Prusa i3 problems, a story of madness

So in the last month or so, I have been experiencing feed problems on my RepRap Prusa I3. At first tops didn’t fill in correctly, then I started to notice wall issues and eventually large prints would not complete and every second print had to be restarted because the filament just chewed up.

It became incredibly frustrating to print anything. I assumed (incorrectly) that the problem lay with the new version of Mattercontrol (the software I used to use for slicing). Initially I thought it was the built in slicer, so I switched to their implementation of Cura. This helped initially in terms of finish, especially when I moved from 0.4mm layers to 0.1mm layers. But it wasn’t a week again until even that didn’t work nicely anymore. Switching to Cura itself did nothing to resolve the issue. Madness set in and I kept playing with settings, but with no improvement.

I did some research, and did find that their may be an issue with the hobbed bolt that the Gregs Wade extruder uses on this machine. Honestly though, I ignored that. I mean, come on, its been working all this time, why now all of a sudden. I kept playing with feed settings, new filament, but yes, eventually it sank in. I pulled the bolt form the extruder and found that inside the carved channel some of the ridges had bent because they were so thin.

My only conclusion is that over time they wear down. Strange considering you’re feeding plastic and its supposed to be a hardened M8 bolt. So I searched for a quick resolution. YouTube abounds with quick fixes using a tap mounted to a drill. Most looked kind fo dodgey, but hey it was worth a bash. I ran out to the workshop with gay abandon, fumbled a rig together in the vise and churned a new hobbing into the place where the current one was. The idea is to just deepen the “teeth” and so get a better feed.

YA RIGHT!!! Honestly this MIGHT work if you use the same tap that was used when it was first made, and its not going to work if you don’t have the right tap on hand. I didn’t. Not realising this, I brought the bolt back to its old home and again failed to print successfully. Bummer!! So I looked online for a replacement bolt. Another one would cost me 5X what a normal bolt would in the hardware store. Ok, so maybe its done properly and the issues would go away. But shipping is double the price of the bolt. Bugger that, I wont pay R150 for a R10 bolt unless I REALLY need to.

And so, the plan was hatched. Missery wasn’t going ot be my friend and my life wouldn’t be empty of 3D printing sweetness. After much thought on how to accomplish this, and many hours of real life and work, the plan was boldly implemented one Sunday morning.So looking at the bolt, I could see that many, many washers were used on either side to space the gear in such a way that the current hobbing was inline with the hotend hole.

A quick note before continuing, I wish I had taken pictures of all of this. The thought only occurred ot me after I had completed the rig to help me, and so those are the only images you will get here. Sorry. It is what it is.

Looking at those spacers, I thought I could just move those around and get free unhobbed space where I could start a fresh on the same bolt. I took a few hours to cut and massage some aluminium channel and plate. The channel was drilled to accommodate the bolt in a similar fashion as it works on the extruder, exposing the area I wanted to hob. This was then mounted to some wood, and I built a mount for my cheap Chinese knock off  rotary tool. This took some fettling but I eventually got something that I could hinge on the side of the wood. And so with bolt in the jig, and the rotary tool mounted with a cutting disc, I forged into new territory and cut line after line of tooth into the fresh unhobbed steel.

Channel piece for bolt
Mount for rotary tool
Tool mounted and ready for work
Good and bad parts

5 minutes later I was admiring the job and wondering if it was going to work. In it went and I set a few small prints off. The difference was remarkable. From poorly filled and walled prints, to nice even and closed prints with no feed problems in a Sunday morning. Needless to say I was very pleasantly surprised.

So what are my thoughts at this point? If the hobbed bolt is so prone to failure, then surely there must be a better feed design. Surely even doubling up on the bolt count should help the situation. I will be thinking long an hard on an alternative. Another thought was that I wish I had taken other possible causes into account early on. This would have brought me to the solution quicker. At least I now have a way of creating as many new bolts as I want without the cost. I am sure the jig will come in handy again.

A slight footnote here. While I was working on the bolt in the extruder, I noticed that the x-carriage had broken where one of the bearings resides, with that now sort of floating free. So while I have improved print-fu and the bearing is hacked into place, a new x-carriage is being printed.

Hope you enjoyed my tale of woe. Caio.

Adafruit MCP charger holder


I have been playing a little with some second-hand Li-ION cells from an old laptop in the form of 18650 cells. I have an Adafruit MCP 73833 charger that is LiPO/Li-ION capable in 3.7 and 4.2v with variable charge rate.

Nice little board but it is exposed to the world, and anyone who knows 18650s, knows they are frequently referred to as terrorist cells, they get nasty really quickly for no seeming reason. A short across the connector block, for instance, can very frequently result in much heat, fire and in some cases lots of sparks. Not so long ago, I managed to make the connection between  one of these cells and a set of LED’s using just my thumb, and it gave me a very detectable kick. Ferocious little animals indeed.

