Updated CAD Model for Hydra

So I'm about 2-3 weeks behind real-time with my blog postings, but here are some details on our new design for Hydra. We decided to go with a moving gantry because it offered more options for things like toolchangers and other cool technologies we are hoping to add. I also thought that it would offer an accuracy and rigidity improvement over a single leadscrew axis (moving table or single screw moving gantry) because the platform is anchored on both sides instead of just in the middle. Some of our FEA models were showing that if it was only anchored in the middle, the edges would be able to deflect under high loads and limit our attainable accuracy. We also had the budget to afford the extra leadscrew and motor so we went ahead and designed for a 2-leadscrew Y axis. The X axis is mounted on the moving gantry and is relatively straightforward. The X axis carriage is the real novelty piece as is allows for up to 4 Z-axis assemblies to be mounted on it. The Z-axis assemblies are all very modular and we have also designed 2 assemblies; a smaller one for lightweight attachments such as extruders and a larger assembly for something like a spindle. Both these assemblies can be seen in the pictures below

Spindle side showing the XL Z-axis assembly

Extruder side showing one of the smaller Z-axis assemblies with room for a second

Top view showing the build table size

So first off, this design is not finalized. I repeat, this design is not finalized. The biggest thing we need to work on is weight reduction on everything that is moving (X-axis, Z-axis assemblies, Y-axis carriage uprights, etc). All of these parts were modeled using the stock that we were going to make them from, but no weight reduction techniques were used. That is the single biggest challenge we will need to deal with, as currently we are trying to move about 80 pounds of metal using our 2 Y-axis motors. While this may be possible, it would be much more ideal to decrease this mass so that we can achieve higher acceleration and higher transverse speeds.

The main thing we were trying to do was to make a design that would be able to do both milling and high-speed prototyping. This requires great accuracy and strength as well as the ability for fast movements. We have specified some very fast multi-start leadscrews so we should be able to get some good speeds depending on the friction we encounter and how good a job I can do making the chopper motor drivers. In general, speed and accuracy work against each other so it has been quite a challenge to design a machine to work on both of these fronts.

More to come as we are hoping to have all the parts built by the end of the week!