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| picclock's modified i3 3d printer attempt |
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| PeterE:
Looking good! Will be interesting to hear your experiences of the build. You have a number of neat solutions of which some will be on my list for improvements. I hava also been thinking a bit about the extruder, I have the Wades version a bit like yours, but not completely. With the stepper it is a quite heavy bit to be carried by two 8mm bars. Moving the feed to the portal and having a PTFE tube leading down to the hot end would relieve the X carriage of some weight. BR /Peter |
| picclock:
Hi PeterE >>With the stepper it is a quite heavy bit to be carried by two 8mm bars. Moving the feed to the portal and having a PTFE tube leading down to the hot end would relieve the X carriage of some weight. Thats my opinion also. One of the issues with Bowden feeds is that the longer the feed and the more that it bends the greater the likelihood of the filament buckling/jamming. I have in mind to limit the range of bowden movement by supporting the extruder drive above the centre of the X carriage whilst connecting it to the Z bar supports. This would make it a constant height above the head enabling a much shorter bowden length. Re the weight on all the axis. The heavier and stiffer it is to move, the lower the accuracy will be. That is why I am driving the motors closer to the rating. If you think of the motor as a spring, the further it deviates from its intended position the larger the force needed to move it. But this means that for small deviations only a low force is needed. By increasing the motor current the spring is made stronger and better accuracy/repeatability more achievable. Obviously, this only applies within any given motor true step, typically 1/200th of a revolution. I will also incorporate a servo mount for auto bed levelling on the upgraded extruder, so at best what I have is very much a work in progress. One of the things not shown in the photographs is the X bearings. The top one is twice as long as the std prusa ones, and the lower single std one is allowed to float about the z axis, thus all things are true to the top bar. Looking forward to seeing your printer up and running. Best Regards picclock |
| picclock:
Hi All Things have moved on a bit since last post. The bed wiring is now complete, with it passing through the belt attachment for the glass bed. When fully operational one of the first things I will print is cable chains for the X and Y axis. The cork is attached to the heater pcb with a high temp silicon adhesive, and this in turn is attached to the glass with clips as shown. The Z limit switch is sorted, and the Y axis switch fitted. The Z limit switch is one I reused from a scrapped photocopier. Although it is push to make, (default is push to break so that wiring integrity is maintained) the accuracy and repeatability are better than I can measure. I put one of them in my mill vice, connected to a beeping continuity meter and used the Z digital readout to detect the point of switch actuation. The reading at the switch point was exactly the same, so its easily as good as 0.5 thou of travel. Picture with simple mounting and adjuster below. The distance between the print head and bed is an important setting to ensure the correct adhesion of the first level of plastic. Having powered it up, I was able to set this to 0.05mm, by adjusting the screw and re homing the axis. Once the left side was complete I manually adjusted the right side to the same gap. I intend to automate the bed levelling process by using a servo and a limit switch, parts on order. Next, the filament feed calibration. This is achieved by simply marking a piece of filament and telling the extruder to extrude a given distance. For this I removed the extrusion nozzle and set the minimum extrusion temp to 1C in the Marlin firmware. I had an extrusion rate figure from the internet, taking account of the different gear ratios, and in an unusual stroke of good fortune this proved to be exactly correct. I extruded 100mm, and exactly 100mm was extruded :thumbup:. So for a trial print. I thought I would try the blue tape adhesion method first with some hair spray to help things along. I loaded up a new reel of blue ABS filament, sliced the design for a cable chain link in cura, and dropped the file into the octoprint browser window. Had a quick think to see if I had missed anything, then clicked the print button. The bed started to warm to its final temperature (100C), once reached the print head quickly warmed up to its operational temp (230C), and the process commenced. I was very impressed with the fine detail of the outline and its accuracy. All seemed to be going well, with the first layer going down but after 4 or 5 layers the parts started to warp and come off of the bed, at which point I cancelled the print. I thought I would try to improve the bed adhesion using abs juice so attempted to make some from the scrap printed parts and filament dissolved in acetone. I left this for several hours but was surprised to find that it had not dissolved, in fact was not even sticky. I took a piece of known ABS and dunked it and it went sticky almost immediately. :scratch: I was thinking that I had been supplied with the wrong filament type, so I checked out a roll of conductive abs filament, which I had ideas about using for plated items. In doing so I came across the original carton which clearly showed that my blue abs was in fact nylon, and further checking of the order indicated this was exactly as ordered. Its a terrible thing getting old .. . :loco: I have ordered some other colours of abs and hope to show some first printed parts soon. I may have a go using the conductive abs, but this is far from typical due to the carbon loading, so will not be too good for calibration. The white roll of PLA I have may be useful for testing or prototyping but not very good for calibration or working parts. I also think that it would be a good idea to fabricate an enclosure to maintain an even, elevated temperature throughout the printing process, as this would minimise warping. Thanks for your interest Best Regards picclock |
| PeterE:
Looking really good picclock :thumbup: :thumbup: :thumbup: I was given the tip to use a dab of acetone at each corner of a beginning print to make it stick better to the build plate. That should be enough I believe. I will use one of those cottonbulbs on sticks (whatever they are called in english) to get that necessary small amount. Of course that means that I will be using ABS most of the time anyway. The daughter is now nicely installed in her new apartment so time for shop activities is in sight :drool: /Peter |
| awemawson:
Cotton-bud :thumbup: |
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