# How do I use Delta Correction?

Here's the issue with my printer: When printing a calibration object, such as this one: http://www.thingiverse.com/thing:745523

the lengths of the legs on the print are incorrect. When calibrated correctly, each pair of parallel legs on the snowflake should measure 120 mm on each side. Instead I get lengths like 119.53 (across tower A) 120.95 (across tower and 120.11 (across tower C). The instructions are written for the Marlin firmware, and the author has no interest in providing a Repetier version.

I know I'm not the only one with this problem, but I just cannot find a clear explanation. All the printer guides I find don't address this part of calibration.

## Comments

I can't set up my printer - the problem is with print size. I tried to print the above linked "caldelta" circle few times. Every time I have wrong dimensions. This is how I am calculating:

My print size is:

X = 59.9 (reference)

Y= 60.27

Z=59.8

New diagonal len.:

Old * (59.9/expected = new Diagonal len.

213.993 * 59.9 / 60) = new Diagonal len.

new Diagonal len = 213.565

Corrections:

Tower A = no correction as (59.9 has the lowest error and it is already corrected by new diagonal Len)

Tower B = 60.27 - 59.9 = 0.37 (+60mm which is the desired dimension)

Tower C = 59.80 - 59.9 = - 0.1 (+60mm which is the desired dimension)

now I count new diagonal len for tower B and C:

Len B = new diagonal len * ( Tower B / 60) = 213.565 * (60.37 /60) = 213.565 * 1.006 = 214.84

Len C = new diagonal len * ( Tower C / 60) = 213.565 * ( 59.90 /60) = 213.565 * 0.998 = 213.12

Corrections:

Corr B = 214.84 - 213.565 = 1.275mm

Corr C = 213.12 - 213.565 = -0.445mm

So I put this 3 values to EEPROM:

Diagonal rod length, Corr. diagonal B, Corr. diagonal C.

Do you think my calculations are ok?

Every time I use newly calculated numbers I receive bad print size...

Regards

Pawel

I entered my values like below

Horiz. Radius 107 (I am not sure if this value is correct)

D0 - current diagonal 213,84

L (suposed measure) 75

Lx 75.39

Ly 75.04

Lz 74.75

Output for Repetier is:

Diagonal rod len 213.901

Corr diagonal A 0.346

Corr diagonal B -0.019

Corr diagonal C -0.32

Ok. Printed again and my dimensions are still wrong,

Z=74.86

Y=74.6

X=74.76

You did 7 iterations. But how - should I change those 4 parameters again and again?

Have you changed your steps per mm for each motor?

Are you sure your Horizontal radius?

Do you use any auto level solution for your bed?

What kind of auto level do you use - induction sensor, endstop?