Bad surface of layer on the underside of prints - what can be the reason?

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Tinkerer
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Bad surface of layer on the underside of prints - what can be the reason?

Postby Tinkerer » Sat Oct 14, 2017 5:13 pm

Hello again!
The relentless newbie keeps asking funny questions;-)

I have printed several items which required raft and support.
And every time I was a bit disapointed by the underside of the prints.

Attached pictures show the difference between lower and upperside of the prints.
In addition I found some loose filament on this print.
Should I increase temperature? I am currently at 215°C.

So far so good looking upperside of the print:
UppsersideOK.jpg


Ugly, rough looking underside:
UndersideBad.jpg



Thanks & till next time!

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Mecha_Monster
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Mecha_Monster » Sun Oct 15, 2017 5:43 am

It is tough to get good surface finish on that part of the prints.
Try to use dense support option, at least 5 layers and set it to 100% density, that may help

Tinkerer
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Tinkerer » Sun Oct 15, 2017 4:18 pm

Hi,

thanks for the tip reg. support - will try that.

So the temperature is not the problem, you think?
215°C for PLA?

Thx & BR!

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Mecha_Monster
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Mecha_Monster » Sun Oct 15, 2017 6:52 pm

It deepens on the brand. 215 should be fine. but usually what I do is that I star at 190 degree, that's a safe temperature for PLA, and then manually go up (using the touch screen) depending on how the print behaves. a print made at 215 degrees is going to have better layer adhesion than one at 190 degrees, but not significantly. Try to stick to the lower temp settings (around 190)

Tinkerer
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Tinkerer » Sun Oct 15, 2017 11:38 pm

The PLA I am currently using is from Raise3D - came w. the printer.
I'll give a "low temp print" a try.

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Vicky@Raise3D
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Vicky@Raise3D » Mon Oct 16, 2017 2:20 am

Denser Support Layer from Mecha_Monster is also a good suggestion to take a try.

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walshlg
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby walshlg » Mon Oct 16, 2017 4:41 pm

another tip, especially with a curved bottom surface, is lift the entire model at least 10mm in Z and completely cover it with support, This way the support is at least 10mm thick and is more stable than the short supports people often make.

Tinkerer
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Tinkerer » Mon Oct 16, 2017 8:04 pm

Thank you all for your tips!

I'll still have to try the one with higher support from walshig.

But even at lower temps and with dense support I keep getting bad undersides of my prints.

I even tried to print with and without printbed-heating - still the same:-(

Tinkerer
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Tinkerer » Thu Oct 19, 2017 9:41 am

Hello again!

So I tried a print (PLA) with raised object -> higher support structure plus using dense support.
Outcome: underside of print looks a little bit better but still not perfect.
And: it was really difficult to remove the support!
Had to literally cut it of with a small sharp blade (actually did need two blades;-)

Pic: Underside of ball
Ball50_U.jpg


Now I wonder why I always have such little imperfections in the prints.
In this case many little "dots" all around the ball.

Pic: Ball surface. Notice the little dots on & in the surface
ball50.jpg


What can cause this?

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Vicky@Raise3D
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Vicky@Raise3D » Fri Oct 20, 2017 2:46 am

The "dots" look like start points of every layer. You can compare your result with the .gcode file preview in ideaMaker. Check Show Current Layer and move the two sliding blocks below to check the moving path of each layer.
You can change the Layer Start Point's position in ideaMaker or increase the retraction amount and retraction speed to minimize the affect of start point.
But it will be hard to totally remove the "dots", since when layer changes, nozzle will stop extruding and wait for a few seconds to move in X Y directions or move bed in Z direction. During that time, there will have some extra melt filament stays around the nozzle tip.

Tinkerer
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Tinkerer » Sat Oct 28, 2017 12:48 pm

Vicky@Raise3D wrote:...You can change the Layer Start Point's position in ideaMaker...


Hi Vicky,
I'd like to understand this a bit better.
In ideaMaker on tab "other" I see "Layer Start Point Type with [Nearest|Fixed|Random].
What do these mean? Also, when setting a Start Point for X and Y for Fixed Start Point -
what position are these coordinates related to?

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Vicky@Raise3D
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Vicky@Raise3D » Sat Oct 28, 2017 2:26 pm

Tinkerer wrote:
Vicky@Raise3D wrote:...You can change the Layer Start Point's position in ideaMaker...


Hi Vicky,
I'd like to understand this a bit better.
In ideaMaker on tab "other" I see "Layer Start Point Type with [Nearest|Fixed|Random].
What do these mean? Also, when setting a Start Point for X and Y for Fixed Start Point -
what position are these coordinates related to?


Layer Start Point means the start position of each layer.
Nearest means ideaMaker will choose the shortest way to finish the print. Which means, if the layers adjacent have almost the same structure, you will see some continuous layer start points gather together at almost the same position at those layers.
Fixed means the start point of each layer will start at the position you set. If the position you set is out of the model at some layer, ideaMaker will choose a position on model closest to the position you set to start that layer from.
The origin point of the coordinate is at the left front corner of the build space.
Random means ideaMaker will scatter the start point of adjacent layers. So that you will barely see layer point position gathering together to be a continuous line on the surface of the model.

Tinkerer
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Tinkerer » Sat Oct 28, 2017 5:48 pm

Hi Vicky,

thanks for that.
So for example:
Fixed with X;Y = 0;0 means layer start will be at the closest point to the front left of the model, right?
Or if I happen to print some sort of tube I could position the start point inside the model and it then would always have the starting point on the inner line of the model?

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Vicky@Raise3D
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Re: Bad surface of layer on the underside of prints - what can be the reason?

Postby Vicky@Raise3D » Mon Oct 30, 2017 5:09 am

Yes, if the fixed point is (0,0), the start point of each layer will always be the point closet to left front corner.
If the point is inside the model, the start point will still be located at shells. Since shells are always the beginning of each layer. If you have enable Print External Shell first, the start point will on outer shell. If you didn't enable this option, it would start printing from inner shell.


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