Wednesday, 21 September 2011

Removing pulleys from motor shafts

My secondhand NEMA17 motors (purchased from ebay) came with metal pulleys attached.  No, not attached, they were on so tight they could have been welded there, or grown .  No amount of yanking could get them off.

I eventually made one of a gear / pully remover, but could still not budge it.  So I resorted to brute force - an anvil and chisel.  Big hammer + hard chisel + anvil + gear = split gear.  Yay!  Or so I thought.  The aggressive approach resulted in a bent shaft.  That, and half the pulley was still hanging on it.  I used the DIY gear puller to remove the remaining half pulley, which gave me an idea.

For the next motor, instead of dealing a full force blow to the pulley I instead tapped with a low - medium force 3 or 4 times at different locations.  The impact loosened the bond between the shaft and the pulley, allowing me to use the pulley remover to extract the pulley with minimal effort and zero damage to the shaft.

Lucky I had 8 motors - it took 3 tries to figure it out resulting in one completely destroyed motor and 2 very slightly bent shafts.  I only needed 5 for my Prusa, so all is good :-).


Monday, 19 September 2011

How to save yourself an hour when testing your RAMPS

Make sure you set the correct pins in the firmware before flashing.  I'd like to say stuff just magically works after that, but I think being clueless about the pin settings made me recheck all my wiring and connections so it just appeared to work after finally getting the pins right.

More testing tips:
  • Disable endstops in firmware. It'll freak you out when your motors only move in one direction.
  • Test controllers and steppers individually to avoid blowing up more than one thing at a time.
  • Here is the quick way of figuring out how to wire your stepper.
  • Make sure you order pins with your connecter housing (otherwise you'll be left scrounging for connectors in your computer cases).  My fingers still hurt from taking connectors apart.

RAMPS

Putting together my RAMPS 1.3 kit was mostly uneventful.  All soldering was of the through-hole variety and the components were well spaced.

The terminal strips were a bit of a challenge - making them sit up at 90 degrees to the board is something that tweaked my obsessive tendencies.  Getting all the pins upright also helps when attaching / detaching the Arduino and the controllers.   Following the assembly manual, I soldered a single pin of each terminal strip before adjusting the orientation of each strip.

The headers sitting in place, ready to solder.
I taped a piece of cardboard on top so I could...
... flip it over and do all the pins at once one pin on each header
before aligning pins and soldering the rest.
I had to file down this solder pad so it wouldn't hit the
Arduino power connector.
Complete RAMPS with micro SD reader.
Yes, that's red nail polish on my +ive terminals.
I also bought the SDRAMPS in kit form.  It was my first experience soldering surface mount components with a regular soldering iron and it was quite intense.  The though of screwing up $15 worth of kit was constantly in my mind.  Luckily it all worked out (after hunting down some unconnected pins on the SD socket).

Heatsinks
This is really annoying me - my kit came with some heat transfer pads for the heatsinks.  They transfer heat really well, unfortunately they don't do a good job of fastening the heatsink to the stepper controllers so I ditched them.  Since then I've tried using a dab of thermal compound and spot of super glue in the corners.  Works great... for about a day then they start falling off again :-(.  Maybe it's time to get some thermal adhesive.

Tuesday, 13 September 2011

Framed


Erecting the frame was fun!  I suppose anything would have been a welcome change from the anxious wait for shipping.

While I was waiting for my packages to arrive I had managed to buy some rods and cut them to size.   Then I spent the next 2 weeks alternately staring at the tracking info on my packages and looking at the lonely row of unconnected rods on my workbench.  And of course the first package to arrive contained motors, not the most interactive of components...

Soon enough I got my printed parts and it was time to build.

Tools I used:

  • small pliers. (I didn't want to over tighten any nuts)
  • scalpel for cleaning parts
  • 8mm drill bit for reaming holes
  • a copy of the Prusa Mendel Visual Instructions by Gary Hodgson.  I viewed this on my iPad to save paper
  • an "object with precisely 290mm length" and an "object with precisely 234mm length".  Make these out of rod or anything else you have lying around.  I used a wooden ruler.
My ruler jig.  It's a little too flexible, lengths of smooth rod would be better.
Assembling the frame was straight forward.  In short - make a triangle, make another triangle, join them together, now adjust all the rods so the jig barely fits.  The last step takes a longer than you think as quite often one adjustment will affect other parts of the frame.

Triangle, triangle
Join and adjust.  Easy
I did come across one problem.  I was supplied with a bottom thicksheet that was slightly too big to fit between the bottom vertices.  To overcome this I had to completely loosen one side and move it approximately 10mm out.  I also had to make a new jig for this new measurement so everything would be in alignment again.

That's about as far as I've gotten with my frame so far.  My printable parts came with ABS bushings so I've been dragging my feet on doing any of the axes until I figured out what to do with them.  More on that in another post.




Element14 has blazingly fast shipping

Last night I ordered a package from au.element14.com at 5:55pm, barely making their 6pm cut off for next day delivery.  15hrs later I've got the package in hand.  Wow.

