How to Build a D-Bot 3D Printer (Part 2: Frame)

The D-Bot’s frame is built from aluminum extrusion and fastened together with 3D printed parts. Provided that the prints are well made, this offers an extremely rigid framework at a considerable cost savings over metal counterparts. It is however important to choose the right material and test the strength of your parts prior to assembly.

During my first attempt, I printed the full set of D-Bot parts with PETG but failed to do so with the proper settings. As a result of the temperatures being too cold, every single piece was brittle and would delaminate, crack or split down the middle under stress. While this was a considerable setback, the parts were reprinted with higher temperatures and are now much more durable. As such, I advise using a strong plastic such as ABS or PETG and stress test a part ahead of time to ensure it won’t fracture under pressure.

Frame Preparations

The aluminum extrusion must be cut to size with precision. While we can compensate for slight variations in length by making modifications to the 3D printed parts, each piece should aim to be within +/- 1mm.

Since I can’t exactly run a saw in my apartment, I spent days searching for a shop that I could hire to make the cuts. After several absurd price quotes, I found a local redditor that helped in exchange for nothing more than a new saw blade. If you have it available, a Miter Saw with a Non-Ferrous blade is the absolute best choice for smooth cuts in aluminum. Otherwise, a Hack Saw with a clamping Miter Box can product decent results as well.


The extrusion lengths will need to be adapted based on the desired bed size and printer height. If you are following this exact build, the measurements below will achieve a total print volume of 300x300x425mm. For a different size, the vertical beams (4x 620mm) and heated bed frame (2x 433mm) will need to be adjusted. The D-Bot Build Guide also offers pre-measured lengths for a standard 300x200x325 build and an extended 300x300x325 build as well.

PieceCut Size
Piece 1 (20x40)620mm620mm-
Piece 2 (20x40)620mm448mm413mm
Piece 3 (20x40)620mm433mm433mm
Piece 4 (20x40)488mm463mm413mm
Piece 5 (20x20)463mm463mm463mm
Piece 6 (20x20)503mm413mm413mm

Thread Taps

Once the frame pieces are cut to length, we must thread tap several of these prior to assembly. This process essentially cuts threads into the metal, making it possible to screw bolts into the ends. As it was my first time doing so, this video offers an excellent demonstration. It was quite simple after a few practice attempts, where you just turn the tap clockwise about 360 degrees, then back it out half a turn, repeating this until enough threads have been created. Just remember to lubricate the metal with cutting oil before hand as this will prevent the tool from binding up.

As shown in the official D-Bot Build Guide, use the M5 Thread Taps diagram to tap the correct locations. The remaining holes will not be used and do not need to be threaded.

Part Preparations

Before we can start assembling the frame, we first need to prepare several of the 3D printed parts that will be used. For this stage, you will need to have the following hardware…

  • (22) M5x10 Bolts
  • (22) M5 Washers
  • (22) Square Nuts
  • (16) F623ZZ Bearings
  • (8) M3x25 bolts
  • (8) M3 Nuts
  • (16) M3 Washers

Take the 3D printed parts (A) Rear Idler Left and (B) Rear Idler Right and place an M5x10 bolt with an M5 Washer into each hole from the outside. Once threaded, place a square nut on the inside of each bolt as shown in the picture below.

Each part also has 2 square openings that house the bearings, later used for moving the belts. Using (2) F623ZZ Bearings in each, place an M3 Washer in between them and press them together like a sandwich. The side of the bearing with a lip will face outwards, keeping the belt centered in the middle. Have an M3x25 bolt with an M3 washer ready and slide the bearing stack into the opening, then tighten the M3x25 bolt into the plastic and through the bearings as far as possible.

Note: The original Build Guide shows another nut placed on the end of the M3 bolt. I found these slots difficult to use and the D-Bot’s designer stated that they were not necessary. As such, the small slot for a nut can be ignored, where the bolts are held in place sufficiently by the plastic.

Using the same steps, insert bearings into the (A) H-Bar End Left and (B) H-Bar End Right as well. To secure the bearings, the order of assembly is M3 Bolt → M3 Washer → Plastic → F623ZZ Bearing → M3 Washer → F623ZZ Bearing → Plastic → M3 Washer → M3 Nut.


Frame Assembly

With the preparations finished, we are ready to assemble the frame. To give a brief overview, we will first setup the left and right sides separate of each other, then join these using the top, bottom and middle cross beams.

Right Side

Rail-B (Rear Vertical Beam): Attach the Right Rear Idler, Z-Endstop Bracket and Y-Endstop Bracket to the top, followed by (2) Corner Brackets and (1) 3×3 Plate on the bottom. Turn the square nuts where they will slide into the v-slot and make sure they are loose enough to have around 2-3mm of clearance.

