MAD Fellows has always wanted to make a CNC mill but always had some other project we were working on that was more pressing. Well after enough making parts manually Dan Cervo moved the deltabot idea to the front. After a late night session he had done the CAD work and we had a 3D model of what is to be our first CNC mill.
Getting the parts was really quite a bit of fun. We wanted to make the tool out of as many components that we already had lying around either in good stock or the scrap bin. This ended up keeping the cots way down for the build, costing us just over $100 in new parts. We’ll put up plans and a full bill of materials in a later post, but here are the basics we scavenged and bought.
The acrylic came from a number of LCD screens ranging between 6-8mm thick. All the screens were goners in one way or another and were destined for the E-waste bin. So instead of letting it all go to waste we pulled out the acrylic from each screen and wound up with a nice inventory of free acrylic. So we got the material free, we reduced the amount of E-waste that had to be shipped out, and saved the company getting rid of the stuff a small fistful of cash they would have spent to get rid of something useful.
Other bits of hardware were taken from old computer towers and dead printers. Once its up (soon we promise), check out the jumper wire tutorial. Almost everyone seems to have an old computer tower just collecting dust somewhere, but they are full of wires, LEDs, and buttons just waiting to see new life. Don’t forget the motherboards, they have great pins that can be made into really high quality, virtually free jumper wires and some cooling fans have a small bearing that is useful. All of our wiring and the bearings in the idlers came from old towers and the bushing rods came out of dead CD-ROM drives. Printers, besides being a great source of motors, micro switches, and optical encoders, have screws that work great in plastic and often at least one 8mm rod. Our first mock up used the shafts from a number of HP printers (we purchased longer rods to get more build height) and virtually all the screws came from there as well.
A few parts we did buy were specialized and we had no hope of finding or no hope of finding the same part for all we needed. For instance, we have come across working stepper motors in the junk bin but never the same motor twice. This could be pretty problematic when it comes to driving them to say the least. We picked up a set of stepper motors, 500mm long by 8mm Dia. rods, a set of LM8UU linear bearings and GT2 belt and pulley. We already had the Arduino and EasyDriver boards just sitting around.
Once we had all the parts gathered up it was time to head out to Heatsync Labs in Mesa, Az. They graciously laser cut our scavenged acrylic and by the end of the night the mill was press fit together. The mill was assembled with screw, not glue, so that individual pieces could be replaced if they broke. It is a great time to mention that acrylic has many great properties including being fairly dimensionally stable, however, it is elongation at flexural failure is low making it an extremely unforgiving material.
Fully assembled and running, we still needed to make it CNC’ed. Dan was able to modify software designed for a 3D printer to control our mill. This was not completely clear cut as the software expected certain things that our bot didn’t have, like temperature input. But in the end he worked through all the error messages and got that running. The first cuts were on that green flower foam, just in case the machine messed up we didn’t want to destroy a mill bit after all. After that we moved up to acrylic (accidentally), then casting investment, then all the way to aluminum.
The bot will be used to make investment molds for metal casting and so far it seems to work great. We’ll be sure to get some pictures up of cast parts as soon as we get our furnace set up and running. We’ve already begun building a second bot to improve on this design using a similar design but built with angle iron and square steel extrusion. For now though, check out a few photos from the build.