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  • Printing gone to ****

    While SFI members find reasons not to have a 3D section I'll post here where it's properly organised.

    I've noticed over the last few months my printed chassis have needed more and more post printing work. Recently picking up a discarded print from months ago and noticed just how nicely it printed made me decide I've had enough of this it's time to have a look at it.

    I have a Qidi X-Plus and bought it as an upgrade from the Ender 3, it's a solid performer and I normally use CF-PETG

    I had a thought that the profiles may have changed over the three or four software updates so tried a print with the default PETG profile (230°C/50°C) but upped the temps to suit the CF-PETG (250/60) and tried a print...it was garbage and 0.1mm thinner than it should have been.

    Time to go back to basics...
    1. Create a simple test piece with holes and a couple of pillars that resemble some part of a chassis I'm having problems with
    2. Check the bed level - I always do this with the hot end and bed at working temps
    3. I've been using a 0.2mm feeler gauge for levelling but you don't get the same 'grab' as you do with paper so found a little folded pamphlet made of shiny paper which is 0.2mm thick and went through the levelling process, there was a little change here and there
    4. While all this was going on I put a new roll of filament in the dryer for 90 mins whilst I did the test print which did seem much better
    So now I'm printing three chassis for SlotIt inline pods, two for a 3D resin printed Morris 1000 and one for a Carrera Mercedes 300 SLR

    Thank God for SCI and HRW, we 3D 'makers' have a proper place to put info for others to easily find in the future.

  • #2
    Most thermoplastics are somewhat hygroscopic. PETG is one of the worst next to the other common ones. Even if you store your material in a sealed container with dessicant, it's a good idea to dehydrate it when print quality starts to go downhill. Three hours in a convection oven (or dehydrator) at 149F should make a positive impact.

    On using feeler gauges, I have not, but a friend of mine is getting great results on his Ender 3 after using a 0.25 gauge to level the bed. The Prusa has ABL and a Z offset that makes the process work differently.

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    • #3
      I have the green/yellow dessicant and check it every time I take the spool out of the tin. I do dry the spool out when necessary so was fairly sure that wasn't the problem.

      So tonight, 6 hours into a print that looked OK I realised it wasn't printing until I had a look from the front (the Qidi is in a housing) and sure enough filament had stopped feeding...a check on the spool found the problem, the clip I'd printed to hold the end of the filament had jammed the filament preventing rotation of the spool...it's the first time it's done it, headaches come in threes...cleaned the bed and tried again but something was amiss, filament wasn't feeding as fast as it should so I raised the temp to 250...260...time for more investigation.

      Removed the extruder and stripped it down, gut feeling was the PTFE tube needed replacing...I was right. New PTFE, rebuild and try again, the nozzle was cleared from above with a steel guitar string (0.016"/0.4mm) and start with temps at 230 as per the recommended temp on the spool. 230 was a little low, 235 was better, 240 and the flow was constant.

      Re-level now the extruder had been off and stripped, run the slicer again and change temp to 240 and now we're printing again and it looks better at last.

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      • #4
        Good to know it's running well. Not that PTFE can't just wear out, but one of the things I like about the "all metal" hot end (E3D V6) used in Prusa printers is that the PTFE does not go to the nozzle, so is not generally effected by the printing temperatures. There are still plenty of ways it can jam or clog, though. ;-)

        Regarding printing temperatures, I assume you're using a hardened steel nozzle, since you've been printing carbon fiber filled PETG. Steel doesn't conduct heat as well as brass, so you'll generally need a 10 degree bump for all printing temps. That won't help the longevity of your PTFE, if yours goes to the nozzle. It'd probably be worth picking up some Capricorn, or similar higher-temp PTFE tube for that printer, so that it lasts a bit longer, and is less likely to start breaking down and releasing toxic chemicals due to printing at higher temperatures.

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        • #5
          Yeah, PTFE goes into the nozzle on a Qidi, it came with white PTFE fitted (low temp) I bought some of the dark blue stuff (high temp) and cut half a dozen spares. I became suspicious when I couldn't manually feed filament through to see it flowing so something to look out for other filament printer 'makers'
          ...Yes, I fitted a hardened Micro Swiss nozzle.

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          • #6
            I have learned that any issues with printing filament require, first, re-leveling the bed. Second, checking the entire filament feed.

            About equally the issues with the feed have been clapped-out nozzles and overcooked PTFE tubes. Also, once, worn-out knurling on the feeder drive wheel.

            Pulling the PTFE tube is a job, but discovering that the end of the tube has blackened and clogged is oddly rewarding.

