Could use some help with step calculations

I have an Anycubic Kossel Linear Plus, with Marlin 1.1.9 loaded. The steps/mm is now calculated as follows:

// variables to calculate steps
#define XYZ_FULL_STEPS_PER_ROTATION 200 // These are the setting for the stock Stepper Motors, pulleys and Belts on the AnyCubic Kossel
#define XYZ_MICROSTEPS 16
#define XYZ_BELT_PITCH 2
#define XYZ_PULLEY_TEETH 20

// delta speeds must be the same on xyz
#define DEFAULT_XYZ_STEPS_PER_UNIT ((XYZ_FULL_STEPS_PER_ROTATION) * (XYZ_MICROSTEPS) / double(XYZ_BELT_PITCH) / double(XYZ_PULLEY_TEETH))
#define DEFAULT_AXIS_STEPS_PER_UNIT   { DEFAULT_XYZ_STEPS_PER_UNIT, DEFAULT_XYZ_STEPS_PER_UNIT, DEFAULT_XYZ_STEPS_PER_UNIT, 98 }  // default steps per unit for Kossel (GT2, 20 tooth)

Unfortunately my parts are coming out slightly smaller than intended. especially in X and Y (probably Z as well, as it's a delta) - to get the exact size I have increase the scale in the slicer by 1.012.

My question is - what is the correct way to get this enlargement factor into configuration.h?

Or do I have another problem that I've missed?

Thanks,
David

Steps/m look fine more likely to be a delta setting out somewhere

#define DELTA_DIAGONAL_ROD 271.50
#define DELTA_HEIGHT 302.85
#define DELTA_RADIUS 133.22

and what material, you do know that ABS shrinks approx 8%

Edited 1 time(s). Last edit at 12/11/2019 09:13AM by Dust.

Delta settings were auto-calibrated, but that doesn't mean that they're correct!

I'm using eSun PLA+ but I don't know if I need to allow for shrinkage with this material (I must admit that's not a factor I'd considered...)

UPDATE: Just did a quick Google on PLA shrinkage - apparently it's 2.0 to 2.5%, so that is starting to match my results... maybe in the future I will just have to add a 'shrinkage factor' when printing larger items.

Edited 2 time(s). Last edit at 12/11/2019 09:45AM by David J.

Quote
Dust
... you do know that ABS shrinks approx 8%

Are you sure? Isn't it rather 0.8%?

8%, according to this site (first item in a Google search) : [www.fabbaloo.com]

0.8% is right for injection moulding ABS, according to another site I just looked at.