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Buildlog Title: Laser Build (Based on 2.x)

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Builder: karsten
Member Since: 2015-08-13

Friday, June 17th 2016 - 4:53 AM

good day members of this forum!

I almost finished the machine, but i have a problem with one of the Motors/Drivers

I am using this for the Y axis

Motor:.9deg Nema 17 Unipolar 12V 0.4A 32Ncm Double Shaft 17HM19-0406D
Info(http://www.omc-stepperonline.com/9deg-n ... p-121.html)

Driver: Bipolar Stepper Motor Driver Max 3A Current 128 High Subdivision ST-7128
Info(http://www.omc-stepperonline.com/bipola ... p-244.html)

Its connected as bipolar ignoring the 2 cables as is described in the diagram, the motor works but it does a bit of noise, more than enough for notice, i think the problem is the current, but im not sure, can you tell me? and if its possible recommend a replacement how works fine?

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reader comment Comment from: cvoinescu on Saturday, September 12th 2015 - 9:43 PM
_ID_ wrote:Focal length-more is better. At focusing the beam you have the hot spot, witch is the sharpest point in the cone of the beam. After that point the beam starts to expand again and loses its power. So longer the focal length less steep the angle of the cone is. Result is better cut-you have less angle on the edge of the cut.

While that is partly true, mother nature isn't quite that helpful here. If optics would follow geometry perfectly, you'd be exactly right. However, diffraction makes the spot wider and fuzzier than pure geometry would have it. Instead of a double cone, the beam never focuses to a point. Instead, it just goes thin then wide again, like the pinched part of a hourglass -- only fuzzy on top of that too. The carbon dioxide laser has a very long wavelength, so the effect is a significant limitation. For the same diameter lens, a short focal length would have a higher numeric aperture and hence less diffraction, so the beam would get fairly close to a point in the focal plane. A long focal length would have a large depth of field, yes, but its smaller numeric aperture would cause the beam to be much more dispersed even at the exact focal plane. For cutting thin materials and engraving flat objects, then, a short focal length is much better.

_ID_ wrote:Diameter of lens/mirror does not affect the laser beam quality.

The beam width makes a difference, though. For the same focal length, a wider beam focuses closer to a point (higher numeric aperture, lower diffraction), but has a shallower depth of field (wider cones). Unfortunately, the beam width is set by the construction of the laser tube. (Beam expanders exist, but I don't know whether they improve diffraction the same way as a laser with that native beam width; they do make the depth of field shallower, as you would expect.)

Typical focal lengths for small lasers are 25 mm (for fast, precision cuts with small kerf in flat, thin media), 100 mm (for slow, wide kerf cuts in thick materials), and 50 mm (a reasonable all-round compromise, and the best choice for medium-thickness materials).
reader comment Comment from: _ID_ on Friday, September 11th 2015 - 6:14 AM
Regarding the belt length. You can go in one loop around all 4 screws or with 3 shorter belts (1 longer on x axis and two shorter ones on each side of the y axis).

Mirror diameter- more is better-it's easier to to aim the bigger "target".
Lens diameter- the same as for the mirror.

Diameter of lens/mirror does not affect the laser beam quality.

Focal length-more is better. At focusing the beam you have the hot spot, witch is the sharpest point in the cone of the beam. After that point the beam starts to expand again and loses its power. So longer the focal length less steep the angle of the cone is. Result is better cut-you have less angle on the edge of the cut.
Attachements...
Laser focus.jpg
focal length
belts 3x.jpg
belts

Wednesday, September 9th 2015 - 9:31 PM

You are right cvoinescu its the Y axis, sorry :P

I started purchasing some pieces, waiting to arrive :)

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reader comment Comment from: cvoinescu on Tuesday, September 1st 2015 - 12:12 PM
I don't know the answers to the other questions, but the unipolar motor is fine: it's 6-wire unipolar, so it can be wired as bipolar simply by ignoring the center taps of the windings (typically white and yellow wires). FYI, 4-wire bipolar, and 6-wire and 8-wire unipolar, work; only 5-wire unipolar doesn't. Also, are you sure it's the Z axis motor? I vaguely remember the Y axis being a dual-shaft motor, to drive both sides of the gantry.

