printer heating elements

[gaexcalibur]

i have been having a great deal of luck and success printer right now but slowly i am having a problem getting my heating elements for the hot end to go to the temp i want. i am trying to get to 235 for abs and i cannot even get to 225 right now and running it is lucky to hold 220. I am betting i need new heating elements but i am wondering is this common, do you have to replace heating elements in the hot end every few months? i have only had this machine a few months so this is really puzzling.
just really looking for information to see how many elements i need to order when i do my order.
thanks
gary

[Mac The Knife]

One of these will do the trick, http://www.ebay.com/itm/Reprap-12V-40W- ... 33928610d9

[Captain Starfish]

You may find that the heater is heating just fine, but that the thermistor is loose or faulty and isn't reading the temperature of the hot end correctly. Considering how bad this is for your head (can melt the liner, the heat break and all sorts), your print jobs (overtemp cooks the plastic), your health (hello burny plastic fumes), and safety (can cause a runaway which may set fire to your printer): it's probably worth checking first.

Find a multimeter with a thermocouple attachment and check the nozzle temperature against what the printer thinks it is before you do anything else.

[gaexcalibur]

been there done that and i know the thermistor is good and giving as close to accurate readings as i can achieve. i thoroughly fixed it after the first run when the thermistor came undone after that it was correctly installed and i am sure it is not loose. my only thought is the heating elements as when i rebuilt the head a few weeks ago they were misshapen and looked nothing like when i installed them. now they are going bad slowly and surely so i am pretty sure they have gone bad. still curious if this is normal for them to fail after just a few months.

[RegB]

I had a thermistor break free, resulting in a burned up PEEK.
When I ordered the new PEEK and a couple of other things I didn't pay enough attention to the "fine print" that the 6.8 Ohm resistors are sold by the ONE - despite being SHOWN as a pair and the text reminder that two are required. The price per ONE seemed about right for a PAIR, so I "ASS_U_ME_D" the wrong thing.

Long story short, I couldn't find a second resistor locally so I re-used the charred original ones.
They seem to be working just fine, go over 230 on a regular basis and reach my usual 225 in about 3 minutes from room temp.

Aside; I bought a 5 pack of the 12 volt 20 Watt heater cartridges on-line for about $13.xx.
They took about 10 days to get here (Mass, USA) from China.
That is NOT a mis-print, they are TWENTY Watt heaters.
I wanted to maintain the symmetry of the original build (-:

I think it was JJ that warned me in an e-mail message that if the thermistor popped out when using heater cartridges the consequences would likely be worse than what I had experienced - which I took to mean that the stock resistors burn out in a fail safe way.