Can your UM2 printer achieve 10mm3/s ??? Test it here...

[gr5 2,167]

I have a second UM2 print head that was drilled to .7mm diameter to test this very issue. I was able to get up to 18mm^3/sec with this head on my UM2. There's even a video of the feeder spinning quite fast:

http://umforum.ultimaker.com/index.php?/topic/4127-um2-extrusion-rates-revisited/?p=38869

 

[Dim3nsioneer 557]

Thanks guys for the information.

It seems my UM1 had quite a good day today...

 

Why I did the test on an UM1? To compare the two. It might help future users to understand that the UM1 is not the 'worse' model (and of course also not the other way round).

 

If you have a closer look at the two cylinders you see that there are some underextrusion issues starting from around 8mm^3/s after the the letters (where the printer slows down). However the extrusion recovers before the circle is completed. The material flow did not interrupt up to 15mm^3/s.

It was printed at 230°C with DiamondAge PLA Cherry red.

 

[illuminarti 18]

The biggest difference with the UM1 is that the extrusion degrades gradually; as the speed (and hence pressure) builds, so the printer gradually under-extrudes more and more, but in a fairly continuous way. When printing at 15mm³/s, you might only be getting 11 or 12mm³/s of plastic delivery, but since it does that quite smoothly and continuously, the print still holds up and keeps going until it finally strips the filament from trying to push it so hard.

Whereas on the UM2, once you reach the stall torque for the motor, it starts to slip back. This totally stops extrusion for a short time, and so kills the structural integrity of the print immediately.

 

[gr5 2,167]

On the back side of the "15" layer I can see pretty severe underextrusion.

 

[Dim3nsioneer 557]

On the back side of the "15" layer I can see pretty severe underextrusion.

 

I should have made the picture smaller...

You're right. There is underextrusion there. It's visible from 8mm^3/s on as I wrote. It's caused by the letters. There, the printer slows down extremely and after the letters, the UM1 accelerates again. And we all know what happens with the extrusion when an UM1 accelerates quickly: underextrusion. The remarkable thing is that it recovers before the circle at that layer height is completed. The layers at 15mm^3/s without letters don't show the effect. However, they are thinner (as illuminarti mentioned); I measured them to be only 0.35mm thick.

 

[schafe 3]

I recently received a new nozzle, bowden tube and teflon piece. Before I replaced these parts, I printed the feeder parts Daid supplied out of PLA. I will no longer see black specks in the tube and print.

I am happy to report that my printer has printed 5 out of 5 perfect cylinders using Ultimaker's PLA. I have some PLA from Makershed that I have problems with. Once it is gone, I will not order from them again. It's hard/impossible for me to throw away 2 spools of filament so I'll fight it to the end. Using that PLA I printed 1 cylinder that scored a 9.5. The very next cylinder scored a 5. I switched back to the Ultimaker PLA and printed a 10.

I really thought I had a problem with the feeder motor.

I'm not convinced that teflon is the proper material for the white spacer. I wonder if there is too much heat transfering up that softens the teflon. Combine the heat with the spring pressure on the teflon, which seems excessive to me, and you get the deformation we have all seen. I have access to a machine shop and a buddy who is a ceramic engineer. Maybe I'll start a side business making the spacer out of some fancy material. Fancy means expensive.

 

[takei-naodar 0]

I recently received a new nozzle, bowden tube and teflon piece. Before I replaced these parts, I printed the feeder parts Daid supplied out of PLA. I will no longer see black specks in the tube and print.

I am happy to report that my printer has printed 5 out of 5 perfect cylinders using Ultimaker's PLA. I have some PLA from Makershed that I have problems with. Once it is gone, I will not order from them again. It's hard/impossible for me to throw away 2 spools of filament so I'll fight it to the end. Using that PLA I printed 1 cylinder that scored a 9.5. The very next cylinder scored a 5. I switched back to the Ultimaker PLA and printed a 10.

I really thought I had a problem with the feeder motor.

