Raft first layer vs. regular first layer settings...

[patniemeyer]

When I include a raft S3D puts down a nice, thick, first layer but when I remove the raft my first layer is way off / too thin or close to the build plate. It's almost like the "Layer -> First Layer" Settings (which a first layer height of 150%) only apply to the raft. Alternately, is it possible that the Raft is applying the "Additions->Use Raft->Separation Distance" below the first layer? I'm trying to figure out why the heights are so different and how to get my regular first layer to match the result that I get with the raft first layer when I don't need a raft.

thanks!
Pat

[dkightley]

Using a raft make getting the vertical positioning very much easier to get right......so switching off the raft means you need to be much more accurate in your first layer positioning. You say the first layer is either too high or too low.....which is it? It can't be both!

First of all....get your bed levelled and don't fiddle with it! then print a test cube using your usual profile.

If the first layer doesn't stick, you need to drop the Global-Z value in a negative direction by say 0.02 mm and re-print. Keep adjusting until you get the first layer to stick....then adjust in increments of 0.01mm until the bottom is nice and smooth.

If the first layer hardly prints....but sticks, then the nozzle is too close to the bed. Carry out the above adjust & print sequence changing the Global-Z in a positive direction.

A bit about the first layer settings.....which apply to the FIRST layer printed on the bed (ie either layer 1 of the raft if there is one....or layer 1 of the model if no raft. Any value of height below 100% has the same amount of plastic extruded as 100%....the same amount of plastic is squished into a lower height. Any value over 100% has a proportionate increase in plastic...as well as an increase in thickness. SO...if you have the First Layer height at 100% and the layer sticks but has slight gaps, then reducing the height to 90% will tend to fill the gaps.

Also for first layer settings, increasing the width will not fill in gaps. It will widen the extruded strip AND widen any gaps. IE set to 50% and the extrusions will be half as wide....and there will be trice as many strips! Set to 200%...and you get half as many...but wider..strips.

Finally....the raft separation distance only applies to the raft. No raft...no separation distance!

Hope this helps more than it might confuse!

[patniemeyer]

So, let me try to rephrase the question -

The first layer and first line drawn by the gcode for a raft is significantly different from the first layer and first line drawn when there is no raft... The raft line is very thick and appropriate for my leveling tweaks but the regular layer is not. I am just trying to understand why / what settings govern the raft line thickness that are not employed for the regular first layer. The raft line appears to be both thicker and at a higher starting Z height. I have a first layer setting of 150% thickness, which may account for this, but then why isn't it also applied to a regular first layer?

I guess I should just go look at the gcode and see if I can figure out what the difference is, but... what I'm really after is how to match the settings of the raft when I have no raft.

In response to your suggestions (thanks, appreciated) - and I am aware of the general procedure for leveling my printer: I'm using multi-point auto bed leveling and I have adjusted the start script to try different nozzle heights... However none of that seems really applicable if the gcode is doing something completely different depending on whether there is a raft or not...

Any additional info welcome. Thanks.

[opy01]

My father and I both own S3D and it's nice to see we aren't the only ones having this problem. On my old slicer I would get a nice thick line for the first layer with no issues coming loose. The forst layer was was set at .3mm. My layer height in S3D is .2mm and my first layer height in S3D is set to 150% so it should be .3mm. My first layer is always way too thin. We (both my father and myself on 2 different systems) see too thin of lines on layer 1 with gaps, like it's under extruding. When I use a raft, the lines are nice and thick. When I print on the raft I notice the same issues, too thin and not always sticking. Any layer above that is perfect.

I'll set my first layer to 50% on my next print and see what happens. Thanks for your insight on this part dkightley.

[opy01]

75% is perfect when not using a raft. When using a raft I still have the same issue, but it does not impact what I'm doing so far so it's not a huge deal.

[dkightley]

Thanks for your insight on this part dkightley.

Its not "insight"....its what you need to do to get good adhesion for the first layer.

I'll set my first layer to 50% on my next print and see what happens

I know what will happen. Do you? Please don't "twiddle and see"...you'll only get somewhere if you strike lucky! And the likelihood of that happening will be small! Follow the steps I've outlined above and you'll get things right!

And just to clarify....the "First Layer Settings" apply to the very first layer immediately above the bed surface...ie THE FIRST LAYER printed...be it raft or model! There are two things you can do that exclusively affect the first layer of the model when printing on a raft...the Separation Distance and the speed of the printing. My recommendation is to set the separation distance at 0.03mm for PLA...and adjust depending on how easy/difficult it is to remove the raft, and set the first layer above the raft at 50%.