Multi-Function CNC: CalFab, updated weekly (or more) - Pics of Frame Inside

At first I tried working out how I could build a RepRap from scratch. That proved near impossible. Next came the McWire: it too turned out overbuilt and extraordinarily difficult to build due to an overarching need for precision in every drill.

What's the solution? Build a new CNC machine from scratch. Of course, I've learned a few things from past experience. I'm keeping the threaded rod concept from the McWire, and the general, boxy-like design from the RepRap. At the same time I've decided that the lower half of the frame will have the X axis and build area only, while the upper half is responsible for a Z axis moving a carriage holding the Y axis which in turn hold the extruder.

Basically, it's a much simplified and CHEAPER Mendel, but you wouldn't even know it! I'm hoping to add enough space to mount a router on the machine (obviously a bit of structural support will be needed). Later, a laser cutter can be added as well, though that is a bit more complicated .


The basic design, in a crude sketchup 3d model:
[i211.photobucket.com]

Additional pics of the completed (and unfourtunately permanent, next time I'll turn those solid rods into studs) frame are here:

[i211.photobucket.com]
[i211.photobucket.com]
[i211.photobucket.com]

Edited 7 time(s). Last edit at 10/12/2009 08:02PM by Lompocus.

I applaud your ambition.

As far as threading rods goes, are you using lubricant (cutting fluid)? The bigger taps have an adjustment, too.

Don't get discouraged, the thrill of seeing and holding your first printed object is worth it.

Good Luck

Frank Davies

I'm using WD-40, it's what I have on hand atm and has obviously not been helping. I don't believe my taps have any sort of adjustment beyond simply sticking them in the hand tool, screwing them in, working them on the rod. Not even filing (or grinding either) a V at the end helps. I DID get one to stick by threading 7/16-12 THEN 3/8-16 but A) The threads were loose, and after around 1/2" the rod itself was moving in the vicegrip. I stuck these little teeth meant to cut piping that were on the pipe into the rod just to see what would happen, and the rod had two deep gashes after I tried, unsuccessfully, to thread.

But, hey, home depot has a little threading machine! We have an ace hardware around here as well, so I'll look for a chuck or something to prevent the rod from rotating. Otherwise, there goes more $$$ to pay someone else to thread them.

On the other hand, I have most of an extruder drawn and, now, modeled. I'm don't plan to build a bunch of these alone, but for the time being I AM mostly alone in building the first one. Here is what I am planning for the extruder:

-Extruder tip: an endnut w/ a 1mm hole drilled at the end
-Heating + insulation: washers, or a metal nut w/ some kind of insulation?
-Feed system: motor from makerbot + wheel bearing
-Drive system: two small metal beams, 2 holes drilled for guide rods and a third in between for the threading. 4 square nuts riveted to the beams, allow for rotational to linear motion conversion.

The only thing I'm stumped on is a way to heat the plastic filament. From what I've seen, it's essentially a wire running into whatever metal that will be heated up to 130C, but I'm not sure I understand why resistors and such are used for that. I'm pretty lost on the electronics for the moment since I'm planning on using the same electronics used in a Makerbot.

Lompocus Wrote:
-------------------------------------------------------
> The only thing I'm stumped on is a way to heat the
> plastic filament.
> I'm not sure I
> understand why resistors and such are used for
> that.

Resistors turn electrical power into heat. You can estimate the number of Watts of heat by measuring the voltage across the resistor, squaring that, and dividing by the resistance in Ohms. Note that resistance will likely change with temperature so this is only an estimate. The maximum temperature will depend on how much power is being turned to heat, how quickly the heat dissipates into the environment and how high a temperature your materials can stand.

For any degree of precision temperature control you need to "close the loop" by measuring the temperature and adjusting the average voltage through the resistor. Changing the average voltage is usually done by turning the voltage on and off and adjusting the ratio of on time to off time (duty cycle).

Might it be simpler to buy threaded rod?

John: Yes, I know how the resistors will work. I was hoping for a less... crude way . For now it works, though, and it's cheap, too! Simple's always best. Thanks.

R.J.: Originally I had planned to just buy threaded rod. Unfortunately, it turned out a bit expensive for the size I wanted (1/4" was too small, 1/2" too large, 3/8" perfect, cheaper than 1/2", but still too expensive). Secondly, I was hoping to have multiple rods so I could have the print stage glide on top of two guide rods (and now that I think of it, I could even optimize the x axis further if I do that...), but unfourtunately, no matter how greased or how smoothed out edges of a metal contact are, a threaded surface just isn't optimal xD. No, I'm not going to use belts either, at least not yet.

