Ideas for improvement

I need to get a better printout finish. On a friends 3D printer we can produce parts with a very fine finish that I can not reproduce on my K8200; the ridges can be barely felt when scratched with a fingernail .

The product produced with the same file on the K800 has relatively deep and visible ridges about 11 in every centimetre even when the layer thickness is reduced to 0.1 mm. We have maintained the same temperatures on the bed and extrusion head (they are very stable), but we have tried changing filament feed speeds, layer thicknesses, different extrusion temperatures and translation speeds and more. We have made some improvement we are not even close to the sample produced on my friend’s “out of the box and plug-in” printer.

As the apparent “layers” are spaced very regularly and has no relation to the layer thickness, I suspect that I am missing some detail in configuring the Repetier Slicer.

The only major difference between our printer and my friend’s is that he is using ABS filament and we are using PLA filament.

I have very clear photos that dramatically illustrates the differences in finishes but do not know how to attach them to this plea for help.

ANOTHER PROBLEM is how do you ensure a clean filament cut-off when the extruder head moves from one position to the next.

Any advice will be welcomed and appreciated.

[quote=“Oivil”]I need to get a better printout finish. On a friends 3D printer we can produce parts with a very fine finish that I can not reproduce on my K8200; the ridges can be barely felt when scratched with a fingernail .

The product produced with the same file on the K800 has relatively deep and visible ridges about 11 in every centimetre even when the layer thickness is reduced to 0.1 mm. We have maintained the same temperatures on the bed and extrusion head (they are very stable), but we have tried changing filament feed speeds, layer thicknesses, different extrusion temperatures and translation speeds and more. We have made some improvement we are not even close to the sample produced on my friend’s “out of the box and plug-in” printer.

As the apparent “layers” are spaced very regularly and has no relation to the layer thickness, I suspect that I am missing some detail in configuring the Repetier Slicer.

The only major difference between our printer and my friend’s is that he is using ABS filament and we are using PLA filament.

I have very clear photos that dramatically illustrates the differences in finishes but do not know how to attach them to this plea for help.

ANOTHER PROBLEM is how do you ensure a clean filament cut-off when the extruder head moves from one position to the next.

Any advice will be welcomed and appreciated.[/quote]

The lines you mention are called “Z-wobble”.
They are caused by uneven z movement, mostly due to bent threaded rods.
Using a flex coupler between motor and Z rod will help a lot with that.
For reducing stringing set the retraction speed to about 100-150mm/s.

cheers,

Christian

Hi Christian,

Thank you for your advices.
The stinging problem seems to have been resolved and again thank you for that.

As for the layering problem, I will seek a flexible coupling for the Z drive though I am not convinced that the flexible coupling will resolve our layering problem. As I see it, an out of line motor will cause successive layers to be deposited out of position although each layer will be identical. Our problem is that the layering occurs because the “width” of each layer is different so that the end view of a vertical 2mm wide vertical “plate/plane” appears to be a series of “waists”. We would expect any out of line of the Z drive would result in a constant width “corrugated” section.

I would appreciate your further comments on the above. Could you also advise if and where I could best search for a coupling kit.

Once again, thank you

Oivil

[quote=“Oivil”]Hi Christian,

Thank you for your advices.
The stinging problem seems to have been resolved and again thank you for that.

As for the layering problem, I will seek a flexible coupling for the Z drive though I am not convinced that the flexible coupling will resolve our layering problem. As I see it, an out of line motor will cause successive layers to be deposited out of position although each layer will be identical. Our problem is that the layering occurs because the “width” of each layer is different so that the end view of a vertical 2mm wide vertical “plate/plane” appears to be a series of “waists”. We would expect any out of line of the Z drive would result in a constant width “corrugated” section.

I would appreciate your further comments on the above. Could you also advise if and where I could best search for a coupling kit.

Once again, thank you

Oivil[/quote]

If the z leadscrew is not diven straight, is bent or wobbles around free at the end you will have uneven layer heights as a result.
Thus a flex coupler will greatly reduce thet effect. Also straightening the screw (if bent) will reduce that greatly.

cheers,

Christian

[quote=“Oivil”]Hi Christian,

Thank you for your advices.
The stinging problem seems to have been resolved and again thank you for that.

As for the layering problem, I will seek a flexible coupling for the Z drive though I am not convinced that the flexible coupling will resolve our layering problem. As I see it, an out of line motor will cause successive layers to be deposited out of position although each layer will be identical. Our problem is that the layering occurs because the “width” of each layer is different so that the end view of a vertical 2mm wide vertical “plate/plane” appears to be a series of “waists”. We would expect any out of line of the Z drive would result in a constant width “corrugated” section.

I would appreciate your further comments on the above. Could you also advise if and where I could best search for a coupling kit.

Once again, thank you

Oivil[/quote]

Hi, the threaded rod causes two problems that both look similar but are caused by different defects.

  1. Z axis wobble: because the rod is bent or solidly connected and it exerts a force (in the X & Y plains) on the Z axis assembly resulting in layers not being aligned. Effects mitigated by fitting a flex coupler and ensuring the rod is as straight as possible.
  2. Inconsistent Z layer height: because the rod is manufactured as a fixing not an axis drive and the nut does not run concentrically on the thread. The end result is that the rod rotates it causes one corner of the nut to lift slightly then return. This means that during one rotation (1.25mm) the layers will be different thicknesses. As the same quantity of material is extruded during each layer, short layers become ‘fatter’ and bulge outwards taller layers become ‘thinner’ causing concentric ribs. To mitigate this you can try turning the nut 1/6 of a turn in its holder, but ultimately get rid of the threaded rod and replace with something designed for the job, see here viewtopic.php?f=53&t=12999
    I suspect you are suffering with No. 2, the quick check is to compare a print to your threaded rod ( sorry about the focus)