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rich

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  1. Thanks. I have an Ulticontroller I'll give that a go.
  2. Very impressive video Dim3nsioneer. I've not been able to get the g-code M201 to have any effect on my printing. I haven't used plugins - for my test setup I add them to the g-code in a spreadsheet. You are clearly modifying Amax X and Y. I tried lowering acceleration to 800 but the printing is unaltered. Neither have I had any success with M203 - I would like to try to increase the maximum extrude rate because the bridge threads at 150 mm/s are thinner (0.1mm) than those at 20 mm/s (0.3mm) and a bit of arithmatic says the default value of Vmax e of 25 mm/min will not supply the material required at the higher speed. I'd be interested in pushing as much plastic as possible through the nozzle. Any suggestions on why these g-code are not being executed? What version of Marlin are you using? Re the fan .. I use the standard fan. I also use a 50W quartz halogen desk lamp just above and to the side of the printing. I've not succeeded getting it on film but with the naked eye I'm convinced it keeps the bridge threads straight and in the nozzle plane. When the model is cooling the threads buckle out of that plane and move significantly with even minor air currents.
  3. Jonny - thanks for your comments re using the gallery. gr5 - mind? Thank you. I do have more images and there are a few more experiments to come. I haven't looked at acceleration settings - excellent thought. My comment #2 is illustrated in #2 image. Counting from the right, threads 7 & 8, 9 & 10 then 11 & 12 are amalgamated (see bottom near wall).
  4. I had a problem bridging with my UM1 so I decided to experiment with variables such as extruder temperature, print speed, extrude rate, fan on/off, and separation between threads in the first layer. The model used was a simple box with no lid. The bridging threads are approx 46mm in length. Cura 13.11 was used to generate G-Code for the box and a spread sheet was used to generate code for the bridging layer. The material used was ABS. For normal printing I have been getting good results with the extruder at 245C. Although other values were used for the tests (from 243C to 249C) the temperature changes did not have as much effect as some of the other variables. A total of 48 threads were printed in each experiment and extrusion rate (ie dE/dL), print speed (F) and fan state were varied systematically. The results seem to indicate that print speed has the biggest effect, extrude rate next then the fan. The image below shows the result of one experiment, with fan constantly at 100%, extrusion rate dE/dL (Vol/mm) = .0069 for first 24 threads then .0077 for the rest and Print Speed 20 mm/s for first 12 then 40 mm/s for next 12 then 20 etc. Printing from lower right to left. The thinness at start of each bridge may be affected by overlap on wall. The best results are for print speeds around 20 to 40 mm/s with extrusion rate around 0.0069 vol/mm (not sure what units of vol are used in Cura for this quantity). There are several observations I would like to make. 1. For well spaced threads, those that fail to survive do so because their thickness drops to zero just after leaving the starting wall (not the destination wall). This seems to be reduced if the overlap on the wall is reduced. 2. For closely spaced threads (ie. where the hot nozzle may contact the previous thread) failure rate is very high at high print speeds but at low print speeds 2 or 3 adjacent threads tend to amalgamate to form one. Having found some patterns in this behaviour I would like to have a little more control over Cura for bridging layers. Can anyone suggest how I might do this? For example is there some way to have Cura place comments in the g-code at the beginning and end of bridging? Any comments please? PS. I can send images directly to interested parties. edit by gr5: I added your images inline - hope you don't mind. message me if you want me to return to original state.
  5. rich

    Cura bridging

    Thanks for the link Owen. It looks like a few tests are in order - I've cut much of the bottom off my existing model so its quicker but still totally relevant. But Daid's bridging sounds ideal, I would definitely be happy with a 120mm bridge capability.
  6. rich

    Cura bridging

    Hi Owen & Illuminarti. Thank you. I'm not sure that the shorter distance would help because the melting occurs as the nozzle is going past the middle. The slower speed would be good to try but I can only do that by manually changing the g-code or changing the print speed for the complete model. I'll give both a try. How can we change just bridging speed in Cura? Your correct Illuminarti, the Basalt is the 200mm bed from QU-BD and it behaves as you say. Its very flat and great for PLA and ABS. My main complaint is that it takes ages to cool (? an hour - I'll measure it) before I can get the printed model off with a spatula. I use their silicone heater as well.
  7. Hello, I'm having trouble bridging the flat top of a small box-like structure. The rectangle is 70mmx32mm - so the distance to be bridged is 32mm. Cura chooses to do it at an angle which makes it just over 45mm. The lower part of the model prints very well including quite a bit of fine detail and overhang, but the bridging makes the model not useful. The first bridge filament adheres at both ends and looks great -- then the extrusion head moves back across the gap putting the second filament close and parallel to the first. This melts the fist thread in the middle and leaves an impressive looking second thread standing alone with two short pieces of number 1 hanging from the walls. This continues to happen with only an occassional drooping thread surviving in one piece. I'm using a UM1, ABS, V2 0.4mm extruder at 245C, Print speed 100mm/s, SD card with Ulticontroller, recent Marlin, Cura 13.10, Heated bed with Kapton on Basalt and Bed Temperature 110C. Can anyone suggest a way to overcome the difficulty please? I've turned the fan on (during the preceeding layer) and that has a small effect but not enough. I assume that the heat radiated from the nozzle is able to melt the single strands in the middle but not near the walls where the cooling has been greater. Lowering the nozzle temperature would reduce the radiated heat but would probably lower the quality of the rest of the model. If Cura were to enable the initial bridging threads to be much further apart, I think the isolated bridging strands would not get the heat from the nozzle and would survive unscathed. The gaps could be progressively filled - one strand per gap at a time, so the earlier strands would be revisited by the hot nozzle when they were significantly cooler. I guess its easy to say but may be hard to implement. Any suggestions/comments would be greatly appreciated please.
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