Jump to content
UltiMaker Community of 3D Printing Experts

Loading DLL in Cura


Recommended Posts

Posted · Loading DLL in Cura

Hey forum,


I am trying to use a DLL inside a cura plugin but for some reason it wil not load the DLL for me.

i have a DLL set up that gives coordinates comming from our eye tracker and sends them to the python script.

i have a python script (Script A) that calls this DLL and has a few easy calls for other python scripts to use.


Calling Script A from command line (going through __main__) it loads the DLL and starts outputting coords in a while loop on my cmd window.

When trying to use this Script A in another Script B it does not seem to load the DLL.


Error Message:


2020-08-06 13:45:26,268 - ERROR - [MainThread] UM.Logger.logException [84]: Exception: Error loading plugin PrepareStageSR:
2020-08-06 13:45:26,271 - ERROR - [MainThread] UM.Logger.logException [88]: Traceback (most recent call last):
2020-08-06 13:45:26,273 - ERROR - [MainThread] UM.Logger.logException [88]:   File "D:\Git\Cura Project\Uranium\UM\PluginRegistry.py", line 379, in loadPlugin
2020-08-06 13:45:26,274 - ERROR - [MainThread] UM.Logger.logException [88]:     to_register = plugin.register(self._application)  # type: ignore  # We catch AttributeError on this in case register() doesn't exist.
2020-08-06 13:45:26,276 - ERROR - [MainThread] UM.Logger.logException [88]:   File "D:\Git\Cura Project\Cura\cura\..\plugins\PrepareStageSR\__init__.py", line 19, in register
2020-08-06 13:45:26,278 - ERROR - [MainThread] UM.Logger.logException [88]:     "stage": PrepareStage.PrepareStage()
2020-08-06 13:45:26,280 - ERROR - [MainThread] UM.Logger.logException [88]:   File "D:\Git\Cura Project\Cura\cura\..\plugins\PrepareStageSR\PrepareStage.py", line 14, in __init__
2020-08-06 13:45:26,281 - ERROR - [MainThread] UM.Logger.logException [88]:     sr = SR()
2020-08-06 13:45:26,282 - ERROR - [MainThread] UM.Logger.logException [88]:   File "D:\Git\Cura Project\Cura\cura\..\plugins\PrepareStageSR\SR_EyeCoords.py", line 36, in __init__
2020-08-06 13:45:26,283 - ERROR - [MainThread] UM.Logger.logException [88]:     self.c_lib = ctypes.CDLL("SRPython")
2020-08-06 13:45:26,284 - ERROR - [MainThread] UM.Logger.logException [88]:   File "C:\Users\tom.hendriks\AppData\Local\Programs\Python\Python35\lib\ctypes\__init__.py", line 351, in __init__
2020-08-06 13:45:26,286 - ERROR - [MainThread] UM.Logger.logException [88]:     self._handle = _dlopen(self._name, mode)
2020-08-06 13:45:26,287 - ERROR - [MainThread] UM.Logger.logException [88]: OSError: [WinError 126] The specified module could not be found

my "SR_EyeCoords.py" (calling __main__ does work!)

import ctypes
import pathlib
import time

class SR_Eye:
	__slots__ = ["x", "y", "z"]
	def __init__(self, x=0, y=0, z=0):
		self.x = x
		self.y = y
		self.z = z
	def __str__(self):
		return (str(self.x) + ", " + str(self.y) + ", " + str(self.z))

class SR_EyePair:
	__slots__ = ["left", "right"]
	def __init__(self, left, right):
		self.left = left
		self.right = right
	def __str__(self):
		return (str(self.left) + " : " + str(self.right))

class SR:
	def __init__(self):
		self.c_lib = ctypes.CDLL("SRPython")
		self.c_lib.GetEyeValue.restype = ctypes.c_float
	def GetCurrentEyePair(self):
		lx = self.c_lib.GetEyeValue(0,0)
		ly = self.c_lib.GetEyeValue(0,1)
		lz = self.c_lib.GetEyeValue(0,2)
		rx = self.c_lib.GetEyeValue(1,0)
		ry = self.c_lib.GetEyeValue(1,1)
		rz = self.c_lib.GetEyeValue(1,2)
		eyeL = SR_Eye(lx,ly,lz)
		eyeR = SR_Eye(rx,ry,rz)
		eyePair = SR_EyePair(eyeL, eyeR)
		return eyePair
if __name__ == '__main__':
	# SR_EyeCoords.py executed as script outputs eye Coord every second
	sr = SR()
	while 1:
		time.sleep(1) #sleep for 1 second

