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Homing algorithm for delta in marlin

Posted by Pawan 
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Pawan
Homing algorithm for delta in marlin
May 01, 2016 04:57AM
It tried homing of a Cartesian printer with delta code. All three axes move but they do not stop when end steps were hit. I am curious why as all linear motion should stop when end stop is hit even in delta. Can any one explain this anomaly?
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DjDemonD
Re: Homing algorithm for delta in marlin
May 01, 2016 01:50PM
When an endstop is hit during homing the 3 axes stop. They then slowly feel for the endstops in turn. Do you endstops work when you send m119?

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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Pawan
Re: Homing algorithm for delta in marlin
May 01, 2016 03:14PM
End stops are working. But when an end stop hit that axes are not stopping.
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DjDemonD
Re: Homing algorithm for delta in marlin
May 01, 2016 05:15PM
What printer/firmware/version etc...

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 12:13PM
Firmware:Marlin latest, Printer: Prusai3
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DjDemonD
Re: Homing algorithm for delta in marlin
May 02, 2016 12:17PM
When you say latest marlin do you mean 1.0.2 stable or 1.1.0 rc6 which is the latest?

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 12:20PM
1.0.2
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DjDemonD
Re: Homing algorithm for delta in marlin
May 02, 2016 12:24PM
When I read your original post above you are using delta config on a cartesian machine?

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 12:26PM
Yes...Just playing around until the carriages do not stop after hitting end stops.
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DjDemonD
Re: Homing algorithm for delta in marlin
May 02, 2016 12:34PM
Well I suppose it's an interesting if probably pointless experiment. When delta is defined in marlin the equations of motion used to determine how the axes move are totally different. For cartesian the firmware just has to decide which axis to move and send a number of steps and a direction to the stepper motor drivers.

With a delta it has to use Pythagorean maths to determine how much to move the three carriages. This involves a lot of square roots which tax the processor which is why 32bit boards do better with this than ramps. Personally if ramps were twice the processor speed it would cope just fine.

I'm not sure why your printer shouldn't stop on homing even running delta firmware.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 12:36PM
All this is fine...Why the carriages do not stop when end stops are hit is the mystery.
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DjDemonD
Re: Homing algorithm for delta in marlin
May 02, 2016 12:37PM
Do it work normally if you use cartesian settings on your cartesian printer? Delta settings are for delta printers.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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DjDemonD
Re: Homing algorithm for delta in marlin
May 02, 2016 12:38PM
When you send m119 with an endstop triggered do you see triggered on the console in pronterface.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 12:40PM
Yes when I press with hand.
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DjDemonD
Re: Homing algorithm for delta in marlin
May 02, 2016 01:05PM
Do the axes move the right way? So towards the endstop?

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 01:06PM
Yes...They hit the end stops but do not stop.
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DjDemonD
Re: Homing algorithm for delta in marlin
May 02, 2016 01:07PM
You've got me I have no idea.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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stephenrc
Re: Homing algorithm for delta in marlin
May 02, 2016 01:53PM
Don't the Deltas use the MAX endstops, since they home to the top?
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 01:56PM
Sry, but what is MAX endstops?
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Srek
Re: Homing algorithm for delta in marlin
May 02, 2016 01:57PM
The endstops don't correspond directly with max or min since they are not on any of the cartesian axis.

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
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stephenrc
Re: Homing algorithm for delta in marlin
May 02, 2016 02:04PM
Quote
Pawan
Sry, but what is MAX endstops?

There are two places an endstop can be placed:
MIN is at position 0 of the axis.
MAX is at the maximum position of the axis.

If you're using a RAMPS on a cartesian printer, they're usually not used.
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 02:04PM
Does it matter? In delta, the algorithm is like all three axis motors keep rotating until the first end stop is hit and one of the motor stops, then the other two keep rotating until one of them is hit and stops...then the third. So even when delta firmware is run on cartesian, each carriage should hit and stop.

Does the algorithm activates and deactivates during homing process? Or are the end stops always active? As these settings may be the reason? Where in G28 is this algorithm, can anyone help?
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Pawan
Re: Homing algorithm for delta in marlin
May 02, 2016 02:05PM
I am using RAMPS
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DjDemonD
Re: Homing algorithm for delta in marlin
May 02, 2016 03:34PM
I think what stephenrc is saying is that the three endstops in use on a delta should be connected to the x max, y max and zmax endstop connectors on ramps. If they are connected to x min, y min and z min they won't work. I can check on my kossel later and let you know. Or swap your email endstops onto these pins and try again. But if you are using an i3 why use delta firmware? That's like trying to use .44 ammo in a .38

Edited 1 time(s). Last edit at 05/02/2016 03:34PM by DjDemonD.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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