So a nice cover for the charger was in order. The box is friction fitted, has all the appropriate openings and even has pieces printed to make contact with the on-board LED’s. The print isn’t perfect so the contact isn’t great. The next version of the top should be better. STL’s can be found HERE.

Some more images below:

New LM8UU bearing holders for Prusa i3



So today I noticed during a print that the print bed on my Prusa i3 was wobbly, like a sea-lions bum wobbly. Not conducive to nice prints eh? I really wish they wouldn’t supply PLA parts for 3D printers. The stuff isn’t heat tolerant and just goes bad over time. Case in point is this:

Yeah, its broken. 2 out of 3 were, the third well on its way. It was also printed cheaply (ie thinly) and the texture was rough. So low cost eh?

Well they have now been replaced with

Got them from here. Thanks MartinMajewski, big help.

They went straight on, and its busy printing some more replacement parts for the printer. Think its time to rejuvenate the whole damn thing with some decently printed stuff.

Anyway, CAIO.

Paper Doll Stand


Today I’m talking about something my mother wanted. Shes found these paper dolls somewhere and is giving them to my daughter. Her father made bases for hers out of wood when she was young and wanted something similar for these. With the data given to me, my initial design looked like this:


However, it took too much material, and I took it back to this:

I should have taken video of the drawing process, but honestly its simple enough. 1st rectangle 100mmx50mm, second rectangle top left 100mmx20mm, third rectangle bottom left 100mmx20mm. Fourth and fifth rectangles from inside the area so that it creates a 1mm box in the middle. Extrude base down 5mm, and the centre section minus the slit up 10mm, chamfer edges and that’s it. Final product looks like:

So, anyway, the stl file is available here.




3D – Fish Tank Overflow


In this, the first post under the 3D section, Ill go through the thoughts and process of creating an overflow connector for my large fish tank. I have, until now, used a single pipe, bent over the top of the tank, connected to an irrigation valve that allows me to drain water and refill the tank without much hassle. The problem has been that over time, the pipe has collapsed and water flow has, of late, been terrible. In fact its so bad that last water change I nearly fell asleep waiting for the tank to drain 1/3 of the way. With this in mind, I thought I would create a stiffer unit to bridge the top of the tan, while still using the pipe to connect it to the rest of the system.

I use a clear 16 mm inside diameter, 21 mm outside diameter pipe for most of the plumping in the system, and have quite a bit spare. The design should rest easily on the top of the glass, and obviously be waterproof. The key to waterproofing is to do an acetone wash of the print once it has been completed. This will allow any small holes and openings to be closed.

The unit has a base that is 55mm x 21 mm x 21mm. There is a hollow interior that extends to two upright section which is big enough to fit into my clear pipes.


Final model in Autodesk 123D Design
STL model in Matter Control










The model is drawn up in Autodesk’s 123DDesign software, and exported as an STL file. This is then imported into MatterControl. I have a custom setup for my Prusa I3, which is loaded after the STL, and once some settings are tweaked, like support and fill rate, a gcode file is produced. The gcode file is the final file that goes to the printer. Gcode is simply a text file that has a bunch of printer specific setup items and then a head and feed point set that tells the printer where to send the head, how fast and how much to extrude during the run.

Here is an excerpt from the gcode for this object:

; Generated with MatterSlice 1.0
; filamentDiameter = 3
; extrusionWidth = 0.5
; firstLayerExtrusionWidth = 0.75
; layerThickness = 0.4
; firstLayerThickness = 0.35
; automatic settings before start_gcode
G21 ; set units to millimeters
M107 ; fan off
M190 S110 ; wait for bed temperature to be reached
M104 T0 S230 ; wait for extruder 1 temperature
T0 ; set the active extruder to 0
; settings from start_gcode
G28 ; home all axes
G29 ; Level bed
G1 Z5 F5000 ; lift nozzle

; automatic settings after start_gcode
M109 T0 S230 ; wait for extruder 1 temperature
T0 ; set the active extruder to 0
G90 ; use absolute coordinates
G92 E0 ; reset the expected extruder position
M82 ; use absolute distance for extrusion
; Layer count: 178
G0 F4800 X106.88 Y113.88 Z0.35
G0 X106.88 Y113.88
G1 F1800 E0.00000
G1 F720 X73.13 Y113.88 E1.25335
G1 X73.13 Y46.13 E3.76932
G1 X106.88 Y46.13 E5.02266
G1 X106.88 Y113.88 E7.53864

Below are videos for design and slicing.

The object is available on Thingiverse HERE

So that’s all for the time being. In the next post, Ill show your the acetone bath process to smooth the surface, and how it operates in the final installation.

Cheers for now.

3D – A New Section

Greetings all

I am creating a new section for my adventures in 3D printing. I have had a Prusa I3 for quite some time (years) now and find it really useful to create one offs or hard to come by replacement parts. Sometimes I just print for fun. Well anyway, this section will be for the designs, methodology’s and final outcomes.