I'm not convinced that teflon is the proper material for the white spacer. I wonder if there is too much heat transfering up that softens the teflon. Combine the heat with the spring pressure on the teflon, which seems excessive to me, and you get the deformation we have all seen. I have access to a machine shop and a buddy who is a ceramic engineer. Maybe I'll start a side business making the spacer out of some fancy material. Fancy means expensive.

 

Could i preorder 2? In Case 1 breaks .... but seriously can i preorder?

 

[gr5 2,167]

Maybe I'll start a side business making the spacer out of some fancy material. Fancy means expensive.

 

You might be able to sell them to UM!

Or just 10% of all UM customers maybe?

 

[geeks 1]

Ceramics, I thought about it a while.

 

I finally not because we need here ammortir movement of the nozzle. This is the reason that the spring is over and pushes hard .

 

I think if we were interfacing once more , still have concerns centering on . Understand this . The alignment of the nozzle , and the Teflon tube . Plus it's aligned , less wire is spring .

 

It follows from what I have to say that the boden tube hidden in the upper part of the print head may, if we not pay attention , do not be right . Then the thread harder to be directed towards the nozzle. This is what happens to a lot of 95% using a coil .

 

I think already the newest version of the extruder printed with its metal grommet and largest indoor spaces is a good thing. I have not had the time to review my copy accordingly to a special version of my extruder aec the metal grommet and removing the stiffener that I had installed.

 

For the use of ceramics, I would see this.

The nozzle (very hot), a ceramic piece large enough height that would come almost to the tip of the head. Ie that crosses the black part. And a fastening system of the ceramic tube boden.

 

Not only in this case we would correct centering. But in addition we have a real cooling boden.

 

I may come back with a plan of the idea. But know that it is not simple.

 

[abstract 3]

Just a quick Update from me.

I am still waiting on the replacement Teflon Piece etc from Ultimaker. I don't have any indication of when it will arrive.

Meanwhile, I carry on printing with great care. Most of the problems caused by the distorted Teflon (apart from limiting speed) are problems loading filament (at least 50% of attempts the end gets stuck in the teflon and never hits the nozzle.

Also I am having lots of problems now at the start of prints. There seems to be some issue related to earlier retraction and not getting enough filament to the head early on in the print. I will often get massive underextrusion for the first 30 seconds - this usually messes up the first layer so bad I have to abort. I think the retracted filament is getting snared up in the teflon piece's distorted ripples (see earlier post with photo).

Since I brought the UM2 into my office for all this testing (from outside in the garage), I am using the front panel printing off SD. Ironically when I used to print remotely via Octoprint I always hit the 'extrude' button a couple of times right before starting to print, and waiting until I saw a blob form, then drop to the floor - so the nozzle was always perfectly primed when the print started. With the front panel method I don't have such an easy time.

Anyway. Once I finally get the new teflon tube, I will do the test cylinder prints again, and hopefully we can draw some concrete scientific conclusion from this whole story. My feeling is that the new Teflon will help alot, and combined with a filament feeder, I might possibly make it to 8mm3 per sec...

Here's hoping...

 

[cyan 0]

Maybe give the latest bleeding edge cura a try - I had similar sounding issues with the start of a print that are much better since building the SteamEngine branch of cura and curaengine from git yesterday.

[profepaco 0]

@abstract.

let me tell you how to avoid underextrusion at the beginning of one printing.

I select the file to print. Then, I am using Robert's feeder, I open the feeder and I push the filament. Then you realize that the filament it is really retracted. You can push it about 2 cm without any force.... That's the problem. It seems that when a previous print finish the filament is retracted too much... really too much.

Since I am doing that the under extrusion ends doing the skirt... so no problems any more.

 

[illuminarti 18]

When you finish loading filament it gets retracted 20mm. Similarly when you abort a print. I'm not sure about when you finish a print normally. When you start a new print using UltiGcode, it forwards the filament 25mm to reverse that retraction, and prime the head. It moves it a bit faster than might be good, but it does reverse the retraction.

If you are using Octoprint or other regular gcode file (not UltiGcode from Cura) then the 25mm printing probably doesn't happen so you need to add that to your start gcode section.

