A 3d printable ROV - Also, hello!

Waterproof Housing, Frames, and Buoyancy Methods.
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piercet
Posts: 16
Joined: Sep 16th, 2014, 10:52 pm
Location: Ridgefield, Washington State

A 3d printable ROV - Also, hello!

Post by piercet »

Hello everyone! I'm Tim. I've always been fascinated about Remote operated vehicles, and I have a couple of 3d printers. So, I've decided to build a moderate sized ROV that can be produced by a larger format (12 inch bed) 3d printer, and more importantly, offer the design files to other people so that hopefully the design can grow and improve and maybe introduce more people to this hobby.

What I have so far is located here:
http://www.thingiverse.com/thing:451236

It's basically a free flooding frame, designed to work with 4 Bluerobotics thrusters, with an 8 inch Acrylic tube at the front for a pressure hull. The main frame material is 20mm T-slot aluminum extrusion, which will hopefully make for easy repair, upgrade and modification. The tube and the frame parts cost about $150 from McMaster carr with the hardware. Thrusters and electronics will likely cost you a bit more than that. I figure corrosion will not be a major factor on a scout class hobby ROV initially, and anyone worried about that can paint the metal pieces or mill alternate ones out of delrin

There are still a few pieces that are somewhat fluid in the design at the moment. Carrying handles, the lower cross spars, the float section, the electronics mounts for the tube, the eventual robot arm.

I think I have a decent basic design, but at the same time most of my knowledge is theoretical so If you get time, please take a look and let me know of any suggestions you might have. I'm also quite willing to design up any additional mounts / brackets / parts etc. to go with it if you would like to see something added to the design.

I plan on having a light mounting crossbar on top, and provision for mounting baskets, etc underneath the hull between the skids. The motor mounts inside the frame will likely be redone as I get closer to operational. I'll admit I kind of hurried that aspect of the design for a contest.

I would also be happy to provide the design files themselves in whatever format you would like if anyone is interested in adding to the design themselves, just let me know.

I've got about 1/3rd of the frame printed so far, mainly because the larger pieces take about 8 hours to print on the nozzle I have on the large machine, and I haven't been home to print more of them.

I do have some design questions for people in the near future as well once I get a bit further along (are there electronics packages that offer more servo outputs than the OpenROV controller, any good sources for 8" tube endcaps pre-made, or secondary battery boxes, etc). FOr now though I'd like to make sure I have the frame as dialed in as I can get it

So, if you have a moment, please let me know:
1. do you see any major flaws that I should change right away
2. is there anything you would like to see added that isn't there (angled rear thruster brackets, etc.)
3. Anything else relevant to the design

Thanks in advance!
Tim (aka Piercet, aka piercet_3dprint)
a_shorething
Posts: 289
Joined: Sep 10th, 2013, 5:26 pm
Location: New Jersey Shore

Re: A 3d printable ROV - Also, hello!

Post by a_shorething »

Hi Tim,

I like the idea of 3D printing pieces for this and I've been working on some 3D printed parts for my ROV since I started, including thruster props and some other stuff.

I still haven't gotten 'wet' with my original design either so take my responses from whence they come...


My initial thought would be a concern that an 8" clear tube will have:
1. LOTS of buoyancy
2. A difficult time making penetrations for wiring
3. A difficult time with sealing the endcaps (which I think is also an issue with the OPENRov design)

I think they use a smaller diameter tube and that people have reported issues with leaking/consistent sealing pressure without cracking things.

Specific to the 3D printed design: I have concerns about voids in the parts. The fact that 3D printers work by putting down layer upon layer of material (often at less than 100% density) means that there could be small pockets of air in there. I don't know if a 3D printed object is going to deform and crush at depth. I hope to find out by spring, but as of right now, it's still a variable I need to consider.

Good luck with it though and I'll be watching with interest.
piercet
Posts: 16
Joined: Sep 16th, 2014, 10:52 pm
Location: Ridgefield, Washington State

Re: A 3d printable ROV - Also, hello!

Post by piercet »

The 8" tube is only 12" long. I've seen ROV's with 2 foot long 4 and 5 inch tubes that seem to work well, so I'm hopeing that won't be too much of an issue. Especially once it is 3/4" full of batteries and electronics. I'm planning on using a LEMO watertight fitting for the cable passthrough in a threaded aluminum endplate. The endplate will press against a 3d printed ring on the inside, allowing for an inner gasket surface, has 2 o ring channels, and will have an outer gasket between the flange and the edge of the Acrylic tube. No idea if that is going to work at all though. It's going to be similar to the crustcrawler pressure hull design, except with an additional gasket surface and a 3rd threaded rod to hold the endcaps in.

