My as yet unnamed printer
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As I've ordered my Duet WiFi, I guess I can post details of my printer build so far.
Pics are here.
https://drive.google.com/folderview?id=0B_MwtHtQR_ZvSkZlRWphTnJ3X0k&usp=sharingThe entire design was done using OpenScad.
The concept behind the design is for something which will accommodate multi colour/multi filament printing and with a largish volume. With the large volume comes a desire to have fast(ish) print speed. I decided to use OpenBuild Vslot for the frame. This makes things like linear guides a breeze using their Delrin wheels and "gantry plates". It also gives me the flexibility to change the configuration of axes without too much difficulty or expense.
So, my starting point was the Diamond hot end (one of which I already have on my RRP Mendel). With it's 3 heat sinks angled out at an angle, the Diamond hot end is about 80mm diameter (measured at the top of the heat sinks), and about 80mm tall and weighs in at about 250gm (without any extruders). So I decided to sling it between 2 horizontal X rails, rather than having it hanging to one side. The downside to that is that my X carriage is very wide and I soon realised that my target of 300mm X and Y could not be achieved with a frame 500mm x 500mm so I increased it to 600mm x 600mm which gives my a print area of about 350mm x 350mm (all motors and idlers etc are inboard). Oh, and it's a metre tall giving me about 780mm in the Z direction. Most of the frame is 2040 and I tapped the ends of the V slot rails and inserted button headed screws (two in each end to prevent twisting) which fit in the slots of the other members. Access holes drilled in the sides of the V slot allow the screws to be tightened with a hex key. It makes a very rigid frame but also saves a fortune on angle brackets (and looks neater IMO). Not having access to metal working equipment other than basic power tools, I elected to have the extrusion all cut to length. Drilling the holes through the side of the extrusion without the aid of a drill stand or drill press was challenging enough.
I'm starting with a core XY layout to try and keep the moving mass down. I do have reservations about core XY though, so if it doesn't work out, it won't be too much hassle to change to a simple Cartesian. The idlers are all Open Build, twin bearing supported top and bottom, and I'm using stacked belts to get them as close to the centre line of the X carriage as possible.
The bed is something else. It has 3off 8mm dia x 1mm pitch lead screws to provide 3 point lifting. These screws are supported on a combination of thrust bearings and flanged roller bearings. They are not rigidly attached to the bed. There is an "O" ring which is only just under compression and which will allow a small amount of movement. Difficult to explain - see pics. Other than the bottom support, the screws are fully floating. The guidance and constraint of the bed is provided by 3 vertical 2020 linear guides (Open Builds V Slot, gantry plates and Delrin wheels again). Initially, I only had two guides positioned at the front but found that it was possible to get hold of the rear of the bed and twist it side to side. It was caused by the vertical 2020 twisting as it was only attached to the horizontal members by a single bolt. If I was starting from scratch, I would use 2040 or even 2080 for these guides, and fix then with 2 bolts at each point. However, in this case it was easier and cheaper just to add a third guide at the back. The bed is fixed to the gantry plates using rod ends with ball joints. This constrains and side to side movement but allows some angular tilt as may be necessary for levelling. Initially, the three screws are connected by a single closed loop belt and are driven by a single stepper motor. The plan is to convert it to 3 motors as and when DC42 gets around to writing the code for automatic bed levelling. On the hand, it may end up not needing to be re-levelled after initial commissioning.
The bed is 400mm x 400mm and consist of a sandwich of two 6mm layers of Thermoboard insulation, an 800W 240V silicone heater stuck to the bottom of a 10mm thick machined aluminium tooling plate an top of which is a layer of glass as a removable build surface. The tooling plate was painted with Stove paint and baked in the oven to cure it - I've bought one of DC42s IR probes so this will make the aluminium less reflective. I have 3 pieces of glass so I can quickly swap them without having to wait for the 10mm thick aluminium to cool and also, I could potentially have 6 different pre-prepared surface finishes to print on. I routed a groove in the underside of the aluminium to take a PT100 (yes you can rout aluminium with a wood working router if you take small cuts and slowly).
