Printrbot Jr 1307 Assembly

Assembly directions for the wood, hardware, motors, end-stops, extruder, and hot-end parts of the Printrbot Jr.

  • Author: Tim Stark
  • Time required: 1-2 hours
  • Difficulty: Moderate
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Step 1 Jr v1 (Model 1307)  ¶ 

  • The basic assembly of the wooden kit pieces and other hardware.

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Step 2  ¶ 

  • these are the laser cut pieces you will receive from us

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Step 3  ¶ 

  • As of May 29th, these are the 7 wooden plates that we'll be shipping

  • New revision allows for large Kysan motors on all axes including the extruder motor

  • The box assembly in this new revision has taller pieces to be able to house the larger/taller Kysan motors

  • The new design goes together the same as the old one so no need to worry if this instruction guide shows photos of the older pieces

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Step 4  ¶ 

  • you may find some remnant holes or squares that need to be cut out

  • you can do this with a utility knife

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Step 5  ¶ 

  • #311 needs to have the power adapter installed before you build your JR base

  • the nut will need to be unscrewed off the head of the adapter

  • use a pair of pliers to snug the adapter onto #311

  • Note - in the new revision, this piece along with the rest of the box pieces are taller than the ones you'll see in these next few steps

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Step 6  ¶ 

  • Jr. is designed with the new "washer-less" tabs ... the nut and bolt pair in the red box should be solidly tightened when installed (very hard to reach once the z-motor is in place)

  • NOTE: the pieces are intentionally made to fit very tightly, so firm pressure will often be necessary, but it should be applied carefully and attentively. The pieces are-- of course-- breakable.

  • ALSO: the nuts and bolts can be left only loosely tightened as the build progresses and it gets more difficult to fit the successive parts in place.

  • ease of build - leave the 1/2" bolt and 6-32 nut out for now (green circle)

  • #314, #310, #308, #313, #312

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Step 7  ¶ 

  • in the build video(s), Brook explains that squeaking and creaking are good signs when snapping parts together

  • a tight fit is a strong, sturdy fit

  • #309

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Step 8  ¶ 

  • over-pressuring and over-tightening can potentially damage the box-- snug without straining!

  • NOTE: bolts left a bit loose can be snugged up nearer the end of the assembly process.

  • once bottom is secured to siding, screw the final 1/2" bolt connecting #312 to #308 (green box)

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Step 9  ¶ 

  • Brook provides some helpful tips and expert observations on the design and function of the base and the rest of the Junior in the build videos

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Step 10  ¶ 

  • the z-axis stepper motor is fitted to #317 with four M3 8mm hex-head bolts

  • NOTE: Brook recommends that the motor's wiring face "in" toward the middle of that section of the base. In the picture here, the wires can be seen extending straight down from the motor.

  • wire management - you can zip tie the cables to keep things orderly

  • Note - in new revision you will be using a large Kysan motor on the Z-axis instead of the small motor you see in these photos

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Step 11  ¶ 

  • the z-axis endstop switch position opens toward #313

  • wire management - you can also zip tie the wires to keep orderly

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Step 12  ¶ 

  • the process of getting the base lid into place without displacing the 6-32 nuts can be a bit challenging ...

  • NOTE: the most difficult one to reach later is seen here in the blue circle on the left.

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Step 13  ¶ 

  • the other half of the base lid includes a slide bar mechanism for locking the printbed assembly in place

  • NOTE: the washers are installed between the nylocks and the underside of the base lid (smooth/rounded side to the wood).

  • #318, #319

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Step 14  ¶ 

  • the slide-lock section of the base lid is not fastened down yet and is shown here for reference

  • NOTE: the Printrboard will eventually be installed underneath this section of the base lid.

