Inconsistent printing results using same settings but different calibration models

2

I've got a second-hand Renkforce RF1000 which I've gone into more detail about in this question.

The extruder works however, I get some inconsistent results. First I printed a calibration cube and noticed huge gaps in the bottom layer. Because of this, I increased the extrusion multiplier to 1.05. I noticed there still were some gaps but also other issues, I then printed one with the extrusion multiplier reset to 1.0 and a negative Z-offset. The results are shown below. In every image, the left cube has multiplier 1.0 and the right cube has multiplier 1.05.

Calibration cube results

Then, for a better idea about the consistency, I printed a hollow pyramid. This shows some heavy stringing. However, when printing a retraction test I barely get any stringing.

Pyramid front

Pyramid bottom

Stringing test

Does anyone know what could cause these inconsistent results? I assume some hardware tweaks might be needed, not just slicer settings. Any help is appreciated.

  • I use Slic3r
  • I use 3 mm PLA printed at 190 °C on a 60 °C bed with some glue (doesn't stick without). The first layer is 200 °C with a 65 °C bed.
  • After three layers the fans are enabled.
  • I have a negative Z-offset, it probably isn't calibrated 100 % correctly
  • I don't know the nozzle size (a new one is being shipped) but use a size of 0.5 mm in the slicer
  • retraction length 2 mm & 60 mm/s
  • minimum travel after retraction 1 mm

Print settings: Settings

EDIT: After the recommendations I've changed the following:

  • All belts have been recalibrated
  • The e-steps have been recalibrated through this method. Couldn't do a wall measurement due to a lack of precise tools.
  • Changed first layer temperature to 210 °C and other layers to 205 °C
  • Added two top layers

I printed two new cubes. One without glue and with a Z-offset of 0.05 mm and one with glue and with a Z-offset of 0.15 mm. The results are quite comparable to the original ones although slightly better. Any recommendations?

I'm aware of some cooling issues on my prints. Once a new nozzle arrives I plan on printing the current cooling system again. It's not really blowing air right effectively now.

Cubes from below. Offset written on the bottom enter image description here enter image description here

Stefan

Posted 2020-04-24T17:31:55.343

Reputation: 219

Answers

1

First of all, I would try printing a little bit hotter, let's say arround 210 °C. Secondly, due to how the X and Y letters are being printed in the sides of the cube I would suggest to tigthen both the X and Y belts.

Regarding the gaps, I would first try a flow rate test. You could use a cube like this one.

Using:

  • extrusion multiplier = 1
  • layer height: 0.2 mm;
  • layer width= 0.4 mm ;
  • wall count= 2.

Then measure the walls with a caliper and you should have 0.8 mm walls. Do a couple of measurements, get the average and divide 0.8 by it and multiply by a 100 (100*0.8/average). That's your new flow rate.

I would also try to add 1 or 2 top layers to the print.

For the first layer, I would definitely get a glass bed and use hairspray. The bottom of the pyramid doesn't seem to be sticking well. Apart from this, I'm not really fan of using Z-offset. Just try leveling a couple of times manually with a paper to get it right.

Shupper

Posted 2020-04-24T17:31:55.343

Reputation: 23

1Also, for stringing try changing the retraction length to 5 mm and ~30 mm/s. See if in your slicer you can turn on the 'Combing' option – Shupper – 2020-04-24T21:49:27.803

" to how the X and Y letters are being printed in the sides of the cube". How do you recognize this is printed incorrectly and the belts need tuning? Also I've got a heated ceramic bed, shouldn't that suffice? I don't see why a glass bed should be needed – Stefan – 2020-04-25T07:24:28.233

1

Okay keep the ceramic bed, but try changing glue for hairspray, I really got better results... For the X and Y letters there's an artifact called ghosting/ripple. Here you can see what's about: https://www.youtube.com/watch?v=KaFp6Eqk0QI Anyways, I think your main issue is flow rate... Try calibrating both this and E-Steps and send new pictures

– Shupper – 2020-04-25T20:10:23.747

Thank you but due to the bed being in an enclosure and being connected by wires I prefer to stick with glue as long as it works. I've uploaded some new prints with the other recommendations in place. Could you give your opinion? – Stefan – 2020-04-27T11:33:05.790

1I think it's much better, first layers and side walls are looking nice. Anyways, you will have to do a flow rate calibration (See the blobs in the X and Y letters)... Get a cheap caliper, it will worth it I think you're getting close to solving the problem. You'll just have to find the right slicing settings which is not that easy. Try printing a little bit slower – Shupper – 2020-04-27T19:15:53.167

The problem got worse now that I've got a new nozzle and filament. It seems to be caused by the extruder. I've dedicated a new question to this problem. Thank you for the feedback, it did really help in improving the other problems and slicer settings.

– Stefan – 2020-05-05T10:04:42.457