First Reprap

I have (soft of) built my first reprap - I sourced the parts from a variety of sources on ebay which I regret. All of the pieces are good condition but the plastic pieces are a version of a Prusa i2 without bearings :-(. The description said - "helps you get up and running quickly so you can print the pieces needed for bearings". Firstly I can already see that it may take me a while to get to a point where I can print usable printed parts so the premise of the printed parts i bought is ridiculous! The original x-carriage I had warped after about 2 hours of use, so now I have an x-carriage like this Thingiverse which is much better.

The main issue I'm having is with the filament wandering along the hobbed bolt. The bolt I have is this one although mine doesn't seem to have as much of a notch as the one photographed.

I am hoping that by changing the idler piece for a guidler piece like this one I will be able to sort this problem out. Problem is, I can't print this piece because the filament keeps wandering and ruining the print.

Does anyone have any ideas how I can temporarily make a filament guide so I can print one? I have tried a piece of a credit card with a notch in it blue-tacked to the top of the extruder, a couple of pieces of corrugated card stuffed down the gap between the filament and the sides of the extruder and my hand. None of these methods enabled me to print more than about 6 or 7 layers. The filament seems to slip more when doing infill and retracting, if the two tension screws were not aligned could this add to the issue?

(Sorry about the quality of the attached photo, its from my phone - macro mode isnt very good)

Hi Leinad13,
If you want to "MacGyver" a solution and you have a pointed pliers then you can fashion a wire guide from a coat hanger. I've mocked one up so you can see. Only takes a few minutes and is a robust solution.



Here it is positioned in an old extruder just to show it fits.


Regards,
NumberSix

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[numbersixreprap.blogspot.com]

Thanks will give that a go tonight.

I coat hanger fix and it worked well. I then printed a test cube and realised that now my extruder was working better i was extruding way too much filament. I changed the e steps back to 700 and tried printing a guidler piece, it was going great until about 70% through, when i noticed the head got caught on a small blob of plastic. I let the piece carry on and from then on the layers had shifted along the x by about 1mm. The rest the print was ok apart from it had shifted a bit.

I set the e steps back to a standard 700, but my calcs from when it was pushing too much say i should set it to 534. This seems v low compared to 700. Could it be right?

I am going to try with 534 and see what i get....

For the proper e steps setting, you should measure how much filament is going into the extruder. What I do is put a mark on the filament right above the extruder, reverse the extruder by 50 mm, and measure how much it actually reversed. Multiply your current e steps setting by 50 divided by actual length extruded.

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Hi Leinad13,
Have you read Rich's guide to extruder calibration, here ? That might help a little also.

Why did your first x-carriage melt? What hot-end are you using? A small cooling fan under the x-carriage would be advisable if too much heat is rising to the x-carriage.

It would be a good idea to get some simple objects printing well before trying larger ones. You'll just get frustrated by failures otherwise. The Idler with the filament guide, that you are trying to print, climbs to a narrow tower (which is the guide bit). If you don't have cooling directed to it as it prints the narrow bits, they may remain too soft and just blob on you.

Also, get things running well at slower speeds first. Don't be in any hurry to print fast until you are happy with the quality of slower printing.

What firmware are you using? Setting your firmware acceleration low is the best way to avoid skipping when starting out.
What electronics are you using?

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[numbersixreprap.blogspot.com]

It was the "Slicer is Nicer" article I used to re-calculate my E Steps, I have managed to successfully print a test box and single wall test box.

My original carriage melted because I took the temperature of my hotend way too far when troubleshooting a problem with my extruder. I have a J Head MK IV hotend from reprap.me and was having a problem where the inner PTFE tube was getting pulled back, and eventually ended up going as far as my hobbed bolt. I didnt realise this at the time and just increased the temperature of the hotend to compensate (which worked, but was a big mistake!) This has also melted some of the PEEK on the hotend but at the moment it still seems to be working ok - I guess this can lead to a need for more pressure to be exerted by the E Stepper in order to extrude. Which could be why I am having the filament wandering issues?

I am using RAMP 1.4 and Sprinter firmware, which acceleration settings should I reduce?

I have got a 40mm to fit onto my hotend, which I will try soon - I am also going to try the Z Lift option in Slicer. I got a good print for the first test box so I cranked up the speed a bit (not massively - Perimeters 30, Infill 40, Small Perimeters 20 etc...) and got a rubbish print - also the filament went wandering and needed to be corrected by hand.

