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New to lasers and SLA and need some info

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Jasonpgr:
I've built several FDM printers and am fairly experienced and familiar with them and how they work, but SLA is all totally new to me. So I have a few inquiries before I dive all the way in to this project.

Now that I've found some really reasonably priced laser scanner heads, complete with 405nm laser, and f-theta lens for up to 300mm x 300mm print area, I think this is definitely the way I have to go. The supplier I've been talking to has asked me some questions that extend beyond my knowledge of lasers and galvanometers, seeing as how this is my first project that involves either one that's not a huge surprise. So I thought I'd relay those questions here and see if someone can give me some more direction.

1. Laser power? I'm assuming approx 150 mw would be plenty?

2. digital or analogue galvo? I'm assuming analogue, but I haven't done a whole lot of research on how exactly I'll be driving the galvo? Will I need a separate galvo control board in addition to the ramps 1.4 I was planning on using? Can I control it directly from a raspberry pi? Again, totally new to galvos and how they work and all that, so feel free to enlighten me as to the electronics necessary to pull this off.

3. connecting table? Not even sure what they mean by this, but hopefully someone here knows what they're talking about?

The supplier is a company from alibaba.com and the model they're offering is a Model JD2203 Galvanometer, with a 405nm laser and an f-theta lens lens specifically designed for a 405nm laser and a 300mm x 300mm working area. I'm expecting the total scanning head to come in around $500 or so, which is insanely cheap compared to the other options I've found online from American Suppliers. It's a big enough savings that I'm happy to drop the $500 on one of these scanners and give them a shot. Any feedback or input of any kind would be greatly appreciated since I'm in way over my head on this build.

I'm also trying to figure out exactly HOW all the components will play together. I've been hunting around for some info about what the lasershark board actually does, correct me if I'm wrong, and it looks like it essentially scans an image, line by line, and converts it translates that into movements so the laser will draw the image that is sent (via usb) to the board. So in this instance, it will essentially be working like a DLP Projector. Whatever control software I'm using (would love recomendations for slicers and control software for sla set up) would tell the stepper to move the Z axis up/down, then send an image (rather than a series of gcode commands for all the movements of an FDM printer) to the lasershark board and it will "project" the image onto the resin. Does this mean I could use software designed for DLP printers such as NanoDLP or others if I'm using a lasershark board to control the laser?

I'm attaching the small PDF that the laser scanner company sent me with info about the galvo/scanner head thing I'm considering purchasing. I'd love all the help/guidance I can get!

Macpod:

--- Quote from: Jasonpgr on March 17, 2018, 02:50:45 AM ---
1. Laser power? I'm assuming approx 150 mw would be plenty?

--- End quote ---
405nm 50mW-150mW lasers seems popular for SLA printers. Would those work? Maybe...
This is a challenging question to answer without other system details. Some of these include:
-accounting for resin cure characteristics
-how fast the laser will be scanned
-beam focus
-beam diameter.
I see you plan to use an f-theta lense and that will help minimize some variable complexities.



--- Quote from: Jasonpgr on March 17, 2018, 02:50:45 AM ---2. digital or analogue galvo? I'm assuming analogue, but I haven't done a whole lot of research on how exactly I'll be driving the galvo? Will I need a separate galvo control board in addition to the ramps 1.4 I was planning on using? Can I control it directly from a raspberry pi? Again, totally new to galvos and how they work and all that, so feel free to enlighten me as to the electronics necessary to pull this off.

--- End quote ---
I suspect they are asking if you need a digital scanning head or analog scanning head vs galvo. If you purchase a digital scanning head I presume it will use the XY2-100 protocol and you will not need a LaserShark (nor will the LaserShark be compatible/make sense). If you purchase an analog scanner head you will need an analog controller board such as the LaserShark but first you will need to determine if the input characteristics of the heads input match. I would expect most things would follow the ILDA standard so this would be true but you would need to confirm this. I do not see analog specifications in the attached document.


--- Quote from: Jasonpgr on March 17, 2018, 02:50:45 AM ---
3. connecting table? Not even sure what they mean by this, but hopefully someone here knows what they're talking about?

--- End quote ---

The documents suggest this might be a poor translation and correspond to the mounting interface between the scanning head and laser.


--- Quote from: Jasonpgr on March 17, 2018, 02:50:45 AM ---
The supplier is a company from alibaba.com and the model they're offering is a Model JD2203 Galvanometer, with a 405nm laser and an f-theta lens lens specifically designed for a 405nm laser and a 300mm x 300mm working area. I'm expecting the total scanning head to come in around $500 or so, which is insanely cheap compared to the other options I've found online from American Suppliers. It's a big enough savings that I'm happy to drop the $500 on one of these scanners and give them a shot. Any feedback or input of any kind would be greatly appreciated since I'm in way over my head on this build.

--- End quote ---
That is quite low in cost. Generally this is an indicator that R&D costs could be avoided or that the product has been cost-optimized. I would be curious to know the KPPS rating of his scanning head as well as the stability characteristics in comparison other companies around the world.


--- Quote from: Jasonpgr on March 17, 2018, 02:50:45 AM ---I'm also trying to figure out exactly HOW all the components will play together. I've been hunting around for some info about what the lasershark board actually does, correct me if I'm wrong, and it looks like it essentially scans an image, line by line, and converts it translates that into movements so the laser will draw the image that is sent (via usb) to the board. So in this instance, it will essentially be working like a DLP Projector. Whatever control software I'm using (would love recomendations for slicers and control software for sla set up) would tell the stepper to move the Z axis up/down, then send an image (rather than a series of gcode commands for all the movements of an FDM printer) to the lasershark board and it will "project" the image onto the resin. Does this mean I could use software designed for DLP printers such as NanoDLP or others if I'm using a lasershark board to control the laser?

