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donmilne

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After a couple of false starts with my Ultimaker 2, I finally seem to be making some progress. I started unboxing around midday, it's now 18:40pm.

First setback: I followed the first start wizard up to the point at which the feeder was supposed to pull in filament - but it just got stuck and the knurled wheel ground out a divot from the PLA. Strange thing was that this seemed to be same blue PLA filament that the test print was done in. I could see no way to advance or remove the filament, it seemed to be stuck tight.

Ok, there was four prominent screws on the feeder assembly, so I took it apart to undo the jam manually... and several internal components plonked onto my carpet (and another component on the inside, but I didn't know that yet).

Ok, with reference to photographs on this site I worked out how to put the feeder back together... then when I tried to put the screws back in they just spun in the holes... of course I had no idea that the same screws hold the motor on in the inside.

So, remove the white cover. Now I need one hand to hold the motor, one hand to hold the feeder halves together and in place, and a third hand to manipulate and screw in the screws. Oops! That's more hands than I have. I solved the problem by taping the feeder halves together and somehow made two hands work for the rest.

Finally! The feeder mechanism now seemed to be working - the filament shot along the tube... and five minutes later nothing seemed to be happening. Based on a message here about the filament sometimes getting caught up on it's way to the nozzle, I withdrew the filament again (after all that), trimmed a pointier end, and tried again, holding my breath.

It worked, yay! 40 minutes later I had printed out the robot example, which unfortunately snapped as I was trying to get it off the plate. I've heard that PLA is brittle. Would ABS be less likely to snap?

Right now the UM2 is printing a model I made from scratch using OpenSCAD. It seems to be moving along nicely.

I think that feeder mechanism needs a redesign. IMHO the motor should have it's own mounting on the inside, allowing the feeder to be removed for maintenance. Also the two halves of the feeder should screw or click together somehow so that it holds itself together while I mount it in place.

Also I think the first start wizard should be divided into two seperate steps: levelling of the base, and first time material loading. As it is at present, when one of these steps went wrong I saw no way to backtrack, the only option I saw was to cut the power and start again from the beginning.

Don't get me wrong, I'm still enthusiastic, but I'm hoping you guys are open to fixing these teething problems in a new product.

 

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It seems to have snapped quite cleanly along a single layer, where the robots feet (pedestal?) meets the legs. There's no obvious crumbliness above or below it. I think I just pulled too hard and it snapped along a weak plane.

Is there a trick to separating from a glue surface without using too much force? Run it under warm water perhaps?

Before I even got my printer I'd heard that PLA was quite hard - and therefore brittle. As opposed to ABS which is a bit softer and a lot tougher. Is this not fair comment? The flexibility to use ABS was one reason why I went for Ultimaker.

 

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Was the plate cool when you tried to remove it? When cold the parts tend to come off quite easily. To help it along it's best (IMHO) to use a piece of thin flexible metal such as a utility knife or those things you spread out spackle with. Get the blade underneath the print and gently pry it up. But a small print like the robot really should just pop off once the bed is cool.

The weakest part of a print is between layers. If you print a thin, tall rod (say 10mmx10mmx150mm) standing on its end you can quite easily snap it apart. If you print the same thing lying down you'll have to put significantly more force on it before it breaks, orders of magnitude more.

Layer to layer adhesion becomes stronger with higher temperature but that introduces other issues.

 

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Possibly I jumped the gun on the print cooling. Once it got down to around 32C (I can't now remember which temp that was) I reckoned that I wasn't going to burn myself on that, so I took the glass plate off. Hey, I was keen to get a close look at my first print. :)

When running the robot I'm not sure what temp it used - I'm still learning what the display is telling me. For my own model (same UM PLA) I chose 230C. That being around the middle of the recommended range on the PLA packaging. What are the downsides of being at the higher end of the temp range? Object not cooling quickly enough?

