fire cement is very cheap and you can usually find it just about anywhere like at hardware stores or ebay.

I am going to replace  the resistor with a heat cartridge. Specs say it's 6mm in diameter. I measured the hole  in my heat block. It's closer to 7mm. My question is , what's the best thing  to use to fill in the gap? Some have said to wrap aluminum around it and I read others said use fire cement.Just wondering if  hi temp (650f) silicone gasket maker would work?

The goal is to transfer the heat into the block so I wouldn't use silicone gasket maker.  Foil or better yet fire cement are the way to go.

I'm up to 8 hours or so with the new resistor and it seems to be working nicely. I never timed it, but it seems to heat up slightly more quickly than with the old resistor, but that may be related to a new coating of thermally-conductive grease rather than the resistor.

It may also have been that a cause of failure of the old resistor was that the old grease was no longer providing proper thermal conduction, requiring the resistor to run at higher temperatures in order to transfer enough heat to the extruder.

It has me wondering if it would be worthwhile to check and refresh the thermally conductive grease on a regular basis. I'd be curious to know that Solidoodle does at their printer farm, and what kind of failure rates they have been experiencing.

Jason

Last spring I replaced the hot end with the "new" aluminum one... the heat core is similar to this one

store.solidoodle.com/index.php?route=product/product&path=63&product_id=81

A week ago the heating element burned out. Thanks to some posts on this forum I was able to identify it as a 6.8 ohm, 3 watt resistor. I also discovered that having the resistor burn out is apparently not uncommon.

I ordered a few different resistors from Digikey and this one fit nicely. With a bit of thermal grease I've had it in installed and running for an hour or so. (Knock on wood that I'm not jinxing myself by posting this...)

digikey.ca/product-detail/en/RWM04106R80JR15E1/RWMA-6.8CT-ND/1587898

The part number, if that link doesn't work (which it won't because apparently I'm "Allowed 0 links" was RWMA-6.8CT-ND, and manufacturer part number was RWM04106R80JR15E1

Buying ten of them, they cost about 81 cents each.

Note that I didn't remove the heater core or hot end (I didn't want to have to recalibrate the Z axis... I had it working nicely already) so I just snipped out the old resistor, put some solder and heat shrink on the new one, slid it into place and then connected the red terminal. I have a crimping tool for that, so it was pretty easy, but otherwise just leave some wire on the old socket when you take out the burned out resistor and solder the new resistor directly to the old connector.

Hope that helps anyone looking for a replacement... Digikey can get the parts to you overnight.

Jason

Hmmm... I'm apparently not allowed to put links in my posts... so apologies for those links not working. "Too more links in message. Allowed 0 links." was the error message. Guess you'll have to copy and paste into your browser.