The Linear Guidance System (THE ARTIST)

Play "Can You Feel My Heart by Bring Me The Horizon" to see this post. 

Its a big read this post*, as big as my love for this system. At least 12 minutes read. 

(*Yes, I wrote that in reverse, I write in the way I talk here)

Again, an engineer of the highest order has designed something so fool proof, it's simply world class. 

The only sub assembly of THE ARTIST which took 3 months to design, gather the different parts, manufacture and test. 

This sub assembly took 1 try. I was not allowed to fail on this one. It was expensive. really expensive. took around 450 euros to test different motors and come up with the best control. 

This system is divided into way too many parts. They were all hand manufactured. The post processing was just insanely time consuming. We will be taking about each sub assembly with emphasis on the parts that were designed to standout. You are gonna see me talk a lot in the next 15 mins, trust me. 

This was designed with an engineer's scale of 12

12sS

Yes. The linear guide is rated for a working mass of 60kgs instead of 5kgs. I use my absurd engineer's scale of 12 which I call 12sS - 12s Scale - twelves Scale. But why? such waste of resources? no its becasue you all are so busy specializing robots that they break on shocks. My robots dont break. They are never going to be mechanically obslete, they are made to withstand shocks and human error. imagine some kid who's fascinated by this system. he wants to hop on the linear guide. He won't be allowed to but he can move around on this if he/she is sneaky enough. There's only two biological genders btw.

Back to the 12sS. It also stands for other purposes as well. It enables addition of extra intuitive features which can be an after thought. For example, ohh the robot on the platform is outdated, what do we do? put a whole cobot on it. What does it weigh? 12kgs? ohh you know roland designed it, so its good for 60. Well be careful, the table's not deisgned by him though. 

Animation And 3D View At The Same Time!

Below you will find an animation - interactable in 3D view to show how different parts work mechanically. This animation took a lot of time to make, I had to learn blender from scratch. Really really annoying good stuff. So proud of this animation! Hell yeahhhhh. 

The motor is rotating at around 9RPS and the linear guide is at a speed of 90mm/s.

An Interactive 3D View of The System Assembly - Animated

Here we go, lets start off with the the gantry system. There's 7 topics to discuss below. if you are driving a car at this very moment, be sure to drink... water as well, clearly you are insane. 

१| Linear Guide Gantry 

This gantry system is a very commonly used and available system but it doesn't mean it's a drop in solution. The L.G.G is composed of two linear rods with 4 linear bearing along with a ball screw and nut at 10mm pitch.

It's fast but not without my specially found nema 17 along with the over volted driver. The pitch is 10mm which means to cover a 1000mm distance it would require 100 rotations of the ball screw, it's a lot. Really not that easy for a stepper motor to accelerate and deaccelerate covering 1000mm under 2 seconds but well i made it,

The thing is that the gantry system is not only powered by a stepper motor, its powered by a stepper motor which is not even constrained anywhere. THIS WHOLE DESIGN IS MODULAR. So on top of it being completely disassemble able, its accurate and really fast. You can grab the stepler motor and take it apart from the gantry under a second. Yes. Yes. Yes  it's crazy what i did back then. Ohhh my god. What is this magic i have created. 

Other than the simple linear shafts, ball screw, there's a main plate on the 4 linear bearings. Its a story on it own. Look for it below. 

The gantry system was very difficult to align. The 20 bolts holding each shaft was incredibly difficult to tighten and took a few tries. The washer setup was extremely ingenious. Roland makes crazy good stuff, I can't believe i know a guy like him. Basically what he did was he took 2 normal flat washers and put a petg squisable washer in between them and then tightened the bolts on top of it making a permanent anti vibration constrain, making sure the linear guide when travelling in a case won't ever be loose and the person who will be using it on the go won't ever have to touch a single tool to diagnose it. 

Besides the anti vibration feature on the BOLTS THEMSELVES. Roland actually went ahead and cut rubber sheets into small little custom pieces for the linear bearings, punched holes in them and THEN combined those sheets with 95A TPU printed shaped dampeners, making the linear bearing withstand extreme shocks in case the robot on top of experience sudden weight shifts. It also protects the assembled ball screw im the whole assembly. 

Below there's an interactable 3D view of the gantry system animated to work as intended. The dampeners on the linear guide is highlighted in actual color, rubber(Brown) and TPU (Whitish Yellow).

Gantry Assembly in 3D and Animated

२| Motor System

The motor system as mentioned above was designed to be modular. Fully replaceble and removable within a second or two. 

