DIY MK6 Plus-ish Heating Block
by LukeChilson, published
Description
"Hello MK6 hotend." I said
"I hate you." Came the reply
"I wanted to love you, but you came apart at the seems."
"As if you would know, when was the last time you touched me." She countered
"I could see it, your resistors cracking and going to bits."
(Tearful dialogue continues, segway into abrupt technical jabble)
This is a rework of the stock MK6 that embeds the power resistors in the steel in an MK6 PLUS-esque fashion. It heats up quickly and gives a bit more room for a cooling fan.
It has printed spectacularly for 12 hours, but I cannot speak for the long term success so keep that in mind, should anything happen as I continue printing that would be pertinent I will update.
This is an all or nothing process that cannot be undone. Once you start, you must finish or have a backup plan ie. thingiverse.com/thing:8094 .
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Hey, if your hotend is working great, don't change what ain't broke. Mine broke. To be honest, i've never been a fan of strapping those resistors to the side of the block. They're further away from the thermocouple and filament, are of a different material than the block, awkward to insulate and aim over 75% of their heat dissipation away from the core. As such it seemed they were pulling much more power than needed and had a large lag time making my PID hard to tune and keep stable. This is all compounded by the fact I need to run my machine in a post building shop that is basically ambient and has huge 12ft high double doors open most of the day during more than moderate winds, not ideal. I'm not going to speak for the math, but I can say my bot is operating much smoother, drawing less power, heating up faster, is more temperature stable and the filament temperature seems to more closely match the reported temperature. In the beginning it was an act of necessity as my resistors were cracked and powdering out, but after the fact I can say its running better than ever.
Now, why would you want to do this? Just to get faster heat-up time?
You are still using underrated power resistors that are fragile. You are creating a thermal wall by wrapping the resistors in kapton tape.
Just wondering what flaw of the MK6 this design is supposed to fix. I initially got my ToM (in January) with a MK5, then upgraded to the MK6 when it came out. Happily using it for quite a while now. But you don't miss what you don't know, so what is it I don't know?
oooh, thats an idea. I may check that item out as a high temperature insulator.
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Instructions
Power Resistor Prep:
1. Gently and firmly so as not to break your resistor leads, tap/wiggle your resistors out of their chassis
2. Crack off the insulation surrounding them
3. Use a ohm-meter to confirm they still read 5 ohms
4. Measure the maximum diameter, mine was .2". Your's is probably the same but be certain
Heating Block:
Using a 7/32" (1/4" if daring) drill through your heating block as shown in the picture, taking care to avoid choosing a spot that drills through your thermocouple mount screw. I used a drill press and bought a nice fancy bit specifically for this task, you can skimp on these but I wouldn't recommend it. I'm not familiar enough with drilling this kind of material to give some good tips on method so if you've only drilled wood, do some research on cutting a big thick hole through stainless steel.
Put it all together:
1. Wrap your resistors in kapton tape to insulate them and beef up their diameter so they fit snugly in their newly drilled home.
2. Use that ohm-meter again to check the your resistors are electrically isolated from both each other and the heating block. Check it twice.
3. Kapton a bit around the heating block where your resistors poke out if your nervous like me and don't entirely trust the solder your using from deciding it should goop about a bit while printing.
4. Using solder with a melting point higher than your operating temperature, solder your resistors as in the MK6 assembly instructions.
5. Reassemble your heating block
6. Carefully monitor your new hotend during its first few prints JUST to be sure your house won't go down in a fiery blaze.
7. You're done, AND awesome. How cool is that, huh?
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I don't think you want your resistors insulated, but rather you want high thermal conductivity. I wrap mine in tine foil being careful not to ground out the wires.
You want the wire coil electrically insulated, mine weren't after I removed them from their casing. The Kapton insulates them electrically. I almost made the hole 1/4" to accommodate furnace cement but wasn't certain I had the clearance or steady enough hand to not drill through the side of the block. I can say most certainly you should NOT wrap these in tin foil as they are bare metal in spots and will short to themselves and the heating block.
Now, why would you want to do this? Just to get faster heat-up time?
You are still using underrated power resistors that are fragile. You are creating a thermal wall by wrapping the resistors in kapton tape.
Just wondering what flaw of the MK6 this design is supposed to fix. I initially got my ToM (in January) with a MK5, then upgraded to the MK6 when it came out. Happily using it for quite a while now. But you don't miss what you don't know, so what is it I don't know?
Hey, if your hotend is working great, don't change what ain't broke. Mine broke. To be honest, i've never been a fan of strapping those resistors to the side of the block. They're further away from the thermocouple and filament, are of a different material than the block, awkward to insulate and aim over 75% of their heat dissipation away from the core. As such it seemed they were pulling much more power than needed and had a large lag time making my PID hard to tune and keep stable. This is all compounded by the fact I need to run my machine in a post building shop that is basically ambient and has huge 12ft high double doors open most of the day during more than moderate winds, not ideal. I'm not going to speak for the math, but I can say my bot is operating much smoother, drawing less power, heating up faster, is more temperature stable and the filament temperature seems to more closely match the reported temperature. In the beginning it was an act of necessity as my resistors were cracked and powdering out, but after the fact I can say its running better than ever.