I have Reprap throat/nozzle  trouble.

I have Reprap throat/nozzle trouble.
I have a reprap mk8 (I think) from china, when I bought the reprap it said 3mm filament recommended so I bought 5 rolls of 3mm filament from another seller.
When I recieved the reprap I tried to fit the 3mm filament just to find out it’s of course for 1.75 mm filament. :frowning:
I complained to the seller of reprap but in vain.
I bought a 1.75 filament at local store that worked like a charm, but I ordered a 3mm throat and wanted to convert it to 3mm since I had 5 rolls of filament.
I removed the old throat and changed it to 3mm throat, everything seemed fine. When I print the everything is fine for the first seconds but then the extrudermotor start to skip steps and after a while nothing comes out of the nozzle.
I tried manually feeding the nozzle and for the first seconds everything is fine but then when the filament heat up it seems to get enlarge sideways by the compression and can’t be forced downwards.
If I pull it up and cut off an 2 centimeters (~ 1 inch) so I get stiff filament I can continue feed it through the nozzle for a few seconds until the filament heats up.
Do anything else then the throat differ a 1.75 mm extruder head from a 3mm?
Any ideas?

1)You motor can’t push 3mm try adjusting the voltage or your extruder motor

  1. by throat you mean hot end
    The hot end needs to be cooled for pla, try abs

@Moshe_Kashani Thank you for your suggestions.

  1. I have tried to manually push the filament, how hard should it be manually by hand? Should it be possible to feed the hotend by hand?

  2. By throat I mean the “upper tube part” of the hot end.

You will need to get a hotend that is designed for 3 mm filament. The internals of the hotend for 1.75 mm is going to be roughly 2 mm at the largest diameter.

Ut should be possible to feed the filament by hand though not super rapidly. It has to melt as you feed it through so it’s oozing out like primula cheese.

@Jason_Martin Do you know which part in the hothead is 2 mm? is it the nozzle or the hotblock?

Should there be a PTFE tube in the 3mm throat? there was one in my 1.75 head but none in the 3mm head.

The inside diameter of the PTFE liner will be 2mm if your hotend is for 1.75mm filament. Some hotends don’t require a liner (usually all-metal ones) and you can get issues if the cold side of a hotend overheats. This causes the filament to jam. Get yourself an E3d-v6 and you won’t go far wrong because you can strip these down and re-build them easily with a minimum of tools.

Just in case Mr obvious hasn’t made an appearance did you change the filament size in the slicing software?

Thanks everyone for all help and suggestions.
I have given up on this, I have:

  • Enlarged the holes in the driving mechanism to fit 3mm .
  • changed the throat in the hot end to 3 mm.
  • enlarged the 2.25 mm hole in the nozzle to 3.25 mm.
  • increased the power to the extruder motor.
    All in vain.
    My conclusion for the moment is that my extruder motor probably is to weak to drive a 3mm filament, since 3mm is roughly 3 times the area then 1.75.

Wades reloaded, big motor, e-3d v6 hotend and you’ll be alright. Might be a good idea if you get a mate round to take a look too. Often it just takes a fresh pair of eyes to spot the bleedin’ obvious.

Thanks Duncan, the (obvious) mate suggestion I’ve forgot!