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New Tool Changing System

A project log for Multitool 3D Printer - Blackbox

Blackbox shifts 3D printing towards a multitool manufacturing robot.

Marc SchömannMarc Schömann 08/24/2019 at 21:272 Comments

I'm very proud showing the new tool changing system. Mainly because many new ideas came directly from the community. The new system breaks with a lot from the previous version (which is why I have to redraw almost all outline representations), but this effort is well worth the trouble.

X-Carriage

The X-Carriage now carries only a motor and mainly consists of an aluminum plate. This plate is connecting the linear bearing with the motor and tool changer. The motor attached to the x-axis mates with the Bondtech style tool. That way, only one stepper is necessary for all the tools, which is a massive advantage over other tool changers. It´s similar to the Makerbot smart extruder system, where the tools can be removed from the motor. Bondtech is the perfect platform for this because it already decoupled the drive gear from the motor with it's 1:3 reduction. The motor gear might need some small changes in its geometry to make sure it docks smoothly.

Docking System

Besides the X-Carriage, Blackbox is now using a different docking system for accounting the additional tool weight and ensuring a trouble-free usage. I was using a magnetic system along with a bent wiper, which works well for small tools. But it always was a compromise to gain fast results. The next version will use a system first introduced by Joshua Vasquez. It utilizes a cable-driven mechanic, which I adopted almost wholly. This mechanism is a remote locking system, which allows using a big servo or stepper motor away from the moving axes. The only changes are the bearing arrangement (double-flanged bearing), and I will use shifter cable housing, which is self-lubricating and bendable. 

Direct driven tools

The tools are essentially a shrunk-down Bondtech BMG extruder with additional kinematic coupling. A passive cooler cools the tool, but it can also be air-cooled! Yes, that's right, air cooling will significantly lower the entry hurdle to build this printer. But the best about it is that Blackbox can now utilize up to 6 direct driven tools, which means flexibles can be printed in any tool! The external motor also opens up a vast scope for other power tools, whether it be a syringe tool, a rotation axis, or additional z-axis.

Toolbank & Parking System

The tool bank is now cooled with a single 15x3mm aluminum strip which cools all tools together. The parkin system mostly stays the same; it's just arranged a little different because the extruder gets now picked up by the Y, not the X-axis as it was before. Apart from that the nozzle still gets wiped with a silicone sheet when it's picked up or off. When it's parking a small height adjustable silicone cube blocks any leakage.

Waiting for Parts

While I'm pretty confident that the rebuild will go well due to the great detail in the Fusion Files down to the screw, I'm currently waiting for crucial parts (Chrome steel balls and shafts, Fans, Linear Rails, Bondtech gears). But I already started prototyping the tools and x-axis with PLA.

Summary

Drawbacks

More Custom Parts

The new coupling mechanism uses more parts which need to be gathered and assembled. The lock bolt is an additional custom part.

Advantages

All direct driven tools

The previews system with one direct and x Bowden driven tools was a compromise. Bowden can work, but they are annoying, especially in a tool changing scenario due to the additional leaking. Bowden extruder also limits the maximum speed when used with pressure advance systems.

Easier Electronics

It was necessary to use one of the few boards which support multiple extruder and lots of stepper driver to power several tools. Now only 5 Steppers are required to drive the whole system: one for XYZ each + one extruder motor + one lock motor. Those with high-end boards can use the stepper for three-point z-axis.

Rigidity

X-Carriage is now very rigid and combines many crucial features in one part, lowering the complexity of the surrounding components

Lightweight

The X-Carriage along with a tool is still lightweight compared with the previous solution

Modularity

With the stronger coupling and the blank carriage, tools can be adapted easily

Fewer Custom Parts

This sounds confusing, but with air-cooling fewer custom parts are necessary

Discussions

Carlos Echenique wrote 08/25/2019 at 22:40 point

How are the electrical connections for the hot-end handled? What are the intricacies of negotiating toolhead swaps when slicing the object to be printed?

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Marc Schömann wrote 09/01/2019 at 11:24 point

Every tool has two cables for the heater and sensor along with the PTFE hose. The Slicer workflow is pretty straightforward, you just add a activate and deactivate G-Code, it contains some lines of code which pick the tool up prime the extruder and return to the print.

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