Edges of shallow overhang lifting upwards

After a small break I'm again inseparable from my ormerod, but having an issue or two...

As shown in the image attached, the inner edges of some very slight overhangs are lifting upwards.
It isn't a major issue at first but eventually the lifted edge always catches on the sensor (of other low hanging components), essentially ruining the print.

I've raised a very similar issue before but never managed to correct it.
I assumed the previous failures was because i was printing fairly small components. However, this print component is about 160mm x 160mm. Definitely enough time for each layer to dry!

any thoughts??

any help much appreciated!!

Edited 2 time(s). Last edit at 08/19/2014 04:37AM by 88Zombies.

I've had similar things happen but not so severe as to ruin the print. I fiddled around a bit non-scientifically with it, and I think it got better by reducing print speed and slightly lowering hotend temperature (the lower speed giving it more time to cool off and solidify before next pass).

In this case, you could try adding a thin support wall along/under each "arm" that can then be trimmed off. That would give it something to "stick to" which might be enough to keep it straight.

ahhhh ill try reducing the speed, currently the perimeters were set at 30mm/s (small perimeters 20mm/s) total time 6hours...


yea i think i may have to add 2 small supporting walls on each, was trying to avoid that if i could


thanks for the input

I had a similar problem recently with very the steep overhangs on the tree frog print. The sensor board didn't catch it - I am using my differential IR board and the board edge is 2.4mm above the nozzles, high enough not to cause problems. However, the non-printing nozzle did catch it. My solution was to reduce the travel speed, giving the head time to lift out of the way instead of catching it, and also giving more time for the hot nozzle to soften the plastic.

If you are using the standard IR sensor board and it is too low,you can print a nozzle mount with a little extra depth to lower the hot end. Or you can use a shim on top of the MDF insulator to achieve the same thing.

Edited 1 time(s). Last edit at 08/19/2014 05:07AM by dc42.

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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].

Reducing the speed and adding a shim it is.
Will give this a go tonight.



Would it be a bad idea to add another fan? i have an extra on i sometimes use when bridging...
i would assume the extra cooling could help each layer dry sooner. On the other hand if edge-lifting was to persist it could it reduce the efficiency of the nozzle softening the plastic?

Also, on the gcode, Lift Z on retraction is set to 0... is this correct?


(I have your upgraded sensor right next to my printer, going to try to add it over the weekend, took a little break recently )

many thanks both

The biggest problem when the edge lifts is that the nozzle hits it from the wrong direction (toward the edge), which either knocks the part off the baseplate or causes the stepper to miss a step. So long as the moves all cause the nozzle to encounter the edge in the direction of the slope, the nozzle will lift and ride over it. With several prints I have sat with a file grinding off the sharp edges as soon as I get a chance while it is printing. If the geometry of the part makes it a significant problem, you can prevent the lifting by adding thin (0.5mm) support walls along the problem areas that you break off afterwards.

Dave
(#106)