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Fórum » Only in English » Technologies » Diode Lasers. (Using Diode Lasers with CNC Machines.)
Diode Lasers.
picengraver Dátum/Date: Kedd, 2013-05-21, 23:03 | Üzenet/Post # 741
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Doug,
Glad to see you here.  Jeff really needs the competition to keep him on his toes yes

John


I paint with a blue light beam.
 
Doug Dátum/Date: Kedd, 2013-05-21, 23:59 | Üzenet/Post # 742
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Thanks all.  Don't think will be giving Jeff any competition anytime soon, but I'll sure try later on when machine is completed. 

Doug
 
fefenin Dátum/Date: Szerda, 2013-05-22, 14:41 | Üzenet/Post # 743
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hello,

i'm trying to make a little driver to control my fourth axis, it is based on mc3479 chip and i did had some optocoupler to guaranty my LPT port won't burn in case something goes wrong.




 everything works great exept it is too slow , i'm just able to achieve 1600hz pulsing.

could you please tell me with the video if you think it is to slow or not?



i don't understand why the stepper just stall so soon...
 
JJWMACHINECO Dátum/Date: Szerda, 2013-05-22, 15:07 | Üzenet/Post # 744
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Jeremy,

One problem I can see with that setup is using gears and the backlash that you may get. A timing belt direct from the stepper to the encoder would work allot better. You need to have the stepper move slightly, but have the encoder rotate quickly and will need the ratios worked out properly also to get the 256 steps needed. There is no drag or resistance using the ball bearing shaft encoder, so there should not be any reason to go through all those gears to drive it. I can't see the size of your stepper in the picture, so it may be to small also and that's the reason for your gearing. I use a 1/8" wide kevlar reinforced timing belt and if the belt tension is set properly, there should not be any backlash or added drag to stall the stepper. 
Jeff


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
fefenin Dátum/Date: Péntek, 2013-05-24, 22:52 | Üzenet/Post # 745
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the stepper is very smal and the whole assembly is from a scan/ printer.

the ratio is 1/12  (12motor turns equal 1output shaft turn).
and there is a very small backlash

i have a bigger stepper (for cnc machine) + timing belt and gears somewhere, i'll try to make something out of what i have right now,if that fails, then i'll buy new things...

thanks for your inputs

Hozzáadva (2013-05-24, 22:52)
---------------------------------------------

hello again,

i just tried something else:


this is a big stepper, the poor driver overheat a bit...
i'm still not sure what ratio i should have , but seams to me it is not
right cause with one stepper turn , i've got 4 turns of sensor.
so i'll not have the 256 steps, am i right?

i had no more pulley on my hand , i'll probably have to buy something special but what?

the stepper is driven in microsteps and with 1,8deg per steps.

any advise from the professionals??


Az üzenetet módosította/Modified by fefenin - Péntek, 2013-05-24, 22:55
 
JJWMACHINECO Dátum/Date: Péntek, 2013-05-24, 23:50 | Üzenet/Post # 746
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Actually that may work out pretty good. To get your 256 steps through a 1/2V-5V range of the output of the encoder, you just need to calculate it based on the steps you use for the stepper motor. I say 1/2V because with my 1W that is the voltage to the analog modulation of the driver where it just starts to burn the wood.  Try to set your acceleration as high as possible without stalling the stepper because you want the power levels to go up and down quickly also.

With that 4-1 ratio means your stepper only has to rotate less then a 1/4 turn to get the full range of power for your laser.


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
fefenin Dátum/Date: Szombat, 2013-05-25, 01:04 | Üzenet/Post # 747
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good thank you!,

but if i'm not mistaken, because of microsteps 1.8deg / 2 = 0,9 deg. and 90 degree rotation of the stepper gives = 100 steps.

so i'll never get the full grayscale ?!

did i understood something wrong?

and i also forgot that the sensor is a 1024 value one not a 256 one .
 
