alaris2

did you see the first picture of how it prints tho? where the green is on the outside the print becomes very rough - this was the reason behind my question the other day about loops -> perimeter -> infill vs perimeter -> loops -> infill. I'm not sure the preview is wrong, I think something to do with the slicing is wrong (perhaps because it's confused by some aspect of the model?)

I was having what I thought was a hardware problem, but now I think it's a misunderstanding of how the slicing works. I tried to print a box with some holes pre-drilled in it, but got rough patches on the outside of the box (example image here - http://i177.photobucket.com/albums/w228 ... 000010.jpg ) looking at the gcode, I see the outside of the box is red, except where these weird marks are.. where it's green. I think green is loop rather than perimeter? but why are the loops and perimeter getting turned inside out like this and how do I fix it?

Oh I know Daid which is why I wasn't too condescending, but what we don't know - is it cooking.. or just simmering? if something's going to happen in the next month then I'll hold tight, but if it's 12 months away.. that's an interesting kickstart project, tho it looks to be unsuited to UM since it's 'big heavy extruder on the head' design is it not? it looks almost identical to the makerbot design too.. amazing what people will part with their money for these days

that wasn't a very useful post Daid destroyer - I am so totally with you there, especially #5. I think it's a shame that the UM team don't take advantage of the fact that so many of the people who have bought their machines have an engineering or programming background and could be freely helping them improve the product. I was discussing ways to improve the hot end and extruder only this morning with some engineers here and several good ideas came from it. of course it doesn't help that discussion seems to be split across this and the google forum, further diluting efforts. In particular, I'm aware that similar products are now appearing on the market at 1/3 the price of UM - it was bound to happen sooner or later of course. and the resin printer boys are making excellent progress - they can now cure a 6" square resin at 0.1mm thick in under 20 seconds, making total build time 20*(model height/0.1mm layers) seconds. the cost of resin in the US has now fallen to about the same as PLA, but alas no suppliers in the UK yet. this is a really fast moving area - I invested a lot of money to buy an UM. I'd love to see improvements (and help work towards those improvements) in accuracy and speed before my investment turns into a very expensive XYZ table. so if anyone wants to have a serious engineering discussion about the extruder or hotend, I'm happy to be involved and I think destroyer's points are an excellent starting point.

so after 5hrs printing my first organic shape object and first time I got support to actually work.. I get this.. http://i177.photobucket.com/albums/w228 ... 000009.jpg curiously the object is symmetric but this is the other side.. http://i177.photobucket.com/albums/w228 ... 000010.jpg before another 5hr print, I'm trying to understand what went wrong.. I'd love to hear any theories.. so far I've got: 1) I was printing at 120mm/s - this doesn't really explain the weird pattern or inverse on the other side very well, but Joergen did mention that perimeters suffer at speed, I wonder if this is what he meant.. 2) I foolishly set the print order sequence to 'perimeter loops infill' 3) the organic shape has curves more accurate than can be sliced by Cura so rounding errors lead to this effect. This might explain the vertical symmetry. I've never had anything else print with this poor quality an edge but most of what I print has sharp polygonal edges. 4) belts not tight enough, or perhaps some are tighter than others? does it matter if one side is tighter than the other as long as they all sing? do they have to sing the same note? 5) bed not level. but i don't think this would cause this effect. love to hear your views on this subject - I don't really want to print much slower unless i have to, because 5hrs is already a very long print so 50mm/s is a whole day printing!

so I shouldn't get.. http://i177.photobucket.com/albums/w228 ... 000010.jpg and http://i177.photobucket.com/albums/w228 ... 000009.jpg ?