The glass is proving slightly problematic at the moment. I gave an outline of the requirements to a glass specialist who recommended 4mm thick, toughened, sand blasted and Brite Guard coated. However, when I tried them on the build plate, I discovered that they were bowed by about 0.4mm from edge to centre - like a hump in the middle. The supplier has apologised and stated that this can happen during the toughening process when the glass is heated to 600 deg C. Personally I think it may be caused by the sand blasting which has relieved the surface tension on one side. However, I'm not a glass expert and this guy is. Whatever, they have agreed to re make the glass using 6mm thick (which is less likely to bow) and if that isn't flat enough then they'll make then from un-toughened float glass. Either way, I'll end up with 3 off pieces of 400mm x 400mm glass flat within 0,1mm.
I got hold of some aluminium angle and cut one leg down (metal cutting blade on my band saw) and cut some slots on the sides. These are held in place with wing bolts and clamp the glass to the bed (and also hide the edges of the insulation etc). The front piece of aluminium is just a flat trim sitting slightly below the level of the glass so that it can easily be slid out of the front.
The extruders area work in progress. The Diamond hot end pretty well precludes the use of direct drive due to the weight and size so it's Bowdens. However, AusiePhil and I have devised a plan to have the extruders suspended above the centre of the bed, a bit like a Delta Flying extruder. If it works, I could end up with Bowden tubes around 300mm to 350mm long which, for a 600mm x 600mm frame is pretty good - they'll actually be shorter than my much smaller Mendel. Anyway, 3 off E3D Titans have been ordered (happy birthday to me). Meanwhile, I'm making a start on the wiring.
I'd like to thank the entire RepRap and wider 3d printing community and especially DC42, for all the help and advice which has enabled a multi careered (but non IT orientated) sexagenarian to get this far.
Thanks guys.
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Big thumbs up….. considering trying glass for PLA. Blue tape works too well I find it a pain to remove items.....
and printing direct on PET or Kapton is a pita.... i can stick most things but that first layer is just so slow!
Good luck with the build.
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A quick update on this. My glass supplier re-made the pieces using 6mm thick glass but found that there was still a very slight bow after the toughening process. So, they have made them yet again from 6mm float glass (un-toughened) and assure me that they are now flat. I'll pick them up at the weekend. I guess that is a lesson learned - toughened glass cannot be made flat enough for a print surface.
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Good info, hope the lesson was not too expensive for you!
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Good info, hope the lesson was not too expensive for you!
Thanks for the concern Tony and no, it wasn't expensive. I had given the glass supplier a "brief" rather than a specification and the main criteria was that it needed to be flat. So, when I discovered that it was bowed, there was no argument. They took it upon themselves to try again using 6mm instead of 4mm and toughening it, then when they found there was still a slight bow, they made them yet again out of un-toughened 6mm float. They had also said that if non-toughened was unacceptable then I could have a full refund. It's cost me a bit of fuel taking the glass back and forth but but I'm not complaining given their efforts to resolve the problem. It must have been expensive for the supplier though, as they've made then 3 times and been paid once. However, if anyone asks them for glass for a 3d printer in future, they'll know what to offer.
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deckingman, thanks for the info. I was considering ordering some 4mm black toughened glass, but I probably won't bother now.
The standard toughening process involved heating the glass up above its transition temperature, then cooling the faces rapidly with jets of cool air. I guess the cooling wasn't equal on both sides.
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deckingman, thanks for the info. I was considering ordering some 4mm black toughened glass, but I probably won't bother now.
The standard toughening process involved heating the glass up above its transition temperature, then cooling the faces rapidly with jets of cool air. I guess the cooling wasn't equal on both sides.
