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guoshihui
11-27-2016, 10:29 AM
Hi,

It has been some time since last post, too much teaching these days.

Recently I decided to pick up the robot project again, but would like to push this forward a bit. However, I have the questions concerning, which materials are the HROS1 using for the skeleton parts? I guess these shapes are processed by laser cutting?

http://learn.trossenrobotics.com/cache/multithumb_thumbs/b_400_400_16777215_00__images_assembly_hros1_p2.jp g
http://learn.trossenrobotics.com/cache/multithumb_thumbs/b_400_400_16777215_00__images_assembly_hros1_tilt_ cam.jpg

From my poor knowledge, I guess this is some type of plastic, but would like to know exactly which types of plastic. Many thanks.

Shihui

jwatte
11-27-2016, 01:09 PM
The specifications say "Lasercut Delrin Torso."

I'd expect the body brackets to be Delrin (also known as Acetal and POM.)

tician
11-27-2016, 01:29 PM
I am pretty sure that the majority of the laser cut parts are still a PMMA/PC blend like the other Interbotix kits (previous versions were ABS). In the HROS-1, there is a single delrin shim taped/glued to the bottom-side of the torso plate to act as a wear-plate/bushing between the torso plate and the hip yaw servos.

jwatte
11-27-2016, 02:13 PM
This page says "lasercut delrin torso":

http://www.trossenrobotics.com/HR-OS1

Additionally, when clicking into "specifications" it also says 5052 aluminum brackets for the frame.

It doesn't mention the P95G acrylic at all.

tician
11-27-2016, 02:22 PM
http://learn.trossenrobotics.com/projects/155-hr-os1-kit-assembly-guide.html

5052 brackets for servos
Shapeways SLS nylon head tilt frames
In-house lasercut P95G 'plates' for 'shoes', torso, etc.
In-house lasercut delrin hip shim
Plastic or metal hex standoffs for mounting plates together

jwatte
11-27-2016, 08:14 PM
Exciting! They probably should update their store listing, then :-)

guoshihui
11-27-2016, 11:22 PM
http://learn.trossenrobotics.com/projects/155-hr-os1-kit-assembly-guide.html

5052 brackets for servos
Shapeways SLS nylon head tilt frames
In-house lasercut P95G 'plates' for 'shoes', torso, etc.
In-house lasercut delrin hip shim
Plastic or metal hex standoffs for mounting plates together

There are quite some chemistry words to google before I can fully understand, haha...

Still what does 5052 and P95G mean? I guess it is the specification, but is it plastic or aluminum?

Thanks tician.

Shihui

tician
11-28-2016, 12:18 AM
5052 aluminum - an aluminum alloy with very high formability, so it works well for bent sheet metal objects like the servo brackets as you can cold form them and not have the bends break or require any post-forming heat treatments to keep most bends from quickly failing.

P95G thermoplastic - a blend of PMMA/PC (PMMA/acrylic/plexiglas + PC/polycarbonate/lexan); thinking it a 95% PMMA + 5% PC.

ABS or delrin or polyethylene or polypropylene would all work just as well as the PMMA/PC blend, but plain PMMA would likely break too easily in the torso of a humanoid. The PMMA/PC blend is simply what the folks at Trossen have been using for a while for all their Interbotix kits as it looks nicer than ABS and is safe/easy to lasercut like plain PMMA, but does not break quite as easily as plain PMMA because of the PC content. It does have some of polycarbonate's weakness to threadlocker (a variety of anaerobic adhesives), so have to minimize any contact just like the batch of styrene-rich Bioloid Premium frames that Robotis temporarily released several years ago before returning to a safer ABS-blend.

guoshihui
11-28-2016, 05:44 AM
5052 aluminum - an aluminum alloy with very high formability, so it works well for bent sheet metal objects like the servo brackets as you can cold form them and not have the bends break or require any post-forming heat treatments to keep most bends from quickly failing.

P95G thermoplastic - a blend of PMMA/PC (PMMA/acrylic/plexiglas + PC/polycarbonate/lexan); thinking it a 95% PMMA + 5% PC.

ABS or delrin or polyethylene or polypropylene would all work just as well as the PMMA/PC blend, but plain PMMA would likely break too easily in the torso of a humanoid. The PMMA/PC blend is simply what the folks at Trossen have been using for a while for all their Interbotix kits as it looks nicer than ABS and is safe/easy to lasercut like plain PMMA, but does not break quite as easily as plain PMMA because of the PC content. It does have some of polycarbonate's weakness to threadlocker (a variety of anaerobic adhesives), so have to minimize any contact just like the batch of styrene-rich Bioloid Premium frames that Robotis temporarily released several years ago before returning to a safer ABS-blend.

Hi Tician,

Thanks for your detailed reply. I originally plan to build another robot, so need to build my own skeleton. It seems that if I want to have customized parts of aluminum alloy or P95G, I would need a machine tool (not sure if this is the right word, but I mean a large machine to build the shapes). So maybe I should design by myself and send it to others to do outsourcing manufacturing?

Shihui

jwatte
11-28-2016, 11:03 AM
If you have custom shapes, then it's usually better to design it yourself, and then either learn how to use the tools and rent them (many hacker spaces have laser cutters that can cut some kinds of plastic,) or 3d print them (in ABS or PLA) or send them out.

To cut aluminum, the folks at Big Blue Saw (https://www.bigbluesaw.com/) are pretty good; they use waterjet cutting. They don't do bending, though, so if you need bending in the brackets you have to do that yourself.

To cut plastic, and even thin stainless steel (16 gauge or thinner,) the folks at Pololu (http://www.pololu.com/) do a mail-in laser cutting service. Warning, though, that plain PMMA / Acrylic is too fragile (as tician says) and the "Plexiglas G P95" that is a little less brittle, is not easy to find in batches less than full sheets (32 square feet.)

You can also send part files to Shapeways (http://www.shapeways.com/) to be 3D printed in aluminum (expensive) or nylon plastic (which is very strong and nice for parts.) If you work in 3D CAD, this is often the easiest and least expensive way to go. It's still not "cheap" though, but a few hundred dollars will give you a complete smaller robot frame and it's very easy to work with.

Finally, all of those pieces can be made in sheet metal, and there exists companies that take a project from drawings to completed parts (bent, tapped, anodized, whatever you want.) They do charge accordingly foir full service engineering. Try the folks at Rapid Sheet Metal / Rapid Manufacturing (https://rapidmanufacturing.com/) for example.

Personally, I learned how to use the machines, got myself an affordable 3D printer, and go to a Tech Shop (http://www.techshop.com/) for using the laser, CNC, and waterjet cutting machines myself. Works great for me because this is a hobby, and I enjoy the making parts bit. Membership fees and safety class fees apply.

tician
11-28-2016, 12:53 PM
The Trossen shop sells all the aluminum servo frames, so that part is easy unless you want custom length limbs. Ponoko is another fairly inexpensive lasercutting service that can handle wood, delrin, and several other materials, and was the service I was planning to use for rebuilding an HROS-1 torso to my preferences before I got really low on funds (Ripley still in several pieces and project is largely on hold).