snowygrouch
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Posts posted by snowygrouch
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I would only add 2 comments:
1) If you use direct drive setup, the flexible couplers align 2 of the 8mm axis for you anyway.
2) The other 2 can be fixed axially with these:
http://www.conrad.de/ce/de/product/223735/Stellring-Sortiment
I do not think there is enough room for these lockrings if you dont have direct drive setup.
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Hi,
I would only comment further about the contact area between block and upper hotend. See pic attached.
Also its true it will work alot better when its moving with the airflow...however alot of plugging problems
stem from when people have the thing sittting idle but heated up. So its still worth considering what
happens in that situation.
C.
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Since the pics are not labelled, im just guessing here from looks- but the RH one is the standard V2 hotend and the
LH one yours?
If so, the design on the left looks worse than the V2 hotend from your pic. The hotzone is extending further up
than the V2 hotend.
The design on the left is (if I am interpreting correctly), showing upper side peak temp of 179 Deg C vs 25 Deg C for the V2 hotend. Which means heat is getting higher up, which is bad.
Also stainless steel would be better (16 vs 21 W/m/Deg K) than titanium from conductivity perspective. As well as cheaper.
Unless I am missing something with your pictures you attached.
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Kristen,
You can print the brackets without support. It just means a little cleaning with a knife one one end afterwards
but essentially its ok with no support. Print it so that the end that goes onto the motor face is downwards, and turn
off support.
Even if you decide to use support, I dont see why you should have any particular issue.
Sorry but I dont have time to go and dig out old designs....
C.
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Hi Ian,
I only have a rubbish webcam, which makes useless pictures that do not show any useful level of detail.
I think the potential of the direct drive setup will only be realised with good pulleys.
For me the greatest benefit is just not having to adjust the short belts. The positioning is obviously
better. But how much benefit depends how well setup your belts are.
However there is also a very measureable reduction in moving friction because the load on the bearings
is reduced alot. Replacing the shaft endcaps produced another similar jump in friction reduction.
C.
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Upper half of a mould box for metal casting.
C.
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Here is some of the stuff I am generally printing, sorry but the picture quality is terrible as its from webcam....
However you get the general idea.
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I cannot say for certain, but what I can do is say that with respect to this I did 2 things.
1) I replaced this black plastic part with a steel ball bearing (that fitted OVER the tiny bearing in the middle and has
in the end the same diameter.
2) To test the bite strength, I just warm the hotend - then pull by hand on the filament coming out the bottom
of the extruder. If you can pull it back through the extuder then its too soft. Its not very scientific but
worked for me. With mine I cannot pull the filament back through the extruder even pulling so hard that
the machine is having its two opposite feet lifted off the table.
I dont think the black plastic roller is a very good idea, because the pressure on it is very high and consequently
as you can see the roller is now deformed. This is probably limiting the "effective" spring pressure because
beyond a certain point its just squidging the roller...and hence all the effort doing that is less effort going into
pushing the PLA onto the knurling.
C.
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Tighten two M6 nuts onto the thread. To form a locknut.
Then put a soldering iron tip against the aluminium block, and heat it up.
Grip the "locknut" assembly and screw out the brass piece.
To do this you really need a small vice to hold the thing in the jaws. Hold the thing at an angle on the
corners or the heat from the iron will just go straight into the vice.
Once you suceed, apply copper grease to the threads before re-assembly. This will prevent it
sticking again, although the grease will smell for a few hours of printing as it burns off, leaving
just the copper particles in the gap.
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I think it might also be well worthwhile measuring the YX 6mm shafts.
For linear bearing performance - the tolerance of the shafts is very important for smooth running and accurate position.
http://www.skf.com/binary/12-55843/SKF_6402_EN_11_10_19_GB_high.pdf
pgs 39..42
The recommended shaft tolerance is Ø6 h6
which means it has to be (for best performance)
Max Ø6.000mm
Min Ø5.991mm
If you have a micrometer (a vernier is totally insufficient for this), and measure your standard shafts
I think you will find they are maybe undersize. Probably about Ø5,970 > Ø5,980 range ( I cannot remember
what mine were when I measured them, but it was in this area).
This will cause the bearings to run very badly, as the little balls will clatter around instead of rolling
up and down their slide-ways.
I would recommend replacing the shafts with properly toleranced prescision ground shafts like these:
Of course this is not a magic cure, but will make sure the linear bearings perform to their specification.
C.
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Well yes I could use a vacuum cleaner, or I could use a stick with a brush on the end.
One of them is free, takes 2 seconds to use, is small, uses no power, makes no noise and never clogs
and the other......
C.
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Hi Paul,
This was discussed earlier in the thread, if you align them it helps in one way because at least both pulleys
are trying to do the same thing at once...however, that does not do anything to fix the speed variation.
The clearances that were measured are also discussed earlier in the thread, and are not insignifcant.
By aligning them it just means you have effectively two variable diameter pulleys, varying at the same time. So they are not fighting eachother, but this does not remove the actual speed variation !
Also I think the toothform on the standard ones is not well machined.
I expect to see a really good improvement from these bits.
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Yes,
Something similar is used on some commercial printers I have seen....however, if the printhead is moving to the edge of the printbed anyway I dont see it being massively faster than a wipetower thats printed right next to the part.
Also and more critically the PVA goes "off" when left hot (stationary) inside the printhead.