[profepaco 0]

When you finish loading filament it gets retracted 20mm. Similarly when you abort a print. I'm not sure about when you finish a print normally. When you start a new print using UltiGcode, it forwards the filament 25mm to reverse that retraction, and prime the head. It moves it a bit faster than might be good, but it does reverse the retraction.

If you are using Octoprint or other regular gcode file (not UltiGcode from Cura) then the 25mm printing probably doesn't happen so you need to add that to your start gcode section.

 

Yes, but if I push manually the filament before the prints starts I have never issues...

if I do not do it... problems...

 

[juha-lehtinen 0]

I have done some research on UM2 printers...

Below are some of my results

VG= very good quality

G= good quality

numbers from 3 to 10 (3 is worst and 10 is the best)

When i tried that "speed testing"-gcode, i got these results: UM2

UM2 original machine settings:

Results when i increased nozzles heat up to 230C:

 

[gr5 2,167]

This test isn't about quality - it's about how much plastic can you force through the nozzle in a second before the extruder motor slips backwards. It's checking to see if you have something wrong with your extrusion path (feeder, bowden, head, nozzle) this is not achieving normal ability for a UM2. It looks like your printer is doing pretty well.

 

original machine settings

 

I'm not sure what that means. I guess that must refer to the temperature as I don't think there are any other settings that affect this speed test.

 

[Guest]

From printing cylinders with skipping starting at 8 mm I've been having some troubles lately. So I decided to do the cylinder test again and it looks this. I aborted the print.

Going to read through the thread and look for troubleshooting tips

 

[gr5 2,167]

Ironically when I used to print remotely via Octoprint I always hit the 'extrude' button a couple of times right before starting to print, and waiting until I saw a blob form,

 

@abstract - the feeder motor is almost always off when not printing. Before i start a print I simply grab the filament 20mm below the feeder and slide it upwards.

The retraction amount is normally 4.5mm but there is also an end-of-print retraction that is 20mm. But it's supposed to unretract that at the start of the print but for you I think it's getting caught on your teflon piece.

 

[andrew-white 0]

Got the cylinder print done although it has got a lean to it that can be easily seen in the pics below. From the very little I know other than that it seemed to print ok? Aperature applies some sort of profile to the images when i put them on the computer, look fine on the back of the camera turns them very blue & seems to loose some definition.

 

 

 

 

 

Any feedback much appreciated, assuming the bed isn't exactly level or something is slipping. Have had a couple of prints that looked like the belt had jumped a tooth all off to one side.

 

[cyan 0]

AxelEriksson: have you tried printing it the right way up?

 

[illuminarti 18]

Yes, you have a loose pulley, most likely. Or possibly the short belts are catching. It looks like the inaccuracy is just in the x-axis, so double check the short belt pulley in the back right corner of the printer, and the pulleys on the long belts that run left to right.

You might also need to remove the cover over the motors in the back right corner, and double-check the tightness of the pulley that is directly on the motor shaft.

 

[cyan 0]

Juha Lehtinen: what material did you use to print the cylinders? From the photos it looks like Colorfabb XT, which needs higher temperatures than 230. My spools are labelled 250 - 260, although I've found that's too hot. At about 253 it starts to degrade and go milky white, and the extrusion is very uneven, and it creates spiderweb-thin strings everywhere. At 220 - 230 it starts to under extrude severely.

I'm currently using 248, which prints beautifully, with good layer adhesion and clarity, but it's tough to keep the hotend in the narrow band of acceptable temperatures, it tends to swing wildly for me, overshooting and dipping 20 or so degrees below the target and taking a long time to ramp up with changes in speed and fan levels. Once I've got some more experience with the material I plan to start a thread to collect useful info about it (I found much less on-line than for PLA), but for now if anyone has suggestions I'm all ears.

One more off-topic note: In trying to glue it to metal I found that epoxy and hot glue don't bond very well to it, but cyanoacrylate (superglue) does - I bent the tin can and stripped the outer wall of the bit of scrap I glued to it, although it did discolour a bit.

 

[abstract 3]

@abstract - the feeder motor is almost always off when not printing. Before i start a print I simply grab the filament 20mm below the feeder and slide it upwards.

