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mark-hale

at a complete loss

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OK im running out of options here. Trying to get to the bottom of an underextrusion issue with my UM2. Previous prints of the same object have completed fine but lately i have been getting under extrusion issues.

Have cleaned the feeder mechanism (original UM2), replaced bowden tube, checked the PTFE section which was sightly distorted so used a 3.2mm drill bit to fix that. I have also cleaned the nozzle, see images below for filament removed from nozzle. Despite this I am from still getting intermittent underextrusion problems. These very from either early on in the print or towards the end.

The printer has seen over 500 hours of use, so wondering despite the nozzle seeming good and the PTFE connection also seeming ok. Is it worth replacing these. The only other option I guess is the motor for the feeder? Initially I thought it might be filament problems but getting varying degress of problems with different filament types and manufacture.

Thought would post for any suggestions before I place an order for a nozzle kit. Although with the shape of the filament removed using the atomic clean method, I think this is doubtful

Any thoughts on what to do next would be appreciated.

clean nozzle

IMG 20141225 092256 edit

 

 

Layer height 0.1

Shell/Bottom/Top thickness 2

Fill 20%

Speed 50mm/s (although on UM2 have dropped to 90%)

Temp 215

Filament

Artic White Faberdashery

 

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Hi Mark,

The first thing you could do is start by replacing the feeder. Many use this one for example and it works really well:

https://www.youmagine.com/designs/alternative-um2-feeder-version-two

Additionally it will allow you to swap the filament without having to use the change filament procedure and will let you play with the tension a lot better. Check the additional requirements (2 screws and 1 bolt) before installing.

Also if you feel confident you can try cleaning the nozzle even more. Its not because the filament comes out clean that it is clean. You can disassemble the nozzle and use a torch to burn the excess of plastic. Pay attention to the heater and sensor wire because they are fragile.

 

Good luck

 

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Yeah I have been considering a new feeder, my only reason for not going down this route at the moment is that the UM2 worked perfectly before so i would like to try and work out why it has since stopped.

I have done a full strip down of the nozzle and run a very extensive clean, so pretty sure that is fine. Just would like to work out why its not performing as before.

 

Hi Mark,

The first thing you could do is start by replacing the feeder. Many use this one for example and it works really well:

https://www.youmagine.com/designs/alternative-um2-feeder-version-two

 

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Test Print at 30mm/s. Looks like High friction in he Bowden tube if not the nozzle.

I had similar issues and printing slower addressed this issue. After some mods and testing I was able to increase.

1 Do you have Roberts extruded? Maybe something to try if you don't already have it as pm_dude said.

2 inspect the Bowden tube for small dents or kinks or damage and the ends which can add friction.

3 is there grooves in the filament worn from the feeder? This is usually a sign of high friction. :)

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Not yet to the new feeder, I wanted to try and work out what the problem was before I changed things as previously everything was working fine with excellent results

I have replaced the bowden tube, the only thing left is the PTFE coupler and nozzle

Filament seems fine, did have some groves but after cleaning feeder that seems to be ok

Will give the 30% a go, currently working between 40 and 50%

Cheers both

Mark

 

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I found once it starts it is hard to stop it. Basically for me the knurled feeder would grind the plastic slightly causing eventual under extrusion. I found I could only print around 35mm/s without issue.

I machined a new ptfe part and that fixed it for me. Then I updated the feeder and it only got faster and better :).

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Yes the roberts feeder require 2 additional screws and one bolt. Check the youmagine page for details.

I did not find the M3 screws so I used one 6/32" x 5/8" screw and one 6/32" x 1" 1/2 screw with bolt instead

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OK thanks, that's useful to know

 

I found once it starts it is hard to stop it. Basically for me the knurled feeder would grind the plastic slightly causing eventual under extrusion. I found I could only print around 35mm/s without issue.

I machined a new ptfe part and that fixed it for me. Then I updated the feeder and it only got faster and better :).

 

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Hi Mark, my take on your problem is that for whatever reason there is a moment in time, lasting a short period of time, when your filament is getting "stuck", slowing down the flow. I use Arctic white a lot and have not experienced your problem with it; so I am thinking it is probably not the filament. But have you measured it?, just in case.

A couple of weeks back I was printing some Xmas decorations. I started with a blue then swapped to Arctic white. I kept getting the occasional bit of blue coming out. I did an atomic pull 4 or 5 times and all were clean apart from the first pull, but the bits of blue kept coming. I was about to fit a new nozzle but it now seems to have stopped polluting my white filament. So changing to a new nozzle may well not be a waste of time; a cheap way of knocking out one variable.

As an aside, based on personal experience, you may well be printing the Arctic white too hot. I would print .100 at 50mm/s at 205 and it seems to me that Arctic white is somewhat less forgiving at the "wrong" temp. than most of my other Faberdashery filaments.

I have printed Arctic white at 50mm/s without problem but as someone else posted, I think it is worth dropping the speed for the moment to see what if any affect that has.

 

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OK fingers crossed all seems to be working. I machined up a replacement PTFE section and now with this in place things are pretty much back to normal. One thing I did found out to my amazement was how much the four main vertical screws for the main print head influence things. On reassembly I tightened them up rather more than normal - ended up not even getting the 3mm/s complete on the extrusion test. :eek:

Although having been very frustrating, its been a great lesson on how each part interacts on the UM. Thanks to everyone for their input.

 

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