Raft and bottom layers problem

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chengl03
Posts: 91
Joined: Sat Apr 16, 2016 12:32 am

Raft and bottom layers problem

Postby chengl03 » Fri Jul 14, 2017 3:52 pm

Hello,

This never happened before but now the raft is bonded to the bottom layer of the model so I can only take off the raft that the model isn't sitting on. After the bottom layers, the print is fine. Is it bed leveling that's the cause? And is the bottom layers overextruded?
Attachments
Raft.jpg

Jetguy
Posts: 1793
Joined: Tue Mar 22, 2016 1:40 am

Re: Raft and bottom layers problem

Postby Jetguy » Sat Jul 15, 2017 12:12 am

Sorry for a slow reply on this. I'm not trying to ignore print quality questions but this is frustrating and my answers likely show it. I was hoping others would chime in.

Let's define over extrusion. The whole idea is that you give the slicer the following variables.
Layer height
Nozzle diameter
Filament diameter
STL file

When the slicer slices the STL and creates the 2D layers, the variables input above are used. For example, nozzle size is also how wide the round hot filament noodle will be. That coupled with layer height smashes the round extrusion to an oval shape, either to the bed on first layer or on next layers to the previous layer. In doing so, even linear length of a segment results in known volume of the cylinder smashed. In other words, we know the width, height, and length of the specific segment of gcode extrusion. Given filament diameter, the slicer then can figure out exactly the proper length of commanded raw incoming filament of a known diameter to push into the nozzle to get the correct volume out.

The KEY here is that first layer is a MECHANICAL adjusted gap. When you set the endstop trigger and bed leveling adjustments you set using a 0.20 feeler gauge as supplied with the printer. If there is ERROR in this adjustment, be it a non leveled bed or incorrect overall gap, then first layer and some aspects of subsequent layers will be either drooling on top of the bed and NOT sticking if the gap is too large, or smashing excessively into the bed making wide stripes and the nozzle partially "plows the field" making troughs as it melts it's way through. Even the next couple of layers, the filament and offset of the bed plane to the nozzle travel plane results in layers being smashed.

You can call this over extrusion because yes, in a technical sense the volume of plastic extruded VS the mechanical layer width and height the slicer commanded is different than the actual physical result, but we would never say over extruded, we just call it poor bed leveling or incorrect Z gap.

So as such, if you have a bad leveling or Z gap, absolutely this will make a raft both required to get the print to stick in the nozzle too high spots and raft nearly impossible to remove in the nozzle too low spots.

Jetguy
Posts: 1793
Joined: Tue Mar 22, 2016 1:40 am

Re: Raft and bottom layers problem

Postby Jetguy » Sat Jul 15, 2017 12:14 am

Again, the more you wrap your head around understanding the variables, understanding the relationships of what happens, the better you will be at troubleshooting and not having these kinds of basic problems.

I'm sorry the manual doesn't go into 3D printing "theory" but I would hope after a few minutes of thinking and watching the nozzle actually lay first layer, some of this would really get some of the newer users up to speed.

chengl03
Posts: 91
Joined: Sat Apr 16, 2016 12:32 am

Re: Raft and bottom layers problem

Postby chengl03 » Mon Jul 17, 2017 1:55 pm

Ok, so I re-level the z axis screw to finally got the raft to not be glued to the model. But one problem still kinda exist. The infill layers of the bottom layers (5 layer top and 5 layer bottom settings) is still really close to each other (no matter how many times I re-level the z axis screw) making the print like the one shown in the pic on my first picture but without the raft attach. The thing is, for small print it is fine, but for mid or large print that ring of the bottom infill layers always shows up. The top infill layers is fine, its just only the bottom infill layers is doing this.

EldRick
Posts: 115
Joined: Thu Jun 22, 2017 5:55 am

Re: Raft and bottom layers problem

Postby EldRick » Mon Jul 17, 2017 3:20 pm

Perhaps - don't use a raft at all?

chengl03
Posts: 91
Joined: Sat Apr 16, 2016 12:32 am

Re: Raft and bottom layers problem

Postby chengl03 » Mon Jul 17, 2017 4:49 pm

Haven't tried without raft, so guess I'll have to try to print without raft to see how it goes. Idk why but I just like to print with raft.

