In the past few months I have discovered that there are a few things that are very bad for progress on building a RepRap:
1. Moving house.
2. Changing Job.
3. Red Dead Redemption.
Having completed the above three I am now back building my reprap. I have almost finished the x-axis. See the below photo of my progress. Struggling to find time for the build at the moment so progress is likely to be slow for a while. Drilling and shaping the cast plastic bits is becoming quite annoying, wish I had held out and bought proper printed parts, never mind hind sight is 20:20!
I have also been practising using Solidworks at work, so what better to tune my skills than with the Mendel Solidworks files. See below for some videos I made using Solidworks. I have changed the model quite a bit, fixing a few errors and making the limits rights so you can only move the axes to the allowable positions. I will try and post my adjusted assembly files soon for those who are interested.
Just thought I would write a few words about using SketchUp for modelling with RepRap. I'm not sure if it's just me but very few people seem to be using SketchUp for doing their designs for the project. I really like Google's SketchUp and think it is fantastically easy to use. Capo's recent comment reminded me of the fantastic model he put together of Mendel and prompted me to have a play again myself. A quick look at Capo's blog and you can see how he has used SketchUp in a number of ways for both presenting idea's and for component design.
The below video shows Capo's model that I have coloured then animated.
I've done some more work on the extruder build. I had some problems getting the gears to mesh correctly, I found that the large gear seemed to be slightly ovalised which meant that as it turned the wheel would grind in some places and miss in others. I think I have solved this by filing down the teeth that were grinding using a triangular file (note the red marks I have put on so I know where to file) until eventually the gear wheel was circular. It's still not perfect but should be workable I think. I still need to glue the nozzle assembly in place.
I have also starting working on the x-axis. Beginning with the x-carriage. Nothing too difficult here except the captive nuts. A few of the nut locations had to be drilled to the correct shape to hold the nut, I did this using my dremmel clone with a small drill bit and file attachments, time consuming but works in the end. It is also important to remember which holes have to be drilled at an angle.
The RP parts I have are for Adrian's geared extruder see the wiki here. For this you need some pats not listed on the original BOM list. There are a couple of different screws you need, nothing hard to find on ebay. Main parts you need are a short piece of M4 threaded rod. An M4 "Insert" - this is a splined piece used to grip the plastic filament. An M4 wing nut, and 3 bearings. The splined piece I got from ebay here is a bit different to the one shown in the wiki but serves the same purpose. It doesn't have a grub screw but it is internally threaded so should stay in place with bolts either side of it. It was listed as "Ripmax DYCO M4 x 0.7mm Coupling Insert" looks like it is used in the clutch mechanisms of model cars, trains etc. After a bit of drilling and shaping the parts seem to fit together ok.
First thing I thought I would try out of my plastic parts was the belt splitting jig. I managed to drill the holes ok. The slot was a little trickier, I used my dremmel clone to do this. A tip I have found for drilling the holes in the plastic if you are concerned about it "biting" into the plastic and cracking it is to run the drill in reverse and it tends not to grab at the plastic, but takes longer to drill the hole. Below you can see the finished jig. It worked perfectly and I now have the belts split successfully.
I now have my plastic parts. I finally went for a set of the cast or moulded parts being sold by fotonlabs on ebay for about £150. I decided it was worth the saving and do the drilling myself (I hope). The seller warned me that they had some breakages reported from the postage, and that they would replace any parts that were broken. They were right, a few parts did arrive broken, but they have been very good and are sending replacements out straight away. The plastic is quite brittle, and the seller has told me they are changing the plastic mix to be more flexible. I have had a go at drilling a few parts, and the seem to drill pretty well but I think as the plastic is quite brittle I will have to take care and not rush it.
I will be moving to a new house and job in a month, this might get in the way of making quick progress but I should still find an hour or two here and there.
I decided to have a go at extruding some plastic through the hot end to make sure the temperature I was reading was correct. I used the ramp button to slowly get the hot end up to temperature. Everything went well, at about 160 to 170°C I could start to smell the PLA melting, smelled a bit like burnt sugar. Once it got up to 190°C I had a go at pushing the plastic through, it took some force, but it definitely worked, I can see why people are having problems with the brass nozzles coming out. Everything seems to work so far, woo! Check out the screenshot and video below.
I've done some work building the hot end so i thought I would share. I don't have a lathe so I didn't fancy trying to drill out the brass nozzle myself so i bought one of the pre-made nozzles and barriers sold by reifsnyderb on ebay. I have used bare nichrome wire rather than insulated as I it was much more readily available. I have used 32 SWG nichrome bought off ebay. My thermistor is of the 100k variety and was bought from Watterott.
