Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Mini-Minion - the 3D printer for easy classroom production.

by CaptnBlynd, published

Mini-Minion - the 3D printer for easy classroom production. by CaptnBlynd Feb 9, 2013


This is a Wallace/PrintRbot style 3D printer I designed for quick, multiple builds for a classroom type setting. I have named it the mini-minion because every mad scientist needs a minion. I asked my local community education center if they would consider teaching 3D printing and associated technologies because I wanted to learn more. Somehow, now I'm teaching 3D printing and associated technologies at my local community education center. I have constructed 3 of these frames and completed 1 of these printers already so the files should be solid.

This printer is still in use today. It has been to classrooms, county fairs and seminars. All together, I use this one more than my Prusa. This has proven to be a rugged little printer.


This Thing requires a drill press, a 3D printer and a saw able to make precise cuts. I use a radial arm saw. Most lumber sellers have a saw which they will do a couple cuts for you. The length is not critical on either set of cut parts but they must be EXACTLY the same. The sides are 1 x 4 x 18” which means actual dimensions of 3/4” x 3 1/2” x 18” to those of you who don't know lumber standards. 17 3/4” is fine. 18 1/4” is fine. AS LONG AS BOTH ARE THE SAME. The bottom spreaders are 1 x 4 x 12”. Same applies but there are no holes to drill. I am using a product called AZEK. An extruded plastic meant for house trim. I find it very easy to use and nice looking. Use the bottom spreaders as your guides for setting the threaded rod before attaching it at the bottom. This give you verticle alignment. The drilling pattern is built in to the z axis motor brackets. Simply line the top edge of the bracket with the side board. Drill you boards together. I start by drilling a hole thru both side boards 1/2” from the top and ½ “ from the side that is the diameter of the threaded rods. I use 5/16” you may use 8mm. I then put a 5/16 bolt in the hole to keep them perfectly aligned and do the same on the other end. Put a bolt in it. Position your bracket close to center and drill your holes. As long as you keep the same faces together the alignment will be perfect. I draw a circle on the end of the boards while they are still together to give me a reference in case the faces get confused. Line up the circle, you're in alignment.
The end rods are exactly the same as on a Prusa. The same nut bolt pattern and bearings. In fact, all of the rail system printed parts are from the Prusa depository on Github. I am using standard split cable cover from the hardware store. That is what the “slinky holders” are for. This is optional and frankly not entirely satisfactory.. The file labeled “mini-minion.stl” is a label for the printer. Also optional. The “support-extruder” is optional but it is likely you will need it with any j type hot end.
The reason this is a work in progress is because I need to give more complete assembly instructions BUT if you read the Wallace assembly I have credited as derived from and the Prusa instructions at the RepRap wikipedia site then you should have no real issues assembling this printer just from these notes. More detailed instructions and pictures to follow. The download includes all files and some helpful things like a bed drilling guide.

To print:

Guidler is the extruder 1 set for the size of your filiment
608adaptors (optional) 1
bar-clamp 4
belt-clamp 2
bushing-linear (optional) 11
doubleslinkyholder(optional) 1
endstopHolder 3
hot-end-fan-holder 1
leadscrewCoupler 2
mini-minion(optional) 1
rod-clamp 2
slinkyHolder 2
support-extruder 1
x-carriage 1
x-end left 1
x-end right 1
Xlpulley (optional) 2
Ybrac-t 1
Ybushing 4
ZmotorMount 2
ZmotorMountBracket 2
ZtopClamps 2

Threaded rod, 5/16" or 8mm x 14 1/2" 4 (2 z axis, 2 cross bars)
Threaded rod, 5/16 or 8mm x 16 " 1 (Top bar)
Smooth rod, 5/16" or 8mm x 18" 4 (2 z axis, 2 Y axis table rails)
Smooth rod, 5/16" or 8mm x 16 3/4" 2 (x carriage)

// by making the table wider than a standard heat plate we are able to place the leveling screws for easy access. I do not use the included bed drilling guide. I will provide one as I complete this.
Lower print table 10 1/2" x 6" 1
Upper print table 10 1/2" x 9" 1

* nuts and bolts a lot
Belt 66"
608 bearings 6 (5 if you use an option on the x carriage)
lmu88 linear bearings 11 ( or print bushings)
NEMA17 stepper motors 5
Control board- printRboard-Gen6(or 7)- RAMPS 1 ( I own all 3. I prefer Ramps. Just me.)
end stops 3 ( I like the simple mechanical ones to start)
thermistor, 100k 2
hot end - j type designed 1 (other hot ends may mount. A standard j type WILL)
Heat plate 1
wires and connectors*
I'll start counting
12v 30 amp power supply 1
Hobbed bolt 1
springs 6 (4 for table, 2 for extruder)
T2 pulleys 2 (if you use T2 belt, or print XL pulleys for XL belt)
Sheet glass, 8 1/2" x 8 1/2" with corners cut off 1 or more (people say to use tempered)
Binding clips for glass 4 (see photos)
Sheet cork gasket 8 1/2" x 8 1/2" 1 ( I use 2 layers. For under hotbed.)

If you don't get filiment then you won't be able to print!

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With those X-axis smooth bars so close together, how stable is your x-axis? Any wobble at all? Even when going fast? Speaking of wobble, have you found any problem with the naked top of the Y axis?

The carriage bars are the same as on the wallace (based on printRbot?) since they use the wallace parts. The bed rails are exactly the same as on a prusa but look closer since I made the bed wider to make it easy to access the adjustment screws after the hotbed is installed. I think that I would be likely to add stabilizers to the top of the z axis if I used this myself much. It is a standard wallace/printRbot set-up but There simply must be more "wobble" than on a Prusa or makerbot style. Everything else seems solid. Haven't really put it to hard and fast use so can't really say for certain. I use it mainly as a teaching tool and demo machine. Mostly default settings from slic3r with adjustments for things like extruder speed with the 47/9 gear ratio.

thank you.. have you tried to print these parts in PLA?

I used ABS but I have seen plenty of these parts in PLA. I would not expect any problems using PLA. That said, I do wonder about the relative strength on ABS or PLA parts like the bar-clamps. PLA may be better?

Great! I've tried various designs over the years trying to make a simple wooden frame. My goal was to make something that needed no printed parts. Nothing there. Had some success but nothing with the simplicity of what you've done. Easy to make too.

There are some pre-cut 1x4's in oak, pine, and poplar at Lowe's. Their accuracy is excellent and look good too. I may do one using those. No table saw needed that way.

Take a look at the Mantis CNC design, it uses almost no parts at all. Very easy design, it uses spindles instead of belts, but that can be changed.