The ‘gear’ I’m referring to in the title is my 3D-printer, which I have just replaced.

 

As I mentioned in my previous post, my Geeetech E180 is no longer supported, with essential items like replacement print-heads not available. I have therefore bought a Prusa Mini+ as its replacement. The E180 was cheap and took me some time to optimise, following a rather shaky start, but eventually performed very well, until key components started wearing out.

 

My choice of the Prusa machine was a deliberate move to choose a European product and one that has gained a good reputation amongst the 3D printing community. Unlike the E180, which was smartly styled, the design of the Prusa is strictly functional, with most of its working parts fully exposed. I have stayed with a ‘fused deposition’ type of printer (FDP), because it does not not use liquid resins and other materials that require careful handling and disposal. I recognise that FDP cannot provide as good a surface finish as some other methods but I have found it adequate for my interests in historical modelling.

 

The Prusa Mini+ is supplied either as a kit or partly assembled; I chose the latter course, since my eyesight and general dexterity are no longer what they once were. The packaging and overall presentation of the machine as delivered was excellent, with all the parts firmly secured within the cardboard packaging and all the small parts in individual, labelled, re-sealable plastic bags. There is also a substantial printed manual, covering both the assembly instructions and operation of the printer.

 

Prusa Mini+ Components after Unpacking from Box

 

Assembly

 

Unfortunately, the photographic illustrations in the manual are small and, because most of the printer parts are coloured black, it is difficult to make out many of the details. My troubles started with fixing the soft feet (foam pads). These do not fix onto the obvious flat areas under the plastic end-pieces of the base section but under the aluminium channel sections. The illustrations are far from clear and caused me some hesitation. Fortunately, I found a helpful video on YouTube at https://www.youtube.com/watch?v=xYGaWYKzvsM  This video presentation is rather too rapid to follow on its own, but is very useful to check on any points of doubt.

 

N.B. There are also some, to my mind, dreadful American ‘live’ videos about assembling this printer, where the facts are submerged in peripheral chat.

 

The same problem of poor illustrations applied to many other parts of the assembly task. I still don’t understand the statement from the instructions: "try fitting the “clamp” (XZ assembly) directly on the M3nE nut which you have moved to the centre of the extrusion.”. It took some time for me to work out that the long screw passed through a ‘tunnel’ within the electronics module to reach the nut in the base unit. A diagram like that I made below might have helped a lot!

 

Screws connecting main units

 

It’s actually quite simple, once one has interpreted the instructions, with three screws connecting to nuts that slide along aluminium channels in the base unit. These screws hold the two major components together.

 

There are then several cables to be connected between the two major components. The ‘electronics module’ is very compact, with a high density of sockets and wiring. If you are familiar with the small connectors that are widely used within computers, then it is not too difficult but, once again, the instructions are minimal and more guidance would be very helpful to many people.

 

The first cable to be connected is the ribbon cable that will eventually attach to the display unit. This has to be orientated correctly in its socket. The most obvious guide to alignment is that one side of the ribbon is coloured red but this fact is not mentioned in the instructions, which are therefore hard to follow.

 

The circuit board is referred to as the ‘Buddy Board’. There is no diagram that shows the various sockets on this ‘Buddy Board’ in the electronics box, nor is there any very clear indication as to which connector goes where. Again, I suggest that a diagram like that I made below would help a lot:

 

Electrical connectors on circuit board

 

Finally the lid has to be re-fitted to the electronics box, which is quite tricky, since all the cables have to be squeezed inside. There is a dire warning that ‘The nut must not fall out’. I never saw this nut, so sincerely hope it is safe!

 

That completes the main assembly. There is also a spool holder. The instructions start by stating “Take the two BASE parts”. Actually there are four parts in two pairs, which confused me at first. Note that there is just one hexagonal recess in each part to take a nut. In my experience, it is essential to use one of the screws to draw the nut down to the bottom of its recess, otherwise the screw will not reach the nut when attempting to join the paired parts together.

 

As I stated at the outset, the design of this printer is strictly functional. All the moving and heated parts are completely exposed and there is no back to the display unit, nor is its ribbon cable enclosed.

 

Unlike my previous E180 printer, this machine has a heated print bed and the ‘hot end’ is also completely exposed, so any children need close supervision, if allowed nearby when it is operating.

 

Prusa Mini+ after assembly

 

 

First Start

 

Now it was time to switch ‘on’. The LCD screen lit up and the ‘Calibration Wizard’ started to run; the first stage being a series of ‘self tests’, which were all cleared successfully.

 

Switched ‘on’ and Ready to Print

 

After this, it’s time to load some filament. I pushed it into the PTFE tube and the system recognised it as ‘loaded’. It then carries out ‘Mesh Bed Levelling’, and finally ‘First Layer Calibration’. For this process, the printer is supposed to lay down a zig-zag course of filament across the printer bed, so that the user can make any necessary fine adjustments to the vertical (Z)-axis to optimise first layer adhesion.

 

The calibration proved to be so far out that I could see the filament extruding from the nozzle while it was at least 2mm above the print bed. There is a knob on the controller to adjust the height but the range was insufficient to close the gap. The manual claims that “the ‘SuperPINDA’ sensor height is set from the factory, no need to adjust it now”. Disappointingly, this did not seem to be the case, so I turned to the ‘Help’ pages on the Prusa website, which included instructions for setting the sensor height. I followed the procedure given on the website and did manage to achieve reasonable adhesion within the range of the control knob – just.

 

I suppose one should always expect some teething problems but because this was a relatively expensive machine, compared to the many ‘clones’ that are available, I was not feeling very happy about these irritations.

 

Printing

 

The real proof, however, lies with the performance, so I had prepared a 3D model of a GWR Tilt Wagon in ‘Fusion 360’, to see how it would go. I used the Prusa slicer software, in my 'Windows 10' computer, to prepare the ‘gcode’ file for printing and copied it onto the USB memory stick supplied with the printer.

 

My 3D model of GWR Broad Gauge Tilt Wagon in 'Fusion 360'

 

As soon as the memory stick was plugged in to the socket on the side of the printer, the LCD screen on the printer helpfully showed a colour image of the job to be printed, which I think is a good feature. The printer then set itself up automatically, first checking the printer bed height at several points across the entire surface.

 

Completed ‘First Test’ on Printer bed

 

For this ‘first test’, I printed the central section of the wagon, comprising the floor and side walls. First impressions were good: the rivet detail is clear and the sides have printed very smoothly. There is a little ‘over-print’ in a few places and some fine gossamer-like excess that I had not seen with the old printer.

 

What was most impressive was the quietness and smoothness of the printer, as it carried out its task. When I left it for a while, I thought it must have stopped, because I couldn’t hear it all from outside my work-room, but the job was progressing well and somewhat quicker, I thought, than when using the E180 printer. This job took just 43 minutes to complete, as recorded on the display screen.

 

My impression was of a well-engineered machine that performed its task with a minimum of fuss.

 

This was a considerably better ‘first test’ than when I first started with the E180, just over four years ago, and I have made no attempt to optimise any of the settings as yet.

 

It will probably take me a while to familiarise myself with this machine and its associated software but, apart from the teething problems referred to above, it’s smoothness of operation indicates a good quality product.

 

Mike