I'd really like to go the ABS route too - have you sorted the problems with the heated bed then now? (it was too cool before I think you said?) I'd love to see a thread on how best to convert UM to ABS and your experience with mods etc. (I've seen far too many heated bed threads that I've lost track of which is easiest/best and half of them end in 'it didn't do what I thought it would' or other failures)

thanks Daid - so if i foolishly changed the default sequence to match the first layer sequence, I'd probably expect the perimeters of the object to not attach properly, perhaps even break up on parts with overhang? (since it will effectively be printing in thin air?)

can anyone tell me why I'd want to change the sequence settings? I note the first layer is by default done differently from the others - why is this? what are the benefits of one sequence over another? and has anyone experimented with bridge settings other than 100% - any success stories or otherwise? cheers, nik

this is great and I'm all for it, but I don't feel it's something that's holding the UM back in any way. the 3 biggest problems I keep seeing are: 1) software - good results depend on good slicing strategies and we're lacking in so many ways here. 2) hot end - too many problems with bowden tubes popping out and performance problems that can be traced here or to.. 3) the extruder - which does an OKish job but not an *awesome* job and often lets us down. the places where UM lacks are print speed and quality - anything to improve these is worthwhile.

just for the record.. I tried using grid infill to see if it would improve matters. it does, but not enough. top surfaces are still very rough. I'll drop back to 120mm/s for the time being which seems to be the most before this effect kicks in.

Daid - how does fill density and wall thickness affect quality? or do you mean quality to be 'structural quality' as opposed to (what I assumed) 'perceived beauty of the object'?

really? Cura is defaulting to 0.4mm nozzle size - so I've been assuming that's what I had!

totally agree with you there Joergen - I don't think I have the option of changing speed of infill (unless Daid tells me otherwise?) but I intend to test grid infill and the print order. and destroyer is very right about the cooling - it takes me 7 minutes to print a long thin cuboid with the largest face on the bed. but rotate it 90 degrees and it takes 1hr 15mins. so has anyone had any clever ideas regarding the cooling? we discussed some of the pros and cons of current fan shroud designs in another thread i think..

I've heard of people using 0.35mm but nothing smaller. There'd be lots of bowden tubes a poppin' I should imagine?

well I've not gone beyond 150 yet, because I notice roughness on outer surfaces and today I studied the effects speed has on infill. at 20% infill it's starting to break up - turning into fine strings with blobs on. which is why top layers are rough - they have precious little to sit on top of. this probably means I need to tweak the temperature a little higher (I think?) note too that Joergen mentions a larger than default nozzle - which might be necessary to get enough material out at that speed? it sounds like he's using ABS too, whilst I'm using PLA. anyway, you're right destroyer, with dwindle switched on I find the print looks very good on the outside, but this is partly due to perimeters and details slowing down, however I believe it is reaching some high speeds (this due to the time to complete a print decreasing significantly) and on very large flat surfaces the head is certainly moving at the 150mm/s. most of what I print is 'boxy' and falls in a 4' cube. yes vibrations were definitely an issue at first. I printed Daid's UM feet and coated them in silicone - I'm also working on the end plates to prevent the guide rails bouncing back and forth. incidentally, (some of) the reprap boys are up to 400mm/s and laughing at us ( http://www.thingiverse.com/thing:7652 ) they reckon the UM can't possible go this fast.

I'm currently printing at 150mm/s (which Cura warns me I can't do..) and I'm curious whether anyone else is printing at speed and what quality of prints they're getting? since I'm currently printing in black it's lousy for taking photos of, but I have noticed the top surfaces of objects are printing a little rougher than before. I also note that the first layer is very shiny - the high temperature needed for printing at speed is applied to all layers and my first layer prints very slowly so heats up too much. other than this, no reported problems. I was expecting there to be accuracy problems due to backlash and such but haven't observed anything like this. did I just get lucky or what am I missing?

I think this j-head idea is a good one but I don't have the facilities to make one and join in the experimentation. I would be very interested, especially if it can use a smaller nozzle size, since it might lead to higher quality prints. anyone know if one can be bought?

