JohnFox

It is either the nozzle blocked or the filament has got tangled. Before stripping the print head use the 'atomic' clean up of the nozzle as the first approach. That should clear any junk. If the nozzle stays blocked, then I use the shaft end of a 0.4mm drill bit into the nozzle hole. You have to heat the nozzle to about 200C to soften anything in there, then gently push the drill end in. Once it is in place, slide it up and down to clear the hole. You will have to wrap some tape around the drill to stop you're self getting burnt. Take car and don't break the drill. I use the machine default temperature of 210C for all my PLA work.

230C is too hot for PLA, the machine default is 210C, I would stick to that for the time being as it looks like the PLA is being degraded. Once it starts to degrade, gunge will build up in the nozzle and may hinder the flow. What make of filament are you using?

I have also just bought some Flex-PLA and had some success. I tried and failed to use the feeder. Don't even think about trying it with the standard feeder, it won't work, just squashes the filament flat. You MUST use something like a 'Robert' feeder, which I will get around printing to eventually. As my components are rather small, I withdrew the standard PLA filament back along the bowden tube to the feeder then uncoupled the Bowden tube at the head and pushed the Flex-PLA down the tube. I now had a tube full of Flex-PLA to print with, driven by the normal PLA. Everything else was done as default, 210C, 100% feed rate, 0.1mm layer height and the results were excellent, better quality even than normal PLA. Flex-PLA sticks very well to the glass with Prit Stik glue. OK, it's a pain to do and won't work with big parts but it showed me that the material prints very well, just need to sort the feeder out.

A photo of an screw adjustable foot I made for a scientific instrument. No specific thread type or size but the inner diameter of the left hand part is 18mm. Probably the most satisfying object I have made to date. PLA with layer height 0.1mm It seems that PLA has quite a bit of surface friction, so I used a very small amount of grease for smooth operation.

Just wondering if your temperature sensor is faulty, 230C is pretty high for PLA. Do you get the same results with other types of PLA? I use 210C with the default 100% feed rate. I will increase the infill percentage and I have 6 layers on the top, so the outside is pretty. but the first layers are the ones that are bothering me. look at the first pictures, some lines are incomplete

I think I have just replied to the other thread on this topic. Pretty sure it is due to dodgy slide bearings. Since I changed mine, things have really improved. I would check these out before changing the stepper.

If you are undoing the Z axis nut, just have a go at undoing the slide bearings while you are at it. Try them one at a time, sliding them up and down the pillars. See if the jam up at all.

You are correct, the walls are really poor! Don't think they are due to a Z axis problem because the lines don't cross the doorway. Going back to extrusion again I'm afraid. I now see why your prints take so long. ( do not try ABS with this sort of model, it would be almost impossible to keep it on the build plate ).

Actually UM have responded and sent me a couple of new Z axis slide bearings. The ones I took off felt really rough.

What thickness is the 'floor' you are filling in? Watching my printer do a similar job, it took at least 3 layers at 0.1mm to fill in most of the holes. It could be that that layer is only 0.2mm deep and it only gets a single covering. Your infill, although not perfect, is not too bad. Walls look OK as well. I also think that if under extrusion was the problem you would not get that coil of material at the very start of the extrusion, ( bottom right of the image ).

Do you get any 'tocking' sounds from the feed mechanism at the rear? If so, it's possible that the feed isn't working correctly. If the filament unwound OK? Just wondering if you are getting a tangle or the spool is too tightly coiled. Before trying to change the nozzle I would check to see if the nozzle is clear. I bought some 0.4mm drill bits, heated the nozzle and inserted a bit, blunt end first into the hole and slid it up and down. This cleared out some gunge. You need to hold the drill in some insulating tape otherwise your fingers get burnt. Take care not to break the bit. The odd thing with you photo is that the infill is not too bad, while the bottom layer is awful.

Just like to thank you for giving me an idea. Your photo of the barb fitting prompted me to make a similar, 5mm barb, for a unit I am working on. Didn't think 3D printing would be able to make the unit strong and accurate enough but it can with ease.

There is not a lot wrong with those prints, what size barb are they? Hi! Just to rule out any miscommunication, when I suggested to reduce the speed I referred to the printing speed, not travel speed. Printing speed is the speed your printhead moves at while extruding, traveling speed is the speed it travels at when, for example, crossing a gap (not extruding). Travel speed at 150mm/s is ok. @mfknjohn, could you also upload a picture of the model you are trying to print?

I think the the bed/nozzle gap is too large, it's not having chance to push the filament onto the bed.

I have had similar problems but not quite as exact on one layer as yours, ( mine span 12 - 25mm ). Follow IRobertI advice and move the bed up and down. I my case I couldn't find anything until I unscrewed the Z bearing races and found that they were jamming around this position. My theory was that I had lubricated the Z pillars and the balls in the bearings started to slide rather than roll. Removing the oil markedly improved the situation. Unscrewing the bearings is a real pain by the way, you need a long allen key to get at the back bolts. It could also be the Z nut. Both of these are behind the UM2 logo at the back of the bed. Some bad news - I have reported my fault to UM service with a ticket and they are incredibly slow to respond. :-(

Don't know about the clicking/crackling sound but it's interesting to hear that you get the same 'grinding' noise that one or two of us get when the head moves from right to left while retract is on. ( starts at about 14 seconds in ).

Does it appear on other objects? Try a simple cube and see if it appears then. What does the model look like in Cura X ray mode? It's easy to get a layer missing that you don't know about.

I am getting exactly the same noise in the same situation. It occurs when retraction is on AND the head moves from right to left. The sound does not occur during normal printing/extrusion and you can hear from your video that no noise when the head moves from left to right. any ideas anyone? I can't locate the source of the sound other than the general head area, no vibrations from the X Y axes.

What a clever idea!

Would not have thought the nut would be worn, when you think about it it doesn't get much wear, up and down once a print, not at any great speed. My Z banding problem is concentrated though a band 10-25mm, unlike yours.

Make sure the filament is reasonably straight at the end. If it has a bend it may not feed into the Bowden tube correctly. ( although sharpening the end should have done the trick)

How full is the spool? I have had problems when the spool is less than half full, the PLA was so tightly coiled it couldn't feed correctly, it's like trying to undo a spring. Uncoiling by hand fixed the problem. I'm gong to rewind onto a coil holder, ( bigger diameter ).

Just hit a little bug in the UM2 software. Did a 'Pause', which parked the head and retracted the filament, examined the build, then decided to 'Abort', which homed the head and retracted the filament. Two retraction events! Took me a while when I started the next print to work out why I had no extrusion for a minute or two. Two retraction events had pulled the filament several cm away and it took time to reach the head again.

Have you tried pushing them down to get them level. The screws must be below the level of the heated plate. If not, the glass cannot sit level on the plate and get good heat transfer. Either ask for replacement screws or plate. Worrying that these should get past QC during build.

I have gone with Sketchup. However, all my object are geometric in shape with straight edges and circular holes. It's excellent for that and with a shallow learning curve but I don't know what it would be like with more 'organic' models.