Monday, August 31st 2015 - 9:28 PM

thank you cvoinescu, sshwarts for your answers

Questions! :D :lol:

-- The stepper motors are ok? one is unipolar the one for Z axis with double shaft

-- The belt for Z axis is continuos in the design of the 2.x, modifying the size of the machine affects the lenght, where i can buy it, or what options i have

-- Searching Laser heads in ebay, some of them give this options:

Mirror diameter

Lens Diameter

Focal Lenght

I dont really understand the laser optics calculator of this forum :/ my only guess is it depends of the tube and size of the machine ??

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reader comment Comment from: sshwarts on Tuesday, August 25th 2015 - 5:33 PM
Well said...
reader comment Comment from: cvoinescu on Tuesday, August 25th 2015 - 2:56 PM
sshwarts wrote:You have to consider a few things in cooling. One is that any radiator system can only cool to ambient temperature, you'll never get below the room temperature. Second, on some of my jobs, the laser is running for over an hour so a small amount of coolant gets warm quickly.

That's neither here nor there. A larger bucket will not cool below ambient temperature either. And, if you have enough cooling to dissipate the amount of heat produced by the tube (with an acceptable temperature rise), the amount of coolant does not matter.

That said, a continuously running tube produces some 200 watts of heat (possibly more for the larger tubes), and you need to keep a pretty tight temperature control; a radiator that dissipates 200 watts with only a 10°C rise over ambient would be pretty impressive (several times what's needed for a single-CPU PC). This is why a large bucket is actually a very attractive option: it allows you to operate with less cooling than needed for steady-state heat dissipation, as long as you don't use your laser continuously for many hours at a time.
reader comment Comment from: sshwarts on Tuesday, August 25th 2015 - 1:48 PM
You have to consider a few things in cooling. One is that any radiator system can only cool to ambient temperature, you'll never get below the room temperature. Second, on some of my jobs, the laser is running for over an hour so a small amount of coolant gets warm quickly.

Scott

Monday, August 24th 2015 - 9:46 PM

thats a lot of water!! xD

the laser tube generates that much hot? i planned to put a 360mm Radiator with a Push-Pull configuration to cool it

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reader comment Comment from: sshwarts on Monday, August 24th 2015 - 2:20 PM
You can use say a 100W power supply on a 40W tube, you just can't run it at 100%. Remember this is about controlling current not voltage. The voltage is constant, the current is adjusted for power. For example, I have a 40W tube but an 80W power supply. So at 35% laser power (as set on my DSP controller), that is the maximum current for my 40W tube. With the AWC and it's ilk you can set the maximum so you never go over by accident.

So people have put voltage dividers on the output of the DSP so that it scales the control voltage down giving them a full range of 0-100% (the power supply is controlled by a 0-5V signal where 5V = maximum output current). Other than for convenience, I'm not sure what this would do for you.

The tubing that connect to the laser tube is usually silicone tubing (can't remember the diameter right now) that slips over the fittings (a simply cable tie adds security)--it is glass so you have to be careful.. A PC cooler is great, just make sure you have plenty of coolant to circulate. I use a 5 gallon bucket with perhaps 4.5 gallons in it).

Scott

Monday, August 24th 2015 - 6:01 AM

thank you for the answers!!

rsm5178 wrote:With a higher wattage power supply, you just can't use full power. There is a current limit of the laser tube. I run a 60w power supply for my 40w laser tube. I can only use 38% of the power supply since my tube'S maximum current is 18.5mA.

I know there are people who cut 6mm mdf with a 40w tube. May need 2 passes.

A bigger machine would be much easier to stuff a 60w tube into though....

