Answered Need some help with calibration

Hello all, First of all I want to thank all of you for all of your help. This is my first post but I've been lurking around quite a bit in the past few weeks since I bought my Robo3d. The wealth of knowledge and help you guys give is great, Thanks! So I'm getting pretty decent prints at this point, after a lot of getting used to the settings and seasoning the nozzle and an oiler for the PLA, huge improvement. The first issue I'm having is that the prints are consistently slightly large, I'm talking about a 1" cube printing at 1.01 wide and .980 tall, might be asking too much but I think if it's consistently off, it can be consistently right on? Secondly when I'm printing a vase type vessel that the walls bell outwards, I get a huge mess, also when trying to print a calibration human head. Any ideas would be great!

 

Ok, I will check both and report back. I did change the extrusion multiplier from 1.0 to .95 and then to .90, printing seemed a bit smoother but didn't seem to change the prints dimensionally.

 

Keep in mind that the filament will bulge slightly at the perimeters depending on your nozzle width, layer height, extrusion rate, and filament expansion as it leaves the hotend. I went through the "part fitting" calibration exercise only to find it was a waste of time because after the calibration my solid infill left gaps everywhere. My prints are consistently about 0.05mm oversize on all perimeters weather I print a 10mm cube or 100mm cube. A single 0.4mm wall ends up being about 0.5mm due to the 0.05mm bulge on both sides of the wall.
So, I cater for this in my model designs so I don't have to sand/file as much.
But, Slic3r has introduced a setting to compensate for this by allowing you to reduce all perimeters on the x and y axis by a specified amount, say 0.05mm. The setting is available in the Slic3r experimental build. I haven't tried the new setting yet though.

 

Having said that you could still be slightly over extruding. Reduce your extrusion rate until solid surface infill has gaps then turn it back up until it's solid again. I use this calibration object.
http://www.thingiverse.com/thing:39050

 

My wall thickness did go from 0.5mm to 0.45 when changing from 1.0 extrusion multiplier to 0.9 which makes sense...I'll give 0.8 a try and recheck dimensions. Thanks for the help!

 

I've read that if you have to go below 0.9 you should adjust your e steps in the firmware until your extrusion multiplier is between 0.9 and 1.1, but it's ok to go below 0.9 for testing.

 

I have just found out that the latest version of Simplify3d (2.2.2) has a new setting called Horizontal Size Compensation on the Other tab which works like the new Slic3r setting I mentioned above to reduce the external dimensions of a part to cater for filament bulging on the perimeters. This link has some images to demonstrate it's awesomeness.
http://www.forum.simplify3d.com/viewtopic.php?f=8&t=2042&sid=fa32e8c29a4e2ff670028d0a5263c83c

 

Re: Vase

What could be happening there is that the overhang is simply too great for the printer to accomplish. I notice radii that come up off the bed never come out right due to the initial overhang angle being so high.

 

That sounds exactly what I need! I was able to get my walls on this cube to exactly .4mm when printing with the extrusion multiplier at .80, I tried .75 and it looked fine but I was able to split the walls apart when pulling on them, .80 is perfect! So, how do I change the stepper settings in the software so that the multiplier is back in the range that it should be? The horizontal and vertical dimensions are still off a little but closer than they were, I will check out the software....maybe simplify is in my future!

 

BTW, does the Z offset affect only the starting layer height or does it affect every layer of the print?

 

Those are some super nice prints. It looks like you're a little low on the first layer though which would affect your overall height

Don't forget that the tolerance of a print is a function of the nozzle diameter.

 

Thanks Mike!
So the z offset affects the overall height only because you are raising the bottom layer, does not raise every layer incrementally that amount, correct?

 

Correct, when you set a Z offset it only affects the first layer. After that it will behave as normal.

 

Ok great, Thanks!

 

Those prints look awesome. What slicer are you using?
To change the steps in the firmware you need to get the firmware for your model Robo, install the Arduino software, edit the steps in the configuration.h, then upload the firmware to the printer. You can also set your printer's actual dimensions, max temps, etc while your at it too.

 

They look a lot better now after the help from you guys and this forum, I would be lost without the knowledge base here! I'm using Repetier Host with slic3r.

I did load the software when I got the printer, I'll go through it and see I can figure out the firmware changes, thanks for the help!

 

I 100% agree and still use it regularly. I've just gone bank to S3D to see how it compares to when I used it last and I must say it's finish quality has improved a lot, though now I'm using metric rods. I think it must have issues with rounding or something when using imperial rods. They've also added more configurability which is allowing fit better prints.
I still love Slic3r but I'll be spending a bit more time with S3D now I think.