Assignment 10

I am quite excited about this week as this is basically a hugh group project over two weeks. The assignment includes to make a machine that does something. This is not really specified and leaves us actually all choices but it also leaves us all choices! It is always good to have options but on the other side it is then also difficult to decide on a single project as there are so many cool machines! During the global lecture, we were shown really exiting machines like a 3D printable PCB mill or the developments of InMachines to make open source machines and even much more. Would be nice to make similarly awesome machines but that also depends on the group.

This weeks's assignment were:

• Group Assignment
  • Design a machine that includes a mechanism, an actuation, an automation and an application
  • Mechanical Design: Build the mechanical parts and operate it manually
  • Machine Design: Actuate and automate your machine
• Individual Assignment
  • Document your contribution to the group project on your own website

As this weeks assignment is a hugh group assignment, our lab's website hosts the whole project. However, the individual tasks are only summarized on there and the details can be found on our individual sites.

We started the journey of our machine a probably every group did, with brainstorming. We had many really cool ideas and I would also have been excited to make another machine. During our global lecture, we were shown the Apfelstruder, a machine that is similar to a lathe but cuts apples into desired shapes, symmetrically around the rotational axis. I do not exactly know how I came up with this but it was the week before easter and maybe my brain accidentally swapped the apple with an egg and the cutting tool with a paint brush. When I brought this idea up in the brainstorming session, all of us were really into that idea. It also did not seem too complicated and therefore, we selected this machine.

We also found many machine that can already pain eggs, e.g. the Sphere-O-Bot or the EggBot.

Sphere-O-Bot

EggBot

Within this big group project including designing, manufacturing and building an egg painting machines, the tasks must be split such that not everybody works on everything. For the first part of the assignment, the mechanical design, we identified the following design tasks:

• Frame
• Egg Holder
• Translation Stage
• Pen Holder

In addition to these, the hardware of the electronics, i.e. the PCB, has to be developed in parallel being one task on its own. Later, the programming and automation can be developed which we wanted to do as a group.

From these individual tasks, I was responsible for the pen holder. However, in a later stage of the assignment, I also had to take the task of partially designing the frame as one of my group members was unavailable.

The pen holder is the part of the egg painting machine that holds the pen - as the name says. There is only one interface with another design task, namely the translation stage to which the pen should be attached to. To create a reasonable design, I firstly defined some requirements, then present possible implementations and lastly select one to design, manufacture and implement in the machine.

To set the requirements for a pen holder, several aspects must be researched. These include the ideal contact pressure of the pen on the surface of the egg, common egg dimensions and with this the travel it must be able to accomplish. In contrast to common egg painter machines like the Sphere-O-Bot or the EggBot, we decided on using a translational stage instead of a rotation to move the pen from the tip to the base of the egg. Therefore, it is necessary that the pen can travel orthogonal to the rotation axis that spins the egg.

According to a scientific paper, typical egg diameters range from 43 mm to 49 mm and the length from 54 mm to 58 mm. This results in a maximum radius of 25 mm. However, the egg must be attached to a rotating shaft at the ends to make it spin around its length-wise axis. Taking this into account, only the surface in a distance of approximately 5 mm to 25 mm must be reachable by the pen. This results in a travel of 20 mm orthogonally to the rotational axis of the egg.

Additionally, the contact pressure of the pen on the egg's surface must be taken into account. Here, I found another scientific paper, where the contact forces of a ballpoint pen on paper were measured. Here, they found, that the typical forces range from 1.2 N to 2.4 N. For the egg paining machine, I however considered using other pens than a ballpoint pen, e.g. Sharpie markers or other kinds of felt-tip pens. From my intuition, I would say, they require a lot less contact pressure, approximately 0.5 to 1 N.

