Prusa i3 assembly 1: A sea of parts.

After much researching, deciphering and documenting, I understood enough of the 3D printer design so that I could start assembling it with confidence. If you read other posts, you may remember that the assembly manual was already a topic of discussion:

There’s a step-by-step assembly manual included in the CD, customized for this specific Prusa i3 derivative design, so it doesn’t seem like there’s anything to worry about in this department.

The notion that the document was going to make the process easier was flawed, though, as I ran into several issues while studying it in more detail:

manual flaws

  • Each 3D printed part and its fasteners should have been paired together in individual bags (See image to the left). Instead most screw, nut and washer were tossed together in a single bag.
  • M3 nylon washers should have been provided to cushion the structure from motor vibration.
  • The laconic sentences in broken English puzzled me regularly, specially when the visual information was insufficient to supplement it. Examples (context doesn’t help):
    • “Installed after the negative with a positive picture” (p. 2)
    • “Remove the Y-axis motor good step Part 1 rear rack mounted assembly diagram Press” (p. 6)
  • parts differenceSeveral times I noticed subtle undocumented changes between the design of the part in my hands and the part depicted by the manual.
    For instance, look at the image to the right and notice there’s a ball-bearing fitted into one of the holes of the part seen in the manual.
    First I thought that the part I had received was somehow defective, as none of the included ball-bearings would fit in it’s corresponding the slot. Then I realized there less ball-bearings than sum of the parts that needed them in the manual. From that I inferred that the ball-bearing was eliminated from the design of the part in question. Won’t this change cause the rod to vibrate, producing noise and/or damage to the plastic part?
  • There’s no mention of a heatbed, let alone how to install one, which is weird since one was included in this model.
  • An aluminium base plate covered in a thick film of plastic was also included in the kit and I think it may be a cold printing base. Should I install it along with the heated bed? Should the plastic film be removed or is it there to improve plastic adhesion? Will the plastic film withstand the heat if I try to install it together with the heated bed? When this much guesswork is involved, so many unnecessary questions and research start to get in the way of actually assembling the product. It shouldn’t have to be like this.
  • The screws and nuts that hold in place the printed circuit board (PCB) were not specified in the manual. I’ll just grab one of the leftover screws or buy some, if that’s the case. Also, some sort of spacer (these too were not specified) are required, otherwise the soldered terminals of electronic components protruding from underneath the board will be compressed against the acrylic structure.

I get that some of these changes were deliberately made to cut down costs, but accurate assembly instructions are the least I expected!

NOTE: Although the design isn’t exactly the same, the Prusa i3 Acrylic (manual) design enough similarities with my printer that it can be used as complementary reference, filling a lot of the ugly gaps left by Heacent’s manual.

After realizing the product I purchased wasn’t as well polished as I initially thought it was, I decided to account for and inspect every one of the provided part by comparing them to the ones described in the manual. Even so, because of the already mentioned unreliability of the manual, I still expect to find more missing parts during the actual assembly.

Fasteners were, of course, the toughest parts to check as there many individual types and, in total, a large number of them. The first 3 images bellow show the contents of the four bags of fasteners contained in the kit:

Here’s the final comparative table:

ISO         shipped   needed   diff
--------------------------------------- screws
M2.5 x 10   2         2        0 
M2.5 x 16   2         4        -2 
M2.5 x 25   2         2        0 
M3 x 8      6         0        6 
M3 x 10     10        7        3 
M3 x 16     20        20       0 
M3 x 20     6         2        4 
M3 x 25     15        12       3 
M3 x 40     2         2        0 
M5 x 15     2         2        0 
M5 x 18     0         1        -1
M5 x 20     1         0        1
---------------------------------------- nuts
M2.5        7         8        -1 
M3          51        26       25 
M3 nylock   4         4        0 
M5          8         7        1 
M8          42        38       4 
---------------------------------------- washers
M3 nylon    0         13       -13 
M5          4         4        0 
M8 spl.lock 15        19       -4 
M8          42        38       4

Get the entire comparison here: fasteners inventory.pdf

As you can see, there are quite a few missing fasteners. Apart from the nylon washers, and the M5 x 18 screw – that can be replaced by the unused M5 x 20 screw without issues – there are three other types of items missing!

The tough part now is to find a retail seller in my area that has a good variety of such products and accepts small purchases.

The 3D printed parts were also thoroughly inspected and some issues also became evident.  First I found some plastic drooping on parts passed through by horizontal holes (top-left picture bellow). Maybe the last layer of the hole was too wide and some supporting structures were required; maybe the extruder was too hot and the plastic was too fluid. Regardless of what caused the problem, the solution was quite simple: I used drills – with diameters equivalent to the original gap/screw sizes – clamped by locking pliers to improve the grip (bottom-left picture bellow) and it worked very well!

The last image of the above gallery show a problem that couldn’t be solved by any quick tricks. The first printed layers in this part became partially detached from the heated bed but the printing continued, causing it to look bent on one side with squished layering in the middle. Although the upper face is surprisingly straight, the piece is unusable.

Luckily someone had already went through the effort of obtaining all custom STL files from the manufacturer and made it available on Thingiverse:

printer thingiverse

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