Constructing Janus, by Dirk

[bdring]

I think you should built and test before uploading to Thingaverse. If there is an error, it is a shame to have someone else build it.

[dirktheeng]

good idea... will do!

[dirktheeng]

All,

I'm about ready to put in the order for the laser tube and I wanted to ask about the 2 length versions of the lasers. I am curious if it is worth the cost to get the 800mm version over the 700mm version from coletech. The only advantage that I can see is a bit better beam divergence. Is there any other advantage that would make it worthwhile? Have people used the 800mm version? run into any issues with either?

[dirktheeng]

Well... I ordered the laser and power supply as well as the pump radiator and fans. I got the laser and power supply from qiandingzhensatisfaction on ebay (lovehappyshopping's new store) - $340. I ended up going with the swiftech MCR320-DRIVE-R2. It's a tripple 120mm radiator with integrated resevoir and pump. It was pricey ($205), but I know it will work out well and after adding up the cost of a radiator based system with all the components separate, this wasn't a whole lot more expensive. I know swiftech and they make really solid products. Perhapse the best thing about the MCR320 is the pump. It is a very solid pump and I have yet to find a truely negative review of this thing. For it's size and power, it produces strong flow and pressure head. It can also be speed controlled via a PWM signal. The fans I got were Arctic Cooling F12 PWM. They are super quiet and can be controlled by PWM (5v PPM, ~25khz base frequency, same as the swiftech pump). The nice thing about these fans is that they can all be controlled off of a single PWM signal without putting excessive load on the TTL signal. So I could potentially control all 4 devices off of one logic level signal. I plan on controlling the speed off of the arduino as well as eventually controlling the laser power based on gantry speed through modbus.

I also baught larger tubing for the water supply and quick disconnects for the water and air supply.

I have to get a 12V power supply, an air pump, and an exaust fan yet and I think that is it. This thing will be fully functional quite soon.

[dirktheeng]

I finished the first version of the Monitor Arm.

The concept is to use a threaded rod as the solid pivot and the means of applying a constant frictional force. The constant frictional force should be enough to support the monitor, but not lock it so it can be moved if the clamps aren't engaged.. The clamps with the thumb screws can completely lock the joints in position. All joints have a clamp except the pan joint on the "wrist" as the monitor will be mostly vertical and doesn't have a long lever arm to generate large torques.

Here's a pic of the final assembly on the computer. There will need to be some minor tweaks when I get the actual hardware in place, but this should work well as is (I hope).

Full Assembly

here's a view of one of the clamps from the side:

Clamp Zoom

here's a view of the basic joint assembly:

Joint Zoom

The only thing I haven't modled is the knob that will get put on the head of the cap screw in the above picture. McMaster sells them and it is quite cheap. I will glue the nut to the washer on the bottom and maybe put some sand paper on the washer so that it has a high friction surface that will allow me to tighten the bolt down without worrying about the bottom nut spinning.

[dirktheeng]

All,

I ordered an inline flow sensor. I got the INS-FM17N. I chose this one because I had read a couple reviews of the older style pattle wheel version failing in such a way that the pattle blocked the flow and caused overheating of graphics cards. This wasn't any more expensive and didn't look like it could fail that way. When I get it, I will have to make a bracket to hold it.

here's a pic:

flow meter

This thing essentially operates as a switch that turns on and off once with every revolution. The faster it revolves, the faster the thing turns on and off. This will be fairly easy to read with an arduino.

I also purchase a really cheap ATX power supply off of amazon for $10. This will give me 12V, 5V, and 3.3V with plenty of power for pumps, fans, thermal systems, and an arduino. It was much cheaper than buying a 12V power supply like the 24 V power supply we got from Keeling.

[TLHarrell]

I'll toss in my 2 cents on this...

How much does the monitor weigh? I would seriously consider adding a lever and some springs, or something else to provide counterweight to support the joints if you want them to be tight but movable.