Yes, according to my man (it's actually Gent Glass in Wellingborough), it's a tricky process to get right but there will always be some degree of bowing. They reckon they have one of the best operatives in the business but the best he could do was within 0.3mm across a 400mm width. They tried both 4mm and 6mm thick. The 0.3mm isn't bad but of course for us, that's not flat enough. I guess if you had bed compensation that could cope with a hump or a dish, then you could get away with it. Or maybe, lay it "hump" side down and clamp the edges might flatten it. That's not for me though, I'd rather have it flat and sacrifice the toughening. I also want to be able to use either the sandblasted side or the non-sand blasted side.
Anyway, I managed to get over and pick up the float glass this morning (sandblasted one side but not toughened). I fitted it on the aluminium tooling plate and manually levelled the bed. It's spot on. I can just slide a thin piece of paper under the nozzle with the same amount of friction anywhere on the 400mm x 400mm area. I'm dead chuffed with that. Whether it stays that way remains to be seen. It also remains to be seen whether I can print directly onto the sand blasted surface without any tape/glue/paste/snake oil or whatever. It'll be really good if I can.
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Got the 3off E3dTitan extruders mounted in a sort of flying arrangement so now the printer has grown by another half metre in height. I've also added a means of mounting filament spools (2 lengths of 32mm waste pipe). Tip to toe, it's now 1.7 metes tall.
I'm really chuffed that I've ended up with with 300mm long Bowden tubes for a print area a shade under 400mm square on a frame which is 600mm square and over a metre tall.
I don't know how to add pictures to posts - perhaps someone can enlighten me. Meanwhile, I've added folders named "Extruders" and "Wiring" to the shared google drive folder - link here. https://drive.google.com/folderview?id=0B_MwtHtQR_ZvSkZlRWphTnJ3X0k&usp=sharing
Big thanks to AussiePhill for the idea but also apologies for not using his STL. I needed to tweak the design and it was just easier for me to start from scratch with OpenScad which is all I know how to use.
The extruders are mounted together on a custom mount which is suspended above the centre of the bed on a pulley arrangement with a counter balance weight (printed container with lead shot). This allows the whole thing to fall when the print head is at the extreme corners but the rise again to "lose" the Bowden tubes when it is directly above the centre of the bed. The combined weight of the three extruders with their stepper motors and mount is 905 gms, the counter weight is a little more than this to overcoming and friction and "sticksion" and ensure that they rise up when needed to and prevent the Bowden tubes from buckling. So, there is a slight upward pull and I've fitted cords between the extruder mount and the X carriage so that this pull is not transmitted to the Bowden tubes which are slightly under compression, keeping them firmly attached at both ends.
Inevitably, there is some drag on the X carriage due to the wires and tubes but it is tiny compared to having to lug 900 gms of extruders and steppers around.
A more elegant solution might be to mount the counter weight on a vertical linear rail using a bit more V slot, but I'll wait until I've tested the printer to make sure it's viable.
The wiring is about as far as I can get - just needs the Duet (batch4) but my daughter's wedding is only a couple of weeks away so further work will have to be put on hold. I've braided most of the visible wires and fitted printed labels covered with clear heat shrink. Where possible, I've run the wires inside the Vslot and fitted cable covers which makes quite a neat job. I've used flexible conduit for all the wires from the hot and and x carriage. This still looks untidy to me but there are a lot of wires (heater, pt100, xmin, xmax, hot end fan, print cooling fans, z probe and of course 3 extruder motors) and they have to be long enough to reach all 4 corners of the print area.
I've added separate micro switches to the extremes (max) of all the axes and connected them in series to try and prevent crashes during commissioning or in the event of a probe failure. I've added a separate emergency stop button too. The mains to the heated bed is in a flexible cable chain. The bed plate is earthed, and also connected to the frame which is also earthed in two places and I've fitted an RCD plug to the mains inlet. All the mains wiring is inside a printed enclosure so all in all, it should be safe.
