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"Clumping" how do i fix this

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Ive printed a few items now but on every one of them im getting clumping straight away as you can see from the pic below...

what am i doing wrong here?

layer height: 0.08

s.thickness : 0.8


bot&top thick: 0.6

fill density: 100

prnt speed: 50

print temp: 220



diam: 2.85 (not changed - default pla with printer)

flow 100%


noz: 0.4

speed: 40

dist: 4.5

initial layer thickness: 0.3

cut off: 0

dual: n/a

travel spd: 150

bottom layer 20

infill speed: 0

min layer time: 5





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Something's wrong with "theeasypc.co.uk". Can only load a tiny piece of that photo. Please go to "gallery" (top left corner of this page). Then upload your picture there. Then start a new post and click "my media" next to the smiley face and insert your upload picture into a post.

I refreshed this page 9 times. I loaded a debugger. I just can't get the photo to load more than a little bit. It's still transferring now as I wrote this but nothing is happening.


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At the start of the print, the extruder will purge out some plastic. Are you making sure to remove that with a pair of tweezers before the print starts, otherwise that extra plastic will get dragged into the print. That's what it looks like in your photo - the blob is somewhere that the print head hasn't even gotten to yet, it seems.

I have seen a Cura bug that one person had, where the extruder just glooped out a ton of plastic for no reason at the start of the print... but I don't think that's what's happening here. Make sure you pull off the extra plastic at the start, and if you still have problems, I'll look at the gcode and see what it's doing.

Other thoughts on your photo and settings...

1) The blue tape should be laid better with no gaps. ideally use wider tape to get better adhesion

2) Your top/bottom thickness should be an exact multiple of your layer height, since it prints them using whole layers

3) Do you really need 0.08mm layers for this? That's quite thin, for what looks like a mechanical part. Also, in general, it's best for layers to be a whole number of motor steps high. On a UM1, 1 step = (3mm screw pitch/(200 steps/rev x 8 microsteps/step) = 0.001875mm. More practically, you can just use multiples of 0.03mm = 0.06, 0.09, 0.12 etc, or the points half way between those.

4) You should be able to print your first layer a lot faster than 20mm/s - at least 40. I generally use 75.

5) Do you really want 100% infill on this piece? Most prints can get away with a lot less.


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@gr5 its deffo working. im not sure why you cant see it :-/

@illuminarti thats a lot of technical info and detailed answer and always appriciate people who take a lot of time to write a detailed answer. i will need some coffee to understand "On a UM1, 1 step = (3mm screw pitch/(200 steps/rev x 8 microsteps/step) = 0.001875mm"

1) im going to our local DIY store today to get some tools, knives, better tape etc - just not had the chance.

2) that makes sense about multiples of layer height.

3&5) i was printing a tool holder as i keep losing my hex screw driver... i presumed that using a 0.08 would make the item stronger !?!? and thats why i did a 100% density too... i got up this morning and put the screw driver in and the tube popped off the back very easily... was extremely disheartened.

this is what i was printing


it would be nice to have a guide for strength item settings. guide for speed.

4) ok no problem i will turn up the base print speed on my next print.

Additional: When im trying to level the bed, im finding it very difficult to draw the outer test squares...

a) ive printed off the Z alignment upgrade...

b) lowered tightened all the screw on the bed to the max...

c) set the z switch to about 3mm above the bed

d) raise the bed til the switch clicks (print head 3mm above the bed)

e) run the cura levelling wizard

f) losen the bed screws to bring the bed back up to the print head until it touches the head.

note: some times when i am moving the head from one corner to the other, it leave indentation on the masking tape, which i presume means that the particular corner is to high.

also: the front right part of the bed seems the most difficult to get to touch the head.

g) when i get all four corners touching the head gently with the switch 'on' i continue on the wizard to draw the squares the pla starts to 'string' out of the head... (i use fresh masking tape) but the printer does one or one and a half rotations before the actual pla sticks and starts to draw. (i can provide a youtube vid a little later after i get back from the DIY store)

I presume that the head is too high from the bed, so turn the screw 1/8th anti clockwise to raise the bed, but then the head marks/indents the masking tape - isnt that too low?

either way such a small increase or decrease in height still doesnt give me the squares.

so far i just ignore the squares and print anyway. and it starts to print.


