'd probably run THK rails. For a good balance, I'd run Makerslide for the gantry and THK rails for the other axis. Makerslide is very well designed for this application and parts are easily available. There is full documentation, so you can also pick parts you want to use and fabricate your own.
40w Full Spectrum Engineering 5th Gen Hobby 20"x12" w/ Rotary Engraver
South San Francisco Bay Area - Sales and Support Representative for Full Spectrum Engineering
408-47-LASER - Skype: whitelightlaser-thomas - Facebook: White Light Laser
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Re: Exploroatory laser build questions

Postby Phil B » Thu May 10, 2012 2:05 pm

So for engraving hardwood lets say, is there an optimal power to use for that or do you just run the machine faster if you have more power?

What is a typical speed expectation for raster engraving with a 40w – 100w machine?

PMB
http://benchmark.20m.com
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Re: Exploroatory laser build questions

Postby TLHarrell » Thu May 10, 2012 4:04 pm

Assigning a specific speed and power for a laser is not an exact thing. It will vary depending on a ton of factors including software, hardware, age and power of tube, raster speed, and others. It is advisable to do test cutting of the material to determine the optimal settings for your machine.

Speed of engraving also relies on your DPI settings, or number of scans per inch. The more lines of scanning, the more time it will take. I usually use 250DPI. Engraving time will also vary on how the software handles the engraved areas, and will also vary based on how you set up the engraving. If you are engraving an outline it will take a lot longer than a few lines of text in the middle of an object.

My machine averages about 25 minutes to do a full photo on an area 8"x8". This is only an example. Your results could vary widely.
40w Full Spectrum Engineering 5th Gen Hobby 20"x12" w/ Rotary Engraver
South San Francisco Bay Area - Sales and Support Representative for Full Spectrum Engineering
408-47-LASER - Skype: whitelightlaser-thomas - Facebook: White Light Laser
TLHarrell
 
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Re: Exploroatory laser build questions

Postby Phil B » Thu May 10, 2012 4:48 pm

So what kind of power are you using to do that photo? If you had more power would you be able to do it any faster or does it not matter after you have reached a certain satuartion point.

Is it faster to do a 8x8 photo as opposed to a 8x8 b/w graphic?

I'm just trying to get an idea what the machines are capable of and the time it takes to do it. If they are glacier slow or hard to use then it becomes a deal breaker. I also don't want to build a 60w machine only to find out 120w is the minimum required to be productive.
Phil B
 
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Re: Exploroatory laser build questions

Postby TLHarrell » Thu May 10, 2012 5:47 pm

Specifically, for what you're talking about doing - engraving on hardwood, I assume plaques and/or picture frames - a 40 watt laser will do it. Cost of a laser goes up exponentially with power. Bigger tube, bigger power supply, bigger cooling system, larger case to hold it. On my 40 watt, I can cut up to about 1/4" thick material, depending on the material. Higher power may or may not be able to do better in some cases. If I were to build a new laser, I'd probably head for the 60-80w range just to give myself added cutting capacity.

Think of raster engraving like a big inkjet. The larger area you're "printing", and the more scans you do, the longer it will take. The lighter your laser flying head is, and the better your drive system is, the faster the head can move. Due to using stepper motors, at some point speed cannot go higher due to dropping steps, or the limitations of the pulses sent to the laser for creating the image. More power won't go beyond this limit.

All the images you would send to the laser are black and white entirely. The laser itself is either firing or not as it passes over each "pixel". This is not true of EVERY machine. Some people are working to implement variable power so images can be engraved as a "3D" effect, but the effectiveness of this is limited by the speed of switching a CO2 laser. The newest software for my particular machine is implementing 3D engraving, but doing it with multiple raster passes, thus multiplying the time it takes to complete. It is a nice feature, but I likely won't use it often.

These machines are quite fast at engraving, and the quality of the engraving is fantastic. You've likely seen commercially produced laser engraving on hardwoods before. The exact same effect can be achieved with the Buildlog laser design and others. For the cost, these lasers will easily pay for themselves and are certainly fast enough for hobby level work on up to mid-grade production work with some optimization. Certainly not glacier slow, but on some jobs I run I find something else to do around the laser while it's running. (Note: leaving a laser running without supervision is a bad idea.)

If you're looking for something ridiculously fast, you're getting into scanning galvo lasers... the cost of these is very, very high.
40w Full Spectrum Engineering 5th Gen Hobby 20"x12" w/ Rotary Engraver
South San Francisco Bay Area - Sales and Support Representative for Full Spectrum Engineering
408-47-LASER - Skype: whitelightlaser-thomas - Facebook: White Light Laser
TLHarrell
 
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Location: Morgan Hill, CA

Re: Exploroatory laser build questions

Postby Phil B » Thu May 10, 2012 6:30 pm

So, the power isn’t continuously variable then? I thought it was to do photographs.

