Scaling issue with new build

Hi folks,

I recently got to the point of being able to try my first crown plot (plot against the crown?). While it was very exciting to see the MPCNC doing its thing, the image printed much too large.

The first thing I looked at was calibrating manual jogging in Repetier Host-Mac.

It was going twice too far (20mm when the 10 button was pressed), so in Arduino, I modified configuration.h as follows:

/* #define DEFAULT_AXIS_STEPS_PER_UNIT { 200, 200, 4535.44, 200 } //MPCNC */

#define DEFAULT_AXIS_STEPS_PER_UNIT { 400, 400, 4535.44, 200 } //GBN

That corrected manual jogging (or at least close).

However, the default crown gcode still was very large.

So I created a very simple square svg and converted it to gcode at (I used settings cribbed from the v1 “Estlcam basics” page):

G21 ; Set units to mm

G90 ; Absolute positioning

G1 Z2.54 F2100 ; Move to clearance level


; Operation: 0

; Name:

; Type: Engrave

; Paths: 1

; Direction: Conventional

; Cut Depth: 3.175

; Pass Depth: 3.175

; Plunge rate: 127

; Cut rate: 900


; Path 0

; Rapid to initial position

G1 X10.0002 Y20.0002 F2100

G1 Z0.0000

; plunge

G1 Z-3.1750 F127

; cut

G1 X9.9804 Y20.0000 F900

G1 X0.0003 Y20.0000

G1 X0.0003 Y10.0198

G1 X0.0000 Y10.0000

G1 X0.0003 Y9.9802

G1 X0.0003 Y0.0003

G1 X9.9786 Y0.0003

G1 X10.0002 Y-0.0000

G1 X10.0218 Y0.0003

G1 X20.0000 Y0.0003

G1 X20.0000 Y9.9784

G1 X20.0002 Y10.0000

G1 X20.0000 Y10.0216

G1 X20.0000 Y20.0000

G1 X10.0200 Y20.0000

G1 X10.0002 Y20.0002

G1 X10.0002 Y20.0002

; Retract

G1 Z2.5400 F2100


On my MPCNC, this plots a square 160 mm on a side instead of 20 mm.

Any suggestions where else I might look?



Some additional context:

Using MPCNC813_GLCD firmware flashed to an older Mega2560/RAMPS1.4/driver combination.

Steppers are Nema 17 from v1

No end stops

Mac OS 10.13.3

Details of what repetier reports at connection;

3:29:23 PM: Connection opened

< 3:29:24 PM: start

< 3:29:24 PM: echo:Marlin 1.1.0-1

< 3:29:24 PM: echo: Last Updated: 2017-05-04 12:00 | Author: (none, default config)

< 3:29:24 PM: Compiled: Feb 27 2018

< 3:29:24 PM: echo: Free Memory: 3553 PlannerBufferBytes: 1232

< 3:29:24 PM: echo:EEPROM version mismatch (EEPROM=? Marlin=V37)

< 3:29:24 PM: echo:Hardcoded Default Settings Loaded

< 3:29:24 PM: echo: G21 ; Units in mm

< 3:29:24 PM: echo: M149 C ; Units in Celsius

< 3:29:24 PM: echo:Filament settings: Disabled

< 3:29:24 PM: echo: M200 D3.00

< 3:29:24 PM: echo: M200 D0

< 3:29:24 PM: echo:Steps per unit:

< 3:29:24 PM: echo: M92 X400.00 Y400.00 Z4535.44 E200.00

< 3:29:24 PM: echo:Maximum feedrates (units/s):

< 3:29:24 PM: echo: M203 X190.00 Y190.00 Z8.40 E25.00

< 3:29:24 PM: echo:Maximum Acceleration (units/s2):

< 3:29:24 PM: echo: M201 X500 Y500 Z35 E10000

< 3:29:24 PM: echo:Acceleration (units/s2): P<print_accel> R<retract_accel> T<travel_accel>

< 3:29:24 PM: echo: M204 P400.00 R3000.00 T400.00

< 3:29:24 PM: echo:Advanced: S<min_feedrate> T<min_travel_feedrate> B<min_segment_time_ms> X<max_xy_jerk> Z<max_z_jerk> E<max_e_jerk>

< 3:29:24 PM: echo: M205 S0.00 T0.00 B20000 X4.00 Y4.00 Z0.20 E5.00

< 3:29:24 PM: echo:Home offset:

< 3:29:24 PM: echo: M206 X0.00 Y0.00 Z0.00

< 3:29:24 PM: echo:Material heatup parameters:

< 3:29:24 PM: echo: M145 S0 H196 B62 F0

< 3:29:24 PM: M145 S1 H240 B110 F0

< 3:29:24 PM: echo:PID settings:

< 3:29:24 PM: echo: M301 P17.98 I0.98 D83.62

< 3:29:29 PM: echo:SD init fail

< 3:29:29 PM: FIRMWARE_NAME:Marlin 1.1.0-1 (Github) SOURCE_CODE_URL: PROTOCOL_VERSION:1.0 MACHINE_TYPE:MPCNC EXTRUDER_COUNT:1 UUID:cede2a2f-41a2-4748-9b12-c55c62f367ff

< 3:29:30 PM: echo:DEBUG:INFO,ERRORS

If you are getting the right distance from the LCD the the issue is your gcode/cam. Can you verify this withe repetier as I have laid out on the software page, this is vital that this is correct. You needing to change the firmware points to you using something non standard.

Why not estlcam, we are all much more familiar with it to help.

The scale that your drawing is off isn’t a common one. 8x’s larger? I can only guess you have your svg scaled wrong.

I would try estlcam, follow my crown tutorial and it walks you through all of these checks, including a grid to make sure your drawing is scaled correctly.

DAmmit, MAC, I didn;t notice that buried in there. never mind on the ESTLCAM thing.

Thanks very much for the suggestions… I should have highlighted the Mac part.

[For those who get here from a search, Ryan solved the mystery on another thread. I hadn’t verified that all jumpers were installed under the drivers to put the steppers in 1/32 mode.]

1 Like