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  1. #101
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    Oct 2016
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    On Dollo rebuild I've been experimenting with the extruder positioning. Some while ago I designed an extruder riser for my Tronxy X5S (https://www.thingiverse.com/thing:3271808) and originaly I used it on Dollo too, but then I wanted something more adjustable, so I designed this arm that is built on parts that can be rotated to get the desired position. Works ok, but it's bit wobbly so I'm going to print another arm on the other side to support the extruder better.
    Using an extruder riser allows for sorter bowden tube. I haven't measured the difference but it's about 20cm compared to the original position without riser. Currently I have 2.5mm retraction with linear advance value 0.3. The bowden tube is about 45cm.
    IMG_20200704_112250.jpgIMG_20200704_112345.jpg

    I swapped a Volcano on the Dollo rebuild as I needed the E3Dv6 on another printer. I tried some 1.2mm nozzle printing. It's a kinda new area because the amount of material moving through the nozzle is quite a lot more than normally. Tuning the retraction is hard to get perfect, on my test I didn't get it completely nailed down and it's not just about the retraction amount.
    I printed a couple of pieces to test out full print height and Volcano. Both are ~40cm tall and have only one 1.2mm perimeter. This sows on the owl since some areas aren't properly supported and there's gaps and artifacts.
    Material used was PLA, about half a 1kg roll I think.
    The vase print was supprisingly fast, only about 7 hours.
    IMG_20200704_112840.jpgIMG_20200704_112820.jpg

    Other small thing on Dollo rebuild:
    - swapped X and Y motor gears, they were getting a bit of backlash due to the printed gears starting to get loose on the motor shafts. Did some refactoring on the desing too.
    - currently running Marlin 2.0.5.3 on the SBase and no problems
    - Z accuracy is a bit of problem when using mesh bed leveling, which is expected due to the printed 'bearings' that do bind a bit. With mesh bed leveling, the bed just doesn't do those very small movements. Also the printed Z-rod nut has bit of backlash.
    To combat this I made a poor-mans lock nut from TPU which acts as a kind of psring and takes the slack off, which helps a bit.
    IMG_20200704_114127.jpg
    Last edited by spegelius; 07-04-2020 at 03:47 AM. Reason: remove unused pic

  2. #102
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    Oct 2016
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    184
    On both Dollos I did some Z-axis refactoring by moving the Z-screw to the middle of the Z-rods. I saw some parts tilting slightly caused by the Z-rod being some 30mm invards and the friction of the printed Z-slides and rods. The change in print quality wasn't very noticeable asfter all, I've noticed that using Z-hop seems to kind of hide some inconsistencies in Z-movement, it kind of resets the Z-position.
    IMG_20200704_110228.jpgIMG_20200704_110015.jpg

    I'll be adding a support leg beside the Z-motor, I suspect that the beam holding the motor bends enough to cause some small errors in Z. Not sure if it really matters, but I want to see if there's any difference.

    The fully printed Dollo.2 Z parts are holding together supprisingly well, I've done at least 500h of printing on the Dollo.2 and the parts are still in good working order. I checked them during the Z-screw position change when replacing some parts and there's no noticeable slack yet. Happy to see it's working and there's no need to do maintenance on it all the time.

  3. #103
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    Oct 2016
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    On Dollo.2, I also did some cable management. Same cable chain setup. I also designed a new RAMPS case and redid some wiring from the ATX-psu. I was having some issues with temperatures fluctuating and the problem turned out to be insufficient wires for the 12V input. The problem manifested when the bed was heating, which caused to 12V level on RAMPS to drop and also affected the temp readings. As with it's bigger brother, the wiring is still a bit of a work in progress, I'll need to cut them to correct length and get some cable sleeves done.
    IMG_20200704_105917.jpgIMG_20200704_110004.jpg

    I've been using a printed planetary geared extruder setup for a while (https://www.thingiverse.com/thing:775636) and it's been working quite well. However, due to motor heat, the sun gear started to slip on the motor so I swapped in a Titan I had laying around. For Dollo.2 I haven't seen the need to go fo rised extruder, might explore that later...
    IMG_20200704_105948.jpg

    Both Dollo's seem to be quite reliable printers, even though the print quality isn't perfect. They get the job done as long as you don't expect pristine quality. And they are fun to tinker with.

