alaris2

OK, we're sorry we asked looks good tho, cat brain was my vote btw

it's a shame it didn't come with a heater and thermocouple, it would have been nice to at least have used the other head as second head instead of trying to cannabilise it. double shame given the cost.

very interesting thread there - have you seen http://www.instructables.com/id/Combina ... GH3-Specs/ also? the problem with weed trimmer line is you don't know what's in it. if it's pure nylon, that's great, but what if someone adds fiberglass or similar? melting point there is in excess of 1200C so you'll need to drill it out the nozzle! the purity would seem to be the biggest hurdle to overcome - check your supplier. the temperature probably varies according to purity. there are at least 2 US sources that are known to work fine. hygroscopicisity is a shared problem as you point out - altho how much trouble it gives you will depend on your environment.

out of interest, does anyone know why the new hotend says "temporary v2 hot end upgrade" on the supplied bag? I was hoping for something more permanent

Daid is right about the extruder - I took it off the back of the machine and held it and the noise level decreased manyfold. I'll make some sound deadening supports at some point.

actually i didn't know about welding rods, that's really useful info thanks. I was planning on using 4mm rods because I could obtain them locally and knew they didn't contain impurities then running them through a die to get to 3mm. some forms of nylon (eg. strimmer line) are not suitable since they contain fiberglass and other impurities. nylon has a lot of very useful properties including the higher strength and melting point yes the heated bed thing is a necessity, can't wait for a good solution to this.

well I plan on printing with nylon very soon. I discarded the PC idea when I discovered it absorbs too much water which leads to bubbles and a structurally weak print. i'm not convinced it can be done without more special mods to the hot end. agree with your aim tho - PLA makes good support and 'simple' drafts but is no good for structural parts. ABS is better, but lack of an official heated bed makes it more suited for the makerbots and other printers.

you're really getting the hang of failure as a form of art here Ian

are you saying you are using something atypical then? or just wondering what others are up to?

well done Bertho. there should be some award for most useful contributions towards UM progress and 3D printing technology. so far you would win them all!

totally agree with the last 3 points - as far as the recovery bit goes - if you're using k'slicer, set the prime value after retraction to very slightly less than the retract value and see if it still gives problems. there is sometimes a slight asymmetry caused by molten plastic seeping back down into the nozzle. i suspect the problem is path length dependent too but no slicers take that into account as far as i'm aware.

oh OK, thanks Daid I'll give that a try!

I dug around in my box of bits until I found one strong enough. Bertho gives some info on the right spring on his webpage. I'd go to the local hardware store and pick a spring wide enough to go on the screw, about an inch long, and stiff enough that trying to compress it with two fingers is painful. but we're drifting off topic a bit here check Bertho's original thread and post there..

I think you're right there Daid. by X/Y motor holders - you mean the wooden end caps on the top of the machine? I already have silicone padded feet but retraction is what makes the most noise - I can hear that the other side of the house, and that fan on the underside of the machine is waaay noisy too. (like an old tractor some might say

awesome. I saw an earlier version(s) of this using colored markers to do the same job, but this one actually blends the colors. it's undoubtably the future, tho the bulk will need to come down before we can use it!

I did spot the bit about stainless steel Daid, that's why I queried whether it's a PLA specific thing, since the reprap boys have had great success but I suspect they use ABS.. 9mm is good news, the burning the PEEK is very not :( I've had it heating away all night on two occasions when it crashed - no obvious damage other than a plug, and heap of molten PLA on the table. you're right tho, temperature regulation should have stopped too.. I can only assume I got very lucky because the ambient temperature was cool and it reached a steady state just under the danger temperature. is there a reason we can't modify the arduino bootloader? agree about the noise too, altho it's a drop in the ocean compared with all the other noise going on nik

I'll share that thought fj! regarding active cold ends - I'd argue it's a necessity going forwards. if you leave the hotend running at 230C, that heat will still transfer up the heat break eventually without active cooling. worse. the PEEK will insulate it and ensure it goes up. if you're running slowly or not putting out much material the same thing applies as for standing still. the teflon insert will help somewhat but is now the last line of defence to preventing hot plastic being sucked into the bowden by retraction ready to form a plug. I'm hoping that teflon is at least 4.5mm in length... (and in case you were wondering, 'who leaves the hotend sitting idle at temperature?' well that's what happens when a glitch on the power supply hangs the arduino - your hot end stays hot. all night or all week until you find it's stopped..) but the main reason I'm gutted about the teflon and PEEK still being there and no active cold end, is that this still limits the maximum temperature we can work it. this means no extruding nylon for example (at 320C) or other upcoming materials. but I suppose that's being optimistic since we still can't really print ABS properly and even PLA curls rather too much without an official hot bed. so roll on the hot bed!

given that retraction is now a solved problem.. what's the perceived advantage of towers? nice print Ian - suggest you order the bearing because it's the hardest part to substitute. it really has to be the size Bertho specified. get the stiffest spring you can lay your hands on - if you can compress it with your fingers, it's not manly enough for the job.