With the above mentioned aspects, the requirements are:

• Attach to translation stage
• Tip of pen touches the egg shell on the top
• Contact pressure between min. 0.5 N and max. 2 N
• Allows for a vertical travel of 20 mm
• Pen diameters are max. 18 mm

There are many mechanisms which are able to implement the requirements, which are however all loaded but able to move vertically in case a bit of force is applied against the tip of the pen.

The first mechanism that I thought of is a spring loaded pen. In case the tip of the pen has any contact a load would be applied length-wise that compresses two springs on either side of the body. The two springs even out the forces on both sides but need stabilization. For this, circular rods are placed inside of them. Linear bearings on the top will ensure less friction for the movement.

Lastly, the pen is inserted through a circular hole and fixed by tightening a screw that presses the pen into one part of the circular hole. To allow tightening it, a nut is placed in a slot that is traversed by the screw.

Spring Loaded Pen

The second mechanism is similar to the previous one but instead of using a mechanical spring, the loading is achieved by 3D printed springs or flexures. For the design shown in the image, I got inspired by a design on this website, where a CNC pen was equipped with a compliant joint to allow for a linear motion.

Due to very thin strips of 3D printed material, deformation is possible. Here, with a clever arrangement of these deformable strips and thicker, very rigid parts, certain movements are achieved. For the design as shown in the image, a linear motion should be achieved. With the rigid vertical bars on the sides, the movement should be constricted to a linear one while the horizontal thin lines allow for the deformation.

Spring Loaded Pen with Flexures

The pen is again held in position as for the previous mechanism.

The third and last option for a mechanism is slightly different. Instead of making anything deform like a mechanical spring or a 3D printed flexure, this design is loaded by weight. On a vertical standing part, i.e. the mount, a hinge is attached in the bottom. On the other side of the hinge, a lever arm with a pen on its end is attached. The tip of it is simply loaded by the weight of the lever arm. In case more pressure is needed, a screw can be used to attach a weight to it. The slot is also quite lengthy to precisely adjust the pressure.

The pen is also attached to the holder with a screw and a nut tightened onto it.

Weight Loaded Pen

As there are many options but only one can be implemented, one mechanism has to be selected. There are various criteria like simplicity, costs and availability of resources.

The first mechanism with the (mechanical) spring loaded system has one major drawback namely the availability of the right springs. As the travel or the decrompression in this case should range from 5 mm to 25 mm with forces between 0.5 N and 1.0 N, the springs must be very soft and potentially very long. The spring constants should be below 0.2 N/mm. However, these springs are not very common and thus rather expensive. Therefore, I actually decided against this option.

The second option with the flexures 3D printed was really interesting. There are many different possibilities for designing this compliant joint. I actually looked for solutions to implement linear joints online just like this one I mentioned previously. Here, I found a YouTube video, that I found really interesting. Please do not mind the purpose of them experimenting with linear compliant joints but they just present really many different possibilities and some really cool ones as well!

However, also for this option, there is a drawback namely the retracting which is actually valid for the first option as well. When a pattern that should be drawn on the egg is interrupted, e.g. when it does not consists of a single line, the pen must be retracted or lifted from the surface. However, when this is done an the retracting motion does not happen exactly orthogonal to the surface of the egg, the pen would firstly stay in contact while in unloads and by this still draw on the egg. This might destroy the painting. Even though I would have liked to experiment with 3D printed flexures, I also decided against this one.

This only left option number three, namely the pen that is loaded due to a lever arm with a weight. I could only find one minor drawback which is that the movement of the pen would not be exactly linear but slightly curved as a hinge is a rotational joint. However, with a sufficiently long leaver arm (> 10 cm), the motion achieved within 20 mm of vertical travel can be seen as a linear motion.

The first aspect of the pen holder I designed in Fusion 360 was the mount to the translation stage. At this point, I already new, how the translation stage would look like in principle and what components will be used. To generate a motion, a stepper motor would rotate a trapezoidal spindle with a backlash nut placed on it. The nut's rotation is restricted with a linear bearing inside of a block carrier that is mounted onto a shaft. Due to this restriction and stabilization, the nut moves linearly.

