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jcosmo

Infill not reaching inner perimeters

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I'll start with a photo:

http://flic.kr/p/cyGnnQ

Can anyone suggest why the infill is not reaching the edges of the inner perimeter (the border around the 'box' that is cut out of the shape I'm printing).

I'm using Cura for this, and printing relatively slowly (30mm/s) (see the blobbing, is this because it's slow?), I can provide the settings but I don't know if they are relevant.

The things I'm investigating:

- Loose belts: I don't think this is the case, as I've tensioners on them, they play a nice high pitched sound when twanged.

- Improperly aligned axis/belts: I've done a full re-alignment, and have printed a variety of calibration shapes and they are coming out true to form.

- The axis moving back and forth (along the line of the axis): I have not checked this fully yet, but it seems to me that there could be a whisker of possible movement by the axis rods.

- improper settings in slicing: I don't know where to start with this one, I've observed it in things sliced with both Cura and KISSlicer, but I'm no expert in tinkering with the settings.

What makes me more puzzled is the way that the infill doesn't reach the inner perimeter but does reach the outer one. You can see in that photo that the fill doesn't reach the left side of the inner perimeter, but it does reach the left side of the outer perimeter.

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The blobbing on the first layer is usually because the bed it not at the perfect level. Usually the 2nd layer will flat this without problems.

Belt tension. Did you check the tension of your small belts? You mention you have tensioners, but people sometimes forget that you also need to tension up the small belts by pushing down the motors.

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Thanks for the hints.

Levelling the bed gives me huge amounts of grief :)

Spent a while on it last night and had got pretty happy with it, but I'll check again - I can see how it would cause blobbing if the head pushes stuff around.

I've not checked the small belts recently - a cursory look seems that they are ok, but I'll make certain. I presume there isn't such a thing as 'too tight' for these? Just push the motors down firmly and tighten the bolts? I seem to recall someone suggesting in a comment on the build instructions that it could be good to file a flat area onto the drive shaft from steppers so that the pulley screw has something more to bind against - is this a possible area for slippage?

Is slippage or inaccuracy really likely to be the problem, given the way the fill reaches the other edges, in all directions, but just not around the centre? Is it perhaps a problem in my model (built using sketchup) and the combination of settings I've used?

A query regarding the small belt for the Y axis: it doesn't run straight up/down the way the X axis one does - this has to be normal I presume, given the positioning of the motor and the axis rods (rails? terminology anyone?). The belt doesn't touch wood anywhere.

I presume oiling all the rods occasionally can't hurt - what about the bearings at each end of the rods?

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While pulley slippage can happen, this usually results in layer shifts, not the problems you see now. And yes, there is no "too tight" for the short belts.

It's not a problem of the GCode or the model. You should be able to see this clearly in the GCode preview of Cura.

And a bit of oil never hurt anything ;-)

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I certainly have possible movement front-to-back in the rod that runs front-to-back on the left side of the machine.

It's the only one where this is possible and I can only presume it's not a good thing - there seems no good reason to want to have movement in that area.

Any hints on what could be done to fix this? Those rods should - lightly - rest against the wood stops I presume, but it's not like I can bring those any closer together. That leaves me with trying to pad the inside of one end or the other :(

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The rod is slightly short then. More people have that, but other then the sound it makes, it should not matter, as the movement of that rod is not translated to movement of the head.

You can pad the inside of the caps with some kind of filling. (Soft padding or something might work)

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Ok, I can see how it shouldn't have an impact on the position of the head, though it can minutely alter the alignment of the belts it carries (x axis) to the rods (drive for y-axis belts) under them. On that point do you have any hints or technique for aligning these, of is close enough generally considered good enough?

Whilst tightning the short belts I found 2 of the pulleys had come loose, and have tightened those. one of these I have failed to get tight enough to stop it being able to translate along the rod, am concerned the pulley nut is damaged or has damaged the rod underneath it. Ill take it apart completely this evening.

Thanks for all your help, it's got me finding problems much faster than random guessing :)

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A few hints can really help in identifying the problem.

Unaligned belts only cause belt ware as far as I know. So that shouldn't be causing your problem. Lose pulleys however, is a real problem. (but some pulleys are more critical then others, as I printed all my TITAN parts with 1 pulley missing the set screw)

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I presume oiling all the rods occasionally can't hurt - what about the bearings at each end of the rods?

Ultimaker (Erik) told me that for the new Ultimakers (2012) it is not neccesary to oil the rods, it could even get worse...

The bronze bushings don't need oiling. Just keep them dry and clean, oil could just gather dust

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My rods started looking a bit rusty in places. Just a micrometer of rust here and there. Then I got the sounds. Those stopped temporarily after one oiling, and now hopefully permanently after the second. The rust is being worn off.

So I think oiling is better than not oiling. Not oiling didn't work. Oiling did.

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