Design and 3D print a robotic arm with fusion 360 and the FABtotum

Today we take a look at a simple but interesting project that made a few months ago. As the title implies, we designed, printed, assembled and tested a 3 axis robotic arm.
Parametric CAD and 3D printing allowed to do almost all of this in a day or so.

This is part 1 of 2. The second part comes in next week. Let’s get into it.

We started by designing a modular arm, one that could be printed in multiple copies and bolted to make the primary arm.
This design was first used as a proof of concept on 5 axis machining we did back in 2016.
The objective here was to create a very simple, easy to print and rigid structure that could be used for simple object manipulation.
The structure for it won’t need to be extremely stiff but we designed the arm as stiff as possible anyway.

The arm ends with the motor holder on one side (standard nema 17) and a standard FABtotum chuck on the other. So that you can have compatibilty with the 4th axis chuck we designed a few years ago. (This was designed in fusion 360 too).

With all the parts in place it was time to export them to STL and into a slicing software. For this project we used Simplify 3D, but any will do.
We filled the build platform with all the parts needed to make two axis (i.e: two arms!).

We used the Print Head Pro with our Orange PLA filament. Nothing too fancy but pleasant nonetheless, and reminescent of industrial heavy duty machinery.

To 3D print the parts we took advantage of our small industrial cluster of FABtotum 3D Printers, a set of internet-connected units we always have ready for production, prototypes and personal projects.
We connected using the my.fabtotum.com interface and uploaded the updated design files.

The print itself was made without batch controls (all parts at the same time). This allows to use the entire build surface since parts can be as close as possible between them.
In the next images you can see the build plate extracted to show how much space was still available should we wanted to make a fourth axis as well.

Once removed from the build plate, the parts were assembled with bolts seaparately.

On the third image of the previous row, a variant created with the 4th axis chuck attached.

The arm will be mounted on a single motor (axis A) that will rotate around the vertical axis. The other two motors will respectively lower the arm and tilt the forearm.

With those 2 orange arms assembled we proceeded bolting the two together, making the B and C axis respectively.
The range of motion of this arm isn’t comparable with 4-5 axis robots but it’s enought to do some simple pick and place of objects.

This will indeed be the application we will implement in part 2.
In Part 2 we’ll create the base and the forearm in fusion, design and build a simple electromagnet so that the arm is able to pick up metal objects from a container and deposit them in another.

There are many uses for 3D printing in the industrial field.
One way to do so is by using directly 3d Printing, i.e. directly making parts for your products.
Another way to use 3D printing “indirectly” is as a mean of supporting manufacturing and assembly efforts in the production line.

In fact, one of the easiest ways to incorporate digital manufacturing in the production line is in fact by using 3D printed jigs and fixtures to optimize the production workflow.

Another example is the one used as a fixture  here: a support for assemblying a complex object.
A fixture is then used to place the part in place and  assisting the worker in the assembly phase.

just like the other example above the main advantages are the following:

• Parts fit only their designated spots (reduced errors, misplacements)
• Quickly populate the assembly with parts (efficiency boost)
• Parts are correctly oriented,spaced and can be fastened/glued togheter with no human error. (improved precision)

When designing a fixture a lot of things should be taken into consideration:

• ergonomics: how to make the fixture ergonomic to handle/use
• tolerances
• assembly procedure

Thankfully 3D printing allows to iterate multiple versions of the same jig/fixture in a matter of hours so that changes can be made.

the Jigs and fixtures projects can be saved and kept in one’s own archive to be used when needed.

Jigs are used to fix the object to work on from moving relative to the tool.
In this example we’ll take a look at how design, manufacture and deploy a jig for retooling of a plastic case part.

The problem that was solved with 3D printing was to hold a piece for CNC milling on a ABS plastic case.
The Jig was created with a CAD modeling tool and tested in a CAM environment in order to plan the gcode sequence.
As a result all positions and offsets (including home position) were accounted for directly in the design phase.

Since the design phase is relatively quick in a CAD environment, more time can be dedicated to iterate the design phase with a physical prototype.
In this case the position of the part and the snug fit we wanted to achieve was essential for this kind of milling processes on an high number of pieces.

Finally, as the images shows, the CAM itself can be simulated with the digital design itself to keep quality,safety and usability considerations as an high priority concern.
While not this is the case in this example, The jig itself could be even considered sacrificable during certain operation, so that a part of the jig itself is milled to free the part or to reach certain spots.

