[Planning] Laser plotter, belts and rods.

[GlenniT]

So, I've been studying CNC for about a week now, and I'm still stuck around the whole moving across the axis. I'm thinking of using timing belts, nema 17 step motors, arduino and Easydrivers for the steppers.

Whats annoying me is I dont know a whole lot about belts and dimensions on steppers.

For the linear rods, I'm gonna use a 16MM rod, along with SC16UU linear bearings. Would this work? my work space shouldnt be any longer than 400MM x 300MM

The motors I intend to use is the Nema-17 Single Shaft motor.

The pulley I intend to use is the STEPPER MOTOR DRIVE PULLEY 30T 3/8" .2p Would this fit on my steppers? Or even my belts?

The belts I intend to use is the TIMING BELT OPEN ENDED 1/4" WIDE 0.20XL CNC

Would this fit together? Pulley with the NEMA 17 steppers, and the pulley with the belt? And how do I go around connecting the timing belts together, seeing how its open ended? And what would be the best way to connect the belts to the axis'?

For now, it will only be a 2 axis laser plotter.


Might be a lot of questions, but I hope someone out there could point me in the right direction.

- Glenni
- Frustrated teenager.

[louieatienza]

When I was working for a sign company and awards company I ran a laser table. It was branded NewHermes but I believe they were made by Epilog.

You might be OK with unsupported rail if all you're doing is vector cutting, but if you decide to do raster cutting (like etching a photo) you might have problems with the laser beam shaking. You also probably need high acceleration/deceleration, so I'm not sure how well the small steppers will work.

The machine we had also used timing belts, but the pulleys were smaller than 30 tooth IIRC. It also housed the laser in the rear of the machine and used optics to bring the beam to the work, so if you're going this route you need to be sure your axes are light, yet stiff... Also, the table movevd up and down, first to accomodate different sized work, and second to adjust the focal point of the optics....

[Walky]

The bore for that pulley is way too big, it won't fit those steppers.

Also, there are at least two more problems:

1) The 30T pulley will give you a max of 0.03" resolution at full step, 0.015" at half step (microstepping is not linear so I'll stop at half-step).

2) Torque might be unusable with a direct pulley drive setup using such a big pulley with such small motors, when moving such weight around.


IMHO it would be better to get nema23 motors and a matching 1/4" bore 10T pulley. A little extra pulley reduction sure won't hurt, but I think a 10T pulley and Nema23 would be able to move the machine at a nice pace.

Regarding the open ended belts, they're supposed to be fixed at both sides of the axis and make the pulley with the motor move along it.

Why do you want to use an Arduino? will you write your own software?. AFAIK the Easydrivers can be connected directly to the computer's parallel port to be controlled by any step/dir controller software such as Mach3 or EMC.

Check Carolbrent's other items, he has a wide selection of pulleys and belts.


What is your budget?

[GlenniT]

Originally Posted by louieatienza When I was working for a sign company and awards company I ran a laser table. It was branded NewHermes but I believe they were made by Epilog. You might be OK with unsupported rail if all you're doing is vector cutting, but if you decide to do raster cutting (like etching a photo) you might have problems with the laser beam shaking. You also probably need high acceleration/deceleration, so I'm not sure how well the small steppers will work. The machine we had also used timing belts, but the pulleys were smaller than 30 tooth IIRC. It also housed the laser in the rear of the machine and used optics to bring the beam to the work, so if you're going this route you need to be sure your axes are light, yet stiff... Also, the table movevd up and down, first to accomodate different sized work, and second to adjust the focal point of the optics....

The shaking problem you mention, I'm not sure how much shaking there will be. I'm making it a rigid build.

Still sketching it up tho.

As for speed, I dont see why it has to be like superfast, I'm sure the NEMA 17s can handle it? But what do I know.

The Z will be in a fixed position, might add it once I get the X & Y up and running, so the focusing of optics shouldnt be a problem, for now.

[GlenniT]

Originally Posted by Walky The bore for that pulley is way too big, it won't fit those steppers. Also, there are at least two more problems: 1) The 30T pulley will give you a max of 0.03" resolution at full step, 0.015" at half step (microstepping is not linear so I'll stop at half-step). 2) Torque might be unusable with a direct pulley drive setup using such a big pulley with such small motors, when moving such weight around. IMHO it would be better to get nema23 motors and a matching 1/4" bore 10T pulley. A little extra pulley reduction sure won't hurt, but I think a 10T pulley and Nema23 would be able to move the machine at a nice pace. Regarding the open ended belts, they're supposed to be fixed at both sides of the axis and make the pulley with the motor move along it. Why do you want to use an Arduino? will you write your own software?. AFAIK the Easydrivers can be connected directly to the computer's parallel port to be controlled by any step/dir controller software such as Mach3 or EMC. Check Carolbrent's other items, he has a wide selection of pulleys and belts. What is your budget?

Budget... I recon around $500-700. Already ordered arduino and easydrivers with misc things.

10T 5/16 .2 would be a more fit pulley? Gonna read around a bit more, but most likely going out later, seing how I just turned 17 an hour ago :3

As of why the Arduino, is cause I could use GRBL. I havent even considered paralell ports.

