I have a C3d with a K40 and played with smoothie for a while

CAD & CAM Tool Chain LaserWeb/CNCWeb Suppport
1

I have a C3d with a K40 and played with smoothie for a while and decided to try grbl. Wasn’t happy with the raster. So far everything appears to be working, mostly. One thing I noticed between smoothie and grbl is the mA meter. When I’m cutting a simple vector with 100% laser power, the meter shows 5mA even though the pot is set to 10mA (test fire button). Using smoothie the same job with 100% power always moved the meter to what I had the pot set to. With grbl it appears to show about half, yet I’m still able to get almost the same cut. I’m pretty sure there’s no way I can cut 1/8" birch plywood with 5mA and 6mm/s. I’m using M3 for the gcode start and $33=5000. Could PWM explain the lower value for the mA meter? Shouldn’t M3 just turn on the laser without using PWM? Is there something I’m missing somewhere?

Here’s a simple square and a circle.

G21 ; Set units to mm
G90 ; Absolute positioning
M3

;
; Operation: 0
; Type: Laser Cut
; Paths: 2
; Passes: 1
; Cut rate: 6 mm/s
;

; Pass 0

; Pass 0 Path 0
G0 X70.67 Y219.43
G1 X30.67 Y219.43 S100.00 F360
G1 X30.67 Y179.43
G1 X70.67 Y179.43
G1 X70.67 Y219.43
G1 X70.67 Y219.43

; Pass 0 Path 1
G0 X81.67 Y210.02
G1 X81.05 Y209.21 S100.00 F360
G1 X80.50 Y208.36
G1 X80.00 Y207.48
G1 X79.56 Y206.56
G1 X79.19 Y205.62
G1 X78.88 Y204.65
G1 X78.64 Y203.66
G1 X78.47 Y202.66
G1 X78.37 Y201.66
G1 X78.33 Y200.64
G1 X78.37 Y199.63
G1 X78.47 Y198.62
G1 X78.64 Y197.62
G1 X78.88 Y196.63
G1 X79.19 Y195.66
G1 X79.56 Y194.72
G1 X80.00 Y193.80
G1 X80.50 Y192.92
G1 X81.05 Y192.07
G1 X81.67 Y191.26
G1 X82.33 Y190.50
G1 X83.05 Y189.78
G1 X83.81 Y189.11
G1 X84.62 Y188.50
G1 X85.47 Y187.94
G1 X86.36 Y187.45
G1 X87.27 Y187.01
G1 X88.22 Y186.64
G1 X89.18 Y186.33
G1 X90.17 Y186.09
G1 X91.17 Y185.92
G1 X92.18 Y185.81
G1 X93.19 Y185.78
G1 X94.21 Y185.81
G1 X95.22 Y185.92
G1 X96.22 Y186.09
G1 X97.20 Y186.33
G1 X98.17 Y186.64
G1 X99.11 Y187.01
G1 X100.03 Y187.45
G1 X100.91 Y187.94
G1 X101.76 Y188.50
G1 X102.57 Y189.11
G1 X103.34 Y189.78
G1 X104.05 Y190.50
G1 X104.72 Y191.26
G1 X105.33 Y192.07
G1 X105.89 Y192.92
G1 X106.39 Y193.80
G1 X106.82 Y194.72
G1 X107.20 Y195.66
G1 X107.50 Y196.63
G1 X107.74 Y197.62
G1 X107.92 Y198.62
G1 X108.02 Y199.63
G1 X108.05 Y200.64
G1 X108.02 Y201.66
G1 X107.92 Y202.66
G1 X107.74 Y203.66
G1 X107.50 Y204.65
G1 X107.20 Y205.62
G1 X106.82 Y206.56
G1 X106.39 Y207.48
G1 X105.89 Y208.36
G1 X105.33 Y209.21
G1 X104.72 Y210.02
G1 X104.05 Y210.78
G1 X103.34 Y211.50
G1 X102.57 Y212.17
G1 X101.76 Y212.78
G1 X100.91 Y213.34
G1 X100.03 Y213.84
G1 X99.11 Y214.27
G1 X98.17 Y214.64
G1 X97.20 Y214.95
G1 X96.22 Y215.19
G1 X95.22 Y215.36
G1 X94.21 Y215.47
G1 X93.19 Y215.50
G1 X92.18 Y215.47
G1 X91.17 Y215.36
G1 X90.17 Y215.19
G1 X89.18 Y214.95
G1 X88.22 Y214.64
G1 X87.27 Y214.27
G1 X86.36 Y213.84
G1 X85.47 Y213.34
G1 X84.62 Y212.78
G1 X83.81 Y212.17
G1 X83.05 Y211.50
G1 X82.33 Y210.78
G1 X81.67 Y210.02
M5 ; Switch tool offEnd
M2 ; End

