Prusa i3 3D printer

[Gina]

Those £170 I3 kits are available for £149 HERE  and I can see nothing wrong with buying one of these and working on it to improve is as Dave has done with his.  It will give you a start by being able to 3D print parts which you can use to upgrade.  Once you have any sort of half reasonable 3D printer you will be able to get going. 

You may find you can only go so far without replacing virtually everything and then it's probably time to use what you have and the experience gained to build a printer from scratch though I can't guarantee it costing you less than a good quality kit but it's much more satisfying

One thing with a RepRap printer is that the software/firmware is free and being constantly improved by an army of conscientious amateurs.  Also, there are so many of these out there in the world that parts are cheap.

[tekkydave]

They should be complete. If you find one you fancy post a link and I'll check it out. I would recommend getting one with an aluminium frame rather than the wood or acrylic version as they are more rigid.

[Gina]

Yes, that's a good point.  That one I linked to looks like wood.

[Stub Mandrel]

I have a pretty well equipped model engineering workshop, so I'm not worried about beefing up the frame, adding anti-backlash nuts etc. But I would like to start with a kit build rather than end up with missing bits etc.

This one looks better engineered than most, and its big (too big?): Aluminium Frame Prusa

Or this cheap kit?  Easy to make a more robust frame.

Or this from a UK supplier for less worries but not as elegant or big as the first option?

[tekkydave]

The first one looks a bit unconventional and the frame a bit flimsy. The others are more like a regular prusa i3. Personally I'd go for the last one due to the UK supplier. It is pretty close to what I originally bought.

[Gina]

Yes, I thought the frame on the first one looked flimsy, particularly with all the weight hung off it and being so high.  It could be braced to the bottom part of the frame I guess.  I also didn't like the control box sticking out the side - makes it very big!

The third is twice the price of the second but would mean less work and cost to get into a first rate printer.  My general rule of buying things is not to go for the cheapest as everything is likely to be produced down to a price at the expense of quality.  This doesn't apply to everything though, only the more expensive items.  If your only requirement is for something cheap and cheerful that will give you 3D printed parts from which to construct a printer with virtually everything new then the second would suffice I think.

[Stub Mandrel]

I think I would as likely to machine as print parts. Looks like No. 3 is the favourite. I have a sneaky finance plan which I will work on over the weekend.

[tekkydave]

I suspect with many of the cheaper kits, including mine you will get a small but limited support from the supplier to build it initially. The Chinese kit is perfectly fine but the support may be very limited. In truth you will get more support from other builders like Gina and myself. I got some good support from the Reprap Forums and just general googling.

[tekkydave]

12 hours ago, Stub Mandrel said:

I think I would as likely to machine as print parts. Looks like No. 3 is the favourite. I have a sneaky finance plan which I will work on over the weekend.

Just had another look at this kit and it has a decent construction manual which mine was lacking. Worth its weight in gold if you havent built a 3d printer before. I guarantee once you have it built you will start seeing improvements you can make

 

[tekkydave]

I have started using these crimp connectors to terminate wires into screw terminals. It helps particularly with the Ramps where the fitted terminals are a bit weedy for the 11A wires. They can be trimmed to length and also because they are flat its possible to insert more than one in a terminal.

 

[tekkydave]

Spent most of the day building a Mosfet driver board for fan control. There are 3 spare servo output pins on the Ramps so I built a board with 3 identical circuits. I will be using one to control the extruder fan initially and the other 2 are spare for now. I copied the D8-D10 Mosfet circuit from the Ramps schematic, using IRF3205 n-channel Mosfets which is what is fitted on my Ramps.

The completed board. 

Installed in some free space in the RPi half of the enclosure

 

[tekkydave]

I have connected up Channel 1 of the Mosfet board to the Ramps. The Mosfet input (White wire) connects to the Ramps D6 pin (signal pin for Servo 2).  The extruder fan connects to the Mosfet output. I have used the 12V-AUX supply (adjacent to D2) to supply the board.

I then made the following simple change to the Configuration_adv.h in Marlin:

#define E0_AUTO_FAN_PIN 6
#define EXTRUDER_AUTO_FAN_TEMPERATURE 50
#define EXTRUDER_AUTO_FAN_SPEED   255  // == full speed

Uploaded the sketch and hey presto - the extruder fan only turns on when the extruder temperature is above 50C.

