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View Full Version : Ok, so whats wrong?



Davek0974
25-02-2014, 03:24 PM
I fitted my 3d pile of bits together today and mounted the head on my CNC table but the results were less than useful?

I can't seem to get any material extruded, well practically none anyway.

Its just slipping the feed rollers, even with a hefty push by hand on the filament while the motor is jogging produces nothing more than a tiny blip every minute or so, you can feel the motor trying to feed.

I was expecting to see a thin thread extrude but not so.

I have tried raising the hotend temperature all the way to 250c but no change really.

The head is a 0.3mm one and i have uprated the motor as my drivers only go as low as 1.5A and the supplied motor was only 0.84A.

I calibrated the A axis by removing the hot end and feeding filament then measuring it etc that seemed the right way to set it?

I have speed in Mach3 set to 100 and acceleration to 20 i think.

The code seems to run fine at least.

Have i started out with a bad head or too small a nozzle for PLA??

Any suggestions?

This is the head BTW...
http://www.ebay.co.uk/itm/291009647156?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Neale
25-02-2014, 05:26 PM
Things that occur to me, in no particular order and with apologies if you've already checked...

Is the hot end really at the temp it says? I'm not sure what PID controller you are using but there are various common thermistors in use and they are all calibrated differently. In the end I calibrated mine by taking out the filament and shoving the business end of a thermocouple down the filament hole so I was reading temp actually inside the nozzle.

Looks like a direct drive from stepper to toothed drive roller (or whatever it uses) which does need a bit more urge on the stepper than a geared drive but if it's slipping, then there is enough drive but not enough grip (maybe). Can you release the pressure/grip on the filament and just shove it by hand? I'm more used to 3mm filament but you can get it to ooze through the hot end with firm hand pressure and I would expect your 1.75mm to do the same.

I'm guessing that you have calibrated the extruder by telling Mach3 to push out a known length of filament, and checking that it has done so? Was that with the nozzle removed? Current versions of Slic3r expect this to be the length of filament going in; older (much older) versions used the length of extruded filament coming out which wasn't that easy to measure... I've no idea what values you would expect to see in Mach3 but acceleration on the extruder motor is a pretty meaningless quantity, I suspect, as the motor (especially with direct drive) hardly turns at any real speed.

Can you measure the actual nozzle diameter (by sticking a bit of fine wire or drill up it)? It isn't blocked, maybe?

Is the filament easy to push through with no roller pressure or nozzle? In other words, it's not oversize for the feed tube, etc?

Davek0974
25-02-2014, 06:35 PM
Hmm, the head was calibrated exactly as you describe, I took the hot end off and just fed filament and measured it.

yes it's a direct drive via a small brass gear and pressure roller.

i will try measuring the temperature tomorrow, I presumed it was not far off as at room temperature, the display was spot on, I'm using a Rex C100 pid controller.

i have tried forcing feed by hand but could not get anything more than a smudge out. I will try withdrawing the filament and checking the hole.

am I right in guessing I should get a continuous thread of PLA out?

Clive S
25-02-2014, 06:40 PM
I have tried raising the hotend temperature all the way to 250c but no change really. 250C is way to high for PLA at that temp it should just ooze out. As Neale has said is the thermistor calibrated you could check it with dipping the nozzle in boiling water and see if the temp is around 100C. If the thermistor is not quite touching the hot end that could be another problem.

Going off memory the thermistor should measure about 100k at 20C but they are all different. One way to calibrate the amount going through is to mark the filament say every 10mm for about 200mm with a felt tip pen then instruct the soft ware to send say 30mm then you can work out if it is short or long. without the nozzle on, then when you get it near do it with the nozzle on.

If you have the heat too high it will burn and block the nozzle. Just my two cents worth. ..Clive

Davek0974
25-02-2014, 06:47 PM
Thanks, this head has a K type thermocouple on it so no resistance to measure. I will try and check calibration tomorrow, I have a bare thermocouple thermometer somewhere, should be able to pass that down the head to the tip if I can get the filament out.

the filament was feeding very nicely 100mm for an instruction of 100mm so it was set right but the feed just slips when head is fitted, there is no way it would feed as I couldn't even force it out by hand.

i may have made it worse by overheating then so a clean out is in order I think. I'll warm it up and prick it through with some wire etc.

Neale
25-02-2014, 08:42 PM
I run PLA with a nozzle temp of around 190C although I tend to fine-tune this depending on the particular batch of filament I'm using. I don't have enormous faith in the exact temperature as I don't know how accurate my thermocouple is, but that's a reasonable starting point anyway. You should certainly get a continuous fine thread of filament coming out - anything else means poor print quality.
Definitely a problem if you can't feed filament by hand, and it sounds like nozzle not hot enough or blocked - good luck with unblocking what's in there at the moment!
I'm interested to see how you get on with the PID controller. I spent quite a lot of time tuning the parameters of mine (built into the Sprinter code) to get best warm-up time with minimum overshoot and best stabilisation. I have built a couple of hot ends with different heater power and now have two different sets of PID parameters (especially the P and I components) to get best results. I'm curious to know if the commercial PID controller has some kind of self-learning to achieve the same results.