Trapezoidal Spindle with Backlash Nut Generating the Linear Motion

Linear Bearing in Carrier on Rod to Guide Motion

For the mount of the pen holder I therefore started with a flat block on the XZ-plane. Then I designed four screw holes according to the linear carrier. Between the screw holes, I also fit a high block, which has the shape of the nut cut into it with four screw holes. The dimensions for these parts are not parametric as I had the exact components already. The only parameter that I used was the one that defines the height between the midpoint of the backlash nut and the bottom of the piece as I did not yet know in what distance the linear slide and the trapezoidal spindle will be placed.

Additionally, I increased the height of the mount in general to be able to position the lever arm above the egg. For this, I drew a sketch on the side and extruded it.

Mounting Part of the Pen Holder

Increasing the Height of the Mount

Then, I created a hinge in the very top on the side of the mount. For this, I again drew a sketch on the side and extruded it onto both sides of the mount. However, this joint must be rigid but without a lot of friction. Therefore, I decided to use two small ball bearings with a certain inner and outside dimension as well as a specific width. Therefore, I negatively extruded this shape from the inside into the previously created shape for the hinge.

Next, I added two arms on the side for holding a servo motor. For this attachment, I got inspired by the Sphere-O-Bot. The arms attach the servo right to the pen holder part right under the hinge. Here, I simply measured the dimensions of a servo motor and designed the arms with the measured dimensions. As the mounting part of the servo however is not completely flat, I had to add somme small 45 degree cuts to the arms.

Hinge for the Lever Arm of the Pen Holder

Arms for Mounting the Servo Motor to the Pen Holder

Furthermore, to allow the screws and their screw heads to fit through the bottom of the piece, I used a tapered cut that made these triangular cuts in the side of the mount going to the bottom of the part.

Lastly, I also added some chamfers and fillets to make the part stronger and more stable. With this being done, I was also done with the first part of the pen holder. Therefore, I could proceed with the second part, the lever arm of the pen holder.

Mounting Part of the Pen Holder from the Front

Mounting Part of the Pen Holder from the Back

For the lever arm of the pen holder, I started with creating a flat block with a circular hole in the front. Through this hole, the pen will be inserted. Therefore, I also attached a pen-fixing mechanism that was inspired by the Sphere-O-Bot. It work with a slot, that is wide enough for a nut that is inserted into it. However, its dimensions do not allow the nut to turn. A screw is then inserted through the nut into the circular hole for the pen. By turning the screw, it extends into the circular hole, eventually reaches the pen and fixes it in position.

Next, I extruded another flat block behind this part with a slot in it. This can be used to attach weights at specific positions to the lever arm to finely adjust the contact pressure of the tip of the pen on the egg shell.

Furthermore, I added a hinge in the end of that block which will sit between the counterparts of the hinge on the previously described part.

Pen Mount and Slot for Pressure Adjustment of Lever Arm

Hinge of the Lever Arm

To be able to retract the pen, a servo motor simply lifts up the lever arm. To do this, the lever arm needs a bulge on the bottom side of the lever arm which can be pushed up. This, I modelled with a sketch on the plane orthogonal to the length axis of the lever arm. Then, I extruded the sketched profile to create the shape shown in the image.

Furthermore, I added some marks to the slot to mark the position of the weight in case it needs to be adjusted precisely. This was done with a sketch on the surface and a negative extrusion into the part.

Bulge for Servo Motor to Push the Lever Arm Up

Adding Marks to the Slot

Stabilizing the Pen

Then, I wanted to add another circular shape for holding the pen to stabilize it even more. As there is no space available below the current part, I firstly extruded a small high box on top of the flat part. Then, I used the previous sketch for creating the circular hole for fixing the pen and extruded it with an offset to the end of the block.