The retraction amount is normally 4.5mm but there is also an end-of-print retraction that is 20mm. But it's supposed to unretract that at the start of the print but for you I think it's getting caught on your teflon piece.

Hey Folks.

So an update from me.

UM sent me some replacement parts, and I just fitted the new Teflon Piece, new Bowden Tube and new bowden tube clip on the print head end. I also printed a little pulley to help position the filament before it hits the feeder.

First print, all defaults:

Thats a result... no babysitting, no extra hot, no flow rate mods. 220 degrees right from the file, no tweaks.

So... I think we can conclude that the issues I was having were related to 'snags' in the Teflon and perhaps the bowden. Also, I noticed that the old bowden tube was decidedly floppy at the print head, and I could see the internal dimension was larger that end compared to the feeder end (wear ??) the new bowden does seem to be more firmly fixed into the print head.

However...... I still had a problem loading material, it stuck at some point inside or past the teflon piece and would not load. I tried straightening the filament, and loading again - but still stuck.

So, I just homed the head, and used move material - this time it came out fine. The critical point here is the location of the head as we get material flowing. When in the material load position its front and centre, with the bowden tube quite 'stretched' out, and probably pulling and causing a bigger curve at the head end.

When homed for move material - the head is back left, with much less pressure on the bowden tube.

I believe this may be important, and perhaps the material loading head position should be further back. Also, I am hoping the filament will feed in OK at the start of each print, after its 20mm retraction after printing,

I have also got a new nozzle, and the newer weaker spring for the feeder - I may add them next, but I think for the most part my major problem is much better.

I suppose the question is whether this is going to be regular maintenance for UM2. Are we going to have to change the teflon piece every 4 or 5 months ? If so, I think UM need to make this a low cost sundry item easily available to order from their site (and perhaps at international local vendors).

I didnt go as far as printing one of the alternate feeders, although I suspect they will add a little more.

Ultimately, as I suspected, this whole issue is controlled by a symbiotic family of:

1) Control of angle of filament as it enters the feeder, plus - on the floor coming up is better than on a reel on the back.

2) Feeder tension, design etc. Make sure its not full of bits of torn up filament. Alt feeders may help a little. Feeder can cause filament dings when it skips and these get stuck further down the path.

3) Clean path into the feeder end of the bowden tube, otherwise feeder kicks will snag here.

4) Friction in the bowden (some people tried WD40 with improvements). If the feeder is chewing the filament, it may snag more everywhere, maybe less tension needed ?

5) Angle of Bowden tube into Print head - same as into the feeder, needs to be straighter, to help it as it hits the teflon etc

6) *Critical* - teflon part condition - age seems to create distortions which are prime points for filament snagging, especially when loading new material, and starting a print after the 20mm retract.

7) Temperature - for fast prints a bit more heat can help keep things moving, but this might end up compromising the teflon creating issues down the line.

All these things need to work in harmony - so stop looking for the 'one fix' for this problem and embrace a holistic approach to the entire filament path.

Thanks for everyone's support and comments. Next time I print for real, I might actually try going faster than the stock 50mm/sec 0.1mm layer.......

Now my UM2 is going back into the garage, and my relationship with it will be thru Octoprint again.

Cheers

Mark

 

[andrew-white 0]

Yes, you have a loose pulley, most likely. Or possibly the short belts are catching. It looks like the inaccuracy is just in the x-axis, so double check the short belt pulley in the back right corner of the printer, and the pulleys on the long belts that run left to right.

You might also need to remove the cover over the motors in the back right corner, and double-check the tightness of the pulley that is directly on the motor shaft.

Thanks illuminarti the pulley was loose and up against the cover, a lot of swarf was left in the hole from machining thy could do with a couple of new cutters in there UM2 machine shop.

 

[gr5 2,167]

@andrew - tilting indicates friction in general - usually near the motor or the short belt from the motor to the first pulley or near the pulley. Push the head around with power off and see if friction is worse on the X axis. You might not be able to see it. Look to see if black belt (short one) is rubbing while pushing head back and forth.