JJWMACHINECO Dátum/Date: Szombat, 2013-05-25, 02:52 | Üzenet/Post # 748
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The fact the encoder has 10bit resolution (1024 value) is irrelevant. I use the exact same encoder. There are no image to g-code program that can even implement 1024 shades of grey. 

The best shade value you be able to get is 8bit (256 shades) so you need to set up your motor's steps in the Motor Tuning configuration menu to get the 256 incremental steps needed for the 1/2-5 volts out to the laser driver. I don't know of any other way to explain this to you.


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
fefenin Dátum/Date: Szombat, 2013-05-25, 10:24 | Üzenet/Post # 749
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Idézet

The best shade value you be able to get is 8bit (256 shades) so you
need to set up your motor's steps in the Motor Tuning configuration menu
to get the 256 incremental steps needed for the 1/2-5 volts out to the
laser driver. I don't know of any other way to explain this to you.
got it since a little while...

you are talking about the steps of the motors, i'm talking about the steps at the encoder:

i'll never be able to achieve 256 encoder steps with my ratio, cause the minimum is 100 steps per turns.

1/4 turns of the motor is one full rotation of the sensor, great , but one quarter turn of the motor is only 50 full steps or 100 micros steps not 256 . more than 100 micros steps will lead to more than one turn of the sensor,

the motor resolution is not good enaugh, so i'll have to change the ratio if i really want a 256 resolution.

"I don't know of any other way to explain this to you either"

if i remenber your ratio is 1/3 , it must be a lot better...

anyways i'll probably try out like that as soon as i get the driver.

JJWMACHINECO ,thank you for your help.
 
Dave Dátum/Date: Szombat, 2013-05-25, 13:05 | Üzenet/Post # 750
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I must not be understanding this, but doesn't a 1.8 degree stepper need 200 full steps to complete a single rotation of the motor shaft (360/1.8)? Or 400 steps at 1/2 micro-stepping? As an alternative, perhaps the counter/dac circuit posted earlier would be easier? I had mine driven by mach3's C axis step and direction lines at 10,000 steps per inch giving me a full 5 volt output at a 'depth' of 0.0256 inches.
Dave
 
JJWMACHINECO Dátum/Date: Szombat, 2013-05-25, 13:26 | Üzenet/Post # 751
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I guess I'm getting confoosed, which is not hard for me to do.  wacko

Is it a Inch to metric difference? Based on what your stating, you will need a 1.5625-1 ratio to get 256 incremental steps for 0-5V output from the encoder? That seems like allot of rotation of the stepper motor to be able to run the gcode smoothly.

Dave, my Z axis 1.8deg stepper is set at 10160 steps, so that is close to the 10,000 steps for your DAC setting. If I remember correctly, the metric setting in the manual says to set it at 400.


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
fefenin Dátum/Date: Szombat, 2013-05-25, 13:32 | Üzenet/Post # 752
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I agree that's the thing i don't get.cause with a 400pas steps + 4times réduction we will not get the right resolution??

Az üzenetet módosította/Modified by fefenin - Szombat, 2013-05-25, 13:35
 
Dave Dátum/Date: Szombat, 2013-05-25, 13:38 | Üzenet/Post # 753
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I'm talking about the stepper motor itself, without anything attached to it. A full rotation of 360 degrees divided by 1.8 degrees per step = 200 steps for one turn of the motor shaft. If the motor control board is set for 1/2 micro stepping, one turn of the motor shaft will take 400 steps. 1/4 microstepping would take twice that, or 800 steps per turn, etc.
Dave
 
JJWMACHINECO Dátum/Date: Szombat, 2013-05-25, 13:49 | Üzenet/Post # 754
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So what your saying his limitation is the motor control board, not the stepper motor itself?

Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
Dave Dátum/Date: Szombat, 2013-05-25, 14:00 | Üzenet/Post # 755
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It's true that the microstep setting will affect how many steps are needed for one revolution of the motor shaft. The stepper motor is fixed at 1.8 degrees per one full step pulse. I think that the micro stepping stuff sets the motor current on each motor winding such that one mach3 step pulse results in the motor moving less than one 1.8 degree step. You'd have to figure out how many steps equate to one full turn of the encoder shaft to get the pulley ratios, but math makes my head hurt. smile
Dave
 
JJWMACHINECO Dátum/Date: Szombat, 2013-05-25, 14:00 | Üzenet/Post # 756
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I know on my DOS CNC stepper machines, they have dip switches on the motor control boards to set for 400,800 or 1600 steps per revolution. Then you set in the controller program the steps per Inch based on ratios of pulleys and screws like in Mach.

Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver

Az üzenetet módosította/Modified by JJWMACHINECO - Szombat, 2013-05-25, 14:07
 
Dave Dátum/Date: Szombat, 2013-05-25, 14:08 | Üzenet/Post # 757
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Exactly. Then you have to figure the steps per unit so that you know the 'max depth' setting to use in picengrave.
 
fefenin Dátum/Date: Szombat, 2013-05-25, 21:25 | Üzenet/Post # 758
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thank you Dave!!

because i thaught i was crazy.
so to everyone to be sure what that was about:

with a normal stepper (400 steps per turn in microsteps)  we want a 1/4 turn of the sensor, because we really want 256 values not 1024 (1024 is for 1 full turn)

for sure we can have a quarter turn on the sensor with reduction or not , but we need 256 real steps.

if i'm not mistaken (please tell me if i m wrong):

we will need to do less than one full stepper motor turn because one turn is 400 steps, we want it to be as fast as possible so the least the number is the best it is but we don't want to sacrify resolution .

we want 256 steps on the stepper to lead to 1/4 turn on the sensor (256 analog values)

this is then math (i'm really bad at that) :

in microsteps one real motor step is 0.9 degres >      (resolution x steps)/full turn = need_turn_for_256_steps

256*0.9/360 = 0.64 that means we need to do 0.64 of a turn to get 256 steps that is 230.4 degrees if i'm right (360*64/4)

so last one: if we really truly want a 256 resolution at the laser driver and from the software Gcode:

we will need to make the motor turn 230.4 degres and drive the sensor with a 4 to 1  reduction (4 at motor 1 at the sensor)
or we will make the motor turn 360 degres and drive the sensor with a ???? ratio

like that we would have true 256 steps of laser power from the Gcode to the analog value.

does all of that makes sense?
 
JJWMACHINECO Dátum/Date: Szombat, 2013-05-25, 22:42 | Üzenet/Post # 759
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Jeremy,

Like I said before, the 10bit (1024) resolution of the encoder is irrelevant in calculating this ratio. The full revolution of the encoder is relevant. If you will be using the quad Denmark driver card, it needs 0-5V to the analog modulation to get the full range of 0 to full power to the laser diode. The encoder only outputs 0-5V in a 0-360 degree rotation. If you only use 256 (1/4) of the 1024 resolution, that's only a 0-1.25V so you will only be using 1/4 of the analog voltage output from the encoder. This will only give you 1/4 of the max power out from your laser diode. 

Dave, I think your right, your DAC circuit may be a better option and easier to explain. yes   Explain away.  up


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
fefenin Dátum/Date: Szombat, 2013-05-25, 23:17 | Üzenet/Post # 760
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thanks again,

i agree the DAC circuit would be more convinient.
where i'm not sure about what is said: the motor is able to do steps between the steps according you??!

maybe you have special drivers or maybe i have , but between two microsteps i have no way to make a step.

there is nothing to do with the sensor or the ratio.

nothing will happens  between 0.9 degres angle for me anyways if i put the dip switch in my driver board on 1/8 of steps, and if i pulse step input 8 times, the motor will not move eight steps but less because it's resolution is too poor for that .

can somebody confirm that?? please

and please could you  try to do a full 0 to full power test and tell me how much real steps your motor did (or how much rotation in degres) , not the sensor just the motor ?

please try it on your machine

after that i'm not talking about that again if you wish ,i don't want to piss you off, (hope it is not already done)

regards
 
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