Davek0974
25-02-2014, 08:57 PM
Yes the pid could be an issue, they tend to like more thermal mass, this thing heats up in about 45 seconds!

it does have auto-tune and I've run it once, not had a. Chance to check the parameters yet.

not sure how to unblock it yet, any suggestions?

Neale
25-02-2014, 09:03 PM
I've seen suggestions on how to clear overheated and blocked nozzles but can't remember details as I've never (luckily) had to do it myself. A bit of directed googling on the reprap forum site will probably turn up some ideas, though.

Clive S
25-02-2014, 10:28 PM
Yes the pid could be an issue, they tend to like more thermal mass, this thing heats up in about 45 seconds!

it does have auto-tune and I've run it once, not had a. Chance to check the parameters yet.

not sure how to unblock it yet, any suggestions? Acetone will dissolve it ok, its also good for cleaning the bed the stuff you buy for finger nails etc quite often has a wax in it to make the nails shine so it is not good for the job.

I have bought pure Acetone off the web in the past. I am surprised that the nozzle will heat up in 45 seconds. ..Clive

Neale
25-02-2014, 10:53 PM
You can generally buy acetone anywhere that sells glass fibre supplies (yacht chandlers are good but only if you're near the coast!) as it's used as a cleaning solvent.

Heating up time is a function of how much heat you can get into the hot end - my second attempt uses a couple of wirewound resistors as heating elements and draws around 4A - 48W of heat going into that small object heats it pretty quickly although mine might be nearer a minute to get to temp.

Clive S
26-02-2014, 07:55 AM
Acetone will dissolve it ok, its also good for cleaning the bed the stuff you buy for finger nails etc quite often has a wax in it to make the nails shine so it is not good for the job.

I have bought pure Acetone off the web in the past. I am surprised that the nozzle will heat up in 45 seconds. ..Clive This is one place SHL 1 Litre (1000ml) 99.9% High Quality Acetone CHILD PROOF CAP | eBay (http://www.ebay.co.uk/itm/SHL-1-Litre-1000ml-99-9-High-Quality-Acetone-CHILD-PROOF-CAP-/370553401559) .. Clive

Davek0974
26-02-2014, 10:24 AM
Ok, I warmed the head slowly towards melt point and pulled most of the filament out, it was indeed jammed solid by swelling in the head support bolt, it took considerable force to remove it.

The head is now clear but the jet is solid, could not even probe it when hot with 0.3mm hard steel wire, totally blocked. As it's likely buggered I am going to drill it through with a 0.3mm drill and try that. It could possibly be a bit of swarf in it?

I can see how the heat spread up the support bolt and melted the filament before it reached the hot-end, but what I cant see is how this head could ever work the way it is built. I have seen the same unit on eBay listed as PLA/ABS suitable but they are all 0.4mm, that seems to be the only difference?

Will need to find a way of thermally isolating the support tube I guess or at least a way of bleeding more heat off of it???

Interesting stuff.

FatFreddie
26-02-2014, 10:54 AM
Is there a fan on the hot end?

Many designs actively cool the feed tube so that there is a rapid temperature transition between it and the hot end, this stops filament that is warm enough to easily deform but not hot enough to flow expanding under feed pressure and blocking the feed tube.

See http://reprap.org/wiki/RepRapPro_Mendel_hot_end_assembly for an example of an actively cooled hot end.

Davek0974
26-02-2014, 12:57 PM
Yes it has a fan, this is the head...
11707
The hot end has a short gap between it and the support/cold end about 10mm, the cold end is about 15x10x45mm and supports the fan which blows into the feed cavity. This end does not get hot really, very easy to touch even after some time.

The major difference I can see is that it has no PTFE liner at all??

I got it working for part of one print and made this.
11708
Ok, its not too pretty, the bottom 4 or 5 layers are missing as i was fiddling about trying to get the plastic flowing, once working it went ok, but 10 seconds after the print finished it was blocked again, turned it off and gave up as there is no point trying if it wont feed reliably.

I have asked the seller for a refund on the grounds that it does not work.

Seriously thinking about buying an RS-Ormerod printer kit now.

FatFreddie
26-02-2014, 02:30 PM
That's not bad for a first attempt!

My only experience with hot ends is the RepRapPro mendel one which has been good (no jams) but that's a bowden cable type (you're better with direct drive if possible).

Seems a shame to give in when so close but the Ormerod does look like a nice machine.

Davek0974
26-02-2014, 02:45 PM
Thanks, I did just get it going again, release pressure, force material by hand very hard and flush through, tighten feed pressure and start print, again the first layers failed, then worked ok then it failed near the end.

Again, blocked solid.

