# Specific 3D Printers, Scanners, & Hardware > CTC 3D Printers >  Skipping layers?

## vtswordfish

Hey all! I have been printing on the CTC for a bit now, really love it, the print quality is great once you dial it in, but I have been having a strange issue on mostly taller prints, it seems that it 'skips' a layer every now and again, any ideas on what may cause that? I have tried slowing it down, but have seen this behavior as low as 30mm/s, have messed with temp settings and no luck either. Most of what I've read is it could be a filament tangle, speed, temperature, or z axis related, any thoughts? (the small jittery layers is what i mean)
IMG_5379.jpg

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## bigo93

It's not skipping, that is due to shrinkage due to parts cooling faster than others I believe.

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## vtswordfish

No it's definitely skipping, I've watched it on those layers and it's like it's not putting them down, I can't decide if it's the z axis having an issue or if it's not extruding well in those areas though.

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## EagleSeven

> No it's definitely skipping, I've watched it on those layers and it's like it's not putting them down, I can't decide if it's the z axis having an issue or if it's not extruding well in those areas though.


Have you checked the filament-extruder drive-Gear, 
to see if it needs cleaning ?
(teeth of gear can get filled with plastic,
causing filament not to feed properly)

I use an Xacto-knife and small wire-brush to clean it.

Here's a video about how to do that:
(CTC is similar to FF, your extruder may not have the Arm type assembly)
http://www.bing.com/videos/search?q=...390&FORM=VIRE7

Note: we upgraded to the spring-loaded Arm type,
since it seems a little more reliable,
even though it is a little more difficult to assemble

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## vtswordfish

Just checked the gear on the extruder, seemed to be fine/clean. Did some other checks on it and still am kind of at a loss on it. I thought about upgrading to the spring loaded extruder block, which one did you use for yours?

Also it has randomly started randomly showing a bunch of jumbled mess on the LCD screen, not sure what's causing it, bad sailfish flash maybe? Its weird because I've printed on it probably a couple hundred hours now and it just started that!

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## EagleSeven

> Just checked the gear on the extruder, seemed to be fine/clean. Did some other checks on it and still am kind of at a loss on it. I thought about upgrading to the spring loaded extruder block, which one did you use for yours?
> 
> Also it has randomly started randomly showing a bunch of jumbled mess on the LCD screen, not sure what's causing it, bad sailfish flash maybe? Its weird because I've printed on it probably a couple hundred hours now and it just started that!


I found a Set of Arm type extruders on eBay, at low cost,
from a place in UK.
I can look for details of that order if you need them ?

Spikes on AC power line to printer can cause the display jumble problem.
Can be caused by an AC type Fan or other device with motors.
Moving power-cords, going to printer's power-supply or to other devices, away from printer Mobo, can help also.

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## bigo93

You can also print them out, couple of prints out there

http://www.thingiverse.com/thing:231310
http://www.thingiverse.com/thing:42250
http://www.thingiverse.com/thing:53125

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## vtswordfish

I went ahead and grabbed one of the arm extruders off the bay, hopefully that'll help with feeding (which I suspect may partially be the issue). I went ahead and cleaned everything out while I had it apart earlier, going to do some oiling of the bars and all that and will give it a go tomorrow sometime!

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## EagleSeven

> You can also print them out, couple of prints out there
> 
> http://www.thingiverse.com/thing:231310
> http://www.thingiverse.com/thing:42250
> http://www.thingiverse.com/thing:53125


Yes, if you print them you still have to locate the correct springs, bearings, screws and bushings,
which seemed difficult when I tried to find them, mainly the proper type spring. 

But if one ever gets damaged or broken I will certainly try printing a new one !

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## EagleSeven

Yes, I think putting a drop of oil on bars, often, really helps,
as long as you clean away the dust that collects at ends of bars, in the oil.

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## bigo93

> I found a Set of Arm type extruders on eBay, at low cost,
> from a place in UK.
> I can look for details of that order if you need them ?



Can you give me a link for these, cant seem to find them on ebay. Thanks

lol just found them

http://www.ebay.co.uk/itm/3D-Printer...lfvZl0hAxmaP-w

http://www.ebay.co.uk/itm/3D-Printer...qglbAUXOWXJCnQ


It's better to pay the extra £6 and get the metal one right?

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## EagleSeven

> It's better to pay the extra £6 and get the metal one right?


I've not tried that metal-one design,
the plastic ones work Great !

The teeth on Gear, that comes with metal design,
do Not appear to be Sharp enough, they look flat at tips.
 So need to find out if original Gear will work with that design ?

Note: the metal one does appear to have spring-pressure adjustment
but I'm not sure if that is really needed ?
that may be handy if doing flexible or softer type filaments

(Personally I would go with the Plastic design,
since the original gears should work with them,
but you need to determine, for sure, that they will)

(The plastic ones, I got, Came with good gears but are slightly different diameter than originals,
so you need to find some extruders that Come with good, correct size, gears)

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