Hybrid Machine Design

[nnfuller]

Combined Additive and Subtractive Machine

Additive manufacturing has come a long way in the past decade, specifically in the areas of FDM (Fused Deposition Modeling). We have seen astounding growth in methods, precision, materials, and speed. Still, certain instances occur where the desired combination of traits for a specific application aren't attainable in a single step. Here post processing such as vapor finishing, sanding, or even post machining have been used to help create parts that more fully satisfy the demands of industry.  Post machining shows perhaps the most promise for creating engineering grade parts, due to the high level of controlled precision compared to the previously mentioned methods. It is also the only process which can increase the precision of a 3D print. Up till now post machining required a second highly sophisticated machine, with additional work holding and tooling. This is the issue which this project will attempt to address. Below are my comments on Pros and Cons of Hybrid Manufacturing.

Pros

Increased precision

Because the printed object isn't repositioned, there is no uncertainty as to its location.  The standard practice of touching off reference points can cause problems when using a 3d printed part is uncertain dimensions.

Increased Throughput by Decreased Print resolution

Parts designed to be post machined can be printed faster at lower resolution, then have critical areas machined to tolerance. These parts could be thought of much like a casting, where non critical areas remain rough while other precision areas are honed within the desired tolerance.

Machined Internal Cavities

At a high level of functionality, this machine could be capable of more than a 2 step process, machining geometry after any number of layers had been printed, accessing areas that would later be covered by additional material,

Cons

Increased Machine Cost, Weight, and Complexity

Because the system must have the all the traits needed of both a 3D printer as well as a mill, there will be certain trade offs required which will likely result in greater weight and cost, while a head that can alternate between additive and subtractive processes will be more complex than a single purpose head.

It is my opinion that the benefits mentioned above outweigh the potential detriments and obstacles presented by combining these two processes into one machine.

[nnfuller]

Yes the RAMPS 1.4 board was chosen because of its low cost and modularity which allowed for the shopbot stepper drivers to control gantry. The TinyG is a cool little board and I haven't seen it before, thanks for the link!

As far as choosing the shopbot, I think it's a great first attempt. The only real shortcoming comes from its lack of z travel which in its unmodified state leaves us with about 4 inches of print height. Obviously a custom set of axises would be better but that was an increased level of complexity that wasn't desirable for the first iteration.

[nnfuller]

Well after increasing the pressure on the extruder, and adding a induction proximity sensor to the additive head we are finally printing in PLA. Our next step will be to add a heater to the bed so that printing with other materials is more possible. After that it will be time to get the spindle under control and start to machine printed parts! Really excited at the progress being made. Here are some pictures and video of it's first test print (please note that the settings for printing still need to be refined, it seems the retraction is a little high on this first print).