I measured and cut an approx 6 ohm length of the nichrome. The way i went about wrapping the nichrome onto the nozzle was to wrap the wire in the valleys of thread, then I "unscrewed" the nozzle which left me with a nice uniform spring of nichrome. I could then wrap a layer of Kapton or (Koptan - as mine is) tape around the brass to insulate it from the nichrome. I reapplied the spring of nichrome and taped it down with more Kapton. I wound a second spring of nichrome back up the nozzle over the first layer - this was a bit more rough than the first but I took care that there were no contact points between the nichrome coils. This was then sealed with yet another layer of Kapton.
The thermistor was applied with the leads well separated and the glass bead as close to the nozzle tip as I could manage. I am now a little concerned that the nichrome heating element is quite close to the thermistor as I have read that this can damage it, but I don't get that if it's rated for over 300°C how it can be. However I have a couple of spare thermistors in case I have made a mistake. The thermistor was secured in place by more Kapton.
I had a couple of goes at crimping the leads using different methods without much success, I think I really should have done this before applying to the nozzle. So my final solution was just to do the old split and twist the wires together, then added a bit additional security with heat shrink. This seems to hold the wires fairly securely.
I re-tested the resistance to make sure it was still approx 6 ohms across the nichrome.
I unscrewed the nozzle from the PTFE thermal barrier and applied PTFE tape to the thread on the brass nozzle, and screwed the nozzle back in.
I used a bit more Kapton tape to hold the wires in place and some more over the nozzle to provide some extra insulation.
I have spent some time time trying to get the extruder board up and running. I hit a few snags along the way, and thought I would document them in case it helps anyone else.
Firstly is uploading the firmware, as with the motherboard you can use jumpers if you are unsure of your 10 pin cable, just make sure you get them correctly aligned, they are the opposite way round to the mother board so you have to put the extruder board on its back if you want to do it this way. First problem I had was getting the arduino software to correctly upload the firmware I was starting to think there might be a problem with the board. After a bit of looking on the Internet I saw many comments about pressing the reset button just before upload, I tried this and after a few attempts it worked! I was amazed. What I had to do was hold the reset button down, click upload, wait for the text to appear then let go of the reset.
The next was the wiring, i was baffled at first by how to set it up, there wasn't many clear instructions, but I did stumble upon the "official" guide which is hard to find (here is the link). On this site it shows a picture of how it is wired up. I copied the wiring and got some action when I tried starting the RepRap software, except to start with I was getting zero readings on the temp. It took a few attempts to get everything working, I'm not sure what I changed but it seemed like the boards needed to be started in the correct order, and having good solid wiring certainly helps, I've started using some premade jumper cables rather than the IDC connectors.
The extruder stepper now steps when i click extrude, and the thermistor is reporting the correct temperature. The only annoying problem is that the stepper makes a high pitch whine whenever it is not stepping, I tried trimming the pot down and it didn't help, just stopped the stepper from turning. I tried switching to the software PWM set current bypassing the pot but it didn't help either. I've been tracking the temperature and the stepper isn't getting hot so I'm not worried, but the noise is annoying. See below for a video of the setup printing the minimug.
I have been buying alot of hardware recently and think I now have most of the vitamins for the RepRap Mendel. I still have not got the RP parts under the hope that the cost of printed parts would drop when more people started getting printers up and running. Anyway I thought I would make a list of the suppliers I have used in case they are of any help to people building in the UK.
The last thing to buy are the plastic RP parts. What a headache looks like there are 3 options, buy a laser-cut version for (approx £150 + tax + delivery) but I am put off this option as there modifications to the design and different hardware requirements. 2nd option is recently there has been quite a few moulded plastic parts being sold by a guy in Ireland he is offering free delivery and as it is EU so there should be no customs tax. He has so far sold 2 grades A and B, the big downside is that the holes require drilling, this would be a real pain but for the cost saving it might be worth it. The sets are going for about £80 for B grade and £150 for A grade. 3rd option is fully printed parts. This would be my preferred option if it weren't for the cost. There seem to be very few people printing parts. One main contributor is the RepRap-god amongst us Nophead, who seems to be single handedly supporting the RepRap cause. Another is Adrian Bowyer himself, but despite promises of random buy-it-nows of £40 only one has been sold at this price, and not that many many sets have been up for auction. Because of this low supply and high demand these sets are reaching premium prices, there is a quite a range from about £200 to £450!
I've moved on to testing the TechZone Remix stepper motor controllers. I've wired up the boards in a test bench set up. I was confused at first that the motors were only turning one way, clockwise, until I worked out it was because the end opto sensors were not plugged in so the software thought they were in the home position and hence would not allow them to turn the other way. I was surprised how straight forward everything was to put together. The ABCD wiring I was worried about earlier was not a problem, it was the correct ABCD same as the standard Makerbot electronics. The video below shows one of the first tests, this is the set up printing the minimug object. Note that the y and z axis only rotate clockwise as there are no opto sensors attached.
