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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.

Measurements

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)620mm463mm413mm
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

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