Sunday, February 14, 2021

Linear Actuator, vol3

So.. I realize this actuator is not very good looking, and is pretty inefficient with respect to length (IE stroke length over static length). The main issues causing this are the extra length of the ball screw and the extra length of the motor shaft which are not very useful. I would shorten these if I had a lathe, although I could probably get an 8x10mm coupler if I just hack off the threaded section.

Another factor to the ugliness is that I want to machine the least number of components and I want to use the cheapest, most readily available parts off the internet. So we have the FrankenActuator:

You can tell the back portion is not quite finished yet, as it houses the optical encoder, and nominally another mounting heim.I may also enclose the motor and coupler with some small sheet metal or carbon sheets bolted to the two mounting brackets.

This is one of my first mechanical actuator designs, so I learned a lot and  had a bunch of fun. I am ordering most of the parts now, and will get a prototype together soon. For the three parts that require custom machining: I will 3d print them for now. Theoretically they can all be made on a 3-axis CNC with some small aluminum stock.

Wednesday, February 10, 2021

Linear Actuator, vol2

 Okay more progres... I have gone through some churn, and thought about a lot of different designs. I think the most affordable thing to do here is go with some shitty nut brackets and the cheapest Mcmaster parts I can find. Here is what I have so far...


The nut bracket is a 9 dollar chinese part from amazon. I tried designing my own carriage, but the quote that came back from the machining house (xometry and protolabs) was like $300 plus for 3 pieces. I think I can get away with shittier but cheaper parts. Currently there are two parts on this that would require custom machining, but thankfully I think a mill would do fine, and won't require a 5-axis. One hopes.

The next two bits to make are the back housing and the retention bracket. The latter will hold the linear rod and ball screw in place, and firmly attached to the motor housing. These will probably be the most pain in the ass. Let's see what corner cutting and shenanigans I can get away with

Monday, February 8, 2021

Linear Actuator, vol1

One of my larger flight vehicle projects requires... 3 linear actuators. They need to have high support force, fast stroke speed, closed loop, electric, and be easily programmable. This is a tall order for most any linear actuators on the market. I did get some quotes from people, and it turns out the're like $5k a pop. I definitely cannot afford that, so I have to make them myself. Which is also fun :)

I got inspiration from two sources: 

Gabrael's linear actuator uses a BLDC motor with a traditional ball screw, but also two 16mm carbon fiber smooth rods: one acting as a guide and the other as the end-effector. WeWato does something similar, but with more carbon guiding rods. Each seem to use drylin smooth glide bearings, which are cool..

I have started my design here... There are still some more blocks to make, but figured I would post this update. The end-effector is steel, and requires weldnuts for the heim ball joint at the end. I could have tapped the tubing, but then I would need a large heim or some weird adapter. The weld nut seems easier.. just need a small weld bead. (I don't have welder... yet...). 

The next step is to make the retainer block: the part after the coupler, which prevents the ball screw from falling out, and attaches the assembly to the motor. Then I will add in some guide rods (maybe using the existing holes in the ball nut??) and an end guide holder. Then I think a sheath of tubing over the whole thing.. and some way to mount the back of the motor. All in flux, but I am learning a lot and having fun..

The "Import Mcmaster Carr Part" feature of Fusion360 is unbelievably fuckin powerful, and is totally dangerous :)

cutaway shots are sweet....

Sunday, February 7, 2021

A Homemade 3D printed deadmau5 head, vol1

So I have been a big fan of the artist deadmau5 (Joel Zimmerman) for.. well over a decade now? I have always wanted to make a faithful replica of his famous mau5head, so I started. I figured since I have a colossal 3d printer, I might as well take advantage of that. I have split the main head portion into two pieces that can be printed without support, separately. Each print was about 26 hours. I then glued them together with two part epoxy, and will be sanding it down soon. 

I will add primer, and then do a glossy white paint. Once that is finished, I will work on the ears... I still haven't decided if the ears should be printed as well or made of a lighter material. The head is currently made of PLA, about 2.5 ish mm thick... I would love to make some giant PCBs with addressable LEDs on them, so I can make a small spectrum analyzer, but we shall see... I also just want to have it be a cool decorative piece.

Making it more comfortable... I might add some foam and some PC fans. This project is a slow burn one, pretty low priority right now.

I think the goal is to make it look like this: (image from here)


Wednesday, February 3, 2021

3D Printer Closet

 I have recently been working on my 3D printers (they are creality and therefore always need some sort of tending to..) and decided to put them away in my little Harry Potter closet under the stairs. They look pretty tidy, and I added a bench LED strip as well to keep things lit.

My CR10S-4 required some servicing on the BL touch sensor, so I was able to easily pop out my Ender to work on it. The sensor got bent during a malfunctioning print. I came down one night and found the X carriage belt had consumed the entire print and smooshed the BL touch sensor pretty badly. 

The 10S-4 is still too loud, despite dampers, so I may perform a trinamic motor driver swap. Although it's quite invasive.. maybe there is a mother board upgrade 

Testing the IMU380ZA-200

I have the breakouts in! Started testing all the IMUs and so far they each have something to say, but I want to do some more in depth testing to see if there are any failure modes. Someone mentioned to me that I might see them reset after a couple minutes, just due to the hinkiness of where I got them from: eBay. Their modules did that at least.

I am thinking I could get away with this though, just with some clever fault detection, isolation, and recovery. Integrating off a backup gyroscope for a couple seconds probably isn't the worst. But who knows. I just need to make sure it doesn't happen during a critical point in operation :)