I'm presuming everyone has seen https://docs.google.com/presentation/d/ ... slide=id.p altho i didn't see a link on this proper forum, only on that old google one. initial thoughts are: +1 - nozzle and tube are integrated. good move UM. +1 - a heat break at last. I'm not convinved brass is the right choice, it should be stainless steel (apparently they tried that and it didn't work, but it works fine for the reprap boys, maybe fine for ABS not PLA?) -1 - that PEEK part still. ugh. and yet another part - teflon this time. -1 - bowden tube not threaded. still relying on those blue & white clips. actually I've found a great use for those blue clips - put them on the quick release fitting on the extruder end and they help retraction. they actually work for that purpose. -1 - no active cold side, so leaving the machine at temperature is still likely to cause problems that might sound overly negative, but isn't intended to be. actually good on UM for finally getting around to doing something about the hotend, but very sad they didn't involve the community more - what could have been an awesome upgrade looks fairly mediocre instead. as several have already commented, threading the bowden solves the (only?) problem that UM seem to have addressed here. I think destroyer had the ideal wishlist in another thread.. never mind. I might order one anyway to give it a fair try but will probably end up making my own new hotend now.

I haven't tried flexible PLA so can't comment, but it would seem both V2 and V3 started life as a bolt and therefore will tend to twist the material slightly. this is very apparent with the V2 and gives the characteristic shoelace effect on the PLA. some people have queried whether this constant twisting is good or bad, it has been blamed for all manner of things - I've seen no evidence to support this which suggests bad workmen, tools, etc. However, one thing that does seem to have an effect is during retraction. if we retract - does the PLA follow the original grooves in the material, or are new grooves cut into the PLA? if the former - does this mean less grip, therefore the stock extruder is more likely to fail (hence explaining why Berthos extruder makes a better job with retraction) - or if the latter, do we not risk grinding the filament to dust if there are too many retractions in a small area ? I would be interested to hear whether we think the V3 makes any difference in this regard. just being cleaner cut doesn't seem like an incentive to 'upgrade' (I've only once needed to clean my V2 bolt)

I should add that I am using the V2 bolt with no problems. a V3 bolt is not necessary to 'fix' the extruder problem. You're right about the bearings - I had to order one since it's a little non-standard and I think Bertho uses netfabb which messes with hole sizes. I had to file the part a bit to make everything move smoothly. an extra 0.5mm clearance wouldn't have gone amiss.

that's the one Daid. the H3 one you found Ian should be similar but may take more construction and I haven't tested that one. Bertho's is excellent for the simplicity with which it gets the job done. I've never needed to mess with that part of the machine since I made one so can highly recommend. Bertho also did an excellent job on his website of explaining and testing it. this is the one upgrade that everyone should have. (Bertho should pay me commission too

thanks Ian! regarding arduino hanging - there were several threads on this previously - rather than repeat everything, I'll link to the original thread on the subject viewtopic.php?f=7&t=986 yes filament variation is a big problem in its own right and often to blame for a failed print, but not always. others seem to have had this problem too. is UM CE marked? if not, then susceptability to conducted or (more likely) radiated noise is likely the problem. codemaven> in cambridge. I've been printing for about 5 months now. prints varying from about 7 minutes to 38 hours. Sander> a new extruder is a good move, altho Bertho's extruder mod is excellent and I've found no problems with it. I'd be interested to see what improvements could be made over it. the problem with variable print quality seems to be that less material is coming out the nozzle - unless you can measure the filament variation and adjust the speed of the extruder, I'm not sure how you can fix the problem easily? I currently do this manually - when a print starts to go wrong, I now use M221 Sxxx to adjust the material rate to fix the problem before the print fails completely. this has saved many a print but of course requires me to babysit the machine. :(

Ian > can you turn this into a new thread for us please so we don't clutter up this topic?

yes please post details. have they finally done away with that nasty PEEK part? is it affordable? is it actually going to make a difference?