--- End quote ---
The lasershark driver (that runs on your computer) accepts x/y coordinates and power intensities for the laser channels, stuffs these into buffers and sends them over usb to the LaserShark. The lasershark in turn prints out these coordinates at the designated kpps rate you configured the points to be displayed at.

the lasershark_hostapp github repo provides two means to use this:
1. You can use lasersharklib to integrate the lasershark libraries into your codebase and drive the LaserShark as fast as possible
2. You can compile lasershark_stdin and pipe samples in a simple text format into the application. This latter approach is less efficient, but much easier as you do not have to learn how to use libusb/etc.

In this repo are two examples of how to use lasershark_stdin. One is lasershark_stdin_circlemaker. If you pipe this into lasershark_stdin, a circle will be drawn. The other is lasershark_stdin_displayimage which will line-by-line display a png image if you pipe the output into lasershark_stdin.


Your software would need to control the z-stepper motor (i.e. you could write a python app that controls this between layers). If you can get software to present you with a png image of each layer you could theoretically adapt it, but you would need to have some integration glue on and (all of which you should be able to confirm before buying any hardware).

Jasonpgr:
Thank you for the extremely thorough reply! So I'm slightly modifying my laser build as the company from China I was working with ended up being a lot more expensive than I had previously expected. Their lenses are incredibly affordable though, so I'll definitely be getting their f-theta lens that covers a 300x300 print area.

The total cost ended up being around $2400, but they were also charging $700 for their laser alone, so I said no thanks on that one considering the galvo doesn't need to move all that fast since it needs to go slow enough to be able to cure, and it doesn't take a super powerful or fancy laser to cure UV resin. So I figured it wouldn't hurt to save some money on these two areas.

As for the rest of the components, I've been hunting around on ebay/amazon and all that and these are the ones I've come up with instead.

for a cheap simple laser
https://www.ebay.com/itm/405nm-100mW-Blue-Purple-Focusable-Dot-Laser-Module-TTL-Long-time-Working-12V/322293392564?epid=1794342367&hash=item4b0a2ee4b4:g:0lUAAOSwCGVYAG34

and for a laser galvo
https://www.ebay.com/itm/30Kpps-High-Speed-Laser-Lighting-Galvo-Scanner/112841533160?epid=13015689010&hash=item1a45e126e8:g:tr8AAOSwyTValkuQ

If you have any components you'd recommend for a 3d printer that you've used or seen used, I'd appreciate whatever advice you've got.

Jasonpgr:
Actually, the original company got back to me and they suggested another product they have that is a galvo scanner with the housing, the f-theta lens for a 405nm laser, set up for a 300x300mm scan area, all the mirrors, and galvo bits and a laser that mounts up to the head, and they said they could do that one for $700 total. That's about the cost of just the lens from other companies I've seen, and these guys sell tons and tons of scanners and their reviews look pretty solid. I think I'm going to go this route as long as you think it should work for a high accuracy 3d printer set up. I'm going to attach the manual for your to review and let me know what you think.

Also, it turns out they can do it in either a digital, or analogue. Which option would be easier to integrate into the software? If I went the digital route rather than analogue with a lasershark board would I need some kind of usb dongle to send the xy coordinates out to the galvo motors? Could I use a standard arduino set up of some kind like an fdm printer? But rather than sending steps to a stepper driver, it's basically sending steps to a galvo motor? I've got a lot to learn before I'm able to make this happen so I appreciate whatever help I can get.

Macpod:

--- Quote from: Jasonpgr on March 27, 2018, 03:40:39 PM ---Actually, the original company got back to me and they suggested another product they have that is a galvo scanner with the housing, the f-theta lens for a 405nm laser, set up for a 300x300mm scan area, all the mirrors, and galvo bits and a laser that mounts up to the head, and they said they could do that one for $700 total. That's about the cost of just the lens from other companies I've seen, and these guys sell tons and tons of scanners and their reviews look pretty solid. I think I'm going to go this route as long as you think it should work for a high accuracy 3d printer set up. I'm going to attach the manual for your to review and let me know what you think.

--- End quote ---
It sounds interesting for everything and having a pre-assembled head with galvo/power supply/galvo amplifiers/laser/controller could save you headaches. I couldn't comment on if there were any areas of concern without a datasheet but hopefully from my first reply you know about some of the things to look out for (i.e. monotonicity/linearity)


--- Quote from: Jasonpgr on March 27, 2018, 03:40:39 PM ---Also, it turns out they can do it in either a digital, or analogue. Which option would be easier to integrate into the software? If I went the digital route rather than analogue with a lasershark board would I need some kind of usb dongle to send the xy coordinates out to the galvo motors? Could I use a standard arduino set up of some kind like an fdm printer? But rather than sending steps to a stepper driver, it's basically sending steps to a galvo motor? I've got a lot to learn before I'm able to make this happen so I appreciate whatever help I can get.

--- End quote ---

This will be dependent on the software you are integrating with and the speeds needed. If starting from scratch digital would be easier. Going digital may increase you price estimates as the equivalent of a Lasershark will need to be integrated into the head but even so it may be worth it.

If you go the digital route you will still need something to output XY2-100 protocol. An Arduino could be sufficient or in conjunction with line level shifting/etc according to the head's input requirements.

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