Can someone recommend a good source for a hotend compatible with 1.75 filament with a reasonable shipping cost to the UK? If possible an Idiot / Melt proof one would be ideal for me

leinad13 Wrote:
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> Can someone recommend a good source for a hotend
> compatible with 1.75 filament with a reasonable
> shipping cost to the UK? If possible an Idiot /
> Melt proof one would be ideal for me

[e3d-online.com]

That one is an all metal design, no PTFE or PEEK. I have one, but have only used it with polycarbonate since most of my plastic is 3 mm. It seems to work well.

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Help improve the RepRap wiki! Just click "Edit" in the top-right corner of the page and start typing. Anyone can edit the wiki!

Hi Leinad13,
I'm using Marlin, not Sprinter, but I suspect the Acceleration settings will be marked with suitable comments. If you're unsure what's typical for Sprinter then a quick question/post to the Firmware section of the forum should get you some feedback also.

What's more of a concern is that you say you may still have some melted PTFE in within the PEEK insulator on your hot-end (if I'm reading you correctly). That's not a great situation as it could be restricting the movement of your filament. You'll be going around in circles trying to calibrate if that's the case as you won't be getting consistent feed.

When the entire hot-end assembly is working smoothly you should be able to push filament through it by hand with only moderate resistance. If it's not working like this then getting the stepper to force it through isn't ideal, and can lead to problems. As you say, it could be why your filament is drifting or even buckling.
I think you are aware that the hobbed bolt you are using looks to have the hobbing a little shallow. Typically, there is more of a dip in the hobbing, which keeps the filament aligned also.

Have you any photos of the damage to the PTFE? You might want to replace that. What shape is the PEEK insulator in? Any damage to that?

What size hole is in the nozzle (.5mm, .35mm?). If it's a small hole it could account for the back pressure also.

Why did the PTFE back up into the hobbed bolt? There should be a hollow lock-nut at the top of the PEEK to keep the PTFE in place in the J-head design.

If you are taking the hot-end apart again then some photos would be of value, if you want any help repairing that assembly.

Best of luck with it.

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[numbersixreprap.blogspot.com]

Thanks numbersix, I got a fan and adjusted the tension on the extruder idler springs and hey presto I managed to get a few things printed. Since the last time I posted I have switched over to Ubuntu as Host OS for the machine and have updated some of the toolchain. I was Using an out of date version of Pronterface and Slic3r on Windows. The lift option in Slic3r has helped alot i think. Here are some photos of objects printed at 0.3mm layer height.

1
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5

EDIT : Looks like dropbox doesnt allow embedding of shared images (whats the flipping point in being able to 'Share' them then). I have repalced the images with url's!

So I managed to get printing and this meant that fixing and improving went out of the window for a few days However last night, I decided to take the layer height down to 0.25mm. My print failed on about the 3rd or 4th layer twice, the filament had wandered and was no longer aligned with the teeth on the hobbed bolt.

Does reducing the layer height increase the amount of pressure needed to extrude?

Someone sent me a PM saying the hobbed bolt might not be of the highest quality. Is this someone just trying to sell something or is the hobbed bolt quite poor? (I will try and get some better pictures tonight or tomorrow)

Edited 2 time(s). Last edit at 01/29/2013 08:39AM by leinad13.

You're making good progress there Leinad13! I like how you got carried away when you got it working and "fixing and improving went out the window"! Sometimes, you just gotta print! Brilliant! But then you decided to push your luck and lower the layer height!

You probably need to get the e-steps calibrated a little better though now that your extruder is working a bit better. You seem to have a bit of blobbing which suggests over extruding. When you lower the nozzle to .25mm you could be getting greater back-pressure if you are over extruding.

What size nozzle are you using?

Your hobbed bolt doesn't look great. It could do with more depth to the teeth. That would certainly help with traction.

Did you fit the new idler you printed? The one with the guide?

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[numbersixreprap.blogspot.com]

I haven't fitted the new idler guide yet - I got over excited and sort of forgot about it! Will try it tonight. I have ordered a new hobbed bolt from emaker which looks like it has more of a groove and deeper teeth : Link

My nozzle is a 0.5mm J head Mk IV - I am going to do a bit more fiddling around tonight, if I dont have much luck I will wait for this new hobbed bolt and see if that helps.