Some shopping, some bodge reversing

I took the day off work today as I needed to attend a private appointment this morning, so I figured I would use the rest of the day to progress with the Mendel.

Shopping
I stopped by the shops and managed to accumulate a number of goodies:

• Sandbar resistors to reverse the bodge on the power supply.
• Some connecting posts to make the power supply more universal
• I picked up a new multimeter which includes a temperature sensor.  (I figured this might be handy and they were on special).
• For the print bed I managed to locate a heat resistant glass cutting board which is 189mm x 288mm.  As the bed is only really constrained in the one direction I figured this was perfect, so I bought a spare.  The to side has a texture, but the bottom is smooth, so I'll simply use it upside down (See pictures).
• The Veho USB microscope I ordered also arrived. (I'll play with that later).

Reversing the bodge

I spent most of the afternoon turning the old PC power supply I am using into a universal 12V power supply.  This involved fitting a switch salvaged off an old plan printer, some connecting pins, and a sandbar resistor to act as a latching load.  The article I based this on mentioned cable tying the resistor to the case as a heat sink, but as I have a number of old CPU heatsinks and fans lying around I fitted that instead.  Probably overkill, but better safe than sorry.  The only mistake I made is that the fan is noisy and I didn't test it before soldering it in.  Doh!!

Bodge Alert, but it melts plastic!!!

I ended the last post saying that I needed to try out the heating.  Of course this wasn't going to be something I leave for very long.

I am using an old lab power supply that I was given by someone on FreeCycle a while back.  I didn't expect it to make the grade as the ammeter only goes to 4 amps.  I did try it however, but no such luck.  I then went to dig out the various old PC power supplies I had stashed away in the garage and found this handy article on the web.

My power supplies are all AT, not ATX, but I grabbed the one with the highest power rating and decided to try it out.  Reading the article I realised that I needed a decent load resistor which I couldn't find on any of the scrap electronics boards (mostly out of old printers or PCs) I have (I'm not very good at electronics so didn't know what I could use instead.).

I decided to try the supply without a load resistor, but that didn't work, so I then opted for the other trick mentioned in the article which talks about using an automotive bulb.  I happened to have an old 2CV headlight lying around looking for a job, so roped it in.  As you will see from the pictures, this really is a bodge.  Don't do as I do! (i.e. Kids, don't try this at home).

I will tidy this all up later, but I couldn't wait to see if it worked.  What I can tell is this.  My LEDs on the heated bed PCB don't work, but the bed does heat up.  Also, the extruder works.  My first bit of melted plastic is pictured below.  Now I really am motivated to sort this out.  I have Friday afternoon off, so hope to be printing by the end of the weekend!!!

Extruder Mounting

The first think I noted was that the design of the extruder means that I have should have fitted it to the carriage before final assembly.  I also think I need to figure out the hot end wiring at the same time, else I'll be tearing it down again.

PCB Heated Bed Mk2
I started with the bed.  I had bought a load of DiBond FR as it is meant to be fire resistant, so should handle the heat better.  While reading up on how to fit the PCB heated bed, it also became apparent that the purging notch is no longer needed for the bed.  Great, that means my DiBond can be used without cutting, although it does make it larger than the PCB/heated area.

I also noted some people commenting about using some insualtion under the PCB.  Prusa himself refers to air being a better insulator than wood in his post on mounting the PCB.  I happened to have some heat resistant fibreglass matting from a plan printer that I dismantled (I had kept all the nichrome as well as this was before the days of PCB & resistor based heaters).  So my final solution is going to be the following sandwich:

• DiBond FR base
• Fibreglass matting (8mm)
• PCB (resistor side down to get concave warping)
• Heat resistant glass (bulldog clipped to the rest)

To make up for the 8mm height loss  fibreglass matting, I am going to trim down the printed springs I have (well actually, I'm slipping them over the side of the DiBond, see the pictures).  I've read they break anyway and people have moved on to using real springs. Heck, come to think of it, if I mount the PCB on floating bolts then the fibreglass matting will provide some spring anyway (but I'm not taking that risk right now).

In order to use the centre hole for the thermistor, I drilled a corresponding hole in the bed plate and cut a hole in the fibreglass matting.

The PCB board and thermistor is now wired up and the bed mounted as per the pictures below.

ParCan Hot End

Next up, mounting the ParCan MK2 Hot End.  As I mentioned above, I had to strip down the extruder to mount it to the X-carriage, but that went quickly as I knew what I was doing.  I cut a small notch to clear one of the long bolts, that being easier than cutting the bolt.  I then reassembled the whole lot and started on wiring the hot end.  It went really easily thanks to ParCan supplying some bootlace ferrules with his kit, so that the wires are simply crimped.  I then insulated them with some Kapton tape.

I did however note that this hot end is very close to the x-carriage.  Looking at the later Prusa Mendel carriages with the LM8UU bearings, they are MUCH slimmer which would result in the hot end being further from the plastic.  I expect to get some heat damage on the carriage, so this might have to be the first area to change.  Pictures below!!

The next job will be to locate a suitable piece of glass for the bed.  I know a lot of people are using normal glass, but I prefer going with the safer option (as many others are) of using heat resistant glass.  Glass place mats or pot stands should work, so I'll be keeping an eye out for something suitable.  If anyone out there knows where I can get a 20cm x 20cm glass pot stand, please let me know.

However, in the interim, I am sure I'll be trying out the heating and starting to calibrate the machine.

Sanguinololu Setup

According to the supplier "Think3DPrint3D", my electronics was already flashed with Sprinter by Kliment and they user Kliment's Printrun/Pronterface to control it all, so after connecting it should just run.  Great!!!

