Delta calculator back to basics

Hey Delta builders!

The Delta calculators are just too complex and have to many custom fields and fudge factors.
This calculation needs to be perfect.
Is it easyer to work out the frame size and arm length on paper?

From what i have found you need arms at 60 degrees in home centre position
You also need the nozzle to reach the edge of the desired build size without going below 20 degrees.

Simple math or what?
because my brain is melting

Add a top view to show the actual build size.

I'm far from a delta expert, so folks with opinions, feel free to correct me.

But I've built one printer and helped a friend configure another, and really the only thing I would be worried about is not going less than 20 degrees on the outside edge of your build area. Everything else can be accounted for in firmware.

You don't need 60 degrees in home center position: that's more of an incidental that comes with the arms being long enough to reach 20 degrees on the outside edge.

You want your two rods for each arm to be parallel of course, and you want your arms all to be the same length, but as long as you can reach everything you want to reach horizontally it's just math from there. Math that the firmware handles for you.

If you're assuming the length of the extrusion on the vertical and horizontal side is the input to the equation, I think that is invalid. It doesn't account for the offset from top and bottom to account for end stops, carriage vertical and horizontal, and bed height

[www.mathsisfun.com]

Using the math on that page, I came up with 235mm for rod length for my mini kossel, which is 600mm tall with 240 mm horizontals. However, if you use the diameter of the bed and the 20 degree angle, it gets much closer to my "center to center" rod length of 215 mm (not actual rod length, that has to come from subtracting the length of the actual rod ends from this calculated value)

215.4338016 (=(220/SIN(20))*SIN(90))

The settings in Marlin are a mystery. I have no idea how the 163 value I have for "delta radius" works. But it does, and it makes the travel from side to side flat enough.

At the end of the day, both the 235 value and my 215 value would probably work fine. you just lose some vertical head room.

Edited 1 time(s). Last edit at 08/04/2015 03:58PM by thetazzbot.

I just ordered 2020 extrusions for my delta printer. The horizontals are 400mm and the verticals are 800mm and I´m currently printing the Kossel 250 parts from ultibot.
My extrusions are a bit longer than the Kossel 250 ( 340 & 700 ) and I´d like to know, how to calculate the rod length?

Thx
Olaf

I created a calculator for these, though it is by no means perfect.

[docs.google.com]

It uses the 20* at print edge to determine arm length. It does lack info such as end stop height and effector offset.

Kyler

Thanks KylerK,
I just tried it, but got confused by "printer height". Is it the vertical extrusion length or the distance between the horizontal extrusions?
The difference between arm length and rod length is based on which ball roller? Traxxas or magnetic or...?
-Olaf

Olaf,

Printer height is the distance between horizontal extrusions, I've fixed it.

This calculator was built around the cherry pi system originally, so magnetic or non-magnetic in the new cherry pi IIIs.
I updated the calculator to allow input of the ball diameter (was originally 8mm constant).

The max full print height is a rough estimation, does not take into account the print bed thickness or a few other small parameters.

Any other ideas are welcome to add and/or modify for more general use.


Thanks
Kyler

Ok, looks better now.

What exactly is the definition of" Base extrusion to Vertice"?
End of the vertical to center of the horizontal or,
end of the vertical to the middle of the horizontal rear face?

The arm/rod length calculation is including 2x 5mm magnets?

Anyway, it seems that I´m spot on with my extrusion and rod length, I ordered.
I was lucky to find offers for 400+ 800mm extrusions as well as 300mm carbon rods. No need to chop them
I also found a 300mm diameter glass plate, that will fit too.
Can´t wait until the parts arrive..
-Olaf

The arm vs rod length is 2 x ball diameter, so in your case yes 2 x 5.

The "Base extrusion to Vertex" is hard to explain, the picture in the spreadsheet is the best way to understand it.
If you were to extend the 3 base extrusions until they met (forming an equilateral triangle) they would create a vertex. That length is what it is asking for.
Its basically solving the length of the sides true triangle formed by the base extrusions. You measure from the inward edges of the base extrusions to the point they meet. The value originally inputted should be close enough for most builds that have corner pieces made for 2040 tower extrusions.

Kyler

Subbed

how about a true calculate or estimate print height considering the length of the hot end tip to bed

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