Saturday, September 09, 2006

 

Mothra rises to face Godzilla

Full-days work today, but I made a lot of progress, as you can see:


For linking each platform to it's threaded bolt, I carefully smashed a 1" coupling nut into its guide-hole



At first, the X platform was very tight. Wasn't sure exactly what was wrong, but I wiped it all down with WD-40 and it worked perfectly. FYI, a power drill is perfect for doing end-to-end friction tests :-)


It's definitely a pain to get those rods perfectly in-tune with the sliders. I actually drilled slightly larger holes on one side so I could have some room for play. Once I decide it's perfectly aligned, I'll squirt some hot glue or polymer into the hole to tighten it. Hot-glue actually has some bounciness and might even help lower vibrations.



While I fully intend on making this a polymer extruding repstrap, it will be a lot easier for the time being to just strap a dremel tool to the end for testing. I'm still pondering different extruder designs, whether peristaltic or psi pumped or standard filament driven.



Motors still have to be mounted/tested and I still have to solder all the control boards, including the JDM programmer. So while it's still quite a ways from being finished, it is a good example of building a repstrap frame on a budget.


Any questions on what tools/methods were used in making this, or requests for more pictures, or anything like that; feel free to ask.

Comments:
Looking good! :-)
 
Konichiwa Reiyuki san! (sticking with the Japanese theme)

I'm sorry if I may have missed you explaining this in another post, but what are you using to slide your carriages on? I'm guessing 1/4 inch steel rod?

Nice to see all the photos. I can't build, but I can look!
 
Sorry for the delay

what are you using to slide your carriages on? I'm guessing 1/4 inch steel rod?

Yep. 1/4" rod. And the sliders are a combination of brass bearings and 1" nylon spacers.
A drill press is almost neccesary for perfect alignment, but for mounting the rods, I drilled extra-large holes for aligning, then I plan on setting it firm with hot-glue once it's all smooth.

I heard the idea of using drawer slider carriages for mounting, and if I hadn't already started, I would probably use those on at least the bottom platform. They're only 5-6 bucks each and can slide perfectly smooth.
 
reiyuki,

could you elaborate a little bit more on what you're using for the carriage slide? specifically i'd like to know more about the bearings and spacers you're using. where did you get them, what do they look like, etc? thats basically my next step, so it would be awesome to have some guidance.
 
could you elaborate a little bit more on what you're using for the carriage slide? specifically i'd like to know more about the bearings and spacers you're using. where did you get them, what do they look like, etc? thats basically my next step, so it would be awesome to have some guidance.

All the parts I got were from Lowes, but any hardware store will have similar parts. It will be in the hardware section, in misc hardware like 'bearings and spacers'.

For bearings, and for the bottom platform sliders, I am using 1/4" diameter brass bearings. It's basically a tube with a bevel on the end so it dosen't slip in farther than it should.
Brass bearings are also used on the threaded rod to keep it in place but spinning. The threaded rod is held in place with 2 washers and locknuts, aside from te bearings.

Sliders for everything else are .256 x 1" nylon spacers. These are basically just little white plastic tubes that are mounted inside each platform. These will have to be glued to the carriage, but not until everything is running smoothly. Also note I'm using 2 end-to-end in a few places to keep platforms paralell.


I'd like to use real thrust bearings, but for XY axes, brass friction bearing seems to work fine. If I HAVE to, I may go to a bike shop and pick up some real bearings, but I want to keep my design pure and hardware-store buildable.
 
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