Defcon:Blog Keklkakl blog blag

OpenCoreBot update: Aluminium extrusions and Parts!

I've settled on "OpenCoreBot" as my working title for my 3D printer (as mentioned in the previous post). The project plan started when I was looking for already existing 3D printer projects in the open-source/open-hardware realm based around aluminium extrusion. I was also looking for a design that did not use the "moving y" concept, simply because of the experiences from my DIY mini-CNC router. Using slotted square extrusions in mechanical buildup of CNC equipment has been close to a norm a long time. This kind of construction gives some important advantages, among them high flexibility and rigid constructions. What I did discover when looking at existing designs, was that there were a few open-hardware friendly designs based on the Mendel and Prusa designs, but other non-moving-y designs generally did not use open components other than printed and motion-control parts.

Slotted aluminium extrusions has traditionally been a market of several proprietary, copyrighted and even patented extrusion profiles. Misumi, 80/20, 6040, TSLOTS and MiniTec are a few of the names in the business. However, as the Maker and Open Hardware communities and ideas are spreading, a few alternatives have emerged. I hope to learn of more of them,but the ones I know of so far are: MakerBeam, OpenBeam and V-Slot. These are all made with OSI-friendly licensing on the technical drawings, and permit both independent manufacture and derivative works. The extrusions currently have few manufacturers apart from their "original", simply because the cost of tooling and extrusion manufacture is quite high, and it makes very much sense to use economy of scale. But, the fact that these have been made by and for Makers, the cost of these extrusions is significantly lower than the proprietary options. As an example, the 80/20 20x20mm t-slot costs around $30/m while the open V-Slot 20x20mm comes at $10/m.

When I started my design, I did not know of the OpenBuilds V-Slot 20x20mm. The MakerBeam is a tiny 10x10mm extrusion, and I quickly decided this would be too small to provide the rigidity I need for a printer of usable size. So, I've designed around the 15x15mm OpenBeam profile. At less than $9/m before VAT/shipping, it is very cost-effective. I ordered my extrusions from MakerBeam.eu, and when my order arrived, I was impressed by product, packaging and shipping-time.

After completing the design-draft that I showed off in my previous post, I sent off the OpenBeam order, and then went on eBay and picked up an assortment of linear motion components that are needed in my design. Those parts took quite a while longer to arrive than the OpenBeams. No surprise there, all parts were "Free shipping" from Asia to northern Europe. While waiting for all ordered parts, I've kept my first-iteration printer (i.e. my DIY-CNC repurposed to a printer) running more or less constantly pushing out plastic parts. The result is a considerable collection of parts:

Pictured parts are:

• OpenBeam 15x15mm extrusions in 9cm, 30cm, 49cm and 100cm lenghts (49cm are cut from 1m) (CC licence)
• 40cm optical rods in 8mm diameter (simple standard item)
• 40cm optical rods in 12mm diameter (simple standard item)
• LM8UU linear bearings (Generally available design, standard item)
• SC12UU linear bearings (Generally available design, standard item)
• SK12 rod mount (Generally available design, standard item)
• NEMA17 stepper motors (Industry standard)
• 3D printed plastic parts from my own design, these will be open-source licensed and published when design nears completion
• Standard screws and fasteners in METRIC dimensions 🙂

Among the printed parts are T-shaped, L-shaped fastening plates, and angle-brackets. I could have used OpenBeam/MakerBeam plates and brackets for these parts, but I simply forgot to include them in my order, so I decided to print them. While printing, I did a quick calculation, and these printed parts will be weaker than the molded/metal parts from OpenBeam, but will also be less than 1/3rd of the cost per part.

I have a few more parts to print, a few Bowden-extrusion related parts in shipping, but assembly will start very soon now 🙂

I will keep adding progress pictures to the photo-gallery at http://photos.defcon.no/2014-11-05-opencorebot as the build progresses.