How was this important? Well Henry wanted the whole system to be taken apart within a few minutes and packed in a flight case. In this case the most vulnerable part is the motor to ball screw connector. It could be damaged in an instant. Ohhh why not just remove it every single time? Nope not possible the motor must be contrained extremely well to make sure the ball screw rotates accurately and precisely, otherwise the vibration from the connector will break both the motor and the ball screw assembly. So? Roland comes to rescue. He didn't constrain the motor at all. Instead he designed it in a way that the motor sits on a printed piece of PETG along with thick rubber feat that absorb the vibration and stop the motor from twisting on itself. The connecter itself had a really thick tpu piece which absorbed all the imperfections in both X and Y rotational axis. 

So, the motor was as mentioned NEMA 17, a NEMA 23 was tested, it was too powerful and too heavy. I hooked a longer NEMA 17 for testing as well, it was very powerful as well. A pancake NEMA17 was chosen and it was found that at 32V to its driver, it was able to achieve 150RPM under 7 kgs of load on the main plate. EXTREMELY FAST. It was tested a few hundred times with no wear and tear. 

Below is a very simple sub assembly of this motor system with its shaft animated to show rotation along with the connector that connects to the ball screw. 

Motor System in 3D and Animated

३| Aluminium and PETG Frame

Well well well, here we go with the most time consuming part of this project. Btw, its not just blocks of metal and plastic supporting the gantry. Roland doesn't do normal things ahahaha. 

The aluminium blocks, there's two of them, on both of the extreme ends of the frame. There's 4 PETG blocks in the middle, but why not just another piece of aluminum, well well well because I can actually engineer things.

First off, how did I get those blocks? I had this friend called "felix the chat" who strangely and randomly one day offered me the blocks and after thinking about the compatibility with my project, I took up his offer at 20 euros but for some reason when I went there to get it, he raised the price to what it was on the internet the first website he saw. It was still cheaper than what I was getting on the internet so all good. Also he gave me an invoice ahahahahhaha. What a guy. 

So how come this combination? Well those aluminum blocks are light but not light enough with all the gantry and other stuff attached. Hence light weight PETG is used to support the weight of the load on the main plate when running. How can you be sure of making the PETG and Aluminum has the same alignment? THEY DON'T! THEY CANT HAVE! The middle part with the PETG blocks dont touch the ground much because the gantry is tightened on either side hence its a bit concave, meaning the middle part is lifeted by 0.05mm to 0.075mm upwards under no load, however its pushed down to the ground completely under 5kgs intended load. 

This seems unnecessary? No its not! This system is meant to be carried around, again if the middle part is not designed light, it will bend the gantry up and down much more and the ends would end up never touch the ground introducing permanent curvature to the long rods. It's better for the gantry to be bent on the ends with the heavier blocks as that can be self healed just by running the main plate over and over with a 10kg load if needed, this cannot be done with aluminum blocks fixed in the middle and the PETG blocks on the ends.

There's more to it, the PETG also acts as absolute alignment blocks as they are 3D printed to be perfect and since the aluminum blocks were processed by me manually the holes are ever so slightly not aligned, the 3D printed blocks fix it by pre aligning the linear rods perfectly for it to be later contrained absolutely fantastically to the aluminum blocks. So yeah this design isn't made in a day. It was thought of again and again and again. Every single thing on it was thought of under extreme intoxication of whiskey and cigarettes. Ohh man, I smoked hard. Good stuff it is on the roof of studio de roro, don't tell my mom tho <Side eyes smiley>.

So that's the engineering on it. Now the aesthetic part. Ahahahah there's a lot. THERE'S A LOT. First the color, Yellow and White. It's destiny, 'it' told me to use those colors for this project. The aluminum blocks were painted with dark grey primer and the top and sides were painted with triple thin coats of white metallic matte paint. But before they were painted, I hand sanded them by making custom sanding blocks of 240, 400, 600, 800, 1600, 2500 sanding paper. It took a long time for all sides to be perfect. All 6 + 6 sides. Such a crazy time I used to live in. Why custom blocks? Unnecessary? Man you do some unnecessary stuff? Bruh I don't, "Felix the chat" sold me bent blocks and marked the bend with arrows. It was the slightest bend, however was considerable because this assembly belongs in a museum so I had to make it perfect. Hence, the custom blocks. These blocks were half as long as the aluminum blocks and they were used very very lightly against the blocks so the blocks could be sanded on the top against the bend, removing it. This way the top side if sanded correctly would be dead straight for the rods to be perfectly attached.

Vibration dampening again? Yes Monsieur/Belle demoiselle, beneath all the blocks there's rubber feat hand cut on all the keypoints. Just look at the models later to see what keypoints. Basically all the points of mechanical attachments and sources of potential vibration. They were also used to correct bend in the parts if any still left. 

