Cheap Prusia i3 Optimization

I built a Mendel 2 about 3 year ago, I got it printing well enough to print some replacement parts for it - but after about 6 months of problems i gave up and its been in the shed since... Recently, I came across Prusa i3 kits on Ebay for ~£150 and thought "lets give it another go!". So I bought one of these [www.ebay.co.uk] and got it up and running in 2 days. I plan on leaving on review on ebay soon, because this kit was fantastic. The x and y axis were already built upon delivery, I was expecting maybe a week of evenings to construct this but it only took 2.

So I now have an i3 up and running and was pleasently surprised by the good quality, considering I havn't done any optimization or calibration (just bed levelling). I have printed a few test models using the standard speed settings in Slic3r, smaller models are fine - but when printing larger objects the speed goes up and I am having some issues with the extruder. It looks like its not extruding enough at higher speeds, but at lower speeds its absolutley fine.

I'd like a bit of help with the following queries :

The kit came with this electronics board - [www.geeetech.com] - the firmware version reports the following when connecting : [www.dropbox.com] - I'd like to update the Marlin version but am a bit nervous because I don't have the known config value that its currently running with. (All the instructions for this kit are in Chinese) Is there any way of extracting the config values from the compiled firmware using g-codes commands or similar? As this is a kit I don't really know the physical properties of the velts and pulleys etc....

This kit was advertised at being capable of 120 mm/s print speeds. I have been having issues at about 70 - 80 mm/s, the line of extrusion looks 'jiterry' a blob then small line, then a blob then small line. The blobs are small and it results in a net like finish on walls. After doing a bit of research I think the issue is either being caused by - too low extruder temp or not enough torque on the extruder gear. Today I am going to try a faster print at a higher temperature and see if its any better. Any other suggestions or things I can check?

m503 will show you most but not all settings

In particular its doesn’t list thermistor settings, endstop settings and any movement inversions or board type (the latter being MOTHERBOARD 7)
Endstop setting and movement setting are not really an issue... the thermistor settings is a big issue.

Edited 1 time(s). Last edit at 05/29/2016 07:07AM by Dust.

I have a scratch built i3 and print at 50 mm/s. It would be nice to be proved wrong but I don't think an i3 could print anywhere near 120 mm/s

Steve

A lot of the so-called specs of these kits are based on the mathematics of the motor steps/rev and the microstepping of the controllers. That leads to ridiculous specs like 5 um resolution, speeds like 120 mm/sec, etc. One of the hard facts of life of FDM printing is that you trade speed for quality. Notice there is never any mention of print quality in any of the specs. So while the motors may be able to move the extruder carriage at 120 mm/sec, they don't tell you that the resulting print will be garbage. What does 5 um resolution mean when the printer's frame wobbles around while printing?

It's common to see claims of ABS compatibility in open frame printers even though the bed heaters can't get the bed up to ABS print temperature (or take so long to do so that you'd never bother trying to print ABS) and the prints will delaminate because there is no warm print enclosure.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

The linear head speed doesn't tell you anything about the volumetric rate required of the extruder until you factor in the layer height and extrusion width. You can max out the extruder at less than 120mm/s using thick fat extrusion, or you can be well under the extruder's limit if you are using thin narrow extrusion. I was surprised to realise I was close to max during one print until I realised I was using very wide extrusion for infill with relatively thick layers - the volumetric rate was much higher than I normally use.

Thanks for the reply's. I now understand that the print speed is limited by the volumetric rate.

In general, i'm quite happy with this printer - I didn't expect perfection, but within a week I had some decent prints. I put pictures on dropbox as its easiest for me, sorry they dont allow inline use on other domains. (Click on the url to see the picture, its not a nasty virus!!!)




While printing the frog, I noticed that the left side (when looking at it) was raising up a bit and the nozzle was dragging. I think this is because the extruder fan is on the right side and keeping the right side of the print cooled a bit and the left side needs extra cooling?

So i started designing a fan mount in OpenSCAD and started to print a test print this morning - to see if its accurate enough with the nut holes etc... The first layer seems to be printing well, until it gets to the small holes - it seems to fast and so the PLA doesnt; stick to the bed at all. Could this be first layer height, I thought it was ok - because the skirt and rest of the first layer seem ok? I've attached a link to a video demonstrating this. I am using Slic3r and have turned the small perimeters speed down to 5mm/s. Subsequent layers seem ok - but the first prints too quick. Should i switch to using Cura, instead of Slic3r?

Video