My electronics package from TechZone finally arrived! I think it has been held up at UK customs for almost two weeks. For those of you not familiar with the TechZone Electronics Remix, they are an alternative to the Makerbot set, you can find out more here. There was some debate about the ethicacy of the electronics at first but I think that has all been resolved now. In my defence I was all set for buying the Makerbot set but they were out of stock.
Anyway, I thought I would post some pictures of the unboxing for anybody considering a purchase. My first impression is of how small they are, i knew they were smaller footprint than the Makerbot set but boy these are tiny!
Impatient to start testing the stuff out I decided to start with seeing if I could upload the firmware (the bootloader is already pre installed). This is done by connecting the motherboard to the USB TTL boad via the 6 pin ribbon cable. I can't say I managed it straight away, I had some problems getting decent connectins at the connectors. So switched to the jumper method described on the wiki page. After using jumpers it worked a treat just as per the reprap.org build instructions. The only thing I noted is that you have change the COM port in RepRap software preferences. I don't think this is mentioned in the build instructions, but is important for running the motherboard test.
Just thought I’d share this. I’ve been playing with the RepRap software and thought I would brighten up the shortcut to the reprap.bat file by giving it a proper icon. See below for the icon file and what it looks like on the desktop. To get the icon to show, download the .ico file by following the link, right click on the shortcut on the desktop, click properties, click customize, change icon. When prompted just find the .ico file you downloaded.
I got my cheap power brick off ebay yesterday so I decided to adapt it to the Mendel standard XLR connector. The power brick was only £9 inc the lead and the seller even threw in a European power adapter, not bad, hope it lasts. The connector was a sinch to solder up even for me! Double checking the polarity with a multimeter I hooked up the positive (red) wire to pin 2 of the female connector. I've also received the male chassis connector so I've temporarily put it in place using a cable tie.
I have taken delivery of the bearings. Ordered from a nice bloke off ebay all the way from the Netherlands - Gubbels Engineering. Actually worked out cheaper than getting from RS so I went for it. Quick delivery and no customs charges. One step closer, can't wait to start building.
Stepper motors have arrived. I ordered 4 NEMA 17’s from Zapp Automation, 3 for the axes and 1 for the extruder. They look ok but I will have to wait until I have the electronics before I can test them.
They are of the 6 wire unipolar variety code SY42STH47-1206A. According to the datasheet the wire colours correspond as follows:
Coil 1 = Black & Green Coil 2 = Red & Blue
Therefore for the RepRap setup I need to connect:
A = Black B = Green C = Red D = Blue
The Yellow and White wires are the centre leads for each coil and so are ignored I’m sure I have read that the ABCD on the TechZone Remix electronics may be wired differently so I will need to check the above set up.
I have been working on cutting out the thick sheet parts. The way I have chosen to do it is by printing out the templates from the original dxf. I used Paint Shop Pro to open the dxf files, though for some reason it didn't seem to preserve the scaling so I had to the then scale the pictures to get them to the correct size, (I hope I got it accurate enough!). I then glued the templates to the thick sheet so I could cut around them and drill the correct holes. I found I could also import the dxf files into SketchUp see below for the thick sheet models I have created from the dxfs and put into google's 3d warehouse.
I am making the thick sheet parts from 6mm thick MDF bought from B&Q for less than £4. I have cut them out using a jigsaw and junior hacksaw, finished using a Dremel and sand paper.
RepRap Mendel Thick Sheet Motherboard Plate 6mm thick. Converted from the dxf drawing files provided @ http://objects.reprap.org/wiki/Mendel_materials_preparation To find out more about the reprap...
RepRap Mendel Thick Sheet Stepper Plate 6mm thick. Converted from the dxf drawing files provided @ http://objects.reprap.org/wiki/Mendel_materials_preparation To find out more about the reprap...
RepRap Mendel Thick Sheet Purge Plate 6mm thick. Converted from the dxf drawing files provided @ http://objects.reprap.org/wiki/Mendel_materials_preparation To find out more about the reprap project...
RepRap Mendel Thick Sheet Bed 6mm thick. Converted from the dxf drawing files provided @ http://objects.reprap.org/wiki/Mendel_materials_preparation To find out more about the reprap project...
RepRap Mendel Thick Sheet y-chasis squashed frog 6mm thick. Converted from the dxf drawing files provided @ http://objects.reprap.org/wiki/Mendel_materials_preparation To find out more about the...
Easiest thing to do on the list is the thin sheet cutting for the Opto end stops. As suggested I have used recycled metal from a drinks can cut with some good scissors. If you're doing this yourself watch out for the sharp edges.
