3 months in and still bad prints

[chriscook8]

I feel like I'm running around in circles trying to get the calibration right on the Max. I'm using Repetier-Host 0.84 with slicer 0.9.8 and PolygonHell's repetier firmware.

The single wall test (no retraction) seems to start out well then goes off. More substantial prints like the minimug end up with polyps (9mm retraction @ 100mm/s, 0 lift ).

Some directed pointers would be very welcome.. I'm getting frustrated.

Thanks
Chris

[Polygonhell]

Lets start with the single wall test print with no retraction, until you can print that you're wasting your time printing anything else.
What layer height are you using and what extrusion width?
It looks to me that that layer height is too large for the extrusion rate.

[chriscook8]

So this one was .2mm at 45mm/s with .55mm width.

The first 8 or so layers are clean and tight, though they seem to get smaller / constrict. as they rise.

[Polygonhell]

First slow way down start at 10mm/s and even with that you will probably need active cooling.
If you have no way to cool when printing, print 3 or 4 of them at a time.

Speed is just about the last thing you want to ramp up.

[mhackney]

Is this PLA or ABS? What is your temp preferably checked with a thermocouple? I found that the extruder acceleration and current were too high and backed down to 1250 for acel and 175 for current. With ABS at least, high acceleration and lots of big retracts seem to add up and actually temporarily plug the nozzle for a short period of time. The little calibration single wall cube did the something for me until I figured this out and corrected.

Also, as Polygonhell recommends, slow down to 10mm/s until you get this sorted. It might help to post hut configuration.h so we can take a look see.

[chriscook8]

World of difference... of course it's super slow.. My trusty, but cheap, calipers measure the wall at 0.6mm thick and 22mm square, 9.7 tall

Very fine, tight lines. There is a little back and forth movement at the layer change that's visible. There is bowing in from the first layers to the high ones. Is that just the contraction of the plastic when it's not attached to the platform?

I'm printing in ABS@244C (PID calibrated, but I don't have an outside method to verify the temp), the Heated bed is set to 65C but it's the phebe ! with the termistor on the far outside.. my IR thermometer says the center of the board is usually around 95-100c.

Extruder acceleration is at the firmware default, 4500. And i've done nothing with regards to current (it's a rambo 1.0e board)

Thanks, for your help.. what's next?

[Polygonhell]

I'd say your probably still printing too hot, I'd start dropping the temperature in 5 degree steps until you start to see either delamination or the extruder starts skipping.

[mhackney]

I agree, I think you are printing too hot and seeing shrinkage as the ABS cools. Don't worry about the speed right now, once you have things dialed in, ramping up the speed is easy.

[chriscook8]

So I tested the one wall prints at a variety of temperatures. 244, 240, 237, 234, 230, and 227. Things didn't really break down until I got to 223. The other prints were substantially the same, with slight variations in the puckering at the corners. If I did a few more runs of each maybe I could discern a pattern, but for now I think 240 looked the best with 227 coming in 2nd.

What would the affect of a fan on the print surface be for ABS? Would the faster cooling prevent or exaggerate the puckering (where it constricts in at the corners)?

I may have a case fan somewhere I can test it out with.

What is the next step 'calibration print'?

[Polygonhell]

the cooling fan stops the plastic being flexible faster, this is particularly important for tall thin objects, or objects with thin parts, or objects with severe overhangs where if you can't cool it fast enough you end up with the printhead pushing the plastic around leading to a mess.
The problem with a fan for cooling on ABS, is that it can lead to cracking and delamination if you aren't printing hot enough to fuse the new material to the old material.
With PLA I will print with as much cooling as I can get on a part all of the time, because it's always never a detriment, with ABS I'll look at the part and decide, for example I fing the belly of the treefrog to be almost impossible to print without cooling, but I wouldn't bother for most structural printer parts.
Sometimes it's better to print multiple copies of an object increasing the time per layer without increasing the time on a layer that it is to actively cool.

[Polygonhell]

Forgot to ask, how hot is your bed?
The 240 one looks OK to me, and I'd start with that.
You should follow the rest of my calibration post at this point, measure, adjust flow rate and print a 100% filled cube to verify.

[chriscook8]

The bed is set at 65C but it measures closer to 100C on my infrared thermometer.

[Av8r RC]

Are you sure it was reading in C? If so you may have the the wrong thermistor selected in the firmware. And if that's the case the hotend is probably wrong also.

What firmware are you running?

[Jimustanguitar]

You should follow the rest of my calibration post at this point

You mean the "Extruder Calibration" thread, right? http://forum.seemecnc.com/viewtopic.php?f=54&t=1163