*EDIT* essentially, this was just one huge rant about threaded rods and locknuts.

Edited 2 time(s). Last edit at 10/12/2009 07:21PM by Lompocus.

Update for October 8. BTW, Crap, I've got 10 days before an arbirary deadline I set some time ago reaches me. Things that I WILL have done by October 18:

1. Everything

Alrighty...

-I'm no longer going to make any more attempts at threading that damn rod. Instead, here's a better idea: filing and generally roughing up and indenting a very small 1/2" section that is 1" away from the edge of the rod, then using an adhesive, probably a kind of cold weld, to create sturdy enough joints. I'd prefer to have threading, then nuts, then the welding stuff (I cover everything as many times as possible!).

-Besides that, I need to get two 2' segments of 3/8"-16 threaded rod and one 1' segment of the same. These will be attached to the frame with (crown?) nuts and pins. I need them to move freely, but stay in the same general area (the guide rods do most of the stabilizing, but redundancy is always good).

-MOTORS! I'm thinking: Drill 3/16" hole ~10-15mm into the 3/8" threaded rod. Then, stick the (unfortunately perfectly round) shaft into that hole and make it stay there with an adhesive.

Likely, because I'm doing this relatively quickly as a proof of concept, the entire build is going to be permanent. For the frame and motors, I'm looking for future solutions that don't involve welding. Hopefully I can get all of the above done by tomorr, the 9th. Pictures to come tomorrow!

Sunday and Monday:

• Rivet square 3/8"-16 nuts (two) into Z stage to allow for movement.
• Need to build a build stage mounted on the x-stage. Hrm... suggestions? ATM I'm thinking cardboard + double sided tape with some more square nuts, or sheet metal.
• Build and attatch frame for extruder. Thanks to someone, I might have a good extruder!
• For this coming week (Tues-Fri) ->If the mechanics work (and they will): Order electronics + wires ($200-$210), Order stepper motors and extruder motor ($70). As you can see, this is where the majority of the $$$ goes.
• Weekend of next week, or the week after that: Extruder time!

This is an incredibly simple 3d example of how the extruder will be housed and move. But, hey, who doesn't like pictures from time to time? To be made from wood (of which there is an abundance for cheap).

[sites.google.com]

*Edit*: The JB Weld is working pretty well. I'll post some pictures of the finished frame without motors later today.

Edited 1 time(s). Last edit at 10/10/2009 04:26PM by Lompocus.

So it is October 12 and I finally finished the damn frame. That puts me about a week behind my ridiculously ambitious schedule (Hint: that's why it was impossibly ambitious ). Oh well, at least I'm a third of the way there.

Things that are done: The FRAME! It actually moves now, all that's left to do is add some grease so it moves smoother. That was around $70, so this is the wallet-friendly CalFab/RepStrap.

Pics:
[i211.photobucket.com]
[i211.photobucket.com]
[i211.photobucket.com]


There are two smaller threaded rods visible from the top. They're just 1/4" rods that I've used for putting tension on the smooth rods. Since the smooth Z-axis guide rods have a tendency to wobble, I add tension as needed and pull them closer together or further apart. It keeps the guides as perfectly perpendicular to those little wooden blocks as possible.

Things that are not done: Electronics, Extruder, and Motors.

Electronics: As soon as Makerbot has some available, I'll buy the $175 electronics pre-assembled package they have available.

Motors: There goes another $45 for motors from makerbot. In the meantime I'll come up with some way to attach motors I currently have (very similar) to the drive rods. I'm using a pulley for the Z-Axis, currently I'm trying 2 rods, one on each side of the Z-stage. If that turns out to be too unstable, I'll move to 4 rods, one in each corner. Suggestions on how to implement pulleys/gears?

Extruder: Frank Davies, thanks for pointing out your extruder. I sent you an e-mail and you probably didn't get it or something. In the time between now and Makerbot making more electronic kits available, I'll be working on it (~5 days).

Edited 3 time(s). Last edit at 10/12/2009 08:03PM by Lompocus.

This is why I hate external hosting services like Photobucket. Images disappear.