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Robot Arm

jcdammeyer

jcdammeyer

John
Premium Member
I've started this conversation under CNC because my desire is to have a robot arm be able to change the TTS tooling on my mill along with maybe even place raw material and remove finished. It's the reason I started playing with the 3D printed harmonic drives as a method of gear reduction for accurate movement of a robot arm.

Seems someone has built an open source project that uses planetary reduction drives on the steppers on line stepper motor/drivers. Along with using Arduino and Teensy modules for the control. It's really an amazing project and well worth watching at least the intro video.

So this thread is going to be the very slow, with lots of breaks, in the building of an arm like this but hopefully at a much lower cost. How?

Well although 3D printed STL files are available the plastic will never be as precise as metal. And the STP drawings for the kit cost $99US. So perhaps the first step is to take the 2D drawings and redo them in Alibre as 3D.

The motors with planetary reduction also have encoders on them. That all raises the price. I have a number of DC motors with encoders from DEC printers. It's possible that for some of the Size 17 axis they might, with harmonic drive reduction be more than adequate.

So anyway. This is going to be a very long blog.
 
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I'm very interested in this. My attempts at cycloidal drives and 3D Printing were failures!

I'm currently working on a 2 phase drive for a NEMA 23 system. Ratio will be around 20:1. Internal bearings on contact surfaces and machined from Delrin and 6061.

Don
 
Arbutus said:
I'm very interested in this. My attempts at cycloidal drives and 3D Printing were failures!

I'm currently working on a 2 phase drive for a NEMA 23 system. Ratio will be around 20:1. Internal bearings on contact surfaces and machined from Delrin and 6061.

Don
Click to expand...
Pictures?
 
One of my reduction gear experiments came from the LinuxCNC group. This one is, believe it or not, 67:1
1675502576405.webp

With really large 3D printed gears. Once I get my tool changer working properly I want to try and make small gears with my gear cutters and somehow create the internal teeth gears. In the same size as the planetary gear assemblies. With a small DC servo the idea is to emulate the stepper c/w encoder and planetary drives.

This project will take quite some time.
 
kevin.decelles said:
Is your spindle r8 on that mill?
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Yes. With TTS holders but some tooling has R8 on the back. Like the spring loaded tap holder, face mill with 4 carbide cutters, large ball bearing chuck to name a few.

So I envision a gripper holding onto the tool. Power draw bar activates either for 2 turns for TTS or up to 18 turns for R8 and then gripper moves down to pull tool out. Then away from the work area to flip it 180 degrees. Then move to storage location x and lower it into place.

It's the loading where I wonder how things might go. Each TTS holder will have to have a taper turned or ground on the end to handle slight misalignment. But that's why I want a really accurate robot arm. No 3D printed material anywhere precision is required.
 
Canadium said:
My wife wants a robot to do the cooking and the house work. I want robots with shot guns for security!
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For 6 mil @ an interest rate of just over 4%, you could get started.

I believe between Alexa and Siri, you could have it all. ( Just contact Elon, ask him what he feels the next Gen Drone will be. (He can be reached much easier than Mitutoyo for example... )

Keep Alexa's drone armed with utensils, add some management software for the duties around the home. Put her on payroll for the added incentive's thou...
Just keep her drone outfitted with the next smartest tech Barbie mobile available, with the optioned out Barbie decal package. Keep Barbie in expensive clothing with the high heals. Then run er' on cooking oil, insects and 3D printed money.
Just like that the wife will be taken care of.

For security, it would be difficult without using Ciri.
A state of art stealth Drone. Fully optioned out 2023 GI- Joe graphics, bearing chinesium lettering. ( Stealth mode lettering ) More than capable of 0-260 MPH, in .02 milliseconds. ( not the slow sleazy KLM/HR we see her in chinanda) Armed with magazines, new and improved GI-Joe figurines, equipped with smart technology and your set.
Use Barbie's payroll in order to finance her new GI- Joe security advancements.
Then use GI- Joes payroll in order to purchase the air space above your dwelling, as high as the next Gen eye can see!
To think, It could be that easy.
 
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jcdammeyer said:
I want to try and make small gears with my gear cutters and somehow create the internal teeth gears. In the same size as the planetary gear assemblies.
Click to expand...

I looked into that for my radial engine, where I had intentions to cut gears. Spur gears, no real drama. Internal gears requires something like a broach type cutting tool & rotary indexing, again not a problem for most home shops. Too small for any CNC 2D profile cutting I imagine. With internal gears, some additional design factors come into play for proper tooth shape/clearance & If I recall, vary by pitch & ID/tooth count so that all has to be reflected in the cutting tool profile. Making that profile accurately becomes more challenging. Do-able with the right equipment but more effort. I've seen 3DP ring gears that appear to rotate nicely, but really not sure about real life mode - resolution, free play, how much load they could withstand. All depends on your application.

But there are lots of relatively inexpensive commercial plastic gears available. Probably more metric options, but I'm assuming you could easily work around that. Same for small spur gears actually.

www.ebay.com

Ring Gear Ring Gears Internal Gear Planetary Gear Plastic Module 1 Teeth 20 -140 | eBay

Part no Plastic internal gear ring gear Pressure angle: 20 ° Material: POM-C natural Mechanically manufactured toothing, very good quality. Helix angle: 0 ° (straight flanks) Part no Number of teeth A. øD OK øC øTK Items: [mm] [mm] [mm] [mm] [mm] [mm] HR1-20 20 35 20 18 2.8 (3x) 29 HR1-30 30 45...
www.ebay.com
 
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