I was considering Acme screws aswell, but all the talk about leadscrews and so on got me confused. How would I even hook it up to my nemas? If I had a clue on how to use Acme, I would most likely do a three axis router :3

[louieatienza]

Originally Posted by GlenniT The shaking problem you mention, I'm not sure how much shaking there will be. I'm making it a rigid build. Still sketching it up tho. As for speed, I dont see why it has to be like superfast, I'm sure the NEMA 17s can handle it? But what do I know. The Z will be in a fixed position, might add it once I get the X & Y up and running, so the focusing of optics shouldnt be a problem, for now.

Well, here is an example of raster engravivng... looks pretty quick to me:

Epilog laser engraver on anodised aluminium - YouTube

Epilog laser engraver on anodised aluminium - YouTube

I don't know how much "dwell" time you can have with the laser on an arbitrary point and keep your tolerances. I regularly cut Plexiglas and Acrylic for awards, and with the lens we had, needed to allow for a .005" kerf when cutting inlays and such (our software at the time did not allow for this.) Having too slow accel/decel would give out of tolerance parts, especially on the corners and curves. For plaques and other "engravings" we used a raster method such as this:

Epilog laser engraver on anodised aluminium - YouTube

Epilog laser engraver on anodised aluminium - YouTube

Our machine was very similar. If you will be doing raster, you'd also have to consider the dpi of your machine, which might affect the size pulleys you plan to use. Also on our machine, the steppers were on the axes ends, with the belts wrapping around the other ends to the moving parts.

[GlenniT]

My build wont even be close to that. I wont even touch metal with a laser, yet. More like foam / wood and paperishthings.

[louieatienza]

Originally Posted by GlenniT My build wont even be close to that. I wont even touch metal with a laser, yet. More like foam / wood and paperishthings.

Aaah, well like I said, if you're going to do profile cutting, you might be fine. Though even raster engraving in wood and foam you need to move pretty fast. You also need to vent the hideous fumes!

[Walky]

5/16" is still too big, the pulley would be off center.
3/16" would be a better fit, but you'd have to use a 5mm drill bit to get it to the right diameter.

If you're planning a hobby level machine, why not start with something simple using printer parts (which have steppers with nice small pulleys and low pitch belts) to get an idea of how it all goes together?. It might sound a little silly at first, but that way you can have a better idea of what you want to do and how to do it, and that usually translate to better results and less cost.

The leadscrew thing is not as difficult as it sounds, really.

What laser will you be using?

Happy birthday

[GlenniT]

I disassembled my dads printer today, he mad. But that is sort of what gave me an idea of how everything in there worked. Unfortunately the motors were servos, not steppers.

So after me and my cat figured how to connect stepper to acme rod, I thought why not use acme rods instead. Would my "wishlist" be compatible with eachother? The 5/16 (8mm) from the stepper, to 5/8 acme. But it only has 8 TPI, will that be a problem? Only gonna do 2 axis now, then once I get everything together, put more time into it.

Gonna use a IR laser, not sure which one yet tho, something cheapish and easily focusable.

Darned cat keeps attacking my mouse onscreen.

- Glenni

[Walky]

What is your budget for the laser? How much power (mW) are you expecting from it?

Do you have any experience with lasers, or direct guidance from someone who does?. They are not something to be taken lightly. I've been into CNC for almost 3 years and I still don't think I know enough about lasers as to try my luck with them. One stray reflection from the laser on a rail or other reflective surface can leave me typing my g-code in braille (or blind someone else), that sure wouldn't be fun. As reference, the common "keychain" laser is 5mW (and even this can cause damage if used wrong), IIRC normal commercial machines can be more powerful than 40000mW. Even a 500mW laser pointer is 100 times stronger than the keychain one and likely to blind you or your cat in one pass.

Also, check your country customs' regulation regarding laser imports, some are very strict about them.

[louieatienza]

Originally Posted by Walky What is your budget for the laser? How much power (mW) are you expecting from it? Do you have any experience with lasers, or direct guidance from someone who does?. They are not something to be taken lightly. I've been into CNC for almost 3 years and I still don't think I know enough about lasers as to try my luck with them. One stray reflection from the laser on a rail or other reflective surface can leave me typing my g-code in braille (or blind someone else), that sure wouldn't be fun. As reference, the common "keychain" laser is 5mW (and even this can cause damage if used wrong), IIRC normal commercial machines can be more powerful than 40000mW. Even a 500mW laser pointer is 100 times stronger than the keychain one and likely to blind you or your cat in one pass. Also, check your country customs' regulation regarding laser imports, some are very strict about them.

The lowest power CO2 laser engraver I know of is 20W. That will cut plexi and relatively thin wood. It gives off tons of fumes (you need at least a 600cfm vent fan going outside) and aside from the beam there is a risk of radiation exposure. You can actually buy the plans to make one pretty easily.

I actually own a Wicked Lasers Spider III Arctic 1W handheld laser. It's like looking at the Sun, the spot is so bright! I had aspirations of using it for cutting, but from what I understand it would be tough to use it to cut accurately since the diode doesn't produce a perfect round beam (it's not a collimated beam.) I've seen a small laser CNC on eBay that uses a BluRay diode, but it only cut paper IIRC.

Since the lens in our eyes focuses what we see to a point in our retinae thousands of times smaller, any laser light entering the eye can be damaging! Specialized glasses made for the specific wavelength of the laser should be worn at all times.