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Step 15  ¶ 

  • the stability of the printbed depends, in part, on this slide-lock making a positive, solid brace on the printbed undercarriage

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Step 16  ¶ 

  • the hinged, x-axis assembly with x-axis endstop attached to the top of the "bearing sandwich"

  • x-axis endstop needs to be installed open toward the bearings with the zip tie securing back onto the wood

  • #305, #306, #307

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Step 17  ¶ 

  • sandwich is attached together with four 1 1/4" bolts and four 6-32 nuts

  • make sure flat side of 307 is installed on same end as x-axis endstop

  • ease of build - hold with one hand as pictured and use your fingers as backing for the 6-32 nuts

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Step 18  ¶ 

  • this wire slot is another feature designed to help minimize the risk of wiring pinches

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Step 19  ¶ 

  • install the belt pulley onto the x-axis motor

  • look for the flattened side of the motor rod and seat the pulley screw on that portion of the rod

  • your belt pulley will have either a 1/4" bolt (as pictured) or a 1/16" hex screw to secure it onto the motor rod

  • You may have to back the screw out a tad before the rod will fit in.

  • Note - in the new revision you will have a large Kysan motors, install belt pulley onto one of the large Kysan motors just as described here for the smaller motor

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Step 20  ¶ 

  • the wooden plates will arch or even crack and break if over-tightened around the bearings

  • NOTE: the endstop wiring pass-through holes in the hinge arms help prevent the wires from being pinched.

  • ease of build - put the x-axis motor cable through hole in 307 first and then the x-axis endstop cable second (red circle)

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Step 21  ¶ 

  • the nylon bushings nest inside the 608 bearings

  • make sure 1/4" washer has rounded edge flat on the wood surface, sharp side on the 608 bearing

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Step 22  ¶ 

  • now is the best time to install the belt for the x-axis

  • insert on the side with the x-axis endstop

  • feed the belt between the 608 bearing and the 8 mm bearing

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Step 23  ¶ 

  • the hinge rod has a flat end and a tapered end

  • NOTE: the tapered end of the rod is generally easier to work through the base holes.

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Step 24  ¶ 

  • work on one layer at a time when getting the hinge rod through the assembly

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Step 25  ¶ 

  • this is also a challenging step due to the need to place multiple pieces in order in a very tight space

  • ease of build - we recommend you glue together two of the bushings

  • set of bushings go in between #307 and #310 (red box)

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Step 26  ¶ 

  • the rod should be approximately flush with the outside face of the base when installed fully against the motor housing

  • NOTE: the hinge rod should not be hammered into place against the z-motor.

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Step 27  ¶ 

  • Note - these photos show the new revision for the large Kysan motors for both Z and X axis

  • The assembly of both of these axes are the same as the older design

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Step 28  ¶ 

  • wire management - rotate the x-axis carriage up and then zip tie the motor and endstop cable together at #310 (green circle)

  • take the remaining motor and endstop wiring and zip tie them individually to keep the interior of your JR orderly

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Step 29  ¶ 

  • the base bottom must be supported when installing the z-axis smooth rods

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Step 30  ¶ 

  • attach the two 303s to the two 304s

  • all bolts are 1/2" except for one that is 3/4" and is threaded with a 6-32 nylock (green box)

  • make sure that the slots correspond on each piece

  • NOTE: The belt is mounted in the opposite direction in the video. Make sure you mount it in the direction shown in this manual.

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Step 31  ¶ 

  • print bed and platform assembly

  • four 3/4" bolts go through the print bed #301, sandwiched between bed and platform will be four springs

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Step 32  ¶ 

  • attach the left side of the platform to 303/304 with 3/4" bolt and 6-32 nut

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Step 33  ¶ 

  • x-axis smooth rods can now be installed-- slowly and carefully-- on the sandwiched bearings

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Step 34  ¶ 

  • attach the print platform to 303/304 with 3/4" bolt and 6-32 nut

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Step 35  ¶ 

  • the open slot is "inside," close to the center of the printbed width, and the belt feeds through the 4-sided slot first and back through the open-ended slot last.

