Z Offset Pronterface & Cura

I had this running perfectly yesterday, but today not so good. Something has always puzzled me, I will describe where I am, and perhaps someone should tell me where I need to be?

Ok, I am using Pronterface and Cura. I tried Slicr but it didn't give good results. Yesterday Cura gave me what I was looking for. I have disabled the 'use integrated Slicr' in Pronterface. All slicing is done via Cura. My STL files are created in Openscad, exported as STL's, then opened in Cura and the Gcode saved. The Gcode file is then loaded in Pronterface.

Ok, the confusing bit.

On the screen where the plater is displayed in Pronterface, there is a 'bed'.
By changing the Z Offset in Pronterface to '0' I can get the model to sit flat on the bed.
'But' should this setting be the same as the Z Offset that I send to the Smartrap during set up, or, should it be left as 0?

On the Pronterface interface, I home the printer.
Lower the hotend until it touches a sheet of A4 paper.
M114 to get the Z position.
M555 to send the Z position to the printer.

I cannot get that 'perfect height' for the hotend. It is either too high, or too low, never absolutely spot on.
Should I be setting up both Pronterface and the M555 using + or negative values?

I am obviously not doing something right, but having searched all over the web, I cannot find out what the Z Offset in Pronterface actually does (apart from visually move the platen/model relative distances up and down).

The reason this question arose was because I was printing a very small item, and was only getting the top half printed. Looking at the platen display, it was sunk into it, but adjusting the Z Offset in Pronterface started causing problems.

Can anyone assist, this is driving me crazy??

Many thanks

Rob

Well your close,
First lets get this out of the way...pick either the m555 or the z-offset in the host software...not both. I always just use the m555 and thats it.

My method to set Probe height is as follows
Run G28 X0 Y0
Then I G1 X100 Y100 (Replace the xy cooridinates for your bed center)
G30 ( this will probe the bed 1 time)
after the bed is probed I start lowering the axis by either 1mm or .1 mm depending on how close your probe is until it just grabs a peice of A4.
then its M555 z(whatever your move down distance was)
M500

That is my starting point then I will adjust by .05 until I get a first layer I am happy with.

If your not dead set on pronterface you might check out the newer version of Repetier host, it has cura slicing built in. I havent used pronterface in a long time so I cant really compare.

PS the M555 will expect a positve numbe in entry, it will move down that far after the probe, negative will raise it.


Good Luck!!

Edited 1 time(s). Last edit at 03/23/2015 03:10PM by djinn5150.

Quote
djinn5150
Well your close,
First lets get this out of the way...pick either the m555 or the z-offset in the host software...not both. I always just use the m555 and thats it.

Ok, I have set Pronterface Z Offset to 0.

Quote

My method to set Probe height is as follows
Run G28 X0 Y0
Then I G1 X100 Y100 (Replace the xy cooridinates for your bed center)
G30 ( this will probe the bed 1 time)

Ok, all done.

Quote

after the bed is probed I start lowering the axis by either 1mm or .1 mm depending on how close your probe is until it just grabs a peice of A4.

Ok, all done.

Quote

then its M555 z(whatever your move down distance was)
M500

This is where it goes strange.
Using M114 at this point gives me '-20' , yet the hotend is only a paper width off the surface.
By raising the hotend manually from Pronterface, the Z '-' value is going down, so if I raise it 10 the M114 will return -10?


When you say M555z ("whatever your move down distance was"), are you referring to the figure provided by M114? Or should I be doing an M114 at the G30 point?
Sorry for my confused state, I am so close, but just missing that magical piece of info. The Z baseline isn't 0 for some reason, I am guessing it is something to do with the levelling sensor?,

Quote

That is my starting point then I will adjust by .05 until I get a first layer I am happy with.

If your not dead set on pronterface you might check out the newer version of Repetier host, it has cura slicing built in. I havent used pronterface in a long time so I cant really compare.

PS the M555 will expect a positve numbe in entry, it will move down that far after the probe, negative will raise it.

I gave Repetier a go in the early days when I built the printer, but switched due to the easier interface for setting things up.
I intend printing from an SD card, but I until I know that I can print from a pc, I daren't go near that for now.

Many thanks for your help.

Rob

Yeah I don't even bother with the m114, unless you set g92 z0 before you start going down, m114 will pump out the distance its traveled since the printer was initialized. I just remember how many times I have to press my down value...i.e. my z offset is 2.7mm I press down 1mm twice and down .1 7 times to get the paper to grab, or down .1 27 times to give me 2.7mm. Then its m555 z2.7 m500 then a single layer test print. If i get good adhesion I run a calibration cube and check to make sure its not pushing out on the first few lawers if so I just judge how much i need to shorten my z setting by, I usually go by about .05 mm so my next setting would be m555 z2.65 m500

Make sense?

FWIW, I had a lot of trouble with this when I first started too, took me a long time to get the feel for a good first layer, it will come in time, try not to get too frustrated.

Quote
djinn5150
m114 will pump out the distance its traveled since the printer was initialized.

Well I may be barking up the wrong tree, but I set the 'paper height', unplugged the printer, plugged it back in again, and then got the M114. It was 0.00?
I sent M555 = 0.00 and the nozzle is on the bed.

I am assuming that when I power down tonight and switch on again tomorrow that everything will remain constant and I can fine tune it...?

So actually I need to correct myself, m114 is the location according to travel since last home / initialization. So if say your at 15mm reset the printer and call m114 it will tell you 0, Home it and it should say 0 again...or at least the probe difference, Hopefully someone will chime in that might understand it a little better then I do. But I believe that to be the case. At anyrate once your probe is set you should be good to go for a few prints, I tend to recheck every print session, or at least once a day. Just kind of depends If I notice my adhesion not as strong or bulging out to a side on the first few layers I know my offset is off and I need to adjust it. M555 0 would set your z probe height back to 0 so when you go to print it will be however hiigh your nozzle is from the bed once it probes It shouldn't vary much

After a bit of faffing about, I got it figured out at 3.40, though perfection would be 0.01-3 higher. Just had it printing at 220% print speed and back to the excellent print quality.

I can't thank you enough for your assistance, I would have been pulling my hair out over this one.

Many thanks

Rob

Glad I could finally pay forward all the help I've gotten in this group.

Happy printing