This time i fitted a large thin washer between the hot and cold ends to dissipate heat from the stud tube, all that gets hot now is the last 5mm of tube before it enters the hot end and it still jams.

The only thing i haven't got is a PTFE liner, maybe that's all that's needed??

Just guessing of course.

It is annoying, but there again it is eBay junk once more, but I really dont want to start throwing more cash at this if the Ormerod is any good.

FatFreddie
26-02-2014, 03:53 PM
Do you have room for the PTFE - mine is just under 4mm diameter.

The Ormerod looks good but it depends how stiff the construction is - I couldn't find any proper reviews of it and the RepRapPro website is offline.

Davek0974
26-02-2014, 06:04 PM
Hmm the stud looks a bit wimpy to fit a sleeve.

I've been looking at the ormerod for a few weeks now, the few vids showing it on YouTube seem to be pretty good, self replicating, the metal parts seem pretty standard stuff too. Had a chat with our son today and have agreed to go halves on one, should be here tomorrow.

Apart from the troubles with my trial setup, the base machine is destined to be a plasma cutter next week and once you start cutting steel, it gets messy very quickly, not good for 3d stuff. I was just mucking about with the the 3d while waiting the couple of weeks I had to for the plasma cutter to arrive :)

Neale
26-02-2014, 06:41 PM
My extruder is a printed plastic unit, which feeds the filament through a PTFE spacer to the hot end. PTFE isn't the greatest material out as it does tend to deform slightly when hot and under pressure and I've had to drill out my spacer once or twice to stop jamming - it may be PTFE but if the 'ole up the middle ain't big enough, the filament won't get through no how! Out of interest, have you checked how consistent the diameter of your filament is? I understand that not all PLA is the same - some can vary somewhat in diameter.

Davek0974
26-02-2014, 08:00 PM
Yes, I measured the PLA today while testing, it's supposed to be 1.75 but measures up at an average 1.69 over four points.

any chance of a picture of your head ?

FatFreddie
26-02-2014, 08:52 PM
Thats about average - better a bit under than over :-)

Let us know how the Ormerod goes - it looks like it addresses all the niggles I've had with mine.

Davek0974
26-02-2014, 09:32 PM
Will do ;)

Pointy
24-03-2014, 12:53 PM
Had a chat with our son today and have agreed to go halves on one, should be here tomorrow.

Did you get the ormerod and was it any good?

I could be tempted when they are back in stock.

Regards,

Les

Davek0974
24-03-2014, 07:07 PM
Well, not only have we bought one, I have also sourced and supplied a major upgrade to it that totally transforms it. :)

it's a fantastic little machine and has printed several very useful parts so far.

get on the reprappro forum and have a look-see.


Dave

Pointy
25-03-2014, 05:49 PM
Ooooh you tease!

I already watched a bunch of videos and read some of the forums. I think I am sold, RS have them in stock too! That checkout button on the basket is looking tempting!

Whats the major upgrade, could it be a modulated IR sensor + fan control + illumination board?

Regards,

Les

Davek0974
25-03-2014, 07:14 PM
I have that one too, not fitted yet.

my upgrade is an aluminium bed support plate, the kit comes with an mdf support but it shifts and twists all the time, a need was spotted and I stepped in, had some cut and am now supplying builders with the upgrade, it really does transform the ormerod.

Pointy
26-03-2014, 11:40 AM
I have that one too, not fitted yet.

my upgrade is an aluminium bed support plate, the kit comes with an mdf support but it shifts and twists all the time, a need was spotted and I stepped in, had some cut and am now supplying builders with the upgrade, it really does transform the ormerod.

I haven't clicked the checkout button yet, but I am seriously considering it.

Do you have any aluminium beds left?

Regards,

Les

Davek0974
26-03-2014, 07:08 PM
I haven't clicked the checkout button yet, but I am seriously considering it.

Do you have any aluminium beds left?

Regards,

Les

of course, I'm keeping them running.

also working on the next upgrade now.

:)

Pointy
26-03-2014, 07:43 PM
of course, I'm keeping them running.

also working on the next upgrade now.

:)

I actually liked the look of the Velleman K8200 (http://www.rapidonline.com/Tools-Equipment/Velleman-K8200-3D-Printer-525459) but it looks like the RepRapPro Ormerod has a slightly better modding community.

Regards,

Les

Davek0974
26-03-2014, 07:54 PM
I too looked at that one, pop in Maplins quite regularly, I liked the way the RRP one was open source, not sure if the velleman one is or not.

the RRP forum is brilliant, some very clever types hanging around there, issues get fixed very quickly.

Pointy
26-03-2014, 07:56 PM
I'm sold, I've gone and clicked it!

I'll PM you about the bed.

Regards,

Les

Davek0974
26-03-2014, 08:30 PM
I've got them on eBay too :)

Pointy
27-03-2014, 11:19 AM
I've got them on eBay too :)


I did send you an email direct, but I have just found you on Ebay and ordered one, so ignore the email.

Regards,

Les