  • the zip-tie cap must be positioned so that it does not catch on either wood plate in the printbed base "sandwich"

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Step 36  ¶ 

  • two or three teeth of extra belt length should be enough to both get a zip-tie solidly fastened and allow for future adjustments

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Step 37  ¶ 

  • careful positioning of the zip-tie caps allows for maximum print area

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Step 38  ¶ 

  • the z-rod coupler assembly includes a 3/4" length of vinyl tubing for the motor mount arm and 3/4" bolts

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Step 39  ¶ 

  • Brook also recommends that the threaded rod not actually touch the motor arm but have a fraction of an inch of separation from it inside the z-clamps

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Step 40  ¶ 

  • assemble with four 1/2" bolts and four 6-32 nuts

  • do not attach middle holes for #329 (red box)

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Step 41  ¶ 

  • 4 - M2 8mm screws

  • Using 1.5mm or 1/16" allen wrench secure the fan to the fan mount.

  • Screw through the back of the fan into the wood.

  • Screws should be almost flush to the front side of the fan mount.

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Step 42  ¶ 

  • NOTE: the 3/4" bolts start through 328 and end by fastening 330 to 332.

  • CAUTION: as with many of these fastening steps, the bolt-ends will likely extend past the last layer of wood, so under-surfaces can be damaged in the process.

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Step 43  ¶ 

  • 2 - 1/2" 6-32 screws

  • 2 - 6-32 hex nuts

  • Facing the fan, route the fan wiring through the left hole in part #332, the hot end wiring will also feed through this same hole.

  • Note - Depending on the hot end that you receive (ceramic or cartridge) you may want to wait to put the fan mount on later in your build (photo #2). The cartridge hot end is much larger and will not fit through the slot in the red box. The ceramic will fit through if you feed the lead wires through first.

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Step 44  ¶ 

  • the y-axis belt-clip/bar-end combination is a stack of two 333 parts and 334 at the back fastened with two 3/4" bolts starting through 334 (red) and one 1.25" bolt with a 6-32 nylock (green)

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Step 45  ¶ 

  • this assembly sandwiches the y- and z-axis bearings, supports the threaded rod nut, and provides the y-axis motor mount

  • NOTE: the y-axis endstop switch is already attached to 321 (with the "mouth" opening up the edge of that part-- in the yellow box). This switch can only be correctly-- and most easily-- installed when the stack is not fastened together.

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Step 46  ¶ 

  • for 608 bearing installation refer back to step 20

  • sandwich the eight 8 mm linear bearings in the respective slots and hold the layers together with three 1 1/2" bolts in the holes (green circles)

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Step 47  ¶ 

  • nut capture assembly

  • using three 2 1/2" bolts secure the nut capture frame

  • Note - the 2 1/2' bolts will only be long enough to go halfway through #321

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Step 48  ¶ 

  • screw in the remaining four 1 1/2" bolts

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Step 49  ¶ 

  • insert #327 into slot

  • ease of build - the fit is very tight and you may need to sand down the sides

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Step 50  ¶ 

  • the stack is bolted started through 321 through to 323

  • NOTE: please refer to steps 18-20 in this guide for assembly/installation of this motor-pulley-bearing system.

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Step 51  ¶ 

  • the assembled y-/z- stack from another angle

  • zip tie the y-axis motor and endstop cable

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Step 52  ¶ 

  • as a frame of reference, the belt teeth can be seen facing the end-stop switch, passing under the 608 bearings and over the motor-mounted pulley

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Step 53  ¶ 

  • Note - these photos show the new revision with the large Kysan motor on the Y-axis

  • The assembly is exactly the same as the older design

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Step 54  ¶ 

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Step 55  ¶ 

  • the same zip-tie cap concerns apply here (please refer to steps 28 & 29 )

  • NOTE: the second picture in this step highlights the z-endstop actuator assembly mounted on 327.

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Step 56  ¶ 

  • a view from above the mounted upper carriage with the z-rod nut inside the 324, 325, 325 assembly

  • In the next step we assume you have already assembled the extruder. Please see the Extruder assembly guide.