The ATX power supply will need some modification to supply power. Usually this involves placing a large resistor across part of the supply to create a load condition. Most power supplies like this will not turn on without seeing a load. Run a Google search on using an ATX PSU as a benchtop power supply for electronics. It's a fairly common hack.

On the inline flow sensor, you could simply hook it up to an LED. If the LED is flashing, you have flow. Solid on, or off = not good. Unless you like adding Arduinos...

I'm no expert by a long shot, but figured it'd help to think of these items a bit.

[dirktheeng]

I'll toss in my 2 cents on this...

How much does the monitor weigh? I would seriously consider adding a lever and some springs, or something else to provide counterweight to support the joints if you want them to be tight but movable.

The ATX power supply will need some modification to supply power. Usually this involves placing a large resistor across part of the supply to create a load condition. Most power supplies like this will not turn on without seeing a load. Run a Google search on using an ATX PSU as a benchtop power supply for electronics. It's a fairly common hack.

On the inline flow sensor, you could simply hook it up to an LED. If the LED is flashing, you have flow. Solid on, or off = not good. Unless you like adding Arduinos...

I'm no expert by a long shot, but figured it'd help to think of these items a bit.

Hey thanks for the ideas!

The monitor only weights about 10 lbs. The joint I am most concerned about is the elbow. I am sure that the clamps will be able to lock the joint, but I dont' want the monitor to fall if I ulock them. I've thought about using a spring/lever arm to help support the joints, but I am not sure that this is what I want to use. I've also thought about a momentary switch and some sort of solinoid or motor to unlock the joints... the idea is that you grab the monitor with both hands, push the momentary switch (mounted on the back near where your hands grab it) which acts to release the joint, you move it to a new position, release the momentary switch, and the thing just stays there. I would have to use some springs to lock the joint and have a powered mechanism to unlock the joint so that if the power is lost, the joint says locked. I haven't come up with the mechanics to do this yet, but I've been kicking around some ideas.

I knew about the ATX issue from times past workign on diagnosing problems with PC's. I don't recal which wires need connections, but I knew that was on the internet too.

The idea of a visual/audio alarm is something I have been thinking about too. Eventually, I want to use the arduino I already have as a modbuss/brains connection to Mach 3. The arduino will handle reading the flow rates and passing the info to Mach3 which will display the flow rate on a DRO. I will probably also add a LED and/or a buzzer to alert me if the flow fails.

I also found some very inexpensive analog temperature sensors on spark fun (thermistors, diodes etc). I can read the voltage with an arduino and calibrate in software. I can read the temp in several places and display that info as well. I just need a little thermal epoxy to set the sensors in place.

[TLHarrell]

How about this design for a monitor arm? Gives you far better ability to move the monitor around side to side, front to back and swivel. Allows it to tilt (bracket at the top), and you can adjust height by keeping the bottom post long and moving it up and down in it's brackets on the side of the machine. It's a far simpler design. It also allows you to drop the monitor flat against the side of the case for storage (if that would ever happen...).

bracket.JPG (12.89 KiB) Viewed 17227 times

Of course, I would totally over build it myself and use steel shafts and bronze bushings for the joints, rectangular steel tubing for the rest, and would pass the wiring through the arm pieces.

Seems to me like you're going total overkill on the electronics end of things. Might as well go all out on other stuff as well.

[metalman]

Dirk, I have an arm for the monitor on my CNC plasma table. It gets a workout and is very handy. Besides holding an old CRT type monitor, it also has a keyboard shelf below the monitor. Unlike yours, it's made of heavy sheet metal and has counter balance springs. The monitor is a lot heavier than your flat screen but the arm is rock solid. All the joints are held by friction, and the counter balance springs. There is a parallel link to each arm joint to keep the monitor upright. Both the top and base swivel.

I really like the look of your wooden box frame. There is one thing I noticed on your joint design that may cause a problem. The long bolt at the pivot points might need a tube between the two sides to keep the tension even on both sides and eliminate any buckling at the joint. Another option would be to use a short bolt on each side and tension as needed.

Jay