Printer Radius Clarafication

[altarke]

As a Rostock use I have paid may fair share of late night printer calibration procedure. My question is with regards to the actual parabolic ( concave or convex) motion of the end effector and the relationship to the actual numbers in the Arduino Firmware. When we increase the number, I understand we flatten the parabolic "imaginary" motion, when we decrease the number we make the parabola "higher". What I want to know is, when we modify the value of "Printer Radius" we raise the outer edges of the parabola (hence - flatting it from the bottom ) or we lower the center and the outer edges of the parabola remain as before (hence - flatting it but from the top) ?

Thanks
Altarke

[Polygonhell]

I believe the center point doesn't move regardless of what you set the delta radius to.

[altarke]

I believe the center point doesn't move regardless of what you set the delta radius to.

I am thinking of making an end effector with adjustable head height - so if I get the head to swoop to the outer edges of the bed with no problems then if I will move the head to the center it's unlikley to sit properly at the center. Now instead to going back and forth changing the printer radius and readjusting the screws all we need to do is "drop" the head to the bed center and change the printer radius as needed - this way ther is no need to readjust the screws again and again.

I need to know if this logic is good or not - any thoughts?

Thanks

[Eaglezsoar]

I believe the center point doesn't move regardless of what you set the delta radius to.

I am thinking of making an end effector with adjustable head height - so if I get the head to swoop to the outer edges of the bed with no problems then if I will move the head to the center it's unlikley to sit properly at the center. Now instead to going back and forth changing the printer radius and readjusting the screws all we need to do is "drop" the head to the bed center and change the printer radius as needed - this way ther is no need to readjust the screws again and again.

I need to know if this logic is good or not - any thoughts?

Thanks

Very good logic, very difficult implementation.
If you could come up with this you could change the world of Delta printing.
Not only is the hardware involved, the firmware would need to move the head in response to its position.
Theoretically the firmware should be doing that now but it apparently does not.

[bdjohns1]

I believe the center point doesn't move regardless of what you set the delta radius to.

I am thinking of making an end effector with adjustable head height - so if I get the head to swoop to the outer edges of the bed with no problems then if I will move the head to the center it's unlikley to sit properly at the center. Now instead to going back and forth changing the printer radius and readjusting the screws all we need to do is "drop" the head to the bed center and change the printer radius as needed - this way ther is no need to readjust the screws again and again.

I need to know if this logic is good or not - any thoughts?

No need to reinvent the wheel.

You just need to use software offsets for your endstops. Assuming you're using Repetier-based firmware like most of us, there are a few flags in Configuration.h in the firmware source - you can specify the number of steps to offset the end-stop position as opposed to screwing with screws. They're also available in the EEPROM, so you can tweak them using the EEPROM dialog in Repetier-Host, or sending the right M-codes to the printer.

DELTA_X_ENDSTOP_OFFSET_STEPS (and Y and Z)

If you've got 20-tooth pulleys and 16x microsteps (the standard configuration for any later v1 and all v2 RoMax), then each step should be 1/80 mm (0.0125mm).

In that case, what I'd do is use some brass feeler gauges to establish how far I'm off on each end stop, and use that to figure out how many steps I need to offset by.

[altarke]

DELTA_X_ENDSTOP_OFFSET_STEPS (and Y and Z)

If you've got 20-tooth pulleys and 16x microsteps (the standard configuration for any later v1 and all v2 RoMax), then each step should be 1/80 mm (0.0125mm).

In that case, what I'd do is use some brass feeler gauges to establish how far I'm off on each end stop, and use that to figure out how many steps I need to offset by.

if I get your idea right it would be considered "soft Endstop adjustment" but it would still not have any effect on the printer radius value. \What I am proposing is along the lines of first getting the end stops to be adjusted right and then changing then "Printer Radius" to assure horizontal motion.

[lordbinky]

That'd work fine if your towers are all at the precise angle and distance from the center point and the arms are exactly the same.

Your compensating for alot of things during the radius adjustment. Also, the way the delta math works out, endstop adjustments for one tower affect the adjustment to the other towers. Deviations from an ideal build is also why the center point changes (it changes less as you get closer to the correct settings though).

Also, Polygonhell is right, the center point doesn't move in height (the cartesian Z axis) when you change your printer radius. If your build is mathmatically perfect, your position at the base of the towers (perimeter) would all equally change in their height above (or below) the center Z height. If you don't have a mathmatically perfect build, then they will not be perfectly equal in their distance from the bed at the perimeter when you change your printer radius, and you have to re-adjust your endstops to compensate. When you re-adjust the endstops so the points at the base of the towers are equal, this is when the center point moves around in the cartesian X/Y (ie where the center point is on the bed), and to a much lesser degree the height of the center point is changed as well.