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I'm replacing the heater resistors in my hotend, and noticed that there's plenty of space in the pre-drilled holes. I can fit a 4W or even 7W 6.8 ohm resistor in there. Is there any advantage to sticking with a smaller (physically) 3W resistor? Any advice on getting the heat efficiently out of the smaller resistor and into the hot end? The mismatched radius seems like it has very little contact with the aluminum.

djdelorie wrote:I'm replacing the heater resistors in my hotend, and noticed that there's plenty of space in the pre-drilled holes. I can fit a 4W or even 7W 6.8 ohm resistor in there. Is there any advantage to sticking with a smaller (physically) 3W resistor? Any advice on getting the heat efficiently out of the smaller resistor and into the hot end? The mismatched radius seems like it has very little contact with the aluminum.

Do yourself a favor and at least get a ceramic heater cartridge. Better yet just replace the hot end with a E3dv6

If you increase the wattage of the resistor, it won't act as a heater any longer.

I would recommend going with a cartridge though - they're very effective. Toss in a threaded thermistor while you're at it.

g.

geneb wrote:If you increase the wattage of the resistor, it won't act as a heater any longer.

I would recommend going with a cartridge though - they're very effective. Toss in a threaded thermistor while you're at it.

g.

That's not right. The resistance determines how much heat is generated in the circuit. The power rating is how many watts (in the form of heat) that resistor package is expected to dissapate in open air without failing. However, potting in a heatsink can greatly increase the effective heat dissapation and wattage rating, which is why the 3W resistor works at hot-end power levels. If you want to select a different resistor, pay particular attention to the temperature ratings. Generally only some of the wirewound resistors are suitable for hotend temperatures.

I agree with the advice to get a heater cartridge instead.

An E3D is on the shopping list, but $2 in resistors gets me up and running again. I guess my question was... it seems a bigger wattage resistor is a snugger fit, and would transfer heat better, but a smaller wattage resistor concentrates the heat in one spot (if you pot it right). Which is preferred? Did SeeMeCNC choose a smaller diameter resistor on purpose?

I think it was chosen a while ago, back when they still recommended packing aluminum foil around it. I would think that a larger resistor would be better though, as you have less insulation from the RTV. (lower wattages may also have been cheaper)

If you are still using resistors, I have an Edsel automobile I could sell you.

Eaglezsoar wrote:If you are still using resistors, I have an Edsel automobile I could sell you.

If you really have an Edsel for sale, I really have some money.

gary

nitewatchman wrote:

Eaglezsoar wrote:If you are still using resistors, I have an Edsel automobile I could sell you.

If you really have an Edsel for sale, I really have some money.

gary

10 to pick from here with a broad range of prices
http://www.hemmings.com/classifieds/?ma ... &year_max=

nitewatchman wrote:

Eaglezsoar wrote:If you are still using resistors, I have an Edsel automobile I could sell you.

If you really have an Edsel for sale, I really have some money.

gary

Just kidding, Gary.

Eaglezsoar wrote:

nitewatchman wrote:

Eaglezsoar wrote:If you are still using resistors, I have an Edsel automobile I could sell you.

If you really have an Edsel for sale, I really have some money.

gary

Just kidding, Gary.

You never know when it may be a Shelby in a barn.