Bill,I do not see an option in the MK3 gcode generator for Cura as a slicer. What do I need to change to my current tool changes codes for the MK2 Cura code to enable the MK3 upgrade?
Ok... time to be blunt here. ;-) We are not going to be able to offer an option for Cura on the Mk3 until they fix two major bugs. Cura is broken when it comes to multi-color and their purging strategy fails with more than two colors due to the nature of the way their printers work. Ultimaker printers only have two extruders, and this bug is only present above two. Now, if you want to use Cura but not use a purge tower, you are more than welcome to do it... all you need to do is swap out the button press code with our new routine... or simply load the old Mk2 firmware on your Mk3 system and it'll work just fine... however, the purge tower and the order that colors are printed might not be correct due to this bug.
We're not recommending Cura at this time due to the fact that it requires very advanced users to understand what the issue is and how to avoid it. Think about it this way... our primary market is people who don't understand GCode, nor do they understand the details of what is happening under the covers (and frankly, they don't care... they just want to print Color prints.) But if they attempt to do it with Cura and the 3DChameleon, they will fail, and will blame the new thing... the 3D Chameleon. It's just me that works on these technical issues... and if I support Cura and it doesn't work like it should, I'm the one paying the price for the support tickets and the returns... it's just not worth it... so officially I can't support Cura until they fix the bugs.
Here's a video I did a while ago about the major issue: https://www.youtube.com/watch?v=P_LSrhxD5pk
With it, what you wind up with is parts that have random layers throughout the print because it's not purging them in the proper order.
You can find that issue here and see the team is working on it... but it hasn't been updated in quite a while: https://github.com/Ultimaker/Cura/issues/6909
One other issue is that even if it does purge the extra extruders, it doesn't print the purge on top of anything for those additional colors... it literally prints them in the air with nothing under them... which creates a big mess when it tries to print the subsequent colors. This issue is also being addressed in the same bug fix. Here's the github issue for it: https://github.com/Ultimaker/Cura/issues/14404
Once this fix is implemented, we can add our support to it. As a word of caution, since Makerbot and Ultimaker have merged, we've seen a dramatic drop in support for Cura. In fact, we've seen a lot of bug reports marked Deferred due to them not effecting Ultimaker printers and them "not having time to work on" the issues. These types of issues fall in that category, so don't hold your breath. See here to see some of the issues that need to be fix with purging but have been deferred: https://github.com/Ultimaker/Cura/issues?q=is%3Aopen+label%3A%22Status%3A+Deferred%22++purge If you do happen to get it working, please share your solutions here so others can implement them as well.