  4. #104
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    Oct 2016
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    184
    As seen on ReprapFirmware thread, I started using RRF in my Dollo rework. After some tuning it seems to be working quite nicely. Time will tell if it's going to be my main driver. Luckily switching back and forth between Marlin and RRF is easy, just copy the firmware.bin to sdcard and boot the board. When going from RRF to Marlin, mesh bed leveling needs to be redone though as EEPROM is lost in RRF flash. Such problems don't exist with RRF as all configuration is in files on sdcard.
    Tuning the RRF exposed a problem on the printer, though. The part cooling is inadequate so redesing is needed, along with changing the 40mm axial fan to radial if possible. Mor on that later.

    I added a Z-motor support for both of my Dollo's. The design is quite simple, the leg just clips on to the Z-motor. The leg is adjustable. It does seem to help, at least on the Dollo rework, mesh bed leveling seems to have much better resolution now. So apparently the beam supporting the Z-stuff was having some slack after all. Haven't tested this on Dollo.2 yet, just finished installing the parts.
    IMG_20200706_163514.jpg IMG_20200706_163532.jpg

  5. #105
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    Oct 2016
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    So I did some tuning on the fan shroud, moved the nozzles closer to the hot end and aimed the outputs towards the nozzle. I printed the axial version since getting the radial version to work might impose some limitations to printer's max Y size. Currently the fan sits under the X-beam, the axial version has plenty of room to be there. Radial on the other hand is a bit harder to get positioned properly. I looked at some fang-type shrouds in Thingiverse for inspiration, for example this: https://www.thingiverse.com/thing:2175956. But something like that will require some intensive modeling and reusing available models probably won't work.
    IMG_20200721_102735.jpg

    Anyhow, I printed couple of benchies and there seems to be a bit of improvement, but still has issues. First one is sliced with KISS, variable layer height 0.15-0.35, 0.6mm nozzle, fan 100%. I also reduced perimeter/solid overlap and retuned my extruder e-steps since it seems there's a bit of over-extrusion in some points, causing the inconsistencies of the extrusion.
    IMG_20200721_102402.jpgIMG_20200721_102443.jpg

    Next one is sliced with PrusaSlicer as I wanted to see if the slicer has an effect. 0.2mm layer height, 0.6mm nozzle, 100% fan. The default print speed of the profile I modified was bit faster than on KISS an that shows on the ships prow. Also PrusaSlicer has adaptive layers now it seems, I haven't tested that yet.
    IMG_20200721_102427.jpgIMG_20200721_102451.jpg

    I'll need to design a fan shroud that uses a radial fan, axial just seems to be too inefficient. Designing those ducts similar to the fang-design will be an interesting challenge with OpenSCAD, doable, but not sure if looking forward to it...

    For this printer, I'd say the quality is good enough as it is since I mostly print mechanical parts that doen't need very high level of quality. Also with 0.6mm nozzle the layer heights usually are around 0.3mm or more so the small deviations probably just fade away. Still, would be nice to get this sorted out.

  6. #106
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    Oct 2016
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    Got a shroud modeled for radial fan. Positioned it below the X-beam, seems I can get away with it without reducing Y-movement much. Printed in ABS, with a load of supports. PrusaSlicers supports are quite good, but with ABS I had to design in some custom supports without gaps, because some parts of the prints weren't bonding enough to the supports and were lifted off due to curling. OTOH, the supports were quite easy to remove. Win some, lose some.
    IMG_20200722_150746.jpgIMG_20200724_113530.jpgIMG_20200723_104555.jpgIMG_20200723_104602.jpgIMG_20200723_104608.jpg

    It does seem to help, the radial fan I have are quite powerfull. Currently running one @ max 45%, could maybe go bit more higher. Defining max speed for fan in RRF happens with M106 X122 (122 being the speed 0-255). The prow on the benchy is now definitely better. Other parts, the same. Is suspect that the layer issues are due to the Dollo itself, there might be some backlash or some other mechanical inconsistency going on. Also some small zits, can't seem to get rid of them with Volcano. Maybe a really long wipe would do it. Well, not going to pursue better quality, the machine works well on more coarse prints and that's enough for me (for now).

