LIGHT WEIGHT MATERIAL FOR INDUSTRIAL ROBOT ARM 3

[justin9490]

Hello,
I am working on a 3 DOF Industrial robot which is 500 mm Arm (Manipulator) length, 30kg payload and 3-6 m/s speed.I am trying to reduce the arm weight without compromise in the structural stability that's why I am looking for strong material in low weight without burn hole in my pocket. I would like to go with Aluminium but i don't have any experience in Robot side. Please share your thoughts. Has anyone had bad experience with Aluminium for robot arm?


Thanks,
Justin

 

[arunmrao]

Several options using 3D printing are available. Look for them, they will be attractive in terms of price and properties.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[Compositepro]

Where light weight and stiffness is desired almost nothing can compete with carbon fiber. Where cost is important aluminum is usually the best alternative. Steel can be an option if you can use very thin material.

 

[MintJulep]

Geometry likely more effective than material.

 

[IRstuff]

First thing you need to do is to determine the positional stability and accuracy, followed by velocity. Then, you can find the smaller subset of materials than can support your requirements.

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[tbuelna]

The best option for your one-off part is CNC machined from wrought aluminum. Your robot arm will likely require precision attachment interfaces, and they will need to be machined. So you might as well machine the rest of the arm at the same time. To keep costs down, design the arm so that it can be machined with a minimum number of set ups, fixtures and tool changes.

 

[Tmoose]

So 30 kg, almost 70 lb payload.
What does your 500 mm/20 inch arm weigh now, that weight reduction is important?
Is the "structural stability" acceptable with the existing arm and those velocities?
Or is this all at the design stage?

A large diameter, thin walled tube is tough to beat if bending and torsion are important in modest sized structures.

https://www.tonyfoale.com/gallery/750_Suzy/Suzy03.jpg

Tapered, if you want to get fancy. Rectangular sections may make the details for introducing point loads a little easier.

Like Tbuelna said, The end joint details are critical. They are likely to become the weak links pretty quick.

As always, pictures and drawings help communicate a problem in ways that a question consisting of just a few sentences never can.

 

[justin9490]

Tbuelna,
Thanks for you valuable comment. Actually, we are in same page because I have done two sort of design and I compared which clearly shows me solid arm is better than the joint one for we can't save much more mass because the arm is shot.

Do you have any opinion for Materials (Aluminium)?
I am thinking to go with 2024 what is your thought?
I have uploaded the arm model please have a look this is just for concept.

Thanks,
Justin

 

[justin9490]

Tmoose,
Thanks for your inputs.

So 30 kg, almost 70 lb payload.
What does your 500 mm/20 inch arm weigh now - Around 22 kg but this is not the exact one for I am waiting to gearbox input.
That weight reduction is important?- If posible
Is the "structural stability" acceptable with the existing arm and those velocities?- I haven't checked yet, couple of information i have to get before get into that. I am not getting any positive response from gearbox supplier. Do you have any contacts? I am communicating with Nabtesco and harmonic drive.
Or is this all at the design stage?- All is in design stage.

Please have a look the concept model
Thoughts?

http://files.engineering.com/getfil...9971-46e2-a0a3-29f956378d1f&file=Join_arm.PNG

http://files.engineering.com/getfil...d56-43f2-8556-80cb6adacd41&file=solid_arm.PNG

Thank,
Justin

 

[tbuelna]

The further you get from the shoulder joint, the more important mass/inertia/stiffness of the connecting structures becomes. Based on a 30kg load applied at the wrist joint, it seems that a CNC machined aluminum arm structure could be made lighter than 22kg. If lots of machining is involved, 6061-T651 tooling plate would provide a good combination of cost, dimensional stability, machinability, and strength.

 

[MintJulep]

Kg is a unit of mass, not force.
Mass x Acceleration = force.
It's a robot, with moving parts.
Moving parts must accelerate and decelerate.

We have been given a very wide speed requirement. We do not have acceleration/deceleration of the motion profile.

Therefore at this time the loading is unknown.

How is it possible that anything has been designed without knowing the loading?

Strength is only part of what must be considered. Do not exceed yield strength. Easy.

Deflection and stiffness are probably important. What are the requirements for these?

2024 aluminum is not particularly "strong", although depending on geometry it may be "strong enough" for the job.

 

[SwinnyGG]

Most industrial robots are assembled from intricate and finely machined aluminum castings.

So yes, you can build a robot arm out of aluminum.

With that said... 6 m/s is very fast. The stiffness of your arm is really only important if you care about consistent predictability of movement between nodes in your path. Which you might or might not.

What will bite you is stopping 30kg traveling 6 m/s. Say you're able to get the arm mass down to 20kg.. that's 50 kg total. at 6 m/s that's 900 W of kinetic energy. To stop that mass in 1 second, realistically, you'll need multi-kw servo motor, and your structure will need to be pretty strong to survive. You'll need to provide that servo motor with, at minimum, about 40 amps of current, disregarding efficiencies.

Point is, 30 kg is a non-trivial robot payload.

 

[WKTaylor]

Boron whisker reinforced extruded aluminum tubes for increased strength/stiffness... Or... extruded aluminum tubes wrapped with boron-filament tape [adhesive bonded to OD].

Also... other areas discretely reinforced with boron-filament tape [adhesive bonded in position].

Regards, Wil Taylor

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