I went ahead and installed the pre-compiled version of Pronterface.  When that didn't work I moved on to the latest version from GitHub (linked above).  I wasn't really thinking straight, as the fact that Pronterface was only showing Com 1 should have immediately pointed me at the problem.

What he hadn't accounted for (not his fault) is that I had already messed up my PC while trying to get the Tech Zone stuff working.  The device wasn't being recognised by my PC.  After some googling, forum reading, etc, I figured out I needed to remove and upgrade the FTDI drivers (I'm running XP, so it's a pain, but this doc on the FTDI website helps).

So, now, I have the latest Pronterface, so let's see if this all works?

Brilliant, it connected, so on the testing of the motors.  These are all working brilliantly, however I noted that I have wired the limit switches incorrectly, not finding clear instructions elsewhere I followed a random article which appears to have gotten it wrong.  I need to go and do some reading, but I think I read somewhere that this can be swapped in the firmware, it's either that or redo the wiring.

I'll need to think about this and decide on the best approach.  They are currently wired to normally open, whereas I guess normally closed would make more sense as the accidental disconnection of the limit switch would cause the machine to stop, thinking it is home (which appears the safer option).

I will need to sort out alternate wiring for the extruder motor as the wires are too short.  I am thinking of following nophead's DB9 connector idea.

Next step on the electronics front will be to calibrate the system.  Before that however I'm going to focus on some remaining hardware work.  Namely mounting the bed and the extruder.

Sanguinololu Installation

As mentioned earlier, I bought a Prusa Heated Bed and Sanguinololu kit from Think3dPrint3D.

Communication was fantastic and all the goods arrived this morning as promised, well packaged and labeled.

I then started assembling the electronics. This is much simple than the TechZone ones due to being a single board, so basically the only issues were mounting the board on the frame and wiring all the molex connectors.

For mounting the board, I rough cut a piece of plywood, figuring I could do something better in the future when I can print.

The other difference between these electronics and the TechZone ones is that these use micro switches for the end stops instead of opto's.  Much easier for non-electronics guys like me, but of course I had to find mounting locations.  I figured some out, but they may change in the future when I am able to print some brackets.

Next up I'll be figuring out the Tool Chain updates and trying to switch it on for the first time.

Extruder Experience

In 2010 I bought the plastics for the Wade's Extruder from nophead as per this blog post. As mentioned in today's earlier post, I have have also purchased a hobbed bolt and Mk2 HotEnd from parcan.

I must say, I was very impressed with parcan's service. Rapid delivery, nicely packaged, and it looks like everything I should need. I'll go through this in detail below.

Hobbed Bolt

The package arrived with 2 bolts and a normal and nyloc nut. I thought I was only buying 1 bolt, so that was a nice surprise (hope that's what parcan meant to do and I didn't get someone else's package). I was impressed with the "hobbing", so much so that I'm glad I didn't even try to do it myself. The only observation was that it was a very tight fit to go through the bearing. Looking closely I noted that it was probably just the "swarf", so I put the bolts into my pillar drill and held a piece of fine sandpaper to them for a few sections. no both go through the bearing quite easily (I was concerned that if I forced it thro

ugh I wouldn't be able to dismantle the extruder in the future).

Before and after pictures below:

Parcan Mk2 Hot End

Firstly, here's a picture of the include parts. Great, no hunting around for bits, everything is there and assembled. Not only that, the kit includes a spare resistor and thermistor.

The first thing I noted is that this hot end uses a PTFE sleeve instead of the machined PTFE of old. The only repercussion for me is that my Wade's extruder has a 3 mm hole for the filament, I will need to drill this out. I also noted that the PTFE sleeving seems a bit long. I presume this is in case people are using a different design of extruder. Here are some before and after pictures of the extruder frame with modifications:

I then went ahead and assembled the extruder. See below. The biggest issue was that I was struggling to get the "hobbed" bit of the bolt centred while still having enough clearance on the gear for the motor screws. I then measured the depth of the bolt head hole in the gear and realised that I could force it in further. This solved the problem.

Installation of the extruder will have to wait until I have the electronics working.

RepRap back on track

After about 17 months of absence I decided to get this project back on track.

This was inspired partly by the recognition that I have been spending way too much time working and way too little time on my hobbies, and partly by a revival of interest due to the recent launch of the Raspberry PI. This device is right up my street, having cut my teeth on a ZX Spectrum back in the 80's. I immediately thought that this might tie in with the RepRap, and so did others as I saw RepRap mentioned a number of times in the news articles and forums.

Well, back to the RepRap. As those of you who have been following (or have read my older posts) will know, I have been building a Mendel using Techzone Remix Gen 3 electronics. The failure to get these electronics working properly being the subject of my last post and part of the reason the project stalled.

On re-investigating and knowing that I wanted a heated bed, I contacted "Think3dPrint3D" on eMakerShop (ironically, Jean-Marc of eMakerShop has previously bought some stuff from me) about his heat bed PCB last weekend as I wanted to buy within the UK. He said he was getting some in, and during the ensuing conversation I mentioned that I needed better electronics. This resulted in me purchasing a Sanguinololu v1.3a kit from him (assembled and tested). I figured, there was no point in wasting time trying to figure it out when he already has.

In the interim I decided to also look out for the other bits still giving me grief, namely the nozzle and Hobbed bolt. I ended up ordering both these from "ParCan".

Next steps are to figure out where I am at and start moving things forward. I will post these are separate blogs in order to not have too much in.

Final note for today is that I started by removing the TechZone electronics from my Mendel frame. I will keep them and still try to get them working sometime as I thought it would be a good donation to my brother down in South Africa who I would like to get setup to print as well.