Not the droids part deux.

Today i had a few hours again - this time, i assembled the plastic version of the Moco head (left). Again, this is not the final version, it's missing motors, belts, pulleys and so on, as well as the whole base. On this pic it's resting ontop my manual mini dolly - which is essentially just a 75mm cup for a video head with wheels. Simple, but works perfectly...

It's alive!! (Part One)

Yep, the CNC stuff works now, more or less. After a long night at the studio, i managed to get the thing to do what it's expected. So, it not only moves controlled by the computer, carving out stuff, it does it with at least some degree of accuracy - a  supposed 10 cm move is a real 10 cm move, also according to the tape measure. Also, i found the right combination of software to make the machine accept GCode, the standard format for this type of machining.

That was not exactly a trivial task - i tried dozens of combinations that didn't work. For example, there are many flavors of the controller board i use, Arduino. A piece of software that's said to be "Arduino compatible" may or may not work on any given version of the board. As the software is mostly written by hobbyists, it may easily be that the author of the software has only tried it with one hardware combination.

The board i used for this machine is Arduino Mega 2560. It's bit of an overkill for this task, so it's not too surprising that most CNC software is originally written for lesser (and older) Arduino versions. There's also quite a lot of software for 3D printers out there, which use the same principles as this machine (XYZ motion, GCode instructions), but with the addition of controlling the extruder head which is kind of a hi-fi version of a hot glue gun, and other extra stuff. I tried those too, but honestly my skills (and especially patience) were not up to the task of bypassing all that excess code to make the software work with my crude barebones machine.

I don't actually remember the exact combination i finally ended up using, but i'll try to document that when i get back to the studio. Also, some coding was needed to make my machine work: some basic configuration (i.e. how many rotation steps make one mm of movement) as well as bypassing some code (i do not have end stop switches on the machine, for example).

After all this, the machine works, as said. But just barely. I can already see dozens of improvements that need to be made in order for this to be an actually usable tool instead of just a fun curiosity project. And as far as i've read other people's experiences, that is an endless road. Many people end up doing multiple machines, each better, more capable and accurate than the earlier ones. I wouldn't be too surprised if that happened to me too...

CNC or Moco?

Decisions, decisions... I had one afternoon of free time to work on the project before the holidays. I had most of the parts for the DIY CNC, and the 5mm acrylic parts had also arrived for the alternate plastic version of the Moco head.  I knew i couldn't do both in such a short time so i had to pick one. This time, i decided to have a go at the CNC mill, the reasoning being that if i got that working properly, it would help with the motion control stuff too. Better to have the tools than the product at this point.

CNC mark zero point five.

So i started to bolt stuff together. The CNC mill/3d printer/ whatever uses a lot of the parts from Halsugrip system - i had them readily available. It says something about the versatility of the aluminium profiles that it didn't really take that long before i had the frame done using the standard length pieces (i had done some testing previously which obviously did help). For the linear motion, i used sliding bits on the profile grooves, for now. Will see if that works for real. The linear motion in all axes is powered with Nema 17 stepper motors, which rotate M10 threaded rods.

I bought the zero backslash leadnuts and threaded couplers from dumpster cnc. The quality of the parts seems to be very good. The only complain is that the couplers, while made for a metric system, use imperial hex grub screws for tightening the coupler to the rods and the axle. And of course, i have no imperial hex keys. I guess a trip to the hardware store is needed, or maybe i will replace those with my own screws.

As far as the laser cut parts for the machine go, they're mostly 6,6mm delrin. Wised up from previous mistakes, i tried to make them as adjustable as possible - no exact positions for fixing screws but rather grooves where the screws can be slided around at least a little. Nevertheless, many parts didn't fit at all as is, i had to saw, drill etc. them to bolt my Frankenstein CNC together. Its surprising how despite checking measurements multiple times, and even making a 3D version of the finished gear to see everything fits together before ordering, when i actually get the stuff on my hands, it rarely works the first time.

In theory, the CNC is now built - i have all axes assembled, motors and lead screws in place etc. Unfortunately, i didn't have the time to connect the electronics and bolt on the dremel-like cheap Cotech tool to actually try it out. The design is far, far away from being optimal, so it will be interesting to see what happens when i do. But that will have to wait untill next time...

And now: Delrin

Yep, the Delrin parts arrived, as well as some of the back order parts from Technobots. Most of this stuff will be used for the CNC machine, not the Moco system. Delrin is a pretty cool material, very hard and rigid, and also very low friction. More to follow when i have the time to go to the studio and actually do something with this stuff...

Not the droids you're looking for...