With this, I was almost done with the part. I only cut the hinge to the correct size and added some fillets to stabilize some inner corners and make outer corners less sharp. Please have a look at the images below for the finished model or the lever arm.

Lever Arm of Pen Holder from the Front

Lever Arm of Pen Holder from the Back

I furthermore added some bolts, nuts, bearings and a rotating shaft, a pen and a servo to the design. Most of the components, I inserted by clicking on Insert > Insert McMaster-Carr Component. This opens a dialog showing the McMaster-Carr website. Here, I searched for the desired components and, once found, I downloaded it as a STEP file which inserted the STEP file into the current Fusion 360 design. The 3D model of the servo, I found on Thingiverse. I simply downloaded it and inserted it into the design. As it was however an .stl file, i.e. a mesh, I had to convert it to a body, which I did in the "Mesh" tab under Modify > Convert Mesh with the default settings.

Then, I converted all bodies to components and assembled them. The result is shown below.

Rendered Pen Holder from the Right

Rendered Pen Holder from the Left

As the design generated really customized parts, I selected 3D printing as the manufacturing method. For this, I firstly exported the two parts, i.e. the mount of the pen holder and the lever arm, as .step files. This was achieved by right-clicking on the according body and selecting "Export".

The created .step files can then be imported into the slicer software. I again used my own printer, namely a Bambu Lab X1 Carbon. The documentation of how to use its slicer software, Bambu Studio, I already described in the 3D printing week. Please refer to it for the details.

For the mounting part of the pen holder, I used the "0.20mm Strength @BBL X1C" as I feared the small arms for the servo motor might break off. For the lever arm, I used the "0.16mm Optimal @BBL X1C". For both parts, support structures are be needed. As I had really good experiences with using PETG as an interface between the supports and the actual part, I selected this method also for these parts. During the 3D printing week, I already described how to achieve this. Please refer to this section for the details.

For a higher stability, I decided to print the mounting part and the lever arm on the side. Below you can see how the software sliced the two parts in different angles. Here, PLA is shown in black and PETG in green.

Sliced Mounting Part of the Pen Holder

Sliced Mounting Part of the Pen Holder

Sliced Lever arm Part of the Pen Holder

Sliced Lever arm Part of the Pen Holder

Surprisingly, the print did not take as long as I expected only about 5.5 hours. After that, I took off the build plate and bend it to crack the parts of from it. Then, I exerted slight pressure on the support structure which was enough to remove them. However, on a closer look, I was still able to see few layers attached to it presumably the PETG interface layer. Here, I took a pair of pliers and tried to get under the remaining support layer. This lifted the side up and I could easily peel the layer off. The image shows the peeling on the circular side of the hinge.

Peeling of PETG Interface Layer on the Circular Face of the Hinge

For the assembly, I started with pressing the bearings into their position at the hinge on the mounting part of the pen holder. Next, I inserted the lever arm part between the bearings and out an M5x40 bolt through the bearings. A nut on the end of the bolt's thread kept the bolt in position. Then, the servo motor was attached to the pen holder with two M3x12 bolts and nuts. Lastly, it was mounted onto the translation stage. Firstly, the backlash nut of the translation stage was secured to the pen holder with four M3x20 bolts and nuts. Secondly, the pen holder was fixed to the linear slide with four M4x10 bolts. To finish the assembly and mount, the trapezoidal spindle was inserted through the pen holder and turned into and through the backlash nut.

Backlash Nut Attached to the Pen Holder

Pen Holder with Attached Servo Motor

Pen Holder Mounted with Pen

After paining some eggs with our egg painter machine, it is possible to evaluate the design by means of the requirements.

The first requirement regarded the attachment to the translation stage. This is given with the design as there was no issue attaching the mounting part to the linear slide and to the trapezoidal spindle via a backlash nut. The pen holding part of the pen holder was also able to accommodate for different pen sizes. Furthermore, the design allowed the tip of the pen to draw on the egg shell as the positioning was correct and the contact pressure was within an adequate region. It was not measured but while drawing the contact pressure was not too low and not too high.