So if you drive your machine via a printer driver interface, do you manually adjust the power then “print” or is power set in the printer dialog?

The envelope I’m thinking of at the moment is about 12x30, do you think the gantry needs to be beefed up any to span the distance?

PMB
http://benchmark.20m.com
Phil B
 
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Re: Exploroatory laser build questions

Postby TLHarrell » Fri May 11, 2012 4:34 pm

Most (I am not an expert on all) software for driving lasers allow you to set the power and speed levels per color (red, yellow, green, blue, cyan and magenta usually) and a power and speed setting for engraving (white/black). Photographs are done by converting to an indexed image with black and white only. Some software is better at it than others. I get mixed results using GIMP and RetinaEngrave. Some software does additional dithering and effects to make the image better looking.

As far as where you set the power and speed, it depends on the specific software. On RetinaEngrave, I load up a .XPS file with the linework in it, then assign the speeds and power for each color in the software. There is also the possibility of setting up preset power/speed combinations for each color in a setup file. All laser software operates in a similar way. It's pretty easy once you get into it.

A bit of an odd sized envelope. For a 30" gantry, I'd assume more like 18" or 24" for the other dimension. With Makerslide, I'd definitely consider beefing it up a little with a 1/16" steel doubler plate, some L-channel or an extra piece of extrusion for such a long span.
40w Full Spectrum Engineering 5th Gen Hobby 20"x12" w/ Rotary Engraver
South San Francisco Bay Area - Sales and Support Representative for Full Spectrum Engineering
408-47-LASER - Skype: whitelightlaser-thomas - Facebook: White Light Laser
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Re: Exploroatory laser build questions

Postby Phil B » Sat May 12, 2012 2:27 am

The 12x30 envelope is where I would start, I might expand that to even 30x30, depends on if I intend to engrave a certain product or not.

I’m still a bit confused about the s/w – control aspect. For instance does retina engrave and it’s hardware replace the dsp controller or is it in addition to?

I doubt I would want to use mach3 by itself to control the machine so how does one control / setup the motor settings, switch inputs on a diy machine?
Phil B
 
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Re: Exploroatory laser build questions

Postby TLHarrell » Mon May 14, 2012 6:50 pm

Retina Engrave is a controller card, which would be used as an alternative to the DSP. For the electronics, you will have a power supply, motor controller card (stepper drivers) and either a DSP or Retina (or directly drive the motor controller via parallel port). The Retina card or DSP would then be sent information via USB.

As far as setting up the pinouts for the motors, switches and everything, there's wiring diagrams available here on the site in the support documentation. The DSP will also come with the information needed to hook it up. Once you have the electronics in hand, they are usually well marked as to what connects where. It seems like it's a difficult thing until you have the hardware. It's actually pretty simple stuff. There will be other information to set up on the controller software side of things, and this information is also available here as either documents, or configuration files. As far as the DSP, others would be able to answer more specific questions as I do not have one.

The only touchy/hazardous part of the setup of a new machine is dealing with the high voltage side of things. You need to take your time to make sure the wiring is run cleanly, not nicked, and not shorted anywhere, and that it is firmly connected to the tube. And you need to make sure to start the tube firing with the potentiometer turned way down at first to make sure you do not overdrive it (15ma max recommended). You take each part of the system one at a time, and each system is extremely simple.

For software, usually you would use a package like Corel Draw, Inkscape or other software which is capable of outputting VECTOR formatted information. I personally use Autocad r2000 as I'm really good with it and don't need to learn new software just to run the laser. Once you have the vector lines for cutting, and the images for rastering, you export a file that is compatible with your particular hardware.

If there is anybody near you that has a laser system, or if there is a local Tech Shop, hackerspace, school or whatever, I would highly recommend you taking a trip over and looking through a laser system. Take particular note of how each part of the system looks and is set up. You want to see the motor controller, DSP, power supply, laser tube, mirror X/Y drive system, cooling system and exhaust system. Also see if you can check out somebody setting up a demo cut file on a computer and the process to get it from design to laser. On my system, I can simply pop a few doors to see everything. I can also get a demo drawn, transferred and cutting in a matter of a couple minutes (including booting up the controller PC).
40w Full Spectrum Engineering 5th Gen Hobby 20"x12" w/ Rotary Engraver
South San Francisco Bay Area - Sales and Support Representative for Full Spectrum Engineering
408-47-LASER - Skype: whitelightlaser-thomas - Facebook: White Light Laser
TLHarrell
 
Posts: 386
Joined: Thu Jul 28, 2011 11:30 pm
Location: Morgan Hill, CA

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