  7. #107
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    Oct 2016
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    Having a weird problem with Dollo rework: most prints come out fine, but there's this one box I've been printing and it has what seems to be a layer shift that keeps repeating on the same layer on each print. If I rotate the model 90 degrees, the problem goes away.
    The model: https://www.thingiverse.com/thing:647425. By default the model is oriented so that the open side faces left so the shift happens on Y-axis. This could be mechanical as Dollo is what it is, but the MKS Sbase uses DRV8825 stepper drivers and those are known to have issues with missed steps in some scenarios. I do have tl-smoothers on X and E axes and Y-motors are connected in series so there shouldn't be a problem. But I'd like to be sure so I'll probably hook another board just to eliminate this. My SKR v1.4 Pro arrived some time ago, might as well use that for testing.

    IMG_20200828_192744.jpg

  8. #108
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    Oct 2016
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    Well I swapped the SKR v1.4 Pro in for a test print. The swap wasn't too much hassle, the RRF config from Sbase worked quite nicely as a base for the LPC RRF online configurator. The Trinamic drivers are quiet, the Sbase isn't bad but the DRV8825 tend to have some random low noise coil whine is noticeable.
    Anyhow, the print result was exactly as with Sase, so it's not a problem with the DRV8825 drivers. Just Dollo doing it's thing I guess.
    Will be going back to Sbase.
    IMG_20200829_205415.jpg

  9. #109
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    Oct 2016
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    After taking a closer look at the slop on the axes, I went back to Marlin + Octoprint. RRF doesn't have backlash compensation feature so Marlin it is for now.
    When the motors are locked in position, moving the axes they do have some slop which shows as artifacts in prints in certain cases, for example holes are kinda skewed and as shown with the box, can result in a noticeable shift.
    Need to tune the backlash properly. Still the things I usually print with my Dollos aren't too bothered about small errors in movement...

    Received some goodies, a 340x310 PrintBite and FlexDrive G5 HW kit. I have some 3mm aluminum plate I've already cut, just need to drill the holes, order a heater pad for it and reprint some bed carriage parts to get full size bed.
    The G5 Flex was a bit of a last minute purchase decision, I want to see how well this kind of extruder works. If it works as advertised, you'll kinda get the best of bwden and direct drive - very light etruder, but still direct drive.
    IMG_20200906_190814.jpgIMG_20200906_190829.jpg

  10. #110
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    Oct 2016
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    184
    Alas, another Dollo thread update. Not much changes about the printers, but thought about sharing an general update about how the printers are behaving. Been using both of the Dollos, maybe few hundred printing hours for both and no major problems, but still some smaller issues.

    On the bigger Dollo:
    - a scrub screw fell of from the left Y-axis gear. This jammed the left side of the Y-axis, which of course caused a big layer shift. Re-applied the screw and hopefully tightened it well enough this time, although this could be an issue about PLA strecthing over time and eventually the screws just get loose...
    - had a couple of min temp errors on the hotend, turned out the hotend heater wire had a spot that was getting warm, apparently there had been a kink on that spot and it started failing. Fixed the wire and works so far.
    - small quality issues (the layer shift mentioned above), seems to be related to the X- and Y-axes sleds rocking back and forth a tiny amount when changing direction... maybe yet another redesign coming. I do have few ideas to try

    On Dollo3D.2:
    - current RAMPS setup has some issues, USB connection from Octoprint might take lot of tries before getting a connection. After connection is established, it works stable though
    - having undervoltage issues with Raspi, apparently the 5V I'm feeding to it from the ATX PSU isn't good enough. Might be a reason for the USB issue...
    - In general the power from ATX PSU seems to be bit on the low side, the voltages seem to dip a bit every time bed heater is turned on and this affects even the temp readouts, I get a rare mintemp error when hotend and bed heaters turn on and off and the temps jump few degrees up and down.
    - might be a good idea to replace the ATX PSU with proper 12V PSU, I'm not even using the ATX standby option
    - print quality over 150mm height seems the degrade a bit, apparently the Z-axis needs to be improved

    Even with few hickups here and there, both of the printers still print quite solidly. Currently been printing these table legs with assorted PETGs. Each segment is 210mm tall and has 5mm holes for 5mm threaded rods. Also they are accurate enough that they fit each other, with 0.5mm tolerances modeled in. I do have some improvements planned, but not in a hurry as the Dollos are doing their thing well eough at the moment.

    IMG_20210325_215419.jpgIMG_20210325_215146.jpgIMG_20210325_215458.jpg

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