Close



Results 1 to 6 of 6
  1. #1

    Problems printing layers and getting chewed up gears with MakerFarm's Prusa i3v 12"

    I've had a recurring issue over the past several months with the quality of my prints. I've had this printer for about two years, FYI, and this issue only started several months ago. In the pictured first layer of my print, you can see a pattern forming due to some sort of inconsistency. The patterns are actually raised, as if there's some air pocket that formed underneath where two lines met. You can even hear the extruder head hitting against these ridges while it goes line to line. But in other parts of the same layer, the print is perfectly aligned with no bubbles. This is seriously annoying, as I've tried various things to fix it, and have even reached out to Colin from MakerFarm (he said he'd never seen this before). However, it's technically only an aesthetic issue that happens on each solid layer, EXCEPT...

    This issue may be the cause of my second, bigger issue: my 3d printed extruder gears keep getting chewed up. I noticed from the beginning of purchasing and setting up the printer that there was a fine white powder developing on the gears of the extruder after prints, but it never became a problem for the whole year and a half of printing that I had done. This powder turned out to be the remnants of the small cog gear that goes on the motor. After replacing the original gear, I had the second gear get chewed up after only one 20-hour print, and just yesterday replaced that gear only to watch it progressively getting chewed up as well. So the problem has significantly worsened.

    I'm wondering if there's a relation between both issues. Maybe the extruder head hitting against the developing ridges in the layer is putting extra resistance on the gears causing them to wear out almost immediately?

    Any help would be greatly appreciated, as I can't use the printer in this state - it can't make it through the 20-hour print without the gear going. Below is a link of pictures of the first layer, from the top and bottom, so you can see the inconsistencies, as well as the chewed up gears. Thanks everyone!

    http://imgur.com/a/1fKuD

  2. #2
    Engineer-in-Training beerdart's Avatar
    Join Date
    Feb 2014
    Location
    CT
    Posts
    345
    Does the hob bolt turn freely? Also check the hob bolt teeth for wear and flat spots.

  3. #3
    Technician
    Join Date
    Mar 2015
    Location
    Fenton, MI
    Posts
    63
    I have a 10 iV3. I had a totally different issue and I solved it just last night, maybe you should try it? I found pretty much EVERY critical bolt on my printer had worked lose in the last 18 months or so. Ironically, I also have a find white powder on my gears, but there's no effect on my printing....that I know of. I've yet to print after I tightened everything up.
    Maybe some of the bolts on the extruder carriage are lose (some of mine were) causing the gears to misalign?

  4. #4
    Technician
    Join Date
    Mar 2015
    Location
    Fenton, MI
    Posts
    63
    After looking at your pictures, yeah, check the bolts. The odd pattern looks like waves in sand. That tells me it's a vibration thing, cyclical. That could be cause by lose bolts.

  5. #5
    Staff Engineer printbus's Avatar
    Join Date
    May 2014
    Location
    Highlands Ranch, Colorado USA
    Posts
    1,433
    Add printbus on Thingiverse
    IMO the wavy pattern on the bottom of the print is due to too much extrusion for the gap you've set up. The result is material being squished and squeezed all over the place. It's got to go somewhere. Subsequent passes are affected by the line already in place beside it, so patterns start to develop.

    Regarding the failed small gears, I agree with beerdart on checking the hobbed bolt. You need to at least rule it out. With the motor mechanically out of the picture, make sure the large gear and hobbed bolt can rotate fairly easily. Don't tighten the small gear onto the motor and then install the motor; leave the gear loose on the shaft and mount the motor about where you think it should go. After the motor is tightened, *then* tighten the set screw on the gear. The goal here is to let the small gear position itself on the motor shaft. If you don't you could be forcing a lot of strain onto the gears as the herringbone teeth pull themselves into what seems like an alignment, but really isn't. And then see how the large gear rotates by hand. You'll feel cogging from the extruder motor now, but the rotation should still have a consistent feel to it. If it seems to catch at places, well, there you go. Something's wrong with the gear mesh.

    What material are the gears printed with? I of course can't speak to your small gears, but I've seen some really poorly printed ones. If these are PLA, the small gear requires print thermal management or the teeth are likely not going to be shaped properly. One recommendation I've had for people is to watch the small gear printing. If you see the gear shifting around as the nozzle moves, the print isn't cooling off enough between layers and you're basically trying to print onto the equivalent of soft rubber.

    If you have both the large gear and small gear loose, play with them on the bench and see if the herringbone teeth mesh smoothly. If they don't feel smooth on the bench, they won't be smooth on the printer.

    Have you monitored the temperature of the extruder motor? If it gets too hot, heat will conduct along the motor shaft and start softening the small gear.

    Note that some amount of white powder on the gears is normal, and has in fact been argued OK as somewhat of a dry lubricant.

  6. #6
    Technician
    Join Date
    Mar 2015
    Location
    Fenton, MI
    Posts
    63
    Did you ever resolve this? I was having a similar issue and almost every bolt on my printer had worked lose over the last 2 years or so. I'm curious as to what you found.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •