Ba3dp Part 2: Frame
In the first post of the series I looked at many available 3D printer designs. I also made some choices about the core electronic components. In this post I will decide on the frame build. First off, I should mention that my total budget for this build is 250 Euros excluding printed parts. So after purchasing electronics that leaves me with about 160 Euros for the frame and other mechanical parts.
I really want to have a core XY printer. I find the design very elegant. The downsides seem to be related to properly aligning and tensioning the belts, as well as making sure the frame is perfectly square. Unfortunately most core XY DIY builds out there advertise build costs above US$ 1000. As mentioned before these very often include many extra features (e.g. 3 motor auto-levelling bed). Let’s have a look to see if we can afford a core XY printer. But first let’s talk about frame materials and linear motion
A lot of early printer designs used wood. My CTC i3 came with a laser cut plywood frame. More recently designers start exploring aluminium extrusion. First these were held together with printer parts and screws, but more and more I see full metal frames, made out of alimunium profiles connected with metal fasteners and aluminium plates. These create very rigid frames that can sustain the rapid movement changes and vibration created in a 3D printer.
Some vendors even offer complete frame kits for some models (D-Bot, hypercube evolatuion, BLV mgn cube) e.g. RatRig.
A 3D printer has 3 axes (X, Y, Z) and moves linearly along these axes. This movement is typically driven by belts on the X and Y axes and by lead screws on the Z axis. But there are designs with all belted axes and my CTC i3 printer used threaded rods to drive the Z axis. To ensure the movement is linear the first printer designs used linear bearings on smooth rods. People realised, that even high-quality bearings would start wiggling and create artifacts on the prints. More recently, as chinese clones of linear rails start becoming affordable, many newer designs incorporate these. Linear rails are sturdy rails with a chariot on top that glides on balls. They allow reproducible linear motion. At the same time, they are still more expensive than alternatives.
One interesting idea I came across is to use nylon bushings that sit in aluminium extrusions. Here is an example. This could be a very cheap alternative to linear rails since the plastic used (POM or Delrin) is self lubricating, has high heat tolerance and is very smooth.
My design of choice: LayerFused x301
So with these introductions out of the way, let’s make a calculation for a Core XY design. I recently came across the LayerFused x301 printer design. I like the open structure, which allows to get a clear look at the print bed. Does this design fit my budget? The advertsed BOM is aboce US$ 1400.
I could reduce the costs by taking a few shortcuts: reusing parts from a previous printer, no rails on Z, threaded rods instead of lead screws to drive Z, old PCB heatbed instead of aluminium plate, no bowden tube to route filament to extruder and more. What impact on quality will these omissions have? Let’s find out!
I managed to buy all required parts (excluding extrusions) on AliExpress from a single seller for a total of 102 Euros without duties. This should put me square into my budget. I will include full BOM when everything arrives and I start the build.