 

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Ok, second print completed. This time I waited until the printer told me it had cooled down. I'm seeing some problems with the print quality however. It's basically a cylinder that's various diameters and wall thicknesses along its length. At the end of the tube it's down to a wall thickness of 2mm. This prints as two walls with a narrow gap in between. Is that normal?

Also, there's a kind of shelf halfway down the cylinder. Instead of being solid I see the fill pattern with hairline cracks between each run. Can this be fixed?

I should mention that I used Simplify3D to slice this model because I was concerned by reports of poor support structures with Cura (that internal shelf again).

 

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DonMilne - one pic worth 10 posts. :wink:

More seriously, you just wait till the glass is cold - then the print simply snaps out with no effort. The only trick is to have the patience to wait.

Other than that - my first prints were a total mess. Then, slowly playing with the parameters and using this forum as a guide, the quality improved. Hope, you will get better results in a couple of the days.

 

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230C like you're using a good temp to use in the 50mm/s speed range I think.

I probably shouldn't have mentioned it at all, don't want to lead you astray. But just as an example of what happens with higher temps is that the part will need more cooling, the plastic will become less viscous and start stringing pretty badly and if it's left sitting still in the nozzle for too long it can start causing issues by breaking down (that's with quite a bit higher temp though). For now, just stay with 220-240C and you should be fine.

As for the problem with the model. The two-wall-with-gap is a problem with some slicers. It doesn't think it can fill in the gap with your 0.4mm nozzle. That's my guess at least as I haven't used that particular slicer and I don't know what your model looks like.

Small gaps between the lines can be underextrusion, incorrectly set filament diameter in the slicer, backlash or a slicer issue. If it's an overhang it could be that there weren't enough solid layers to create a nice solid foundation. It's hard to say without seeing the model and what the print looks like.

 

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The only camera I have handy is the one in my phone, and I'm not sure a fuzzy picture in poor lighting would really be all that useful to see the fine detail I'm talking about. I'm happy to share the model, but it's really nothing special: a simulation of a piece of 40mm diam 5mm wall thickness tubing that's been turned down to smaller diameters here and there, including at both ends where it's "turned" down to 2mm. The original the model is copied from really was created on a lathe.

 

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No matter how simple you think your explanation is, we need to see it visually. So please post a picture.

It sounds like your slicer got confused where it got thin. Cura really is a pretty good slicer and most people here can help you with any settings that aren't working for you.

Cell phones take fantastic photos these days and most can get very close for some good macro photography.

Waiting for head to hit 30C is not what robert meant. He meant wait for the *bed* to hit 30C.

 

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Thanks for telling me how great cell phones are these days, I'd never have known. Unfortunately I don't own the generic mobile phone market, I own a specific Nokia phone, and the camera on my phone is not very good in poor light. Anti-shake doesn't work very well on poor contrast images either. Perhaps after I get myself a nice lighting rig I'll start posting photos around here.

 

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This prints as two walls with a narrow gap in between. Is that normal?

 

Not having a picture is really really hard for us. So you mean kind of like printing a box? But round? Where the left and right sides of the box print fine? But the near and far sides don't print at all?

That usually happens if there is something in the model that is wrong - maybe the thickness of the cylinder varies slightly and the slicer gets confused.

 

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Let's call it a cylinder - a tube. It has a inside, outside, top and bottom. I expect this to printed as a solid shell x mm thick with the core filled with whatever is configured. Instead, I find that with the tube set to 2mm wall thickness at the top of the tube I'm seeing an inner and outer wall and a narrow gap in between. I'm not sure that it has an explicit top surface at all. I assume it's a problem of the narrowness of the gap once you subtract twice the shell thickness - it looks like it could be close to 0.4mm.

 

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Or go outside, the sun is a fantastic photography light ;)

 

Quite so. Ah, if only I didn't live in the north of Scotland, and it wasn't the middle of winter. Are you having a really sunny winter there in Sweden?

