layers not fusing properly

Hopefully someone can give me a few pointers.
Im printing this bracket for my daughter, to hold the lamp in her moth trap.
Ive attached an image of the printed piece.
The desighn isntvright yet this was the first print to test the design.

Its got no strength in the print.
It splits horizontaly esily.
It looks like the layers arnt fusing fully and leaving ridges/lines on the sides.



Prusa i2 with .3mm j-head nozzle.
Head at 190c, bed at 60c.
Im using a .2mm layer.
50% fill
I used supports for the cross piece.

What do you think is wrong?

Thanks

Gordon
Ive got a couple of other questions waiting for a reply in this section

I think the 2 issues you mention are separate.

Since you're at 190 degrees, I assume this print is using PLA...

For the strength issue, I would try bumping up the temperature 5 degrees at a time. The filament seems to be laying down nicely but could be cooling too quickly for it to bond well to the previous layer. If you get to 205 degrees and there's no improvement, then come back and we'll look further.

At the higher temp, you may then pick up new issues (stringing, blobs). If you do, then you can add either a desk fan blowing across your print at low speed or add a fan to your print head that cools the print. What you need to wind up with is filament extruding hot enough to stick, but cooling right away after it's laid down.

The other issue, which I think is different, is the layering you see...

If the layers are shifted in one direction, look for loosness or backlash on that axis. If it happens both in the X and Y axis, you may have either a slightly loose extruder (perhaps the hot end is wiggling in the mount), or looseness/backlash on both the x and y axis.

In short, it looks like it prints for a bit on on position, a jerk or other rmovement shifts either the bed or the head slightly and it prints for awhile in a different position. Then another jerk or movement shifts it back or to a 3rd position.

You should be able to achieve a good amount of strength. If that top portion is supposed to be some sort of clip to hold something, it would be stronger if the part could be printed laying down, though the round bottom may make that orientation impossible. It should be plenty strong as is though...

Edited 2 time(s). Last edit at 08/21/2014 05:19PM by ltklein.

Thanks for the reply.
yes its pla.
The head is nice and tight ive got one of the aluminium j-head holders sanwiched between the x-carriage and the wades extruder.
Itsba good tight fit in the bottom of the extruder as well.
The x-carriage on lm8uu has no play that i can feel and all the belts are tensioned.
I have tensioners on both belts to get them tensioned properly.
I did have some movement in the housings holding the lm8uu bearings in the bed carriage, but i used some sugru to take up the slack and theres no play now.
The y-axis nuts on the lead screw doesnt yet have a spring between them as i havnt sourced one yet that doesnt catch on the threaded rod.

Iv just realised something else.
The part is supposed to be 70mm high.
But its come out at 53mm high.

The "design" will be changed. I had considered doing as 2 parts so i could lay the peg bit on its side.
Just getting used to how things compare on screen in openscad and in real life.
So the peg bit is far too thick and needs a cuange as it wont go round the handle it clips on anyway.

When i was doing my first prints of 10mm cubes the dimensions were pretty much spot on.
I was using 210c as head temp.
But a friend recomended i usrd a lower temp. As low as 185.
Can lowering the temperature effect the overall height of the print as well?

Ill give it a go with a higher temp tomorrow.

Gordon

Edited 1 time(s). Last edit at 08/21/2014 05:49PM by gordonendersby.

Quote
gordonendersby
Iv just realised something else.
The part is supposed to be 70mm high.
But its come out at 53mm high.

This sounds like your Z steps aren't properly tuned, doesn't it? Since the shape is ok, but reduced in the z direction, I think there is a problem with the command of the Z axis, namely the Z steps.

Thanks,
Few more thing to check.

Ive done the z steps and got it pretty much spot on.
Used verniers and checked more than a few times when i was putting the values in the marlin firmware.
Also tuned the power for the steppers. Motors dont get hot and the heat sinks on drivers stay below 43c.
I dont seem to be missing steps.

Would The height vary with temperature of the hot end?
Because the 10 mm cube was spot on at 210c.
And 1.5mm shorter at 185c.


Gordon

Edited 1 time(s). Last edit at 08/22/2014 04:51AM by gordonendersby.

Ok,
Tried again this time with the 15mm cube.
0.2 layer
Temp 210c
Height was still short by 1.05mm over that 15mm height print.
So temp hasnt effected height.

So double checked everything was tight and got the verniers out again.
Checked z steps again. Pretty much spot on. 0.03 over. I cant measure any finer.
Checked extrusion and that was spot on. 20mm for 20mm. Id taken a lot of care with tjis when i did it before.
I did find my x-axis was 1mm out left to right. Had compensated with bed. But i adjusted this anyway.

Theres one thing im unsure of.
Wall thickness or shell as its called in cura.
Id used a multiple of my nozzles size at 0.9mm is that too small.
Whats a good wall thickness and can it effect the height?

Thanks

Gordon

Tried larger wall thickness no real chang.
Been at it for about 4 or so hours and my prints are getting worse.
Even if i go back to original settings.
My z-axis has started to stutter sometimes.
Theres nothing binding.
The drivers arnt overheating, motors are cool to touch.
Tried swapping out z axis driver but still stutterd.
Everything wss runn9ng smooth 4 hours ago.

Maybe the arduino mega is getting too hot?
Not come across an arduino overheating before. Played with plenty.
Last time i did a really long session the graphic controller encoder wheel played up and wouldnt select an optionon the menu.
Havnt got a spare mega at the moment to swap out.

Or have i got sub standard drivers?
Im going to call it a day today and let everything cool down and try again tomorrow.
This is getting frustrating.

Gordon

Had anothrr go with everything cooled down.
Couldnt wait till tomorrow.

I really think ive got some defective hardware now.
Double checked the power supply. All voltages good. Plenty of power to run it.
Z axis is stuttering the driver isnt the problem as i swapped it out.
Now the extruder is not always turning.

Something is slowly breaking down.
I think i need to replace the cheap arduino mega.
Ive also ordered some good quality a988 drivers to try.

Gordon

Well, I guess it's often a good idea to switch from cheap and maybe poor quality components to components of high quality, but maybe more expensive.

I had a look at the mega more closely.
Theres a black component marked m3 by the dc jack that wasnt fully soldered to the board.
It wasnt making full contact with the pad.
I soldered it back on but it kept tripping the power supply.
Looks like the regulator is toast now.

Suffering from withdrawal now, havnt tried to print something for days.
Hopefully ill have the replacement by Thursday.

Gordon

New mega fitted and stepper drivers.
Im now back to just before where i was when it all started to go wrong and i had the problem with that print.
Few more test and calibration prints to do.
A 10mm cube came out .12mm short today and about .2mm over on the x and y axis so a little more tuning to do.
Hopefully i can get that part printed soon and it will be better quality.

Gordon