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Step 57  ¶ 

  • take assembled extruder and mount on #329 with two 1" bolts with two #6 washers and two 6-32 nuts

  • Note - do not attach the top 8mm m3 bolt (green circle) into the top of the extruder motor as you will need to access the 1" bolt (red circle) to mount the extruder

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Step 58  ¶ 

  • pull the hotend power cable and hotend thermistor cable through the backside of #332

  • connect the hotend thermistor cable (black/white wiring) to the shorter, clear shielded cable

  • connect the hotend power cable (red/black wiring) to the longer, red shielded cable

  • Depending on the hot end that you receive the hot end power cable may have red insulation or black insulation.

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Step 59  ¶ 

  • once connected, pull wiring back through the left hole of #332

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Step 60  ¶ 

  • 1st - green - zip tie extruder motor, hotend thermistor cable, and hotend power cable together at base of extruder motor

  • 2nd - yellow - extend the y axis fully and zip tie extruder wire set with the y-axis wire set

  • 3rd - blue - zip tie the middle point between the extruder and y-axis

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Step 61  ¶ 

  • 1st - yellow - zip tie all five sets of wiring at the end of the y-axis motor

  • 2nd - green - zip tie into equal thirds the remaining wiring

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Step 62  ¶ 

  • time to install the electronics Printrboard

  • begin with the x-axis wiring

  • x-axis motor cable will connect at the x-mot connector (yellow circle)

  • x-axis endstop cable will connect at the x-stop connector (red circle)

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Step 63  ¶ 

  • y-axis motor cable is connected to the y-mot connector (yellow circle)

  • y-axis endstop cable is connected to the y-stop connector (red circle)

  • hotend power cable is connected to extruder connector (blue circle)

  • Note - look at the two sides of the extruder motor connector, one side is completely solid black and the other shows the wire connectors. make sure the cable is connected with wire connectors facing into the board

  • leave hotend thermistor cable disconnected from the Printrboard for now

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Step 64  ¶ 

  • z-axis motor cable connects to the z-mot connector (yellow circle)

  • z-axis endstop cable connects to the z-stop connector (red circle)

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Step 65  ¶ 

  • time to place Printrboard inside JR body

  • make sure power adapter is pulled up and out of the JR body (green box)

  • angle Printrboard down toward the z-axis rods and pull all wiring up and over the row of motor connectors on the board

  • ease of build - because of tight fit, loosen 1/2" bolts in green circles and remove 1/2" bolt and nut in red circle

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Step 66  ¶ 

  • once board is placed fully inside of JR, connect power adapter into PWR connector on board (green)

  • Note - If you have received an ATX power supply DO NOT connect the power adapter into the PWR connector - go to step 69 for instructions

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Step 67  ¶ 

  • Only perform this step if you have an ATX power supply and Y-adapter cable (yellow/black)

  • Connect Y-adapter cable to PWR connector on board (green box)

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Step 68  ¶ 

  • the hotend thermistor cable can now be connected to the t-ext connector on the board (green)

  • the t-ext connector is the middle of the three white connectors on the right side of the board

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Step 69  ¶ 

  • securing the Printrboard to the JR body

  • two 1/2" bolts are screwed into the two holes on the front of the board (blue circles)

  • Note - screw them into the JR body as far as they are flush with the bottom of the JR (blue squares)

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Step 70  ¶ 

  • reattach the 1/2" bolt and nut (red)

  • before you attach #318, it is good to place a 6-32 nut where the yellow circle is because you will not be able to access once #318 is attached

  • secure #318 onto the JR body with three 1/2" bolts and 6-32 nuts

  • Note - If you have received an ATX power supply DO NOT connect the power adapter into the PWR connector - go to step 66 for instructions

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Step 71  ¶ 

  • Only perform this step if you have an ATX power supply and Y-adapter cable (yellow/black)

  • Take Power adapter cable (red/black) and tuck under #317 (orange box)

  • Route Y-adapter cable (yellow/black) through slot in #311 (red box)

  • Place one 6/32 nut where green circle is because location will nearly be impossible to access once #318 is in place

  • Secure #318 onto Jr box with three 1/2" bolts and three 6-32 nuts

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Step 72  ¶ 

  • this assembled kit is now ready for testing, calibration, and printing

  • NOTE: additional guides for the electronics installation and extruder mounting are in the works. Please see the for updated guides and additional technical support documents. Thank you.

