[Tips] calibrating delta 3d printer

edited September 2016 in Tips & Tricks
Hi all,

I've learn for months to calibrate delta printer.
I've search everywhere how to calibrate it and didn't found the right procedure to calibrate it.
So i make my own procedure to get a precise print result for x, y, z and i post here as my thanks for repetier who has make this great firmware.
English is not my first language so i'm sorry in advance if this post maybe hard to understand.

1. Make all of your towers as pararel as posible. You must make sure diagonal rod at each tower have the same size. Different tower have a little different is not so problem. But at the same tower the diagonal rods must have same size. And you must make sure that connector/slider between diagonal rod and tower is stiff. If it is not stiff you won't get best precise result but maybe still okay.

2. Syncronize all tower's step per mm, not tension. Make adjustable tensioner to get the same steps per mm for all towers.
Check steps per mm each tower by send command to move z.
For instance g1 z120, make mark, then g1 20, make mark. All tower should be go down 100mm. Adjust each belt's tension to syncronize to others. Use caliper to get 0.0x presicion.
This process takes time, if you hard to make all tower 100mm, for instance it's faster to make it all 95mm. Then make it all 95 then adjust step per mm in eeprom.

3. Find the center of you print bed. Move your nozzle there then run g132 s1. This will make your printer remember that center.

4. Take a milimeter block paper and put on your bed, adjust the paper position so it's center at your printer center and horizontal line in the paper is pararel to your front side. If the position satisfy you, glue it so it can't move.

5. This is also a hard part. Need math skill, eye & time.
To do this step you must understand how delta printer works.
If you give a command to the printer, let say g1 x10 y10 z10, it means you order it to go (10,10,10) cartesian coordinate.
The firmware transform the coordinate to delta coordinate.
In delta coordinate, each tower only get order move up or down how many steps. Each tower gets different order to make it achieve the command given.
So mark 6 points at milimeter block to get the calculations, 7 point include 0,0. I use 8 points to make sure.
Let say
1. (0,0,0)
2. (90,0,0)
3. (-90,0,0)
4. (0,90,0)
5. (0,-90,0)
6. (45,45,0)
7. (-45,45,0)
8. (45,-45,0)
9. (-45,-45,0)

Make the nozzle touch 1st point, mark each of your towers with pencil. Move the nozzle to the 2nd point then mark all the towers again. Move to the 3rd and so on.

Write down the distance between each point mark to center 0,0,0 mark at each towers. Here you get the right delta coordinate should be to make the printer go to the points. You must get precise correct distance to get precise result.

To make your printer move correctly there are 9 parameters you should get.
Position of your tower a from center in degree.
Position of your tower b from center in degree.
Position of your tower c from center in degree.
Diagonal rod a, diagonal rod b, diagonal rod c, radius a, radius b, radius c.

Now you have 9 parameters you must have.
From distance of points of each tower you can get the answer with math formula.

6. If you get the 9 parameters correctly. You should be get precise x, y movement. Exactly as you milimeter block. But maybe a little not precise in z direction. Your printer first layer maybe dont have the same thickness at all points. At this point you can use autolevel feature from repetier firmware to fix it.

If you finished all 6 steps above your delta print result should be precise.

Best regards
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