Delta Radius =

Hi

In my Marlin settings for my Delta printer, I have:

#define DELTA_RADIUS (DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET)

Can I turn this in to an actual number, is it just a case of adding together the measurements of the, DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET so it would look like:

#define DELTA_RADIUS 278.50

The reason I ask, is because I was looking at the calibration calculator on the escher website and one of the required inputs was delta radius.

Cheers and thanks for any help given

Bob

Try it, it will either work or it won't. I cannot see any reason why it wouldn't.

Unless the variables DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET are used to perform a calculation related to delta radius in the code elsewhere then it won't make a difference. I don't think they are. They format it that way in order that it was easier to calculate back before auto calibration existed.

Edited 1 time(s). Last edit at 08/01/2017 04:34AM by DjDemonD.

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Simon Khoury

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

DjDemonD,
Thanks for getting back to me. You are right of course, it would need to be referenced somewhere else for it not to work. I will change it and see what occurs.

Thanks for clearing that up for me.

Regards
Bob

Yes you can just put in the figure. I guess Marlin is trying to be helpful, but IMO building it from 3 values makes it unnecessarily complicated.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi
Thanks to everyone who answered and helped me. I made some changes. Although before I went off and done anything, what did occur to me, was that my print bed is only meant to be 250mm, so 278.50mm seemed to far.
I had read somewhere that print radius is nothing to do with delta radius. so, I read up on some of the delta characteristics. It turns out that delta radius is made from the following. The centre bolt of the carriage arms to where the arms are joined to the effector.
It's best to have the hot end as low as possible. then all you need to do is measure from the centre of the effector bolt, out to the centre point of the carriage bolt. That gave me a delta radius of 170mm. I entered this into marlin and it seemed to have no ill effects. I have run out of time tonight, and I will probably need to re-calibrate, but I will do that tomorrow.

Again thanks for your invaluable help, great forum.

Bob

Hope it works out. The delta radius is obviously related to your printer size and arm length but the exact value you use will depend on what works to correct the concave or convex position of the nozzle that results from the delta geometry. Only at the right value does the nozzle track across the bed at the same height. This depends on the endstops being right first. You can then tweak arm length to get x/y scaling right. Each time you change something go back and check the endstop heights.

Seriously consider using something like dc42s wizard at escher3d you just have to measure nozzle to bed heights at 6-10 positions on the bed, stick the numbers in along with your starting parameters and it works it all out for you. Unless you plan to use a probe and firmware that calibrates automatically. Seriously consider this it saves you a lot of time.

Edited 1 time(s). Last edit at 08/01/2017 05:12PM by DjDemonD.

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Simon Khoury

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

Quote
Dr Bob
Hi

In my Marlin settings for my Delta printer, I have:

#define DELTA_RADIUS (DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET)

Can I turn this in to an actual number, is it just a case of adding together the measurements of the, DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET so it would look like:

Bob, the calculation is subtraction, not addition:


#define DELTA_RADIUS (DELTA_SMOOTH_ROD_OFFSET - DELTA_EFFECTOR_OFFSET - DELTA_CARRIAGE_OFFSET)

nicely summed up here


although "marlin firmware without bottom endstops"? Did deltas used to have bottom endstops in the pre-cambrian era?

Edited 1 time(s). Last edit at 08/01/2017 07:22PM by DjDemonD.

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Simon Khoury

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

Quote
DjDemonD
Seriously consider using something like dc42s wizard at escher3d you just have to measure nozzle to bed heights at 6-10 positions on the bed, stick the numbers in along with your starting parameters and it works it all out for you. Unless you plan to use a probe and firmware that calibrates automatically. Seriously consider this it saves you a lot of time.

Funny enough I looked at this, and it was that site that made me post my question. It was asking for my delta_radius and I didn't have an actual number to put in.

It's not that I didn't want to use a probe, more that my OCD wants to do as much by hand first, I want to know the finer points of the delta and it's little oddity's, before giving in to going with a probe. Which I would be happy doing, but only until I know the beast I have.

Its a good idea to try manually calibrating A) the old fashioned way, by setting endstops, then radius, then arm length etc... very frustrating on the whole or B ) using escher wizard. Note if you get odd results change the height differences from positive numbers to negative as appropriate, I always get it wrong first time around.

The reality is its a bunch of complex maths to get that nozzle to track properly across the bed, and if you have a really flat bed and a really precise probe the rest is easy. 0.007 std deviation of probe heights across a 300mm bed.

Edited 1 time(s). Last edit at 08/02/2017 07:25AM by DjDemonD.

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Simon Khoury

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

Quote
frankvdh


Bob, the calculation is subtraction, not addition:

See, I never knew this, but looking at it now, I can see that! Thank you for bringing this to my attention

Oh Man, just as you think you're getting a handle on these machines they get all "you just don't know me at all"

Bob

LOL Bob I've had them for 2 years and only just feel like I understand how to tune them, if I understood the maths behind it like DC,then I might be able to say I understand deltas.

Jedi training is long and hard.

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Simon Khoury

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

on mine i have manuall measure my delta radius which was something 110mm
but after auto bed i have 95mm..i ve never understand why i have so many difference..

Physically measuring the arm length (diagonal rod) is valid as in many cases the best calibration will use the actual rod length. But delta radius is IMO a "virtual" value, whatever works, works.

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Simon Khoury

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