heater resistor not fitting in the larger hole in the heater block

hi members,
got a mendel a few days back and have bit a block here..
after the extruder i started assembling the hot end a am not able to fit the heater resistor into the large hole of the heater block (around 2mm of the resistor is still sticking out of the block).. tried to use a 5mm drill and have drilled it more than 5mm dia but still the resistor does not seem to fit (as when i can closely see now that the resister is a bit bent)... so the question is
- do i need to buy a new resistor / or
- do i keep on enlarging the hole in the heater block as i dont want the large hole to cut into the smaller hole in the heater block
- finally if i make the hole large enough and if they is play on the resistor can i use the kapton tape supplied with the kit to keep it tight or do i use a different tape?..

regards
sujju

Photo will help

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Richmond, New Zealand
Thingiverse ~ YouTube

It sounds like you got a bad resistor. I would get it replaced rather than messing up the aluminum block. The better the contact between the resistor and the block the quicker and more even your heat will be. So you don't want to be enlarging the hole to the point that there is an air gap around the resistor or the heat will take longer to transfer into the aluminum block.

thanks guys...
did try to buy this resistor locally but could not get it here.. will have to place an order with reprap for this and with the aluminium block... i have attached a few pics and in one of the pics you can see there is a small air gap that has come due to the non-uniformity of the resistor... will this cause any issues or shall i proceed enlarging the hole and see to it that the resistor fit into the hole completly???

would it do any harm to file the resistor a touch to get it in.

just a thought.

Airtripper Wrote:
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> would it do any harm to file the resistor a touch
> to get it in.
>
> just a thought.
++++++++++++++++++++
i would not know this as iam a noob electronics... an expert here might give the right answer here.. would love to do this if its a possibility...

The coating on resistors is paper thin, if you file beyond the coating you will expose the resistive material (wire, carbon...) and this would then contact the aluminum block and possibly cause bad things to happen. Also if you cut through any of the resistive material you will change the value of the resistor and it's ability to do the job right.

Don't do it.

Electronic repair tech of 30+ years.

If you have an air gap you can wrap a little bit of alli foil (kitchen type) around the resistor but be careful that you don't short the end wire to the alli block. As Tmorris9 says do not try and cut into the resistor as that will enable it to short to the block.

You can try heating the heater block with a torch (if it's brass) or a heat gun (for brass or aluminum) and then stick the resistor while hot. It might be enough to expand the hole.

Edited 1 time(s). Last edit at 11/17/2012 08:49PM by brnrd.

had this exact problem. i just made the hole larger with my dremel. it did a perfect job. i think a small drill bit would do a good job also. the resistor fits quite snugly however reprappro mendel build instructions say you can wrap a few a bit of kapton tape around the resistor if you make the hole too large and this will work fine. obviously take care not to go in to the hole for the thermistor.

The resistor physical tolerances are awful. They almost always look a bit like bananas... I have had to dremel the hole in the heater block on every extruder I have built so far. Taking out a bit of material is fine, and a better idea than cutting into the resistor (which creates a danger of shorting it into the block itself). I use hardening heat sink compound and once the resistor fits in, I coat it with the compound, stick it in and let it cure for a day. Seems to work fine, especially the latest J-Heads with the 5.6 ohm resistors heat crazy fast when prepared like this.

Thanks a lot guys for your help...
i have gone ahead and sanded the resistor as i felt this was the only way out (have ordered for spares but din't wanted to wait till they arrive)... as you can see in the pic i hope the sanding / filing is minimum??? (only the right side of the resistor is sanded)

It now fits into the block however due to the resistors non cylindrical shape at a certain point (when i rotate the resistor) it "almost" comes through the block, hence i now plan to wrap it with a layer or two kapton tape and will see that it fits snugly and will minimise any air gaps if possible... hope this is fine to proceed???

regards
sujju