Nozzle temperature false?

[Jella 0]

I am printing for a few years now on an UMO. Until now I have only used PLA because it has less shrinkage and warping than ABS. For some unknown reason I have never been able to get any succesfull print if I was printing below 240C. This is strange because the recommended printing temperature for PLA is 210 to 220C.

Recently I have tried to print with ABS. After having resolved the problem of getting the ABS to stick to an unheated glassplate ( first a layer of PVA or woodglue and on top of that Cube glue for Cube printers ), I just can't get the layers to stick to each other. Only at very slow printing speed ( 10-15 mm/s) and maximum temperature ( 260C ) do the layers stick somewhat but afterwards they are easily torn apart. The material does not 'weld' together like the PLA. When experimenting with PLA years ago I only succeded to tackle the same problem by raising the temperature. But now with ABS I am already at the maximum temperature. I am beginning to suspect that the machine is not reading the right temperature from the nozzle.

Is there any way to check if the temperature sensor is giving the right values?

[gr5 2,069]

To check the temp sensor the simplest way that works reasonably well is here:

 

ABS often has layer adhesion issues. This is very common for people new to ABS (including me!). It is caused because the layer below is not melting (not heating enough) when the layer above is laid upon it. Because ABS has a much higher melting and softening temperature.

The solution is heat. Actually if you simply turn the fan off you will get fantastic layer adhesion. Lowering the fan to 30% will help a lot but not as well as turning it off. Unfortunately if you turn the fan off you get bad overhangs and bad bridging. But if you are printing something with 100% vertical walls and zero overhangs this is the best solution.

If you have any kind of leaning walls (not vertical) that are overhanging then you should have the minimum fan and also consider enclosing your machine somewhat to get the air temp up to around 40C to 50C (hotter than 50C is probably bad for the steppers).

Running the nozzle at 255C or hotter is a bad solution because it is so easy to clog the nozzle with ABS at those temperatures - ABS bakes into a gunky, gummy mess much faster than PLA. Leaving it in the nozze at 255C for even just 3 minutes could cause a horrible nozzle clog.

[Jella 0]

Hello gr5,

Thank you for your reply. I have tried your temperature check but I get different results.

My ABS does not melt as 'creamy' as yours in the video. Therefore it is not simple to compare the results. The ABS I use came with the printer 3 years ago. It is brittle and not as tough as the PLA that I use. Perhaps it has taken up moisture.

Only at 260C I get sort of the same result that you get at 220C, but I should be careful not to jump to conclusions; your ABS is clearly different. I think I should check with my supplier whether my ABS is stil OK.

Thanks for your tip on the heat. Having solved the cold bed adhesion stil leaves the printing ambient temperature low. A heated bed solves that too.

[gr5 2,069]

My video uses PLA so you have to use PLA to check the temperature.

ABS is usually *less* brittle (more flexible) than PLA so something is very wrog with your ABS. I have 3 year old ABS that still prints fine (printed some today). I would throw away any brittle ABS.

[Jella 0]

thanks again gr5,

I will check again with PLA. Fortunately I have some in the same color

I think I will buy some 'fresh' ABS to be sure.

[gr5 2,069]

I suspect your nozzle temp is fine and you just to print with the fan off to fix the adhesion issues. Or fan on the minimum (20%? 30%?) to get it to spin and enclose the machine.