ABS extrusion temperature

Hi,

Another post due to the sudden working of my mendel (ish)

I'm testing the extruder. For the moment I'm only worried about making it extrude (not actual shapes or sticking to bed yet)

I'm using ABS with a temperature of 250 (in RepSnapper). I think my filiment driver is OK but not great. It will draw in (and reverse) filiment but not 100% of the time (a little gentle push/pull helps sometimes).

If I just leave it all alone for 5 mins it does extrude - not much, e.g. 0.5cm but the ABS is melting. But is it melting enough? Could I increase the temperature of the heating resister? Or will I blow it up? What is a safe max temp for it?

Or should I give it a go with PLA (I've only about a metres worth)

Lastly - I stupidly ordered some 1.75mm PLA filiment (not 3mm as I intended). Is that usless without a 1.75mm nozzle or could I try it in my 3mm nozzle?

Thanks

Pete

Are you sure that your thermistor table is the correct one? What kind of hot end are you using? It does sound like your tip temperature is too low.

I don't think that 1.75 mm filament would work without modifying your extruder. I wonder if putting a teflon liner of the right size would work.

"thermistor table"?

What's that?
(perhaps the fact I don't know that is the root of my problem?)

Here's what I'm using: [www.mendelfactory.com]
It says on the resister (I think) - 6 Ohm 8V1 - 6%

Also the heater block is about 10mm from the very end of the nozzle. Would it cool back down again in that distance?


Cheers

Pete

Here's the wiki on thermistors: [reprap.org]. As you can see, there are many types.

You should read the wiki on your electronics to find out how to change the firmware for the correct thermistor table. Usually, you would use the Arduino software to edit the firmware code and then load it to the microcontroller.

Hi Flackster,

Some more information on your machine would be good (Firmware version (5D / Tonokip / Sprinter etc), electronics type (RAMPS / Gen6 etc). Sounds like your host software is Repsnapper though

Personally I am finding it difficult to stop my hot end oozing at the end of tool paths, this is (I have been told) that the filament is too hot and it is simply oozing out of the end.

I run my ABS @ 200, and it oozes a little less but enough to destroy some gear prints.


Do you have any other method of measuring temperature available to you? (thermocouple / IR thermometer / robust finger?) That might help you in finding if you are in the right ball park.

Does Repsnapper show the current temperature as 250C when you set it there? Otherwise it would sound like the wrong resistance tables for the thermistor etc...

Hi,

I am, indeed, using RepSnapper. And it's GEN6 electronics. I['m not sure of the firmware version - it's whatever is the most up to date stuff from mendel-parts - I'm a bit worried that I don't know how to answer the question - I suspect I probably should be able to

I bought myself a thermometer that can measure up to 300'C. And then used it to properly calibrate the RepSnapper reported temp to the real one. That was great till I accidentally cut through my thermister leg wire thingies so I can't reattach to it. I just got some (5!) new thermisters this weekend so can rebuild (and re-calibrate). That's tonight job.....

I also got some PLA since that looks like it may be easier to use to start with. (Before I broke my thermister) I moved the Aluminimum heater block nearer the end of the nozzle. It all seemed to work OK (just pushing filiment through by hand). Then I broke the termister so I may ave a jammed nozzle head - Will that just 'remelt' and clear or is it more complex than that?

Thanks for the Info (I now know that 200'C isn't a non-starter which is very helpful as it gives me an acceptable ball park to start in)

Cheers

Pete

I got my hot end working last night (oo...errr!)

By measuring the target/reported RepSnapper temparature against teh real temparature with at thermometer I found that (at around 200'C range) RepSnapper reports a temp about 30'C aboce the real temparature.

That seems a lot (is it?)

Maybe I do have the the wrong resistance tables for the thermistor - I'll put that on list of things to check.

However, I dont' care much right now since at 196'C (225 reported by RepSnapper) I seem to be getting OK PLA extrusion (only pushingthrough by hand currently).

Cheers

Pete

100k or 200k?

Make sure it's right in the firmware...

I was using the wrong thermistor table.

I think I now know how to work out a new one, using the reprap wiki thermistor page details. Next time I need to take my hot end apart (not long I expect , I'll try and update it, recalibate and see how things stand

Thanks to everyone for their input.

Cheers

Pete

Why do you need to take your hot end apart to calibrate it? If you have a thermocouple probe, then you can just insert it into the hot end in place of a filament.

I wish I did have a thermocouple probe. All I have is a thermometer that can measure to 300 deg C, but I need to stick its probe into the hot end while disassembled (it's to wide to fit down a 3mm PTFE barrier).

I quite fancy building a thermocouple probe, though. I'll do some googling at some point......

Cheers

Pete