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If plastic doesn't come out of the nozzle on the first layer (or when leveling like this) - and assuming that the nozzle is heated up, and the filament is inserted ok in the extruder drive, and not ground away - then there are two possible problems. Either 1) the nozzle is too close to the bed, so it can't get out (at least not until enough pressure has built up - then it may ooze out excessively, in a blobby mess), or 2) the nozzle wasn't fully primed with plastic to begin with, and it takes a while for it to fill up with plastic before any comes out. I recommend manually turning the gear wheel on the back of the printer to prime it before you print, or run the leveling test.

That said, I've never actually used Cura's leveling wizard.

Here's how I level the UM1... first of all, move the z-stop (or if you have an adjuster, back that off), so that the z-stop won't be triggered for the first part of leveling.

Move the bed down a bit, away from the nozzle (turn the printer off, and turn the z-screw by hand). make sure all 4 bed levelling screws are in a 'middle' position, so that the screws can go a few mm in each direction as needed. Push the head over near the front left screw, and turn the z-screw and raise the bed until it is almost touching the bed in that corner... a mm or less off. Move the head to each corner in turn, and adjust the screws... check the first screw again, in case it has shifted. The aim at this point is just to get the bed roughly level, and pretty close to the head. And, importantly, you need to keep all 4 screws still somewhere in the middle of their range. If any of the screws has bottomed out during this rough adjustment, or totally come out, move the whole bed one way and all four screws the other way, to compensate. Doesn't need high precision, it's just setting a baseline. Now, set the z-stop, or z-adjuster, to trigger in exactly this position.

Power on the printer, move the bed down a bit, and then home z. It should come back to the position it was in, with the head almost touching in all 4 corners.

Now with the bed in it's homed z position, you can do the precision leveling. Start by heating up the head to a typical print temp - maybe 220. Retract the filament back a bit by hand, by turning the gear, to reduce oozing. Now move the head by hand again to near the front left screw (you might need to disable steppers, first, via the ulticontroller, or Cura/pronterface etc - or wait for 1min of inactivity for them to release).

Slide a sheet of ordinary paper under the nozzle, and then adjust the leveling screw slowly until you just start to feel metal scraping on the plastic as you pull the paper back and forth. Make sure that any resistance you feel isn't just the plastic dripping and sticking to the paper - the scratchy metal-on-paper feel is quite distinctive when you feel it. Once you get to that paper's-width gap, move on to each of the other screws in turn - move the head and adjust until the paper just catches. Recheck the first corner again as it may have moved. Finally. once all four are right, give each a one-eighth turn anticlockwise, to move the bed up that last paper's-width.

And now you should be good to go. :smile: In future, with the z-stop in the right place, all you should need to do is the paper trick in the four corners.

BTW, one problem I had with my bed originally was that the washers on top of the springs were small enough to catch on the edges of the keyhole slots in the bed sometimes, making it very hard to get things level. Check that they aren't caught (the hex screw driver pushed down through the slot is a good way to make sure that the washer is free to move) - and if there's any suggestion of a problem, adding larger washers on top is a good idea. While you're at it, you might also want to replace the 4 screws with longer ones, to make sure they're always firmly anchored in the Delrin blocks.


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Yes, if you wipe the tape with alcohol before printing it will stick so well that you'll tear the tape, taking it off. The tape might still pull off the bed - wider tape helps with that - but the print will stick to the tape solidly. Soaking the bottom of the print in a few mm of alcohol afterwards will help lift the tape right off though.


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and ive come back to it and the bed has moved off the 4 pegs.... hmmmmm either cat, dog, or wife. none of them are owning up to it... has anyone see any bed-plugs that can slot in the bed holes to stop it "accidentally" moving AGAIN.


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Aww, sorry. I tried... I never needed one, as I replaced mine with stiffer springs, that hold it in place pretty well. But I think there's something else on thingiverse that I remember seeing. Failing that... At Maker Faire, UM was using standard little dowel pegs, of the self-assembly furniture variety...


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