The last requirement was regarding the vertical travel. Due to several reasons (see here), the weight loaded design was chosen. This however had one drawback, namely that the motion of the pen's tip is not vertical but rather arched as the hinge only allows rotational movements. For the eggs, that we painted, this design worked well. However, for bigger items, this might be an issue. Here, a longer lever arm might be adequate.

In addition to the curved motion of the pen's tip, the hinge of the design caused another minor issue, namely a backlash in the system. Unfortunately, the tolerances of the hinge were not optimal and therefore, the pen holding part was able to sway slightly back and forth. This was only visible for inclined parts on the eggs when the direction of the drawing was changed while the pen's tip was in contact with the egg's surface. Here, a rod with a diameter of 5 mm could alleviate this issue as the M5 bolt may allow for some play. Otherwise, a spring loaded hinge may also decrease the backlash of the pen.

Approximately a week after the group assignment was started, all of the groups had a rough idea an how their things look like. With these information, the frame was designed by one of our group members. Luckily she was able to finish it before she got unavailable for the second week.

However, things do not always go as planned and the teams, e.g. for the translation stage in particular, had to change the design slightly. Due to that, the frame had to change substantially but our team member got unavailable. Therefore, I took over her part and redesigned the frame to adapt to the changes.

For this design, I also started with defining some requirements and then started designing.

While I started to think of how to adapt the frame to changes that were made, I As always, requirements like an easy assembly, low-cost design and

• Attachment for two stepper motors present
• Suspend the trapezoidal spindle of the translation stage with two bearings
• Limit the end of the trapezoidal spindle of the translation stage
• Suspend the linear rail of the translation stage
• Supply attachment points for adjustable length system of the egg holder
• High stability
• Fast manufacturing process(es)

The last requirement was the one that determined the manufacturing process(es). As time was tight, I decided on using mainly lasercutting for fabricating the frame. Here, the adjustable length system required a horizontal attachment. Therefore, the frame had to consist of a baseplate, that is slightly elevated such that bolt heads or nuts can fit under it to attach the system to the baseplate. Lastly, it had to have some vertical components to attach the motors and bearings to the frame

With the given requirements, the frame already had to have a certain shape. As described above, the frame had to consist of a baseplate with vertical components to it that are all lasercut.

With this general design layout, I started to model the baseplate using Fusion 360. In addition to the material thickness and the kerf, I used mainly three parameters, namely the distance between the axis of the translation stage and the axis of the egg holder viewed form above, the distance between the motor of the translation stage and the fist bearing and lastly the distance between the first and second bearing of the translation stage. These parameters determine the vertical distance between the pair of slots on the top row and the bottom row, the horizontal distance between the top left pair of slots and the middle ones and lastly the horizontal distance between the middle ones and the ones on the very right.

Here, for each mount finger joints with press-fits should be used. Therefore, for each mount, a pair of slots is used. They have different widths as different numbers of material sheets are used for the mounts varying between one and three times the material thickness as defined with another parameter.

Baseplate

After this, I started modelling some feet so that the baseplate is slightly elevated above a ground. For this, I used another parameter called "height" which determines the height of the baseplate above the ground. This simply consist of a extruded triangular shape with cut corners and a slot in the top. With this, this foot can be pressed onto the corners of the baseplate.

However, to further stabilize the baseplate against sagging, I also modeled feet that can go under the plate. These consist of a small block with a heigh equivalent to the parameter "height". To mount them to the baseplate, a bolt must be inserted trough the baseplate and the top part of the foot. Due to a slot on the side of the foot that fits a nut without it being able to turn, tightening the bolt also fixes the foot in place.

Next, I considered modelling the vertical panels for mounting the motors and bearings. However, simply using finger joints for mounting them onto the baseplate is potentially very instable. Therefore, I designed some angle stabilizer so that the mounting panels are fixed in an upright position.