Printing a little of it every layer might totally remove that problem (typical KS wipetower pic. below)
I dont know how important it is for "normal" PLA, although certainly before I got active cooling, leaving a nozzle hot and static was a recipe for a plug in about 10mins flat.
(note the pic is of "Destroyer2012" 's machine - not mine)
C.
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Hi Daid,
I have not tested that, but my opinion is that (esp. with bowdens), a wipe tower for both print
and support material (or print 1 and 2 colours) will be a 100% requirement. I dont think
any amount of clever tweaks will get the ooze away without a wipe facility of some sort.
C.
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Ok Daid,
well if you would benefit from any dual extrusion tests, you know where you can find me !
Happy to try things out.
C.
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Any chance of a "wipe tower" like KS (for dual extrusion, both for the ooze and to ensure the PVA
doesnt "go off" inside the hotend because it will get a bit printed every layer).
C.
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Any news on when you might be doing your first official release for the new Cura Daid ?
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http://www.sdp-si.com/D795/79501184.pdf
These look great, but unfortunatley not available in the shaft sizes we want.....
Perhaps you can get something like this in a 5>8mm size.....
These also look perfect, they have a solid lump of silicon bonded to each end, so should be
great for vibration damping, and probably stiff enough in rotation. However, again
not available as standard in 5>8.
I might phone them tomorrow to see if they will do some specials. I must admit
my UMaker does sound like an angry Dalek.
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I have never tried the 2nd coupler style, and have no experince of it.
Sorry, however it looks like is a bit better at giving vibration isolated coupling..perhaps it might
reduce the noise a bit. But I cannot make out from the pics if its a real bona-fide "zero backlash" coupling
or a not. The ones with the plastic rings and 4 little "bulbs" are really good for allowing for
misalignemnt and play of all kinds, but also pretty skeptical about their angular timing prescision.
I always liked the 1st style just because its always used on engine throttles, which have to maintain
perfect angular alignment. But no idea...perhaps the 2nd one is also good....
C.
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Im sure it probably "works", but I would still suggest its well worth doing another couple of hours
of "googleing" to find a pinchclamp design. The grub will put alot of eccentricity into the coupling
and its not designed to accomodate that - only angular misalignment.
Im just being a typical moaning engineer, so take that into account as well. But since the whole point
of this modification is to get the best possible performance from the drive system it seems
a shame to compromise one of the most important parts of it....
Im sorry I dont have good info on USA sources for this kind of stuff....
C.
https://www.tindie.com/products/diyourfaceoff/cnc-5x8mm-motor-shaft-coupler-5mm-to-8mm/
http://www.amazon.com/5x8mm-Coupler-Flexible-Couplings-26x26mm/dp/B00A2FVGVU
GOOGLE> "5x8mm flexible shaft coupling"
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There isnt really a proper section for this one, but the intended benefit is
"cleaning" the machine...so.
This is a request to UMaker for a small change to their laser cutting program.
Can you please add a slot (as shown) so that we can just sweep out the
accumulated bits of rubbish straight out into a dustpan. The slot needs to be
obviously on the same Z height as the top face of the lower panel inside.
Its currently really annoying to clean out the lower cavity of the case.
C.
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4 reasons:
1) I needed a 3D printer to make complex shaped parts, and my budget was about 2000 Euro
2) I needed the printer material to be open source, as I have no interest in the traditional
printer industry "cartridge scam"
3) I wanted to "get in" on 3D printing at home as its clearly the future of manufacturing.
4) At the time of purchase all the other printers in that price-range were rubbish.
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The loss in XY drive friction is because the motor and XY shaft no longer have
any vertical load on the bearings. So yes, a good thing.
Those new XY blocks look like a pretty good idea. I might try those in a few weeks, I already snapped
one of the little wooden arms. The wood for the machine is (mostly) a great idea, but I wish UMaker
had just done the case from wood and left the smaller parts to something a bit more viable for
small parts. Annywayy
Regarding the noise:
You can get AV mounts for steppers, (I bought some of these actually), but they remain untested and so I cannot say how much positioning degredation will occur after fitting them. Since the only damping method is to allow the motor to move relative to the case....could be its negligable.
http://www.astrosyn.com/section.php?xSec=44&xPage=1
They were pretty cheap, I think something like 8 Euros each.
C.
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please upload short Gcode program that does not work for you.
Then someone can either find an error from the code visually, or just try printing from it.
Stupid question.....but there are 2 ports for the stepper motor for the extruder (in case you fit dual extrusion)....
just making sure you are not plugging the extruder stepper into the 2nd port. I guess not..but....
C.
Fixing Pulley Innacuracy
in Third party products & modifications
Posted
IMO as soon as you start buying anything with a smaller bore and drilling it out later, you are always going
to have unnaceptable runout.
I think unless they are machined in one op. from the formed toothed bar blank, you are just stuffed from the start.
Once you have something as short as the finished pulley, getting it located in the chuck properly will be
very very hard.
Probably you could make up a nice little fixture to do it, and if you have a 4 jaw chuck you can sit
and tweak it all day until its running true. But then the issue is...true to what?
True to the original bore (which will in turn be slightly out from the pulley teeth), or true to the teeth...which
once you have the pulley with the belt flanges pressed on will be very hard to either measure or located onto.
I think the only way is to get them made like Markus. With the right spec from the start. I am sure there are firms
that can do it properly, but its just a question of finding them. Since it looks like Markus has already done so,
for me the reasons to look further just dissapeared (pending me testing them of course !)
C.