2

GRBL or GRBL-LPC? Configuring laser parameters is different between them.

3

Never mind. $33 means you’re using grbl-lpc.

What are your values for $30-$36?

4

Yes, grbl-lpc. I should have been clearer.

$$
$0=10
$1=255
$2=0
$3=3
$4=0
$5=1
$6=0
$10=0
$11=0.010
$12=0.002
$13=0
$20=1
$21=0
$22=1
$23=1
$24=50.000
$25=6000.000
$26=250
$27=2.000
$30=1000
$31=0
$32=1
$33=5000.000
$34=0.000
$35=0.000
$36=100.000
$100=158.750
$101=158.750
$102=160.000
$110=24000.000
$111=24000.000
$112=500.000
$120=2500.000
$121=2500.000
$122=2500.000
$130=300.000
$131=230.000
$132=50.000
$140=0.000
$141=0.000
$142=0.000

5

$30=1000: This means that S1000 will be full on. If you want S100 to be full on then set $30=100.

6

I took that value from here - http://cncpro.co/index.php/65-documentation/initial-configuration/firmware/grbl-lpc-1-1e

Is there anything else specific I should set? So then it really was cutting 1/8" plywood at 5mA?

7

Any value >=1 will work, as long as you set LW’s PWM max value to match. 1000 is just the preference of the person who wrote that page.

8

I used this “preference” because that’s the default of grbl :wink:
The “PWM MAX S VALUE” in LW4 just needs to match the $30 value, as Todd writes.

9

@Steven_Kalmar In your gcode, the S value was 100 and $33 set to 1000, so basically you was cutting with 10% of the power set by the pot.

10

Thanks. I figured I had something wrong somewhere.

11

@cprezzi I defaulted my initial port to 1.0 to match smoothie. I didn’t realize you changed the default on yours back to 1000.0. LW’s default is also 1.0. I believe grbl-328’s 1000 number comes from being a common spindle speed on mills.

12

So then I guess it was really cutting at 5mA. I replaced the craptastic stock mirrors with si. Apparently it made a bigger difference than I thought.

13

Mirrors can make a huge difference… There’s a YouTube video of a guy testing different mirrors and mirror finishing… I can’t find it right now, but you gotta remember that you’ll need to multiply (not add) the individual differences times the number of mirrors!
So if your laser has 3 mirrors (the practical minimum) and they’re 10% more efficient, it is actually 1.1^3=1.331, i.e. 33.1% more power delivered to the plywood!
Also the material doesn’t only have a practical impact on the look of the finish, the actual element(s) have different molecule sizes and distance differences which impact the frequency (or rather wavelengths) they can most effectively reflect. Finally the flatness and finish matter too. What looks flat to our eyes may actually be concave/convex and/or bumpy at microscopic levels, causing slight defocusing and scattering of the laser beam…

TL:DR - yes, mirrors can make a huge impact!

14

.733 will fix M3 on rastering. :slight_smile:

15

I would suggest to use M4 instead of M3 (just for grbl!), as this adjusts power to acceleration.

16

I had originally used M4. I tried M3 to see if it would make any difference with the current draw. It did increase it about 1mA. I’ll test this in the next day or so. Too much on my plate today :slight_smile:

Between the new mirrors and grbl-lpc, it’s like a whole new machine.

17

Yes, it’s gcodeToolOn setting, so easy to set.

18

@Jorge_Robles ​ Usualy we enter the M3/M4 in the start gcode, not the toolOn.