Questions

Questions, we get questions …

Question: The Visible Robot: Why is it so big?

The Visible Robot was designed to be a workstation rather than a standalone robot or 3D-printer. It was designed to accommodate the things that a workstation would require: parts presentation devices—like a tiny conveyor, or a carousel; or tool racks from which it might select the tool or toolbit for the next task. It might even have one or more robots on its periphery to do pick-and-place work between it and a neighboring workstation.

To accommodate these things it has to have a fairly substantial “footprint.”

Question: What’s the true working envelope?

A very astute question.

The true working envelope is the total area that an end-effector—a 3D-printing nozzle, or a router bit, or a drill—can access for work. In the case of a cartesian machine such as the Visible Robot, the end-to-end limits of travel are further limited by the sizes of the axis carriages and even the size of the end-effector.

Assuming that the end-effector acts on a point—as is roughly what a 3D-printer nozzle does, we have to subtract out the sizes of the ‘X’, the ‘Y’ and the ‘Z’ carriages.

The ‘X’ carriage of the Visible Robot is about 75mm (3”) wide, so instead of the 450mm (17.75”) distance along the ‘X’ axis, the actual working distance is only 375mm (14.25”). The ‘Y’ carriage is about 100mm (4″) long. So we have to subtract that out from the 690mm (27.25”) ‘Y’ base_corner-to-base_corner distance. We’re left with 590mm (23.25) working distance along ‘Y’. ‘Z’ is the same story. But on the ‘Z’ axis there are any number of end-effectors that can be put to work there. Let’s take the Finix Extruder mechanism as an example. The height of this device is about 110mm (4.5”). So subtracting out this distance where no work can be done, from the distance between the workbed and the carriage above it—230mm (9”), we get 115mm (4.5”).

So, the short answer is: the working envelope is 37.5cm x 59.0cm x 11.5cm = 25,400cm3.

Or, in inches, that’s 14.25” x 23.25” x 4.5” = 1490in3.

Question: Why three gantries on the Visible 3Bot? Isn’t one enough?

The answer depends on what you’re doing and to what extent you are “in production.”

If you have a large format machine—like the Visible Robot—and you’re only doing 3D-printing on it, well, you can print some pretty big parts! A pair of shoes, for example.

But you may have noticed that an awful lot of parts are small. All the printable parts for the Visible Robot itself was printed one of the smallest 3D-printers available–a Printrbot Jr.

The point is that with the large format divided up into three working areas, you can use that large format to do a number of jobs at once. If you are 3D-printing in all three areas, you could put several parts in each area—even after taking into account the extra space taken up by the ‘Y’ carriages, there is still about 3150cm3 (200in3) of working envelope for each of the three. That’s a lot of space for things to get done!

Looked at another way, some number of smaller machines could do the same jobs in the same amount of time, but they would 1) take up more space, and 2) cost more (with three gantries, you’re taking advantage of using one set of shafts and bearings (‘Y’) and the base for all three gantries).

If the work you want to do is varied; say you want to do some laser etching, some drilling, and some 3D-printing, you might setup each gantry with the tooling to do those things and get on with it—all at once!

Question: For such a big machine, why is the ‘Z’ axis so limited?

One of the big issues for a machine-tool—even a desktop machine like the Visible Robot—is stiffness. A stiff machine is very likely to be more repeatable in its movements and suffer less from early wearout due to parts becoming loose from repeated accelerations. It’s also likely to be faster. With a gantry-style design, there are large “moments”—torquing forces—acting on the vertical ‘Z’ due to horizontal accelerations. Keeping the ‘Z’ axis fairly short limits the effect of these moments–though they are still at play. The compromise is to have enough travel on the ‘Z’ axis to be useful, yet keep it stiff. An alternative, is to let it be tall, but keep the accelerations low.

Question: The Finix 3Struder can mount three extruders!?! Why?

The marketing guy might say “Colors! Pretty colors!” And I’m OK with that, but I think there’s more to having multiple extruders than colors.

There is, of course, the different size extrusions that can be made—say a fine one for the shell, the exterior; a very fine one for details; and a thick, fat one for infill.

But I’m more excited about the different materials that might be used to create sophisticated objects.

It used to be that you printed in ABS or PLA and nylon was an exotic. Now we have new materials coming out all the time: flexible, semi-flexible, polycarbonate, resistive, conductive, translucent, carbon-filled, glass-filled. It seems the list grows weekly.

How about making something stiff on the inside, yet soft and flexible on the outside—like a prosthetic finger maybe, complete with a polycarbonate fingernail?

Too, I’m taken with the idea of laying down the equivalent to a multi-layer PCB by sandwiching conductive traces between insulative traces. Maybe print some resistors to go along with it!

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