For the rest of the parts attached to Rail B, just slide square nuts into the aluminum extrusion from the bottom and move them as needed. The Z Endstop Bracket mounts to the rear and the Y Endstop Bracket mounts on the front with (2) M5x10 bolts each. The endstops should measure 24mm in distance from the top of the beam. Finish by placing (2) Corner Brackets at the bottom of the beam, one on the front and one on the left side, then a 3×3 Plate should be affixed to the end.

Rail-D (Front Vertical Beam): Attach the Right Motor Mount to the top and the same (2) Corner Brackets and (1) 3×3 Plate on the bottom. These Corner Brackets will face to the rear and the left of the beam, while the Motor Mount will face forward, away from the frame.

Rail-J (Lower Horizontal Beam): Place (1) 2×1 Plate on one side and (1) 3×3 Plate on the other. Position doesn’t matter at this point but you can screw them down in the middle to keep them clear of corners and easily accessible.

With all of the 3D printed parts installed, we can go ahead and complete the right side. Rail-B and Rail-D are connected by Rail-J on the bottom and Rail-F on the top. The bottom beam should slide between the Corner Bracket and the 3×3 Plate on each side and Rail-F will lock into place between the Rear Idler and Motor Mount.

D-Bot Frame Right Side

Left Side

The left side is almost a mirror image of the right, with the exception of two additional parts. The spool holder and extruder bracket are mounted below the motor mount on the front beam.

Rail-A (Rear Vertical Beam): Attach the Left Rear Idler to the top, with (2) Corner Brackets and (1) 3×3 Plate on the bottom.

Rail-C (Front Vertical Beam): Attach the Left Motor Mount and the Extruder Bracket to the top, with (2) Corner Brackets and (1) 3×3 Plate on the bottom. The Extruder Bracket sits flush, directly under the Motor Mount and extends outwards from the frame. Before capping the bottom with a 3×3 Plate, slide an extra square nut in the v-slot beneath the Extruder Bracket. Place an M5 Nylock Nut and M5 Washer on the end of an M5x75 Bolt and screw this into the square nut to create the spool holder.

Rail-H (Lower Horizontal Beam): Attach (1) 2×1 Plate on one side and (1) 3×3 Plate on the other.

As we did on the right side, connect the vertical beams Rail-A and Rail-C together with Rail-H on the bottom and Rail-E on the top.

D-Bot Frame Left Side

Center Beams

With both sides assembled, we can now bring them together using the center beams. With the frames sitting upright, place them side by side with Rail A and Rail B on the bottom and the Rear Idlers facing inwards.

Starting with Rail G, slide this in to the Rear Idler assemblies in the top rear of the frame. Leave the bolts somewhat loose until the rest of the center beams have been inserted to provide yourself with more room to work. Now insert Rail L into the bottom rear and Rail M into the bottom front of the frame, between the 3×3 Plates and 2×1 Corner Brackets. Once finished, tighten down the bolts to lock the beams in place.


To complete the outer frame, place (1) 2×1 Corner Bracket on each end of Rail N with M5x10 Bolts and Square Nuts included. This will slide down into the front vertical beams Rail C and Rail D behind the motor mounts. Make sure that it sits flush with the top of the beams and tighten the bolts to secure it in place.

D-Bot Frame Top Front Beam


As a final step, we will attach Rail K which acts as the cross beam for the Z Motors. These are responsible for raising and lowering the build platform, however the cross beam also works to make the frame more rigid as well.

To prepare Rail K, insert (4) Square Nuts on the front facing v-slot. Using the two printed Z Motor Mounts, secure these to the beam using M5x10 Bolts. Now insert this piece in between the sides of the frame, where it will mount to the extra 2×1 and 3×3 plates we previously mounted on each side, Rail H and Rail J respectively.

D-Bot Frame Motor Mounts

10 thoughts on “How to Build a D-Bot 3D Printer (Part 2: Frame)

  1. I’m just starting me D-Bot build myself. Ording parts. I’m following your build. Awesome. Thank you so much for the post. I’m looking forward to the next installment.

    1. No problem, I hope it helps! I am still doing a lot of revisions right now, where I would follow loosely and use both this and the original documents in combination (at least for the time being). I should have the 3rd installment published by the end of this week and completed by next week some time. I ran into some setbacks, mainly small things not noted in the original Build Guide so I am just fixing those up before I continue the articles.