All my settings are in default, idk why it always keep happening, bottom infill layers keeps making that outer ring cause after that, it prints perfect. Also, it looks like once it is at the 4 and 5 layer of the 6 layer infill bottom layer, the nozzle looks like it only move very so slightly above the previous layer which then cause the extruder gears to click cause it can't extrude all the filament through nicely because nozzle is too super close to the previous layer, but come the 6/last layer infill bottom, the z axis moves down fine and the extruder is finally extruding the filament fine again. I hasn't done this before when I haven't changed new parts (motion control board, stepper drivers, touchscreen box).

By the way, I tried turning the z axis screw again so the bed is further, but it only effected the raft not the bottom infill layers so I think the z axis screw is not the problem. Either something is wrong in the IDM setting or something mechincally worng with the printer. Need some help.

Jetguy
Posts: 1793
Joined: Tue Mar 22, 2016 1:40 am

Re: Raft and bottom layers problem

Postby Jetguy » Mon Jul 17, 2017 5:25 pm

So far you provided one picture which doesn't help us figure out what you are looking at.

Nobody wants you to have problems or printing badly, however, you are not learning and not making posts that allow us to actually figure out what you are doing wrong.

#1 Post pictures, Top and Bottom, and side view of the nozzle at the highest resolution you can.
#2 Link the STL you are trying to print. Take screenshot of preview layout
#3 Post the gcode file.

All of these things gives us the settings used and what you actually sent to the printer, to which we compare to the result pictures.
If you only gives us 1/10th of the what we need, all we can do is generalize and guess.

chengl03
Posts: 91
Joined: Sat Apr 16, 2016 12:32 am

Re: Raft and bottom layers problem

Postby chengl03 » Mon Jul 17, 2017 6:06 pm

Best picture right now is the picture I posted on first. See those two lines on the bottom layers near arrow that looks out of place, that has been happening. The raft is fixed it is not glued on anymore but those bottom layers are still appearing. I'll add more info later on.

chengl03
Posts: 91
Joined: Sat Apr 16, 2016 12:32 am

Re: Raft and bottom layers problem

Postby chengl03 » Mon Jul 17, 2017 9:16 pm

Jetguy, I did the best I can in details on what is the problem.

Basically the problem is that the bottom infill full layers, seems like always the 4 and 5 layers out of the 1 through 6 bottom infill layer are smoosh very close to each other but then the last layer of the bottom infill prints fine and up. I tried to take a super close up detail of what I am saying, pictures below. The stl. and gcode files are fine, why, because this is happening to all the prints expect the small test print I did which its still there just that you can barely see it cause it is a small print (1inx1inx1in). I use the latest IDM and has not changed anything, they are all in default, I only increase the number of bottom and top infill layers. But if you still want it, I'll post it later.

Pictures are all bottom of the print. Top printed fine.
Attachments
BotInfillLayers03.jpg
BotInfillLayers02.jpg
BotInfillLayers01.jpg

chengl03
Posts: 91
Joined: Sat Apr 16, 2016 12:32 am

Re: Raft and bottom layers problem

Postby chengl03 » Mon Jul 17, 2017 11:15 pm

A picture where I stop the print after 6 hours on large print with raft (happened always, probably is the cause of the lump of the bottom infill layers). You can see scratches/lumps on top of the previous layer, nozzle was too close to the previous layer. Red line is where nozzle is printing to.
Attachments
Scratches02.jpg
Scratches01.jpg

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walshlg
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Joined: Wed Mar 23, 2016 12:01 pm

Re: Raft and bottom layers problem

Postby walshlg » Tue Jul 18, 2017 4:46 pm

I have seen that too and just ignored it. I think you may want to message Vicky about this

May I suggest trying to print with a slower raft pint speed

chengl03
Posts: 91
Joined: Sat Apr 16, 2016 12:32 am

Re: Raft and bottom layers problem

Postby chengl03 » Wed Jul 19, 2017 4:19 am

I think I kinda know what the cause is. It had something to do with the bed level. I re-level it again (for about 3 hours) and it now is almost not as bad anymore. I don't know why re-leveling the bed made it better but it did somehow.


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