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Step 73  ¶ 

  • These are the assembled photos of the new revision

For more information, check out the Printrbot Jr v1 (Model 1307) category page.

Comments Comments are onturn off

Pay attention to X axis belt installation. At the video it is mounted opposite to the picture in this manual, the video is wrong, the manual is correct.

Antonio Campos Irujo, · Reply

Is there a complete list of necessary tools anywhere? And for steps like step 5 where there are many pieces put together, is there a list of the pieces used accompanying the photo somehow?

lytri, · Reply

Just finished building so thought I'd post these notes to help you and others.

Time: Took me many hours longer than the 1-2 hours to build the main structure. Most of this was fettling parts, going back over bits and checking hadn't overtightened anything critical. If i built another from scratch, probably three hours for the main, an hour for the extruder and an hour to fit / bunch all the wiring in.

Difficulty: If you can assemble model airplane kits form wood then you can build this. You need to be aware that this is NOT a lego kit. It needs careful informed assembly and often you have to research to get some bits right.


Phillips screwdriver

Fine needle point pliers

Magnet (So you can fish dropped bits out of the depths)

Small wire cutters

Stanley knife

Scalpel or small bladed knife

Fine sandpaper

Mallet or wooden block

Wooden sheet to build on (Bolt ends can scratch tables)

EXTRA fine cable ties, about 20

2 part quick set epoxy resin for repairing anything you break!

Fine triangular file

aj booker,

I am blocked at step 57!! how can I make the extruder?

Thomas, · Reply

Thomas -- was in the same boat you're in, but some digging/googling found this:

ManApe GoneWrong, · Reply

Hi !

The Youtube playlist disapered ! I don't find any comments about that, and I d like to finish my Jr. Please where are they now ?

Thanks a lot

yabauche, · Reply

The youtube videos are still gone. I have submitted a support ticket and hope that they will get them back up soon.

In the meantime, it is possible to assemble the kit just based off these instructions. This is what I am doing and I will post clarification comments about things as I figure them out. (Presumably many clarifications were not needed earlier when the videos were still up.)

Ivan, · Reply

My revision didn't have this cable or the associated hole in part# 311. It was no problem to just skip this step.

Ivan, · Reply

What pieces make up this assembly?

(My wooden parts don't have numbers, but you seem to refer to pieces by number throughout the guide)

Albert Filice, · Reply

The part numbers come from the Jr parts diagram from Link to the diagram is here

Brook Drumm,

Clarification: The wiring for the motor should point towards the long side of part# 317. If it doesn't, it will get in the way of the z-axis smooth rods installed in step 29.

Ivan, · Reply

Pay attention to the needle nose pliers in the first image. The zip ties are a bit wider than the holes in the endstop switch and you have to use pliers and pull pretty hard to get them through.

Ivan, · Reply

This step (17) says to secure the sandwhich with 4 x 1 1/4" bolts.

On the Bill of Materials, there is only a single 1 1/4" bolt mentioned, and it's needed for the Extruder. I do not have any in the kit. I used 1" bolts at the time since they fit pretty nicely, however now I realized that I need those for a later step (building the extruder).

How old are these directions, or did I get a different kit?

Albert Filice, · Reply

Step 21: My hinge rod did not have a tapered end

Richard Boothroyd, · Reply

All my rods were the same length

Mike Partain, · Reply

You say "3/4 inch" and the screws end up flush to the other side of the holes. However two pieces put together make up a 1/2" wide piece, and my screws jut out.

It's even more dramatic for the 1" screw and locking nut, which sticks out a whole ton.

Should I be using different screws? I don't want to just start using different ones in case I need them later.

Albert Filice, · Reply

We apologize for the confusion. The guide has been corrected to say five 1/2" screws and one 3/4" screw.