Some final considerations & conclusions on the topic are the following:

• 3D printing makes creating Jigs and fixtures easy and inexpensive
• Different 3D printing technologies can be combined with machined parts to make complex fixtures with parts in tolerance.
• With 3D printing jigs and fixtures can be considered for a very wide range of operations both manual and automated as well as hybrid operations on the piece.
• CAD and CAM design of a Jig and the related CNC machining operation can be combined in one design environment and tested in few hours.
• 3D printing jigs allow to iterate multiple designs in house.
• Jigs designs can be stored and 3dprinted when and where needed.
• Sacrificable fixtures can easilby be introduced as much as permanent ones.
• jigs and fixtures allow control of the process, precision as well as safety and ergonomics for the operator.
• jigs and fixtures are responsible for a sensible reduction in manufacturing costs such as man hours and defects.

In order to use Palette+ with FABtotum Personal Fabricator we suggest to follow these steps.

Mosaic Manufacturing has prepared a very informative article on Palette+ first steps setup. We would advise some comments on how to apply this generic setup to FABtotum Personal Fabricator:

1. Position the Scroll Wheel with Velcro square on the left side, near the top/center.
2. Instead of the provided clip for direct drive extruder you want to use the adapter that you’ve printed and installed over the Printing Head PRO. Insert the Palette+ teflon tube in the adapter. Make sure it does not move out by itself.
3. We suggest to use the latest calibration model that is provided by Chroma when you start its Calibration guide (instead of the Calibration Cube offered to download from the website). Use Cura 15.04.6 to slice the model (here is the Cura profile for using Palette+). Save the gcode and load it to Chroma. Select the filament type and the color, then click Save for Printer. You are going to have the file to copy to Palette+ SD card, and the modified gcode file to upload to Project manager in FABUI. After that, preheat the Printing Head to 200°C, take out Palette+ teflon tube from the adapter clip, start the multicolor splicing, then hold the magnet so that the material goes on in the teflon tube. Once it exits the tube, release the magnet (Palette+ should stop generating material and wait for you to load material in the Printing Head), pull gently about 12 cm of the filament from the tube (Palette+ will generate some material, try not to pull too much), insert the filament in the Printing Head PRO using the lever on the back of it. Then release the lever, insert the Palette+ teflon tube in the adapter clip and use Jog in FABUI to extrude material until you see the change in color, as described in Chroma. Try to extrude small quantities of 1 mm per time so that you achieve maximum precision of the calibration. Honestly, it requires some patience. Once you see the extruded filament to change color, stop extruding, follow the instructions in Chroma and Palette+ screen. After the print you obtain two values to insert to Chroma profile. You may want to import the profile that we provide here.

Using Palette+ for 3-material printing with PVA as support requires a little bit of fiddling with cura.

Mosaic Manufacturing offers a very useful device that allows to print using up to 4 different materials, with just one extruder. That provides a great possibility for 1-extruder printers to create not only multicolor objects, but also to use water-soluble material as support for the overhangs and bridges. After the printing such object is being post processed with water so that the supports are gone and the pure model remains in perfect shape.

However here is a problem that can arise during the print of a 3-color model with the 4th material as support.

After configuration of Cura according to manual (that is very informative, in fact), we can load a multi-color model that consists of 3 different models:

In Cura 15.04.6 we should select each model and choose “Dual extrusion merge”, which makes Cura set a different extruder for each model, keeping them together though

Good, we have 3 models associated to 3 different extruders. But once we decide to have the 4th material as support, Cura 15.04.6 does not allow to do it (starting from Cura 2.x generation there is a setting to choose the proper extruder for the support material). In fact, it is possible to choose only between the first and second extruder, but that means we associate the support and the model to be printed with the same extruder (the same material):

In case we want the support to be water-soluble we experience the following situation where one of the models is going to be eliminated together with the supports:

One way to solve this problem is to create a tiny model, associate it with the support material and then merge it with the other 3 models. I created a simple rectangle 5x5mm large and 0.2mm high, so that it will cause only the first layer of the print:

Cancel all the models loaded to Cura. This new model named tri_support.stl should be loaded the first:

Then load the three models for printing and merge them as before. Check that the Support dual extrusion is set for the first extruder.

After saving the gcode and loading it in Chroma, we obtain thew following result:

The soluble material is now associated only with the tiny rectangular and the supports, that will dissolve during the post processing.
The FABtotum and the Palette+ can both be now initialized with all the corresponding filaments loaded and the print launched as usual.