 

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If you would like answers not just guesses try to post some photos, If you really want the community to help you try to get a desk lamp, a flashlight, a candle, whatever and take a damn picture! Even this photograph can be enhanced by software and get a bit more quality. And as already said a pick worth 10 posts.

Do not forget also the setup, eg, speed, temp, layer height, flow, fan, retraction combing fix horrible, shell?.

otherwise it will be very difficult and time consuming to get started getting good prints based on hunches.

So... if you want guesses, this is my first one:

Right now the problem seems to be user...

 

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Let's call it a cylinder - a tube.... - it looks like it could be close to 0.4mm.

 

There are great chances that what you obtain is... normal.

I assume your printer has a 0.4 mm nozzle. So, you expect to get 5 circles to get the 2 mm wall thickness.

Well, I don't know how Simplify3D deals with extrusion width, but it could do the same as Slic3r does, by adding a very small fraction of 1 mm to 0.4 mm and gets, say, 0.41 mm. With such width there is no more space enough for 5 threads.

Now, if you had 2 perimeters on the outside and inside, in-between most probably you wont get anything.

If this is the case, one solution would be to use a single perimeter, so that the slicer could try to apply the infill between the walls. Once again, don't know about your slicer, but could be specific tricks for it (as there are in Slic3r).

 

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Can the UM2 vary the extrusion width?

 

Yes, definitely. If you set it at .4 I think Cura will treat it like anything between .3mm and .6mm as needed.

 

 

I'm seeing an inner and outer wall and a narrow gap in between.

 

Oh - now I get it. It's probably a bad slicer. I'm not familiar with simplify3D. Does it have a slice view where it shows how many passes it is making? If not you can install repetierHost (it's free) and drag and drop the gcode on and you can explore each layer and it color codes the extrusion amount and shows all kinds of problems like this that you describe.

 

I think this is the wrong forum to ask about simplify3D - you should see if they already have forum - they will probably know the issue in an instant. Cura shouldn't have the problem you describe as long as you set shell to .4, .8, or 1.2 and if shell is < .8 then also turn on infill to at least 50% but I recommend put shell at 1.2 and it should fill that all in I think - you can check in layer view in Cura what it decided to do. Since Cura takes about 1/100 of a second to slice a cylinder you can try 5 settings changes in 5 seconds. The main settings changes to play with are nozzle size, shell thickness and infill percentage. Yes you can mess with nozzle size a little and it will print fine - I wouldn't go below .35 or above .45 though.

 

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I appreciate that this is not the place to expect support for Simplify3D, I mentioned it only for information. My question really was whether this outcome was normal for the UM2 printing something as thin as the top of a 2mm curved wall. My expectation was that it might be, because I assumed that the extrusion width was fixed, and the placement precision finite, so maybe the nozzle just couldn't get in there - and you're telling me this supposition was wrong.

I was thinking somebody would tell me "yes, that's because the bed is too close to the nozzle, or not close enough - and here's how to fix it". Something like that.

Simplify3D does have an animated gcode preview feature, if that's what you mean, but it would take a long time to get to the top of the print... and I'm not sure how accurately it would simulate the UM2 anyway.

 

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This is called the "thin wall problem". There is a "torture test" item on thingiverse designed to test many things including this very problem - it has a box where each of the 4 walls get thinner and thinner.

I have lost track of which version of cura handles thin walls like this better and why and what the issues are/were because cura has changed it's strategy on these twice.

Basically a good slicer can get in there and fill that gap. You can fill .1mm gaps by just underextruding with a wider nozzle as though it's a .1mm nozzle. It works pretty well. The PLA flows in there like honey into a groove. Like spackle into a nail hole even though the putty knife is wider than the nail hole. But you need a sophisticated, mature slicer. And this may be in some obscure option in simplify3d. Or maybe you just didn't tell it to do 100% fill in thin walls or something and it's doing a sparse infill (say 10% infill).

 

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