Brook Drumm,

So, does the teeth of the belt need to make contact with the gear on the motor? The picture and the video makes it looks like only the back side of the belt needs to make contact with te barrings....but then the motor won't make the table move of course.

Benjamin Bond, · Reply

I had trouble with understanding this too. Both bearings touch the belt, with the gear in the middle. The belt enters from the right side, goes in between the bearing and the motor (with the teeth touching the gear), follows the gear, and goes in-between the gear and the second bearing. So it makes a ‾U‾ shape.

Stephen Brown,

For me it was difficult to push the rods all the way into #304 parts. I found it easier to back up and take apart the 303/304 sandwiches and take the rods out of the linear bearings and then:

1. Widen the holes in one #304 plate by tapping the rods into the holes and then pulling them out.

2. Tap the rods into the other #304 plate so they are flush with the opposite side and then leave them in there as I ran them through the linear bearings and attached the other #304 plate.

3. Check the position of the #304 plates for accuracy by test fitting the print bed assembly.

4. Attached #303 plates

5. Attach print bed assembly.

Ivan, · Reply

Parts have changed slightly for the included fan. Now is a good time to install the fan, as getting to screw will be difficult later.

Mike Partain, · Reply

Parts have changed eh? Do you know how did they changed? What part should I use?

Anything helps thanks.

Albert Filice,

Updated the photos to show the new pieces in this step.

Brook Drumm,

You never mention how to attach the fan? Those tiny little hex bolts I'm assuming?

Albert Filice, · Reply

Step 41 shows how to mount the fan.

Brook Drumm,

The 1" bolt in step 40 will stick out past the nylock. Maybe a 7/8" bolt is what we should be using and get in the kit instead.

Carey Radebaugh, · Reply

I came up 1 X 1" short in the end. I also believe the end stop adjustment screw is better off using a 1 1/2, and that would have made up the missing 1". Perhaps the part inventory changed correctly, but the instructions are not up to date?

Mike Partain, · Reply

The photo of the motor in step 41 looks different than the large motor that you get in the kit and that you're supposed to use for this step. The motor shown in the photos in step 41 and 42 (especially if you look at the wires in the step 42 photo) is of the smaller motor, which you shouldn't be using in this step.

Carey Radebaugh, · Reply

Don't use the two M3 8mm shown in the first picture. If you install them, they will get in the way of the Y-axis smooth rods.

Ivan, · Reply

My stop switch didn't come attached as stated, and no screws that work to attach it

Wayne, · Reply

Wrapping a couple of rubber bands around the triple sandwich really helps hold it together while you are putting in the first 3 screws.

Ivan, · Reply

Look at the 3rd photo in step 45 to understand how the pieces are supposed to go together.

Carey Radebaugh, · Reply

The step numbers have changed - the 3rd photo in step 49 is now the helpful one.


where do I find the extruder assembly guide? Also all videos referenced seem to be unavailable???

greg, · Reply

I don't see a longer red shielded cable. Just the thermistor cable and the power cable which is black and black.

Albert Filice, · Reply

You are correct. The ceramic hot end, which you received, has black insulation on the power leads. The cartridge hot end, which is shown in the guide, has red insulation on the power leads. Sorry for the confusion.

Brook Drumm,

how do i wire the fan?

Kevin, · Reply

If you look on the control board there is a two pin male connector on the right hand side above where you plugged in the hotend thermistor cable in step 68. It says "fan" on the board just beneath it, I'm gonna try plugging it in there and hope that it works!


Why should we leave the thermistor disconnected form the board for now? When should we attach it?

Albert Filice, · Reply

Connect the thermistor to the board in step 68. It can be difficult to fit the board into the box of the Jr if the thermistor cable is connected to the board. We connect it once the board is fitted in the box.

Brook Drumm,

There was no mention of hooking up the extruder motor, is there a reason to wait around to installing it?

I'm going to hook it up now...

Albert Filice, · Reply

Step 63 shows connecting the extruder motor.

Brook Drumm,

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