Foot for Corners of the Baseplate

Foot for Attachments to Bolts Though Baseplate

Stabilizer for Vertical Mounts

With this stabilizer being modelled, I had to add some holes for the bolts with which the stabilizers should be mounted to the baseplate.

Then, I modelled the mounting panels. For the motor of the egg holder, the panel was designed using the kerf and one additional parameter, namely the height of the motor's axis above the baseplate. At this height, I drew a circle with a diameter of 23 mm. In a square with an edge length of 31 mm around it, four smaller circles were created with diameters of 3.5 mm. This created the pattern necessary to mount a NEMA 17 stepper motor to it. Lastly, I created a rectangle around it with its bottom side in a distance of the height parameter.

For the other motor mount panel, i.e. for the translation stage, I repeated these steps more or less. However, the height of the center of the motor was defined but yet another parameter.

After this, I also created the panel for mounting the bearings and the linear slide. Here, the linear slide will only reach from the first to the second bearing on the trapezoidal spindle. To fix it in place, a sheet of the material is placed on both ends. To suspend it, another sheet of material is placed on the inside of the outer sheets that have a circular hole where the shaft can be inserted to. Simultaneously, the bearings must be suspended with two sheets of materials as they are rather thick. Furthermore, the end that is not connected to the motor should be closed as well. Therefore, the following panels must be created, starting after the panel of the motor: Firstly, two panels must suspend a bearing, from which the first one is closed for the linear slide but the second one has a circular hole to suspend it. Secondly, three panels must be used in the end. Here, the first two panels suspend the bearing for the spindle and the linear slide. The last of these three is closed for both the spindle and the linear slide. With this in mind, I created the panels with again parameters for the heights of the axis of the spindle and the linear slide.

Lastly, I created the finger joints and the attachment points for the stabilizer of the mounting panels. The image below shows how all mounting panels look like. Here, the one in the bottom left is for the motor of the egg holder, and the other four for the translation stage.

Baseplate with Mounts for Stabilizer

The last design part was the attachment of the adjustable length system of the egg holder. For this, I again created screw holes on the baseplate. I already knew the pattern from the adjustable length system and therefore only used one parameter, namely the length-wise distance of the first screw holes to the mounting panel.

Baseplate with Mounts for Adjustable Length System of Egg Holder

Lastly, I wanted to assemble it. For this, I firstly copied the feet, the stabilizer and some of the mounting panels. Then, I created components from all bodies and gave them certain appearances. For this, I pressed the key "A" to open the appearance dialog and assigned the material "ABS (White)" to all parts, that should be 3D printed, i.e. the feet and the stabilizer, and the "MDF Board" to all lasercut parts, namely the baseplate and the mounting panels. Lastly, I used the "joint" tool by pressing the key "J" to assemble the pieces accordingly. See below how the design looks like assembled.

Fully Assembled Frame

From all parts of the egg painting machine, the frame was the last design that was finished. Therefore, I was able to insert the other parts into the design and assemble everything. Below, you can see how the complete machine design looks like.

Fully Assembled Egg Painting Machine

In total, I was happy with how everything looked assembled with the current values of the parameters which is why I proceeded with manufacturing the parts for the frame.

For manufacturing, two processes were used, namely lasercutting and 3D printing. For the latter, the bodies were exported from Fusion 360 as .stl files using the tool under File > 3D Print. Then, these parts were imported into the Prusa Slicer software. The slicing settings were the default one using PLA and the "0.15mm QUALITY" profile without support structures. Below, you can see how I placed the parts on the print bed and how the slicer has sliced the parts.

Sliced Feet

Sliced Stabilizer

It took about two hours per print job. After that, I removed the parts by bending the metal print bed.

