I've had a look around the forum and not found anything although there is quite a lot under Dual Extruder in other languages. I don't think the latest Marlin_v1 supports having independant steps/mm for multiple extruders. I did find and Issue logged ErikZalm's GitHub repository but I don't think it was ever actioned. I can see 215(!) clones of the repository and before I clone it another time and fix it, I though it prudent to ask if anyone one else had implemented a solution and was tracking the latest updates in Marlin_v1?
The change, its self, looks pretty straight forward. The method plan_buffer_line uses the step/mm figure to calculate the target step count-position for each axis. Admittedly, the steps/mm macro in configuration.h is not directley being used as it's been copied into an array. The extruder number is passed into this method and, so, can be used to index into an array of extruder steps/mm values. Obviously, I'll use the current compiler macros to make the code build the same if we do not have a multiple extruder system or, by default, this new feature is not required.
Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9