Snippet of the PrepareStage.py (using a coppy of the normal preparestage as a base since i'm not that familiar with the plugin development yet)


from cura.Stages.CuraStage import CuraStage

from PrepareStageSR.SR_EyeCoords import *

##  Stage for preparing model (slicing).
class PrepareStage(CuraStage):
    def __init__(self, parent = None):
        sr = SR()                                      #crash on this line
        eyePair = sr.GetCurrentEyePair()


  • Link to post
    Share on other sites

    Posted · Loading DLL in Cura

    I think you need to look at where the DLL is located relative to Cura's working directory. Cura's working directory is the user home unless executed from the command line. So it's probably better to just give it a full path.


    Look into PluginRegistry.getPluginPath to get the absolute path to your plug-in's directory, and combine that with the filename of your DLL.

    I must say though that I've never worked with loading DLLs using CTypes. My SVGToolpathReader works with a DLL (FreeType) that has Python bindings, so that behaves just like any normal module and I can just import it.

  • Link to post
    Share on other sites

    Create an account or sign in to comment

    You need to be a member in order to leave a comment

    Create an account

    Sign up for a new account in our community. It's easy!

    Register a new account

    Sign in

    Already have an account? Sign in here.

    Sign In Now
    • Our picks

      • UltiMaker Cura 5.3 stable released
        In this stable release, Cura 5.3 achieves yet another huge leap forward in 3D printing thanks to material interlocking! As well as introducing an expanded recommended print settings menu and lots of print quality improvements. Not to mention, a whole bunch of new printer profiles for non-UltiMaker printers!
          • Thanks
          • Like
        • 22 replies
      • Here it is. The new UltiMaker S7
        The UltiMaker S7 is built on the success of the UltiMaker S5 and its design decisions were heavily based on feedback from customers.
        So what’s new?
        The obvious change is the S7’s height. It now includes an integrated Air Manager. This filters the exhaust air of every print and also improves build temperature stability. To further enclose the build chamber the S7 only has one magnetically latched door.
        The build stack has also been completely redesigned. A PEI-coated flexible steel build plate makes a big difference to productivity. Not only do you not need tools to pop a printed part off. But we also don’t recommend using or adhesion structures for UltiMaker materials (except PC, because...it’s PC). Along with that, 4 pins and 25 magnets make it easy to replace the flex plate perfectly – even with one hand.
        The re-engineered print head has an inductive sensor which reduces noise when probing the build plate. This effectively makes it much harder to not achieve a perfect first layer, improving overall print success. We also reversed the front fan direction (fewer plastic hairs, less maintenance), made the print core door magnets stronger, and add a sensor that helps avoid flooding.

        The UltiMaker S7 also includes quality of life improvements:
        Reliable bed tilt compensation (no more thumbscrews) 2.4 and 5 GHz Wi-Fi A 1080p camera (mounted higher for a better view) Compatibility with 280+ Marketplace materials Compatibility with S5 project files (no reslicing needed) And a whole lot more  
        Curious to see the S7 in action?
        We’re hosting a free tech demo on February 7.
        It will be live and you can ask any questions to our CTO, Miguel Calvo.
        Register here for the Webinar
          • Like
        • 18 replies
      • UltiMaker Cura Alpha 🎄 Tree Support Spotlight 🎄
        Are you a fan of tree support, but dislike the removal process and the amount of filament it uses? Then we would like to invite you to try this special release of UltiMaker Cura. Brought to you by our special community contributor @thomasrahm
        We generated a special version of Cura 5.2 called 5.3.0 Alpha + Xmas. The only changes we introduced compared to UltiMaker Cura 5.2.1 are those which are needed for the new supports. So keep in mind, this is not a sneak peek for Cura 5.3 (there are some really cool new features coming up) but a spotlight release highlighting this new version of tree supports.  
          • Like
        • 22 replies
    • Create New...