Monday, 12 September 2011

The scrooge's guide to part selection

I followed 4 rules when purchasing my parts:
  1. Save money on items.
  2. Save money on shipping.
  3. Save time sourcing all the items.
  4. Don't try to make things I don't have tools for.  
In retrospect I should have added:
  1. Get good value.
  2. Don't be lazy with research.
  3. Don't rush.
Research
Do lots.... And then do some more.
  • Visit the forums.  
  • Get on IRC and ask questions.  
  • Look through the wiki.  Pull up a chair and get comfortable because you're going to be here a lot.  There's a buyer's guide (I just realised how important that link is) and an Australia supplier list.  
  • Get in touch with local reprappers.  Maybe you've got a nearby hackerspace that could help you out.  
Hotend (Wildseyed is AWESOME!!!)
Wildseyed's simple hotend
After asking around for opinions about hot ends (the one time I wasn't lazy with research or rushing) Wildseyed himself offered to send me a complete hotend of his own design.  Sir, I'm sincerely thankful for your generosity.  I'll be posting my experiences with his hotend when I'm up and printing, maybe try to source the parts and make my own.

Motors 
I got some used NEMA17 motors from ebay.  They work and they're cheap, what more can I ask for.    They're even better value considering I bought 8 for less than AUD$60 delivered.  That leaves me 3 extra for a small CNC :-)  I just hope they have enough torque for the extruder.  The only down side is that the pulleys harder to remove than something really hard to remove.  So you may want to pay extra to get seller to remove them for you.

Electronics
Full RAMPS Kit + SDRamps kit from RepRapWorld in the Netherlands.  They were running out their RAMPS 1.3 kits for the remarkable price of ~AUD$115 (sorry, sold out now).  They have great service and are always promptly replying to my emails.  I highly recommend them, but be warned that the package doesn't track once it leaves the Netherlands (2 weeks of nail biting taught me that).

Printed Parts
The printed parts and vitamin set came from a seller on eMakerShop.com.  The parts were ok (just ok) - they needed a lot of work to clean up (more on this in a later post) but I guess they are functional. And they had ABS bushings (#!@!).  If I had done more research (rule 6) and not rushing (rule 7) I would have gotten better value (rule 5) for my money getting a set of parts from Greg Frost for a little less (but I'd have to make the thicksheets myself and source all the nuts and bolts etc.) Oh well, I'll be printing my self a new set of parts soon anyway.

Rods
A few Aussie reprappers seem to be buying their rods online.  $20 for shipping?  err, don't think so.  I sourced my rods locally.
  • Get smooth rods from stainless steel merchants.  They'll sell it in really long lengths, mine were 4m long.  Be prepared to tape (that's right, use duct tape / electrical tape) the rods to your roof rack to take them home. Ring around, I got mine for $3.30 a metre.
  • Get threaded rods from fastener shops.  They sell by the metre.  Mine cost $5.  Ring around, prices vary quite a bit.  While you're there get your nuts and bolts and washers.  Don't go to Bunnings (check the prices yourself though, don't take my word for it).  I was quoted $8 for a pack of M8 nuts, I think that's half the price of Bunnings. 
  • Use the phone.  Yellow pages is your friend.  Most of the places that sell this stuff don't have web sites and the ones that do don't usually have a price list.
  • Most industrial suppliers are closed on weekends.
Misc
  • Kapton tape and PET tape from dealextreme.com.  It's cheap.  It works.  The kapton held up no matter how much I stabbed it with a hot soldering iron.  Your mileage may vary though.
  • Jaycar is expensive for most components.  Make sure to check element14 and rs for prices before buying anything from Jaycar.  All I got from Jaycar is a flux pen which I needed for soldering the SDRamps board.
  • Power supply - doesn't everybody have at least one ATX power supply gathering dust in a dark corner?

27 days and 12 hours ago I decided I wanted a 3D printer

The Thing-O-Matic, SUMPOD and Prusa.  Can you
guess which one doesn't have an advertising budget?
30 minutes later I was convinced I wanted a Thing-o-matic.  3 seconds after seeing the price I realized I had to do more research.  Thus started my journey along the path to building my own RepRap Prusa.

To be fair to Makerbot, the Thing-o-matic is reasonably priced kit for a 3d printer that wouldn't look out of place in a lounge room.  But the inital price and the weeks of lead time (shipping to Australia already takes forever) had me backing away from this purchase.  All the kits I investigate had long lead times and high prices.  The only kit I was seriously considering was the SUMPOD (their capitals, not mine), good looking and relatively kind on the wallet but there was a 12-week wait and a real need to scratch a DIY itch.  Then I found the Prusa.

Reasons I chose the Prusa:
  • can be low cost
  • upgradeable
  • can be sourced quickly
  • large build area
  • lots of documentation
  • can print it's own parts
  • potential to be very accurate
  • constantly evolving
  • upgradeable (it's very important to me)
  • lots of community support
Reasons against:
  • the aesthetics aren't wife friendly, so it will it stay on the workbench
  • potential to be very accurate - getting good prints will need work
  • upgradeable - this thing has the potential to be a money pit.  Australian money is plastic, maybe with the right extruder...
  • it doesn't vacuum, but I have a neato for that
2 days later I ordered my parts from all over the interwebs and began my 16 days of fasting waiting for shipping.