I agree with you there destroyer. the fan is currently treated as a binary thing (tho I note Cura does let you change the percentage the fan is on) whereas it really ought to be far more intelligent and take what you're printing into account. that fan you're using is quite a broad one - should be great for large objects but probably not so useful for fine or tall objects (eiffel towers). I'm using http://www.thingiverse.com/thing:17768 which is great for the latter, but does suffer some design flaws (fan is too big and blows half the air back out the inlet). I should swap fans depending on what I'm printing really. but i'm too lazy so leave this one on all the time now... note how since the air exits immediately beneath the nozzle, it's prone to being reflected by the bed and cooling the nozzle - I think the larger one you showed me won't be so susceptible to that - but I can print some awesome overhangs and bridges from any angle. I think the fan shape and control really should be selected on a per-print basis..

it's possible - I haven't messed with the FW at all. Thanks Flo, that's an interesting line of experimentation there. I can recommend Daid's Ultimaker feet for experimenting with dwindle. I don't think it's just speed that makes the print better (but you're right that prints will take longer with dwindle and the slower speed at extremities is bound to be improving quality there). The feet consist of several layers of 45 degree lines that decrease in length - without dwindle, those shorter lines move the same speed as the longer lines and the PLA is oozing out the nozzle the whole time leading to excess material being deposited at the shorter lines which makes a mess of the print. with dwindle on - the problem disappears and I get a perfect print. I'd take a photo, only it was printed in black and it just doesn't show well. the thing i can't explain is why dwindle should work - I had expected it would print slower on the short lines now. That calibration pyramid works well for retraction but I can recommend Daid's feet for dwindle testing (and I'd love someone to explain to me why it works, or even if anyone can reproduce what I'm seeing here) cheers, nik

I tried printing Daid's Ultimaker feet last night with dwindle. without dwindle (retraction only) the first 10 layers or so are just a mess. with dwindle on, it comes out perfect. really impressed with these settings - however the printer makes the weirdest noises so you have to prepare yourself for that! I generally don't print things with support, since I've never had any success with support ;( Joergen's comment is interesting, since I've observed exactly this effect on similar parts, but it was always due to aggressive retraction i found. I do think the 4.5mm retraction might be too much - I have also had perfectly good results from 2mm. it would be interesting to hear the logic behind the numbers, or is it just trial and error?

I confess, I also really miss that duplicates button. sometimes I just wanted 4 Ultimaker feet to print out and hitting the duplicate button was so easy..

Cura doesn't need a manual. it just works.

I'm rather toying with the idea of just writing my own slicer now since it's quite easy I see however, that both you (Daid) and destroyer have had a go at this already - what happened next?

well the method Daid is using to fine tune the position with a slow print is similar to what I've been using. I did some experiments today with fans and thought I'd share the results. fan on for first layer - requires a skirt to work, because the fan comes on after the Cura 'warm up routine' which causes the nozzle to cool down, so no plastic will stick to the bed for about 20seconds. fan on second layer - first layer is much better, maybe the first 3-5 seconds of plastic doesn't stick to the bed, so some cleaning up still required. but the second layer now suffers the cooldown and the perimeter of the second layer suffers as a result. note, this is not the stock fan. my observation with the thermal camera is that the head is very close to the bed, so most of the air is bouncing straight off the bed and cooling the nozzle. this problem may also occur on subsequent layers with large flat surfaces. the cooling effect exceeds the rate at which the nozzle can heat up again and causes thermal fluctuations. switching the fan off on the first layer doesn't really help this (in my case). it may work if the bed is slightly further away (Daid's 0.3mm suggests this is the case) or with different fan shrouds. so I think 'the answer' is the fan should vary according to the properties of what's beneath it (bed and model), but that's not really an easy thing to do. so my solution was to modify the start g-code. I now switch the fan on near the beginning of the warm up routine. result? far less pre-extruded material being dragged around (yes I was plagued by that too Robert) and excellent sticking. I can recommend this but I'd be interested if others find the same results or if it's very bed-level and fan shroud dependent. cheers, nik