Layer Bonding issue

Hello ,i have a problem printing large parts with PLA. The layers on the thin walls dont bond and break with little preasure while the bottom part is really strong like you see in pictures.

I am priniting at 200C with 65C hotbed.

How thick are the walls, and what speed are you printing at? I print PLA at 185C (except for first layer at 195C) and I haven't had layer bonding issues on the parts I print, although I generally make the walls at least 2mm thick.

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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].

The PLA that came with my ormerod was printing really good at 185C ,the one i am using now tried at 185 and didnt stick well and found that 200 was good temperature ,i dont have any problem on smaller prints but on large the walls just dont stick together good and break up like in the picture ,dont know mybe just the wall gets too cold when the printer puts another layer on top of it? will be trying at 205 next but mybe will have to try some other Manufacturer of PLA.

I suspect that it is a warping issue rather than a layer bonding issue. As the print warps it will pull apart at the weakest point, which is often the bond between the part and the bed (giving an obvious warped appearance), but can also be at a layer if the part is stuck well to the bed.

The warping is usually at a corner, but looking at your photos, it may be caused by the fan's backwash cooling one side of the print too much - have you fitted a backwash eliminator onto the fan housing?

For your own designs, make thin walls have rounded corners if possible (the bigger the radius the better), which helps prevent warping.

Dave

Fans backwash? u mean the intake flow? or something else?(sorry i am a noob) , i use the new ormerod designed hotend like in the attachment.

Quote
Darathy
Fans backwash? u mean the intake flow? or something else?(sorry i am a noob) , i use the new ormerod designed hotend like in the attachment.

So the Ormerod fan has a habit of causing an air disturbance behind the fan, if you (carefully) put you hand behind the intake for the fan you'll feel that some of breeze is blowing away from the fan, this cools any part of the print that winds up behind the fan so much that it warps. The community has termed this backwash.

a backwash eliminator looks something like this
[www.thingiverse.com]

but there are many versions out there, the above one is more meant for the 1st ormerod where the fan and the Duet were on the same side, and clearance was an issue

Edited 1 time(s). Last edit at 03/23/2015 05:52PM by shadow651.

Ok so i have printed a front cover over the fan from kwikius on this thread: [forums.reprap.org] and hopefully will fix the problem ,but i am also worrried that the airflow like i indicated with red arrow in the picture wont affect it aswell?


Edited 1 time(s). Last edit at 03/23/2015 06:06PM by Darathy.

Looks like you have the new hot end assembly with the acrylic spacer. Yes, I would expect that the air coming out of the sides of the heatsink might cause warping of large PLA prints at the +X and -X ends, and certainly of ABS prints; although if the exhaust air is warm then it should be less of a problem than the cold backwash from the fan.

If you think it is causing a problem, you could try using a printed part or some cardboard to deflect the exhaust air upwards. Or you could rotate the heatsink by 90 degrees (which will require drilling another hole in it), then block off the bottom with tape.

Of course, it isn't just the fan that causes draughts - you need to make sure there are no draughts in the room too, or put a draught shield around the printer.

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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].

So i have made a Side Backwash duct for the new acrylic spacer hotend. I have included a stl and some pictures if anyone wants to give 1 a try.



Edited 1 time(s). Last edit at 04/05/2015 08:27AM by Darathy.

Looks good! Now I just need to add mounting points for my hot end board. Do you have an openscad or other source file for it?

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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].

I designed it in Solidworks ,it is in the attachment.

I have not actualy tried it on a large print due to my Y end plate is broken and my bed at the far end of X axis is bent down becouse of it but so far as i can observe it does its job.

Edited 4 time(s). Last edit at 04/05/2015 03:01PM by Darathy.

I have redesigned the Duct the include mount for DC42's sensor: [www.thingiverse.com]

if anyone is interested