Raft Gap from Model

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Targo
Posts: 32
Joined: Fri Aug 25, 2017 9:09 am

Raft Gap from Model

Postby Targo » Wed Nov 22, 2017 10:35 am

Hello,
When I print ABS with raft, I often have problems solving the finished model of the raft. The parameter "Raft Gap from Model" shows no effect at all, no matter if I enter 0.2 or exaggerated 0.5. Is this a mistake? Alternatively, I can retract the flow rate for the first layer, but what's this parameter for?
I have tested this with the current V2.6 as well as the current beta.

Frank

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John@Raise3D
Posts: 483
Joined: Fri Feb 26, 2016 8:42 am

Re: Raft Gap from Model

Postby John@Raise3D » Wed Nov 22, 2017 9:28 pm

Targo wrote:Hello,
When I print ABS with raft, I often have problems solving the finished model of the raft. The parameter "Raft Gap from Model" shows no effect at all, no matter if I enter 0.2 or exaggerated 0.5. Is this a mistake? Alternatively, I can retract the flow rate for the first layer, but what's this parameter for?
I have tested this with the current V2.6 as well as the current beta.

Frank

Less flow rate will make the first layer less dense and it may help. Further model to raft gap may help as well. However, there are a few others factors you may want to check.
1. what is your nozzle temperature?
2.Nozzle size?
3. Layer height?
4. nozzle to bed gap?
5. filament brand?

Targo
Posts: 32
Joined: Fri Aug 25, 2017 9:09 am

Re: Raft Gap from Model

Postby Targo » Thu Nov 23, 2017 10:21 am

Here are my parameters for ABS
1. nozzle temp 245°
2. bed temp 110° all closed
3. nozzle size 0.4
4. Layer height 0.15
5. ABS from material4print

The printing works perfectly, mostly I print without a raft directly on a FR4 plate. I only wonder that the parameter "Raft Gap from Model" has no influence whatsoever. Even in the preview, nothing can be recognized, here actually a gap between raft and model should be seen.

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Vicky@Raise3D
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Joined: Fri Mar 25, 2016 3:54 am

Re: Raft Gap from Model

Postby Vicky@Raise3D » Fri Nov 24, 2017 2:27 am

The gap wont be shown in Preview, but it should work during real printing. If you have any interest, you can try even larger gap to check the result more clearly or share your gcode file with us, we'd like to help check.

Targo
Posts: 32
Joined: Fri Aug 25, 2017 9:09 am

Re: Raft Gap from Model

Postby Targo » Fri Nov 24, 2017 6:28 pm

Here is a test file. Once with gap 0 and once with gap 1. At layer -1, everything is exactly the same. In layer 0, Gap has 0 Z at 2.02 and Gap 1 Z at 3.02. That's clear to me. But in Layer 1, the Z height is exactly the same again for both variants. Should not the Z height incrementally build up?

lay-1.JPG


lay0.JPG


lay1.JPG

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Vicky@Raise3D
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Joined: Fri Mar 25, 2016 3:54 am

Re: Raft Gap from Model

Postby Vicky@Raise3D » Mon Nov 27, 2017 8:42 am

Normally the Z should not change from Layer 0 to Layer 1 under the default settings.
But your gap is too big (gap+ first layer height >= first layer height+ layer height), so that the filament of Layer 0 (the first layer of model) will drop off from the Z height you set to stick to the top surface of Raft, so Z value of Layer 1 will drop a little to match.

Targo
Posts: 32
Joined: Fri Aug 25, 2017 9:09 am

Re: Raft Gap from Model

Postby Targo » Mon Nov 27, 2017 7:23 pm

I just do not understand. If I enter a layer thickness of 0.2 and gap between Raft and model of 0.2, G code layer 0 and 1 is output with the same Z-height. This means that two layers with the same height are printed. Try it. Or have I thought incorrectly about that?

I'm sorry if I bother :-)

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Vicky@Raise3D
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Re: Raft Gap from Model

Postby Vicky@Raise3D » Tue Nov 28, 2017 3:09 am

As the gap you set is 0.2mm, and the layer thickness of the Layer 0 is 0.2mm, then the nozzle will move to 0.4mm far to the Raft to start print the Layer 0. And the thickness of Layer 1 is 0.15mm, which means in total, there will have 0.2+0.15=0.35mm thick filament be extruded from Layer 0 to Layer 1. And the nozzle is already at 0.4mm, the space is enough to extrude these two layers.

Targo
Posts: 32
Joined: Fri Aug 25, 2017 9:09 am

Re: Raft Gap from Model

Postby Targo » Tue Nov 28, 2017 5:03 pm

Vicky@Raise3D wrote:As the gap you set is 0.2mm, and the layer thickness of the Layer 0 is 0.2mm, then the nozzle will move to 0.4mm far to the Raft to start print the Layer 0.


That's how I would understand that, but it's not like that. Please try it out and have a look at the GCode.
If the gap is the same as the layer thickness, layer 0 is driven at the same Z height as layer 1. So the two layers are at the same Z height.

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Vicky@Raise3D
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Re: Raft Gap from Model

Postby Vicky@Raise3D » Wed Nov 29, 2017 3:52 am

The two layers are not at the same height, the first layer will drop to the surface of Raft from 0.4mm-height. The rest space is enough to print another 0.15mm-thick layer.


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