...but pretty close. The answer to the question last time was "steel". Even though some parts are still missing, i couldn't help but toss together a mockup of what the Moco head will look like when it's done, using scrap parts. So, what you see in the image isn't the real deal, but the overall shape is more or less correct, sans wheels and some other bits. The steel parts are 0.9 mm thick (the only option available at Ponoko), which isn't much. I was a bit worried about the rigidness, or rather the potential lack of it, but after bolting the parts together the resulting assembly feels rather solid.

I'm simultaneously working on another approach to the same thing: instead of 0.9 mm steel, it will be made of 5 mm thick plastic sheets. When i get that stuff, i'll compare the two for rigidness, weight, durability, look etc. properties. I hope one of these two approaches will work fine, but if not, the next thing i'll try will be aluminium, in 3 or 5 mm thickness. Ponoko can't supply that, but there's yet one more online manufacturer that does, emachineshop.com. I haven't ordered anything from there yet, but i did already download their CAD software and try it out. Works fine.

As a side note, i also made some progress with the DIY CNC / 3D printer. It will be built mainly from the standard Halsugrip aluminum profiles - actually that's closer to their original purpose in a way. I did quite a few tests for track / dolly alternatives back in the day, and some parts i gathered for that purpose will find a good use in this contraption. My dolly protos use skate wheels currently, but one option was to use slider bits instead. They are machined slippery plastic parts that run along the grooves of the aluminum profiles. The moves are very precise, but they required a bit too much force to be used in a dolly in my opinion, and they made a clearly audible swooshing sound which is a no no for any shoot with on location audio. But for the linear move elements of the CNC / 3D printer they will work nicely, i think. The force to overcome friction should be a non issue, my design uses 10 mm threaded rods to drive the XYZ stages, so each full rotation of the motor is translated to only 1.5 mm of linear motion. With that kind of transmission, there's plenty of force with me i hope.

Steel or Delrin?

Just got a word from DHL that a package from Ponoko is about to arrive tomorrow, they wanted to know whether they would take care of the customs and taxes, or would i do that myself. I let them do it. So, tomorrow i'll get more parts - they come from Ponoko New Zealand (though i ordered from USA). I have only two orders in from outside the EU, so they must be either the steel or the delrin parts for the Moco rig. Either way is good, i get to play a little again.

First "somewhat Moco" prototype, summer 2009

The motion control rig has very humble beginnings. As a proof-of-concept (and out of necessity), i made a quick time lapse camera rig two years ago from a RC toy car by changing the motor and modifying the transmission for very, very slow motion and stripping out the excess parts. Then i just put a small sand bag on top of that, and let the camera rest on it.

I used the crude proto to shoot an actual gig, Skanno's corporate video. I started with D90, but being hooked to a laptop for the time lapse trigger soon proved impractical (which reminds me, the Moco rig will need a still camera trigger option too i guess). For most shots, i used my trusty old HV20, a little HDV camera, sometimes with my DIY 35mm DoF adapter (built 2007). I just let it record for as long as i thought i needed the shot to be, then sped up the footage in post. I'm pretty happy with the results i got.

Electronics

Moco dolly/head electronics

Just a quick note, most of the electronics for the motion control dolly/head have arrived, as well as some of the laser cut parts, belts and timing pulleys etc. At this point, it will have three axes of freedom, track, pan and tilt. I spent better part of a day soldering etc. The basic setup seems to be ok now (at least everything powers up). I will test this as is when i get the rest of the parts, running under computer control. The standalone controls (also seen in the picture) can wait until i have everything else working properly. I'm using D9 sub connectors in many roles - they are pretty robust, and work well with pre-crimped cables and can even be soldered directly to boards - most of the connections will not be permanently soldered though, at least on this prototype, for easier debugging and maintenance.

The electronics setup is rather similar to that of CNC mills/routers and 3D printers. I will need to write my own software though. But speaking of CNC, i ordered an extra set while at it, and will probably build my own CNC / 3D printer. So far, i have been ordering 3D printed parts from Shapeways and laser cut parts (plastic and steel) from Ponoko. While this works really well, everything can be done online, quotes are automatic and the quality is great, in the other hand it's not too cheap when the parts are largeish, especially with shipping... and it takes quite a while to get the goods. Having my own gear to make the prototype parts would make things move along much faster. Not so surprisingly, usually the first version of a part doesn't really work too well, it's the 2nd or 3rd generation that's, well, "ok". And between each iteration, there's a few weeks of waiting, not to mention, usually a few hundred more bucks spent.

As a small rant, i'd really like to see similar online service as with Shapeways and Ponoko from Finnish companies - i'd like to get stuff done locally, but i do not want to call a sales representative just to know how much a square meter of 3mm aluminium costs. That stuff should be available online. Especially as i mostly work on this project after hours, and the question usually arises at 1 am.