Now the manufacturing part of the whole thing:

Starting of with the PETG blocks, they are printed solid, mensing 100% infill with the holes in horizontal expansion of 0.05mm and there's a nut hidden beneath each hole. 

The aluminum blocks as mentioned were sanded, primed and then painted. They were first drilled with all the required holes manually by marking all the holes with a a4 printed paper glued to the aluminum block. Then they were tapped with relevent ISO threads. That's it. 

Below are the three different blocks involved. Yeah the two aluminum blocks were different. 

Frame Assembly in 3D

४| Main Guide Plate 

This one was not a joke. It was stressful even for me. The chances of failure was so high on this one. The M.G.P. was no piece of red velvet cake. It was really hectic to make this. I tried 3 different versions of it. The final one as seen had all the features and was aesthetically pleasing as well.

This plate was designed with the following design aspects in mind:

~ Visible Bolts

~ Easy access to the linear bearing tightness screws. 

~ Parametrized patterned hole sets (2 sets in total) for future attachments. 

~ Rigid for 5 Kgs intended load in PETG. 

~ Easy shock absorption. 

~ Square format. 

~ Easily replaceable and fixable.

~ Printable without supports and be a single part.

~ Limit switch carrier. (Wire routing inbuilt)

~ Must have perfect ISO holes with pitch in consideration for fantastic drop in linear bearing alignment. 

With these aspects the main plate was designed very quickly and assembled in only week. The main challenge was setting my 3D printer with settings to avoid warping on this part. That was no easy task. On top of the plate being at 90C, the printer was kept infront of the heater for spatial heating around the part. The filament was extruded at max 40mm/s. Which was very slow however it was done at 265C way higher than needed but it was for the shiny look of PETG. There was no stringing as the rememant of the extrusions was instructed to be filled in the infill at Z change. 

Designing wasn't all that difficult. Designing it to be printable was. The warping was a nightmare. You can't have a warped main plate. It will break the gantry instantly. It must be perfectly flat. The parameter setting was to be perfected and at that time I was nearly 3D printing for 4 years, so I was an extreme expert in making prints stick to the bed. Also a very slight bend is allowed however only if the bend is pusing the linear bearing apart. Meaning a convex, this can be instantly rectified with the bolts tightend diagonally. So with this in mind it was printed with the top side of plate against the printer bed. 

Yeah, each part of the assembly was a very time consuming piece because I think of each aspect starting reciprocally as mentioned in my previous post. I wasn't paid by the company just to sit around and make common stuff.

Besides the printing of it, the main plate was assembled with dampners and other relevent things to the linear bearings and the ball screw nut. It was tested rigorously and the bolts were tightened when the gantry was slowly moving in order to detect alignment faults. 

Alignment of different blocks are so much fun to do. Shame people find it cumbersome. 

Below is the 3D interactable model of the M.G.P. 

Exploded View of The Main Guide Plate Assembly in 3D and Animated

५| Vibration Dampeners 

Well, there's a lot of consideration made in regards to this, kindest human who's brave enough to read my rambles. You have been harassed enough with my dampening techniques. 

Yes I will not harass you any further with these dampenings of various sorts. We must embark on our own journeys not talking about vibration dampners anymore. 

६| Electronics 

Hoho, a Nema 17, a TB6600 as mentioned previously. Along with this an ESP32, four 5V buck and a lot of wires. There was a PCB developed. You can find a 3D view below (unassembled)

The current version has ROS2 on it so yeah, amazing stuff. 

I made two test benches of it as well. Here they are! !!!!UPDATE, 4 months into editing this, I realized I never made any CAD of it and now too lazy to do so. will see later!!!!

७| Miscellaneous Required Parts 

Just take a lot of bolts and throw them at me. JUST DO IT.

There were a few miscellaneous parts, for example a parametrized chain was bought and added for all the cables. I made a 3D model of it. There was an electronics board attached to the back of the main plate to support the robot and it's end effector's (Pen Grabbing System) electronics. Here's a 3D model of one of them. 

Chain Assembly in 3D

८| Software

Secret stuff, It is secret stuff, always is, always will be

९| "The Higher I Get, The Lower I'll Sink" 

Can you hear the silence?

Can you see the dark?

Can you fix the broken?

Can you feel, can you feel my heart-A-aaaa-A---A------AAAA?"

So yeah this system was tested a lot. It worked. This design had around 120 bolts. 100 washers and 30 nuts. Wasn't overboard this time. Quite a normal amount for a gantry of this size and setup to maintain rigidity.

good designs, good life

[ Such amazing stuff done because some people believed in my work from day one ]

[ Roland is me but I am not him, someone make him go away please ]

- Made in Studio de Roro, France by RolandThsive

Have a nice day, 

  - Rohit

The Greatest Picture of My System Assembly