I realise that now I need to keep the 12V ATX power on while the hotend cools otherwise the fan will go off. I was previously having an M81 in my end-gcode to turn the 12V immediately the print was finished. I relied upon the 12V derived from the 5VSB to always power the cooling fan. There are a couple of solutions to this - I could put a fixed delay in the end-gcode or maybe use:

M109 R50
M81

This sets the extruder to 50C, waits till it gets there then turns the power off. From there it can cool back to room temp without the fan and no risk of damaging the extruder plastic parts.

[Gina]

Ah yes, the M109 R50 followed by M81 was what I was thinking of instead of the time delay I'm currently using.  Also, doing it this way saves having to switch the fan separately or to supply power to it separately   I think I'll change over to these codes as it's more reliable than the simple time delay I'm using ATM.

[tekkydave]

Yes, I suppose I could do away with the mosfet solution and have the fan running only when the 12v is on. I may still put the 5VSB to 12V step-up in the box to power the mosfets/fans. I really want the extruder printed parts to be protected if I turn off the 12V manually when the hotend is at full temperature. No need to worry about the M81 in the end-gcode in that case

[Dave_D]

has anyone tried one of these? http://www.gearbest.com/3d-printers-3d-printer-kits/pp_337314.html i might have enough soon to get one

[tekkydave]

Schematic of the triple Mosfet board. Drawn using gEDA. I have labelled the outputs for driving fans but this is a general purpose circuit, copied from the Ramps schematic so could drive anything e.g. hotend, heatbed, LED lights etc.

You will need to view the full size image to see all the circuit lines. The gEDA image export seems to make a mess of the thinner lines in the schematic.

[Gina]

I use the same circuit in my Titan printer to control the print bed heater with the power MOSFET on a nice big heatsink.  Removed the MOSFET from the RAMPS (having blown it ) and wired I/O line directly to the output.  I put the series parasitic oscillation stopper resistor right next to the MOSFET.  The 300mm square bed heater runs at 36v and nearly 20A   It gets hot quite quickly

[tekkydave]

At the moment I'm only driving a 30mm 12v fan (approx 100mA including the led) but the supply tracks on the veroboard will need beefing up if I drive anything heftier. I might add some case lights if I ever get round to completing the fume enclosure.

[Stub Mandrel]

1 hour ago, tekkydave said:

You will need to view the full size image to see all the circuit lines. The gEDA image export seems to make a mess of the thinner lines in the schematic.

I sometimes feel that all circuit and PCB design programs are written by people who hate computer users :-(

[Gina]

1 hour ago, tekkydave said:

At the moment I'm only driving a 30mm 12v fan (approx 100mA including the led) but the supply tracks on the veroboard will need beefing up if I drive anything heftier. I might add some case lights if I ever get round to completing the fume enclosure.

Yes, I remember   Now that's what I call over-engineering   But why not if it works  

I plan to add case lights - LED strips - when I get round to the fume cupboard for my Pilot.  Titan is already enclosed but I've not got round to lighting that yet nor to adding a camera to remotely view the print session.  I'll probably get round to these things one day when I get the enthusiasm but I have this habit of starting new projects and/or flipping from one to another.  But it keeps me happy

[tekkydave]

I suppose it is over-engineered for just a fan

 

[Gina]

Well, I'm quite a fan of your work

[tekkydave]

1 minute ago, Gina said:

Well, I'm quite a fan of your work

Jeez 

I usually over-engineer things - one of my traits. It has caused issues with managers in the past who wanted a quick & dirty solution to save their behinds. I always wanted to take time to find the best solution that would reduce the risk of failure in the future. Don't go into I.T. if you're a perfectionist - you will always be frustrated

 

[Gina]

Sorry about that - I just couldn't resist it  

I think I tend to over-engineer things too.  And I think I must be a perfectionist - I'm always frustrated!

[tekkydave]

I have rebuilt the 5v to 12v step-up board that used to be at the rear of the old case to fit inside the new one. 5VSB input on the left, 12v outputs on the right.

I am using 3-pin connections for any 5v circuits to avoid any potential disasters accidentally connecting to a 12v circuit. All 12v circuits are on 2-pin connections.

Fitted in the case. I have rotated the Mosfet board 180 deg so the 12v i/p is closest to the 12v o/p from the step-up board. I have put plenty of spare pins wherever I can in case extra connections to the 5VSB or 12v are needed. The 5VSB is needed for the RPi and also the servo circuit power.