            I have installed an hour-meter on my Creality Ender 3 Pro. I am hoping to establish a preventive maintenance schedule for my machine. IE - replacing the tube and nozzle every, say, 500 hours run time.

            FYI, my experience with the Capricorn tubing was horrible. The tight lumen of the tubing caused the filament to bind, even though the filament OD was in spec. YMMV. I backed off to the stock Creality tubing. I also decided to modify my machine for direct feeding of the filament. I have been very happy with the change. I haven't tried to find the limit of acceleration. I've been printing everything at 50mm/second. Maybe I could print twice as fast, dunno. I've been tolerant of long print times to avoid issues.

            I have an all-metal hot end in inventory. I bought it quite a while ago, but held off installing it. Probably should do that, but it involves a fair bit of wiring. I'm competent at wiring, but I never enjoy it.

            I've also got a auto-leveling system that I haven't installed. I believe it involves a software/firmware upgrade, something I am even more squeamish about. Bed leveling by hand isn't all that hard, and I don't have to do it all that often. Someday maybe.

            And I have a couple of hardened steel nozzles in stock. For now I R&R cheap brass nozzles.

            Ed Bianchi

            Comment


            • #7
              I'd fit an all metal hot end on my Qidi...if one was available! they're unlike other printers so with such a huge choice of after market parts available...none fit this manufacturers machines.

              I can live without auto levelling.

              ...wish I'd bought a Prusa!

              Comment


              • #8
                Originally posted by Kevan View Post
                ...wish I'd bought a Prusa!
                Which is what I heard every time I asked for advice on what printer to buy. Fortunately, an unexpected bonus at work provided the budget for one, and I've been happy ever since.
                Last edited by MrFlippant; 10-16-2021, 08:07 AM.

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                • #9
                  Well if you're unhappy with your current printer, Kevan, there is a prolific market in popular used and refurbished machines. You might even eBay your Qidi to help pay for one. Buying a used machine can make lots of sense if you're going to install a bunch of upgrades. The condition of key components is of no concern if they are going to be replaced.

                  What originally got me off the dime was the remarkably low brand-new cost of the Creality Ender 3 Pro. And the idea of picking up a second, used one for cheap has been tempting. Refurbishing would not be hard or expensive. Parts abound for cheap.

                  Ed Bianchi
                  Last edited by HO RacePro; 10-16-2021, 09:11 AM.

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                  • #10
                    Well I've spent today trying to get a completed print, the chassis I'm trying to print looks great up to part way up the front axle tube mount then it just fails part way up.

                    I've created a test piece with small holes 1.5mm and 2.5mm also two upstands similar to my chassis. Now I think about it these upstands for the front axle tube holder have always been flaky, I think they're too small so have changed one to be cylindrical rather than oblong...I'll report back.

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                    • #11
                      Half a dozen failed prints later I'm beginning to think it's the stepper that's on it's last legs, the extruder molding hasn't split which is a known problem, it's just not feeding with any power at all.
                      I've swapped the stepper from a spare extruder and it seems OK...I'll try holding my breath whilst trying to enjoy my glass of red wine

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                      • #12
                        I was right, finally got a completed print, the stepper change got the job finished. I thought I was losing it!

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                        • #13
                          ...the red wine was an enjoyable distraction

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                          • #14
                            It usually is...

                            The red wine, that is!

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                            • #15
                              Well I've had fun & games this weekend with this, five failed prints in the same place before trying a stepper motor swap.

                              ​​​​​ ​​​​​​
                              Because I've had to compensate for problems in the slicer the successfully completed print is stringy as a stringy thing and what looks like over-extrusion so today was back to testing.

                              ​​ ​​

                              One reason for stringing is too high a temperature, another is retraction, another is too low a speed between printed islands...and I tried coasting and wiping.

                              The mockup test session:

                              1. Reduce temp from 240° to 235°, enabled retraction with 1.5mm and upped the retraction speed to 70mm/s, set travel speed between islands to 100mm/s and switched 'nozzle wiping' on (not tried that before). - result was a drastic reduction in stringing but I didn't like what was left behind from the 'nozzle wiping'.


                              ​​
                              1. Same temp 235°, increased retraction to 2mm with the same speed of 70mm/s, same travel speed at 100mm/s and switched 'nozzle wiping' off - result was much better and no stringing even inside the vertical slots.
                              ​​​​​​

                              ​​​​​​​ ​​​

                              It's not back to what it was before but now I can at least print again...more importantly I've learned a couple of things I'd not had to adjust before even though I've been 3D printing for 18+ months.

                              Comment

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