If all that doesn't work, I may convert it to a dome lense endcap design with a centerally mounted aluminum pod instead. The endcaps are my biggest worry right now for sure.

I'm printing the frame parts at 100% infil out of ABS (lego) plastic. There will still be microscopic air voids in the parts. but I don't think they will be large enough to affect the structure of the frame all that much even if they rupture at depth. That might actually make the part stronger. The sideplates are about as thick and stiff as a delrin cutting board so i am hopeful they will work well.

Thanks for the feedback!
piercet
Posts: 16
Joined: Sep 16th, 2014, 10:52 pm
Location: Ridgefield, Washington State

Re: A 3d printable ROV - Also, hello!

Post by piercet »

I picked up a smaller video camera housing to use as the rear pressure chamber. My thought is to have a secondary battery bank back there, to better distribute battery weight. Also have an inexpensive milled Robot arm gripper on the way. My plan is to pot the electronics board of the servos in epoxy and fill the gear section with grease and pop a seal on the servo shaft itself. Maybe flood it with oil of some sort. Not sure yet.

I've got 2 of the main side plates finished now. Will print the front top plate this weekend. I should have the milled tube end plates back soon too. It's starting to take shape!
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olegodo
Posts: 222
Joined: Aug 30th, 2013, 9:47 am
Location: Bergen, Norway

Re: A 3d printable ROV - Also, hello!

Post by olegodo »

Hi piercet!

I am also experimenting with using servos in water.
My plan is to have the whole servo flooded with mineral oil. I have also thought about potting the electronics side and filling the gear side with grease, but the problem with that is that the motor and potentiometer still has moving parts in the electronics side of the servo.
I have one servo sitting on my bench that have been filled with oil for months now, and it still works good.
These are so called "waterproof" servos that are sealed with an o-ring around the shaft and gaskets between the different housing parts. this keeps the oil in and water out. but not at any pressure. So to equalize the pressure I will have two 4mm hose barbs, one in the gear compartment and one in the electronics compartment, between them I will run a 5cm length of thin walled silicone hose that will compress a little as the rov goes deeper, but not let any water in.
I think this will work out ok.
Nuckan
Posts: 4
Joined: Oct 9th, 2014, 1:23 pm

Re: A 3d printable ROV - Also, hello!

Post by Nuckan »

Nice setup! I had a plan to print the whole ROV but had lots of difficulies with leakage.




I finally decided to go for acrylic plastic only using the printer for camera pan and tilt mount and motor mounts.

piercet
Posts: 16
Joined: Sep 16th, 2014, 10:52 pm
Location: Ridgefield, Washington State

Re: A 3d printable ROV - Also, hello!

Post by piercet »

Nice looking setup!

I'm not planning on using 3d printed parts for the water seals on the tubes, just the frame components. The main pressure hull is going to be an acrylic tube with aluminum endcaps.

I've made some progress on mine. The main sideplates are all done. I've redesigned the top plates to accomodate a float and a rear secondary pressure hull, and those are in progress. I've also got a better idea of where the lower cross spars are going to go. Once I get those top plates done I can start forming the rest of the float section. I won't have my thrusters until around February, so it won't start looking like an actual ROV until around then.
SeaRobotic
Posts: 1
Joined: Apr 30th, 2015, 12:59 pm

Re: A 3d printable ROV - Also, hello!

Post by SeaRobotic »

Hello everybody!

I am new to this forum, so quickly who I am: a newcomer to the ROV world, but with some background in robotics, electronics and computer science.
My ambition is to fully use 3d printing for my ROV (including for the pressure hull :shock: ). One of the reason is that I have a 3d printer but no lathe or mill ...

I have already done a 3d printed sphere of 10 cm which withstand 10 bars (100 meters depth). The reason why I am posting is that as far I am aware nobody ever use 3d printing for pressure hull.

I have made a video to explain the process, but the main trick is to use epoxy resin to waterproof your ABS parts!


Hoping it will give some idea to others !

Sorry for my english, I am not native speaker :oops:
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