      If you have any problems, don’t hesitate to ask and I will do my best to help out. Otherwise, the D-Bot group on Facebook ( and the D-Bot sub-reddit ( are excellent resources for information and assistance!

  2. Excellent guide, really easy to follow! I’ve been putting my own together but am having real trouble getting the frame to be square. All the extrusions are the correct lengths and pushed flush against each other and the printed parts, but top and bottom of the frames are off from each other.

    I’m using mgn12h rails for the carriage so this problem is amplified here. Did you run into this? If so do you have any recommendations for correcting?

  3. I had already planned on a 300×300 bed and really want to go for the 425 z travel, but I’m just curious how yours is printing if you finished it. Having that extra 125mm would be so useful, but not at the expense of quality prints. I just ordered all of the extrusion that would allow me to do the Z increase but won’t bite the bullet and cut them till I hear that it functions fine at that height.
    Thanks for the quality write up so far. Look forward to the rest.

    1. My print quality on the D-Bot has been decent thus far, not exceptional but could definitely be much worse. The prints themselves actually come out fairly good but the walls just aren’t as smooth as I would like. I don’t think this is a result of the build volume though, there are a few contributors which I just haven’t had time yet to fix.

      The D-Bot is currently sitting on an Ikea Lack Table, which has carpet underneath (not exactly the most sturdy choice). The 300x300x425 build takes up nearly the entire surface area so I can see the table wobble during prints. To further complicate matters, I haven’t quite been able to get the wheels on the extruder carriage tightened up appropriately. It works but there is some play in the extruder when shifting on the X-axis.

      I will eventually swap to linear rails for X/Y motion as that should be much smoother and address any play in the head. I’m sure with enough time I could get the wheels balanced out but they have been quite a pain in my case. I think this is the perfect build volume as it doesn’t really require any additional frame support. My biggest complaint is exclusively towards the wheels.

      1. Hi Brett. I am near the end of assembly of my frame per your cut lengths and my Q rail is too long. The original guide calls for a 448mm piece. Do you know what the length of the Q rail is in your cut list? I know I didn’t use the wrong sizes anywhere else because the rest of the frame is assembled and square. I was pretty careful to double check all cuts and I used your list printed off and checked off as I went. I can obviously just take measurements but wanted to know where I might have gone wrong.

        1. Hi Eli. My build kept the same width & length as the original extended design (the measurements at the bottom of the official build guide). I only increased the Z-height from 325mm to 425mm, so the Q rail was right around 448mm in my case. It is strange to hear that it is too long, it should actually be a bit shorter than the total distance between the two rear vertical rails, where the printed pieces need to fit on to the ends.

          I just measured the distance between my two vertical rails and it was right about 462.8 or so. Can you measure yours and see what the distance is?

          1. Hi Eli, my sincere apologies, this was actually a case of mistaken input on my end when inserting the tabular data. I placed (2) 463mm pieces on the list to cut from the 20×40 rails, where one should have actually been the Q rail at 448mm. I’m going to get that corrected now but you can just shave the extra 15mm distance off one of your 463 20×40 pieces to fix the issue.

            Thank you for bringing this to my attention! I checked my original written dimensions and it was correct, so I guess I just copied it over to the website incorrectly. I used almost the entire cut list from the bottom of the original document (for 300×300 build). I just increased the 520mm pieces to 620mm, then rearranged the cuts to support this.

          2. Haha yeah I figured that was the culprit. It was no problem. Just trimmed it down and it works great. I have the frame assembled and motion in all directions is smooth. One more question. What distances are you using for the Z platform as well as the distsance from K to the outside frsme? I know rail K requires some offset from normal position but not sure how far exactly. An numbers are greatly appreciated. I’m ordering all electronics today.

          3. Glad you were able to get that figured out Eli, sorry again for the little mistake on my data table!

            For the K rail, I actually had to move it as far to the back as possible. A quick measurement looks like about 60mm, but I moved it as far back as possible until the printed parts wouldn’t let me go any further. I initially had it positioned in the dead center of the frame, where this allowed me to have 2 PSU (one for bed, one for everything else). Unfortunately I ran into the issue of the bed frame’s weight on the back causing it to slant, where moving the lead screws as far back as possible was done in order to offset the weight distribution. Eventually I will make a second cross beam (Rail Q) for the front, just to make it more even on both sides, however this works for now.

            For the Z platform, do you mean the distance from the bed surface to the hotend? Since the extruder carriage only moves on the X/Y, I just raised the bed until it was in close proximity to the nozzle (while the bed was fully tightened down). I adjusted the endstop screw to that position and then used the 4 bed screws to tweak the distance more precisely.

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