Rich


So, its the same as it is with a PSU for a Computer, i cant put any PSU for the laser, lets say, 100W for example, and use it with a 40W tube without problems, the PSU just deliver the power needed for the tube


Another Question, i want to use a custom water cooling system from a Computer for the laser tube, but im not sure about the tubing, the laser tube its made from glass, how strong is the tube or how you connect the tubings at it :/

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reader comment Comment from: sshwarts on Tuesday, August 18th 2015 - 1:47 PM
I do 6mm MDF in one pass but very slow and PPI set to 1000 to make the edges decent. One thing I've really learned of late, is how important it is to keep the tube cool to get maximum power out. I ended up putting a small air conditioner in my "laser room" and use a radiator with fan to below the chilled air across.
reader comment Comment from: rsm5178 on Tuesday, August 18th 2015 - 12:17 AM
With a higher wattage power supply, you just can't use full power. There is a current limit of the laser tube. I run a 60w power supply for my 40w laser tube. I can only use 38% of the power supply since my tube'S maximum current is 18.5mA.

I know there are people who cut 6mm mdf with a 40w tube. May need 2 passes.

A bigger machine would be much easier to stuff a 60w tube into though....

Rich

Monday, August 17th 2015 - 11:01 PM

Hi!!

This is my first post, and first of all.... english isnt my native language :P so, if i begin to talk like Yoda please understand me haha

Im 24 years old, studying Industrial Design, and well, as the title says, that is my intention. Do a home build CO2 Laser for cutting and engraving. Its in the school where i start using laser cutters (i didnt operate the machine, just arrived with my files to cut :) :lol: )

This are two of the projects i made with Laser.


Image

Image

Image

And... as a fan of Star Wars.... :mrgreen:

Image

Image


Arrived to this forum a few months ago, looking for information about how to build a machine of this type, now i think i understand enough to start... buying at least hahaha

Dimensions of the machine... i would like at least 60x45cm of cutting area (same as the machine in school) still planing...

This is my Buy List until now, incomplete but i have a few questions :roll:

Switching Power Supply 400W 24V 16.7A for CNC Router Kits 115V/230V S-400-24
http://www.omc-stepperonline.com/switching-power-supply-400w-24v-167a-for-cnc-router-kits-115v230v-s40024-p-240.html

0.9deg Nema 17 Bipolar Stepper Motor 2A 46Ncm 17HM19-2004S
http://www.omc-stepperonline.com/09deg-nema-17-bipolar-stepper-motor-2a-46ncm-17hm192004s-p-122.html

0.9deg Nema 17 Unipolar 12V 0.4A 32Ncm Double Shaft 17HM19-0406D (Question: affects too much that this motor is Unipolar? its for Z axis, the table)
http://www.omc-stepperonline.com/9deg-nema-17-unipolar-12v-04a-32ncm-double-shaft-17hm190406d-p-121.html

50-60W CO2 Laser Power Supply for CO2 Laser Tube Engraver Machine Professional (Question: it would work for 40W Laser Tube? How much Power i need to cut MDF 6mm thick for example)
http://www.ebay.com/itm/50-60W-CO2-Laser-Power-Supply-for-CO2-Laser-Tube-Engraver-Machine-Professional-/221545310032

Set Co2 Laser Head +Mirror + Lens Intgrative Mount Cutter Engraver FL 1.5" to 4" (Question: From China, Is it good? )
http://www.ebay.com/itm/Set-Co2-Laser-Head-Mirror-Lens-Intgrative-Mount-Cutter-Engraver-FL-1-5-to-4-/331329488393?pt=LH_DefaultDomain_0&var=&hash=item4d24c6c609

AWC608 Commercial DSP CO2 Laser Engraving/ Cutter Controller
http://www.lightobject.com/AWC608-Commercial-DSP-CO2-Laser-Engraving-Cutter-Controller-P321.aspx

About the drivers... I am looking to this two, is much difference?

Bipolar Stepper Motor Driver Max 3A Current 128 High Subdivision ST-7128
http://www.omc-stepperonline.com/bipolar-stepper-motor-driver-max-3a-current-128-high-subdivision-st7128-p-244.html

Leadshine DM422C Digital Stepper Driver 20-40VDC with 0.3-2.2A
http://www.omc-stepperonline.com/leadshine-dm422c-digital-stepper-driver-2040vdc-with-0322a-p-75.html

Its all i got for now, i will prepare my next questions hehe, thank you so much forum :D

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