I have the problem of the first layer not sticking to the bed. I have checked the height of the extruder when ‘Z’ is homed and it is correct but when I look at the g-code generated by the slicer after priming the nozzle the first layer begins by setting Z to 0.3. So that first layer is printed with (0.25mm + 0.3mm) 0.55mm between the extruder and the heated bed.
Is this corect?
If not how do I correct this, please?
Repetier V0.84, using unchanged k8200_pla_standard.ini
Hi AlbertHall,
You point out a question I asked myself if the first layer was actually 0.55mm (0.25mm + 0.3mm) but I do not think so. I rather think the first layer’s height calculation deducts a 0.25mm initial offset…
Like others said in this forum: the Z stepper is deactivated while printing each layer. You can take this to your advantage by trimming yourself the first layer’s height (then later adjust your Z-endstop screw).
If the wire “wobbles” at the bed’s surface then you are too far. Too close and it can barely extrude matter out. Try to have it gently “squeezed” onto the bed…
Finally my best advice to have it sticking properly to the bed and avoid any layer’s warping is to rub UHU stick glue onto the bed’s surface. You can easily wash it afterwhile, this works admirably.
/Matt.
Been looking around and I have found, in the slicer printer settings, ‘Z offset’. The mouseover text says:
“This value will be added (or subtracted) from all the Z coordinates in the output g-code. It is used to compensate for bad Z endstop position: for example, if your endstop zero actually leaves the nozzle 0.3mm far from the print bed, set this to -0.3 (or fix your endstop).”
This suggests that if, following the calibration instructions, the Z-home position is 0.25 mm above the print bed then this Z offset value should be set to -0.25mm. Doing this makes that first Z command ‘Z 0.05’, thus making the gap 0.3mm for that first layer.
I haven’t actually measured the gap on the machine yet as I am having a move round, but it does seem to me that leaving the Z offset value at 0mm means that for the first layer the extruder is too far from the print bed
Hi AlbertHall,
[quote=“AlbertHall”]Been looking around and I have found, in the slicer printer settings, ‘Z offset’. The mouseover text says:
“This value will be added (or subtracted) from all the Z coordinates in the output g-code. It is used to compensate for bad Z endstop position: for example, if your endstop zero actually leaves the nozzle 0.3mm far from the print bed, set this to -0.3 (or fix your endstop).”
This suggests that if, following the calibration instructions, the Z-home position is 0.25 mm above the print bed then this Z offset value should be set to -0.25mm. Doing this makes that first Z command ‘Z 0.05’, thus making the gap 0.3mm for that first layer.[/quote]
bad idea. If you use this offset parameter, you may end up with negative Z moves, e.g. when you want to print a first layer with less than 0.25 mm height. That would mean moving past the endstop, and that in turn should never occur.
Matt is right, adjusting the Z endstop screw is the way to go. The 0.25 mm recommendation is there to reduce the chance of the nozzle bumping into the bed surface if it’s not completely flat in the beginning. Once the bed is sufficiently flat (over time due to the heat, or by putting e.g. a mirror on it) and levelled, the distance between nozzle and bed surface can be reduced. This way, the nozzle will move up in the first Z move to the correct first layer height.
Cheers,
kuraasu
I think AlbertHall is right. The zero point in slic3 is related to the bottom of the bed, not the hight of the nozzle.
So I’ve configure the hight of the first layer to 0.050. It works perfect now.
I have taken the alternative route of setting the Z-endstop much nearer the bed. I use a mirror so the bed is flat and a 0.05 mm feeler gauge when setting the Z-endstop, just so the extruder doesn’t quite touch the mirror. Diluted PVA stops larger items warping - much recommended.
[quote=“AlbertHall”]Been looking around and I have found, in the slicer printer settings, ‘Z offset’. The mouseover text says:
“This value will be added (or subtracted) from all the Z coordinates in the output g-code. It is used to compensate for bad Z endstop position: for example, if your endstop zero actually leaves the nozzle 0.3mm far from the print bed, set this to -0.3 (or fix your endstop).”
This suggests that if, following the calibration instructions, the Z-home position is 0.25 mm above the print bed then this Z offset value should be set to -0.25mm. Doing this makes that first Z command ‘Z 0.05’, thus making the gap 0.3mm for that first layer.
I haven’t actually measured the gap on the machine yet as I am having a move round, but it does seem to me that leaving the Z offset value at 0mm means that for the first layer the extruder is too far from the print bed[/quote]
This is the correct answer. The Z offset should be set to whatever extruder/bed clearance your printer actually has. Negative Z moves will never cause the extruder to move down below the Z stop zero point. Try it; zero the Z axis and then enter G1 Z-0.1 into the manual G-code entry box.
The thing I asked myself is we set a first layer height of 0,30. After that layer it is 0,25 or less. This for better adhesion to the bed. But when your first is higher the lines will be less squished so will stick less no? I’ve been asking this myself for a while 
No, at least not like that.
The amount of filament to be extruded is calculated according to the set layer height, so from that point, there’s no difference in terms of “being squished” between 0.25 and 0.3 mm layers.
The advantage of large layer heights for the first layer is, that errors in the flatness of the bed (and calibration of the Z home position) have less effect. However, large layer heights means low resolution, so the setting is split to allow for both, a thick first layer with good adhesion, followed by thin layers for high resolution walls.
Additionally, since we know that the printer cannot move below the Z axis endstop the first layer height must be bigger than the extruder/bed gap. If you followed the build instructions to the letter the default gap is 0.25mm hence 0.3mm for the first layer for the reasons kuraasu mentions.
Hi steve_b,
that’s not quite the whole story. In the default configuration, the printer should not move past the endstop, granted. But it takes only minor adjustments in the firmware and endstop positioning to get a setup that allows movements to “negative” positions. This is quite usual with “large” CNC machines, where an error in the drive train would otherwise result in the overrun and destruction of the endstop (among other things).
If you follow the instructions to the letter, you don’t set the Z offset, so you have to decide at what point you want to deviate from it to get the right setting.
With that in mind, I don’t agree with your point of view and have calibrated my printer differently since I want to be able to use any first layer height without restrictions from the offset setting.
Not sure which part of my two previous posts in this thread you mean.
Cheers,
kuraasu
I think Velleman is wrong to have the nozzle adjusted to 0,25 mm above the bed. First of all as mentioned here, the nozzle is lifted the amount of millimeters set in the configration (i.e. usally 0,35 mm) when a print job starts. Secondly there’s no change the nozzle will damage the glass thanks to backlash in aluminium bed plate and extruder arm (in the default configuration).
I was confronted with a released object during printing (I don’t use any adhesives) and realised I had just leveled the bed again, in good faith according to the manual, leaving the nozzle 0,25 above the bed. I dove deeper into this matter and quickly learned that for good adhesion “it’s very important that the first layer is nicely pressed onto the glass plate” as can be read on ultimaker.com. For leveling they advise a piece of paper between the nozzle and the build plate. That’s not more than about 0,10 mm!
For adjusting the Z-axis I let the nozzle stop just above the glass and make sure the brim is not flattened by the nozzle.
Now the same object stays well fixed. In fact, the bed must cool down, before getting it off.