Printing Circles

[ex-egll 1]

Hi, new to Cura. I am running A Rumba board on the printer with Marlin 1.1.0 BugFix and Cura 2.5 on the PC. My print job is simple, a circular gasket i.d 25.5mm o.d 26.5mm height 5mm.

When printing, the brim around the gasket is printed as a continuous circle, but when it comes to printing the gasket itself the printer will go once round the circle and then reverse the direction for another pass around and then reverse direction again, this continues throughout the print. Bu printing this way I get a small ridge at the point the direction reverses.

Two questions:

Why does the printhead reverse direction each time a circle has been printed.

Is there a setting that would force it to print in the same continuous direction as it does for the brim

Thanks

[gr5 2,230]

If the circle is perfectly symmetrical with no bumps sticking out and no holes sticking it it usually won't change directino from CW to CCW.

However it shouldn't matter. If you are getting bumps on CW versus CCW that means you have some play aka backlash. I would concentrate on fixing the backlash. It can be caused by many things and all are easy to fix. If you have rubber belts they may be too loose (causing play). If you have too much friction that also causes play (belts stretch). Or gears might not be meshing nicely. Or you might literally have a loose nozzle.

Try pushing against the cold nozzle to see if it moves without moving the servos. If you can feel any movement (even if you can't see it) then you need to fix that.

[peggyb 171]

or you can draw a solid cylinder, o.d. 26.5mm and print only one wall with 0.5 line width in spiralize outer contour mode. You might want to test/adjust a bit to achieve your measurements.

[DaHai8 74]

If the circle is perfectly symmetrical with no bumps sticking out and no holes sticking it it usually won't change directino from CW to CCW.

I think what is happening is that the outer shell is printer CW and the inner shell is printed CCW. So when the outer and inner shells are adjacent, you get a whip of filament as it changes direction.

Perhaps setting a Coast at End value would help.

[ex-egll 1]

Thanks for the responses, I agree IF my machine was set up perfectly the change of direction should not matter! Time to get working on tensioning the belts better. Thanks fro the suggestion as to why the direction changes. The comment "Perhaps setting a Coast at End value would help" is beyond my pay grade! Could you possibly throw in a bit more detail?

Thanks

[DaHai8 74]

Sorry, should have been more specific as its not a common setting. In the right pane:

Experimental -> Enable Coasting

If you don't see it, then go to the Settings Menu -> Configure Settings Visibility -> Check All (click on it until a check mark appears in the box)

After you Enable Coasting, you'll see a few more settings you can tweak to fine tune it. Explanations of each setting pop-up when you hover over the input boxes.

Hope this helps.

[ex-egll 1]

Thanks, I'll play with the settings tomorrow