New nozzle... new problems....

Hello Reprappers.
I decided to replace the Hot end on my printer, which was homemade by some guy.

i bought a 0.3mm J-Head nozzle for 1.75mm filament.
I have mounted it with a mount found on thingiverse. (Bowden setup).

Now i cant get any print right.
First off, theres the temperature. I'm Printing in PLA.

The temperature for the hot end is correct when it is not heated (its equal to room temperature). but for some reasing, i have to heat it up to 230 degrees, to get decent results.
Anything below that, will result in infill being more dots, than lines.
How can this be?

next, theres the individual lines on the top solid infill.
If you see this picture:

That is the top of the print. See the lines not comming together??
Heres a picture of the bottom of the print:

Here you see an almost molted looking print.. Lines are completely together.

I am running at speeds a bit lower than slic3r's default settings.

Also, the prints Seem very weak next to the ones i printer easily. When i try to bend Them the layers crack up.
What is wrong?

Sometimes, it seems that my hotend is "picking" up filament, which ends up being a ball just below the heater case. Theese sometimes comes off in huge chunks.

Edited 2 time(s). Last edit at 04/23/2015 03:17PM by Kafledelius.

Smaller nozzle = slower printing. If you print too fast you'll end up under-extruding, which sounds like the cause of a lot of the issues you've described. The printer has to work harder to push molten filament through the smaller nozzle and it works better at slower speeds.

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I dont know if thats all his problem is.
Ive got a .3mm nozzle and i regularly print at 50mm/s but it is a direct drive on a wades geared extruder Pushing 3mm filament.
Maybe it can push more through than a bowden setup but i wouldnt think it would make that much difference.

Can you verify the heater temp with another sensor, maybe a thermistor supplied with a multi meter.
The one ive got has been invaluable for checking stuff like this.

Have you verified that the filament is true 1.75mm and not out of spec.

When you changed your hot end what settings did you change in your slicer?
Your layer heights and first layer heights will need to be changed with a smaller nozzle.
The nozxle to bed gap will need to be more precise as well as bed levelling.
Retraction values will be different.
There may be other tweaks you need to make for a smaller nozzle.
Had you changed the feed multiplyer for your last hotend but not adjusted it for this hot end and extruder?

You may find you need to go back to your earlier caibration prints and work through them again and change the slicer settings to suit.

I know that when i regularly switch between my 0.3mm and 0.5mm nozzle on my hexagon hot end the print profile in the cura slicer is very different and took me a while to tweak. I have a whole directory structure full of saved slicer profiles for different materials(nylon, abs, ninjaflex), nozzle sizes and even colours of abs that i can load ready to print.

Gordon

Thank you for your responses!

Gordon:

I have attatched a screenshot of my slicer settings:




I have not changed my Layer height, its set for 0.2 (should it be higher?)
I have also not changed my extrusion multiplier. Do i have to recalculate the E-steps? or just use a multiplier of 1.1 ?

When you changed your hot end what settings did you change in your slicer? - I changed the speed settings mainly. I lowered it a bit. I also changed the retraction values since this doesnt ooze as much as the previous one.

What changes do you propose i start with trying out?

And isnt my temperature a bit high? Does it have to be this high?

i've noticed that sometimes when doing infill, the plastic turns into dots more than lines. This effect kind of comes and goes..
Heres a picture of the above mentioned:


Update on that print:

I was trying to print a 40x40x10 box.
The box turned out in the right dimensions, how ever. it was so weak that i could crush it with 2 fingers (pressing on top and bottom). This was printed with an infil of 30% at 225 degrees celsius.. Plus i could pull the layers apart easily. Shouldnt this be tougher?

As i mentioned earlier, the plastic crawls up along the jhead and attatches it self just under the heater case.
Heres a picture showing what i mean:


Edited 4 time(s). Last edit at 04/24/2015 08:01AM by Kafledelius.

Oh god...........
My new hot end is leaking...... Guess it makes sense why i have to use higher temperatures and a higher extrusion factor then.....

Does anyone have a good guide on how to take apart a j-head?

Edited 1 time(s). Last edit at 04/24/2015 01:24PM by Kafledelius.

So i had my hot end replaced, and it prints With no leaks (yay!!)

How ever, the Lines Are still NOT melting together..
I am thinking it might be the extruder which isnt strong enough.. Is This an option?
I have tighten the idler as Much as possible, but i Can still move it With my fingers, Without Really applying force to it. It should be alot tighter, should it not?

nevermind

Edited 2 time(s). Last edit at 05/02/2015 03:59PM by Darathy.

Okay

I tried replacing my extruder, with a new better one.

I am still having the issue though.
On this new extruder, its easier for me to see whats happening.
It seems that the extruder is able to extrude filament for a couple of seconds, then stops, and then starts again (The extruder is always running, but the filament is slipping).
If i apply a little force on the filament, it starts flowing again, till i release it.

I can easily extrude filament through the nozzle manually.

What can cause this?
a poor hot end?

1.)Do you have a spring loaded extruder? try tightening the screw so the motor will have more force on the fillament.

Think you for your answer!
No i am not using springs. The extruder i am using is the universal mini extruder..

I have Tried tightening the Screws and there by tightening the idler, but it didnt Seem to help.. And the first couple of Lines is printet perfectly, but Then it stops feeding

If i remove the peak, and try to push filament trough the metal part of the hot end, the plastic gets pushed back up, and not out through the nozzle.. Could this mean anything?