3D Printing the Stabilizers

For the lasercutting, I firstly checked in the Fusion 360 design whether the parameters of the kerf and the thickness of the material were correct. As I chose 4 mm plywood as a material, which was a material that we used in our groups assignment on lasercutting, I did not have to find out the optimal settings and the kerf present for them. Therefore, I simply transferred the value of the kerf, i.e. 0.17 mm, and the thickness of 4 mm to the design of the frame.

Then, exported the needed faces of the lasercut parts in Fusion 360 with the Shaper Origin extension as .svg files. From there, I gathered all .svg drawings of the mounting panels in a single file. This resulted in two files, one for the mounting panels and one for the baseplate. Both were opened on the computer connected to the Epilog lasercutters in our lab.

Firstly, I lasercut the mounting panels. For this, I pressed Ctrl + P in the Inkscape file to "print" it. As the printer was selected to be an Epilog lasercutter, the vector graphics was opened in the Epilog lasercutter's software. In contrast to the lasercutter assignment, I used the smaller lasercutter, the Epilog Fusion Edge 12. Therefore, I firstly selected this as the desired machine.

Then, I selected a vector cut for all parts with a speed of 17, a power of 90 and a frequency of 20, the settings that were found to be optimal for 4 mm plywood during our groups assignment on lasercutting.

I furthermore selected the "Plunger" as the auto-focus tool and lastly positioned the parts on the lasercutter's bed in the software. In contrast to the bigger lasercutter, this one has a camera showing the bed. Therefore, instead of jogging the head of the lasercutter to the desired position, the parts are positioned accordingly. The image below shows the bed with the material placed on it and the mounting panels.

Settings for the Lasercutting

Camera View on the Lasercutting Bed

Lastly, I turned the lasercutter on, pressed "print" to send the lasercutting job over to the machine, turned the extraction system on and started the job by pressing the according button. After it, I repeated these steps for the baseplate with another sheet of 4 mm plywood. The duration of the cutting of both jobs did not exceed ten minutes.

Once, all parts were fabricated, the assembly was easily done. Firstly, the mounting panels were inserted into the according slots on the baseplate. Then, their position was fixed with the 3D printed stabilizers. Here, M3 bolts in various lengths with nuts were used to screw the stabilizers to the panels and the baseplate.

Next, the feet were mounted. For the feet on the corners, the press fit was adequately tight such that their position was secured. For the feet under the baseplate, an M3 nut was inserted into the rectangular slot and positioned such that their circular hole aligns with the hole of the 3D print. Then, some nuts of the stabilizers under the baseplate were replaced with the nut in the feet. During the positioning of these feet, it was aimed for a distributed placement.

The image below shows already a partially assembled machine including the egg holder, the linear slide of the translation stage and partially the pen holder.

Assembled Frame and Other Parts of the Egg Painting Machine

Once the frame was finished, assembled and in use, an adequate evaluation of the frame design is possible. There are several aspects that can be discussed with regards to the requirements.

First of all, several requirements regarded the possibility to attach other components to it. This functionality is given. Also the manufacturing process in general was really quick, including only few minutes for the lasercutting and about two hours for the printing with two in parallel. The assembly was easy and straight forward by using bolts and nuts. For this, the manufacturing was precise enough to guarantee a good fit.

The remaining requirement was regarding the stability of the frame. It must be mentioned that the vertical mounting panels that are attached to the baseplate via the 3D printed stabilizers worked really well. No movement of the panels with regards to the baseplate were possible. However, the stability of the baseplate could be improved. When the machine is carried by holding onto the baseplate, the material appears rather fragile. Maybe a second sheet of material for the baseplate would have been a better option. Otherwise, a design similar to earlier versions of the Egg-Bot would be a better option for stability. However, in my opinion, this would have been a more complicated design and potentially more difficult to assemble. Also, with this design, the adjustable length system could not be attached to the frame.

In total, the design appears a valid option with the given requirements.

• Pen Holder (.f3d): Fusion 360 file of the pen holder
• Frame (.f3d): Fusion 360 file of the frame