HELP finding the issue - MakerFarm i3v 10"

[fkirdis]

Hello fellow reprappers,

I dont know where to start but I've had real hard time pinpointing the issue of my "trial" print of the SMALL GEAER for WADE Extruder. I have Prusa i3v 10" with a Prometheus HotEnd.
I've gone through all possible mechanical issues i could come up with (belt, pulley, alignment/leveling of the axis etc)... My first thought was step skipping but that was not it (i.e motors and stepper drivers was cool enough).

I've tried lowering all the speeds & accelerations (and also temp in some cases) with no effect on the print quality (at least not that much effect). I've tried Cura and Slic3r but that doesn't change much. My first print (left to right on the pic), i later found that the Model was not closed so i changed it to a working model... But again i did not get much of an improvement.

I still suspect something mechanically is causing the problem but guess I'm still a Newbie in the world of reprap (my first printer, got it Dec 2014) to make a final conclusion. When i built my Prusa, I took PrintBus recommendations (really great tips & tricks).

But now I am stuck, I've haven't been this frustrated for a long long time Everything else has worked fine but i can't get this specific print in good quality.
Grateful for all feedbacks...

/Ferhat

[printbus]

What material? What bed temperature? What nozzle temperature? What infill type and percentage? Looks to me like thermal concerns are the biggest issue.

Depending on material and settings, IMO the small gear can be just about the most challenging part many people will ever print. For at least PLA, it can take a good handle on print thermal management in order to get a successful print. What happens otherwise is heat sort of just keeps building up as the cylindrical part of the gear is printing. Things thermally go out of control when the shoulder reduces the print area and layer time. The gear is now essentially very soft material, and newly laid layers don't have a solid foundation to be printed on. The result is the teeth don't hold their shape - people often report seeing the gear shifting around as the nozzle moves (not a good sign). I like to print the small gear with almost solid infill for strength, but that likely aggravates the temperature problems.

If you don't have an effective print cooling fan, about the only option you have is to use a slicer that will lift the nozzle off the print as necessary in order to ensure the minimum layer time and minimum print speed you specify is being met. Set the minimum layer speed to something like 15 or 20 mm/Sec - you don't want the print speed to keep going slower or there'll just be more heat soaking into the print as the nozzle slows down. Set a minimum layer time of something like 20 seconds. I think slic3r is the slicer with an option to lift the nozzle off the print each layer if necessary to meet both of those constraints.

For a small part like this, I try to print on a cold bed if I can if it is being done in PLA. That removes at least some of the heat being applied to the part. Printing on blue painters tape swabbed with alcohol can be very effective for printing cold.

Until I had better solutions to work with, I actually sat there with a compressed air can and applied just a slight amount of air to the top of the print to keep things cool, sort of following the nozzle around as it went. Wasn't perfect, but I at least got a usable gear out of it when I was done. You could also print say six of them at the same time, or print one gear at the same time as some other objects. That will increase the amount of cooling time before the nozzle returns to print another layer.

When I worked through the same issues on the small gear, I learned the value of using something like the gcode.ws viewer to screen the gcode file, watching for problems with too low of a print speed or too short of a layer time.

Also note that the model seems to have the shaft hole undersized. You'll likely have to use a 5mm drill bit to size the hole before it will fit.

[fkirdis]

Hi Printbus,

I think you just hit the spot with "people often report seeing the gear shifting around as the nozzle moves (not a good sign)" as I've seen this on my print. I use ABS (3mm dia), bedtemp is 110 C for the first layers then 90 C for the rest of the print. Nozzle temp is 235 for the first layers, then 225 C for the rest of the print, and I use 100% infill for this print.

I should have thought of this, stupid me... You just found the problem, I've lowered the nozzle temp to 220 C and also changed the minimum layer time to 20s... and I also print 2 set of small gears as this lets it cool even more..

The print is not finished yet (15min left) but the critical part is over and the gear looks really nice for the moment.

Once again thx alot PrintBus!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

/Ferhat

[printbus]

Yeah, but I still feel bad about coming in with an easy answer to a problem that was driving you crazy.

I do swear though - a lot of people end up learning lessons on that small gear...

BTW - welcome to the MakerFarm user community

[printbus]

I might add that a print cooling fan can help, but isn't necessarily the panacea one would hope for in this case. Even with a print cooler, I still had issues with the quality of the few teeth downwind from the hot end. I figured that whatever airflow it was getting was already being partially warmed by the hot end.

Takes sort of a holistic view. Call it zen and the art of 3D printing.