# Specific 3D Printers, Scanners, & Hardware > RepRap Format Printer Forum > MakerFarm Forum >  Slow getting to 110C bed target on 10" i3v

## JimG

Not sure what has changed, but it is now taking a really long time to get my bed to 110C for ABS printing.  I am talking 30 minutes to an hour, or forever! (see below):

A few observations:

1.  The output at the Meanwell 350W PSU measures 12.00V under full load, so that does not seem to be the bottleneck.
2.  At the relay board, the supply voltage has dropped to 11.65V.  So I am losing 0.35V in the 16 AWG wires between the PSU and the relay board.
3.  If I place a sheet of white copy paper over the glass on the bed, it heats in 20 minutes or less.  I think it is blocking the drafts from the fan. (There is a sheet of cardboard below the heater).
4.  The fan on my Hexagon hot end seems to play a major role in this.  Once I left the extruder parked near the center of the bed, where the fan drafts hit more of the bed, and the temps topped out at 93C.
5.  With the extruder in the home position the fan has less influence.
6.  Have not measured the voltage drop across the lighter gauge supply wires from the relay to the bed heater, but based on the warming of the wires I think a fair amount of energy is being lost there, too.

My solution has been to use 105C for ABS, which is working fine for my prints.  The extra time needed to go from 105C to 110C is significant.

I think I would have to change the fan mount on my hot end for 110C to be a routinely usable bed temp.

Anyone else have a similar experience?

Jim

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## printbus

I've been curious - can you read wire gauge markings on the wires going to the heat bed? I know my 8-inch heater uses 16 AWG, and I've wondered if it's the same on the larger heater.  16 AWG is on the small side for handling the 17-18 amps that the 10-inch heat bed requires.  Assuming you have the same 0.35v drop from the relay to the heater, your 200W heat bed is only seeing about 175 watts.  

Is there a chance that the bed thermistor is resting on the cardboard insulator below the heat bed?  That could be causing the bed thermistor to read low.  

If you install the hex hot end fan so that air is pushed into the hot end, people have noticed it tends to create drafts on the bed below the extruder.  Reversing the fan helps defocus these drafts but it doesn't eliminate them.  Clough42 has a cooling system that sends the hot end airflow up from the extruder, eliminating any concern with the hot end airflow.

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## JimG

The heater lead wires are only 18 AWG, which is really too small.  I probably will solder in one or more parallel leads.  I think replacing with a single heavier gauge wire might cause it not tolerate the movements?

The thermistor readings are good.  During my build, I stuck a fine wire type T TC on the underside of the bed to use for confirmation of the thermistor readings.  The TC responds much faster to the heater, but always reads within 4C of the LCD display.

Jim

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## printbus

> The heater lead wires are only 18 AWG, which is really too small.  I probably will solder in one or more parallel leads.  I think replacing with a single heavier gauge wire might cause it not tolerate the movements?
> 
> The thermistor readings are good.  During my build, I stuck a fine wire type T TC on the underside of the bed to use for confirmation of the thermistor readings.  The TC responds much faster to the heater, but always reads within 4C of the LCD display.
> 
> Jim


Oh, man.  18 gauge is definitely too small IMO.  What I've recommended a few times is check into your local R/C hobby store and ask if they have silicone wire.  It's ideal for the bed wires that are subjected to a lot of flex.  The silicone insulation is more flexible than the standard PVC jacket, and the wire is made up of a significantly larger number of finer strands that will keep it highly flexible.  One source says, for example, that their 12-gauge silicone wire consists of *680* strands.  Some neighborhood R/C stores and online places sell it by the foot, so you only have to buy what you need.  It can be pricey if you have to buy a prepackaged amount like 10 feet and only need a couple. 

I've also suggested, simply for good measure, that once the size for the wire to the heat bed is chosen, use the next larger gauge wire for the fixed wire between the heat bed relay and the power supply.  Like you said, it's also possible to double up on smaller gauge wires. There's nothing wrong with that other than the increased bulk of the extra insulation.  

Now I'm wondering if my heat bed might have actually had 18-gauge wires before I swapped them out with some of the silicone stuff I had on hand.  

If you have the chance, measure the voltage at the bed itself so we can calculate how much power the bed is actually getting.

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## Stigern

I have a trick of putting a cloth piece over the bed while the printer is doing its warming up process :P

I think I have 16AWG silicone wires to the relay. So changing the wires to the bed too? Seems likely that they are too small.

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## Drone

For my i3V 10 where I put the clip for my glass makes a major difference. When I moved my clips to the front and back of the printbed it took forever to reach 110c, and when I put them back on the sides it only takes a few minutes to heat to temp. YMMV, but it made a big difference for me. Even where I put the clips on the sides makes a difference.

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## JimG

> I have a trick of putting a cloth piece over the bed while the printer is doing its warming up process :P


Great idea.  Before I developed advanced CRS* that would have worked for me, too ;-)

Jim

*Can't Remember S*&^

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## JimG

> For my i3V 10 where I put the clip for my glass makes a major difference. When I moved my clips to the front and back of the printbed it took forever to reach 110c, and when I put them back on the sides it only takes a few minutes to heat to temp. YMMV, but it made a big difference for me. Even where I put the clips on the sides makes a difference.


Interesting.  I recently moved 1 of the 4 clips a little further from the middle of the board.  Would not have thought that would affect heating of the bed!

Jim

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## JimG

> ...What I've recommended a few times is check into your local R/C hobby store and ask if they have silicone wire...
> 
> ...If you have the chance, measure the voltage at the bed itself so we can calculate how much power the bed is actually getting...


I've got some 14AWG R/C wire on the way.  I thought the 14AWG would be a little more flexible, plus I don't have any crimp fittings or ferrules that will fit the 12AWG.

Plus, I think I will just run the GND wire direct to the PSU from the heater.  The relay board only switches one side of the circuit. That will save a few feet of wire run.

When I make the changeover I will try and remember to take a few voltage readings.  The solder joint where the lead wires connect is hard to get to without a disassembly.

Jim

Jim

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## old man emu

Jim,
 Go to your local Radio Shack (or equivalent). Buy a 5 Amp car horn relay and some 14AWG multi-strand wire. Go home (Straight home, dammit!)

Run the 14 AWG from your power supply to the heat bed via the relay. It is only the +ve wire that needs to be cut so that it is can have the relay connected into that path.

Use the 18 AWG wires to connect the other poles of the relay to the RAMPS board. 

Now the RAMPs board will switch the relay on to allow free flow of current along thick wires from the PSU to the bed.

DO NOT - repeat - DO NOT fit a relay similarly between the RAMPS board and the extruder heater resistor unless you want to let the smoke out of the components on the RAMPS and Arduino boards.

Then go to your local bar and buy a beer for Old Man Emu.

Have a look at this: http://3dprintboard.com/showthread.p...formance/page2

OME

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## printbus

OME, the 10-inch version of the printers from MakerFarm like jimg has come with a heat bed relay.  They have to.  The larger heat bed on those printers can draw 17-18 amps, which is way beyond what the RAMPS board itself can handle.

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## old man emu

You PSU might be 350W @ 12V, but what is the amperage at that level? Theoretically it should be 29W, but what does it say on the spec panel?

OME

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## old man emu

> OME, the 10-inch version of the printers from MakerFarm like jimg has come with a heat bed relay.  They have to.  The larger heat bed on those printers can draw 17-18 amps, which is way beyond what the RAMPS board itself can handle.


I'm running a converted ATX PSU that puts out 18A and the temperature readout on my *mere* 8 x 8 bed rolls over like the amount reading on a petrol pump.

OME

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## AbuMaia

It takes my 8x8 bed about 8-20 minutes to get up to 120C, running through a relay off my 12v 30A power supply, with cork between the HBP and the wood Y bed.

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## JimG

> You PSU might be 350W @ 12V, but what is the amperage at that level? Theoretically it should be 29W, but what does it say on the spec panel?


29A.

http://www.meanwell.com/search/se-350/SE-350-spec.pdf

Jim

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## JimG

> It takes my 8x8 bed about 8-20 minutes to get up to 120C, running through a relay off my 12v 30A power supply, with cork between the HBP and the wood Y bed.


The 8" bed, in theory, should only require 64% the energy needed by the 10" to maintain a given temperature.  Something I did not consider before pulling the trigger on the 10"!

Jim

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## printbus

> The 8" bed, in theory, should only require 64% the energy needed by the 10" to maintain a given temperature.  Something I did not consider before pulling the trigger on the 10"!


What's interesting is that the heat bed on the new 12-inch printer just released by MakerFarm should likewise require 144% of the energy needed by the 10-inch. The product page for the 12-inch heater, however, says it needs 20 amps, which isn't all that much more than the 10-inch.

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## usarmyaircav

I just bought and installed 12 AWG wires to go between the PS and the heatbed relay. I also forgot that I need to remove the glass and heatbed and cut out a hole in the corkboard where the thermistor is.  I think between the two of those I should be in good shape for heating my bed.  A cloth over the top of the bed is a good idea. slight fire hazard I would think.

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## JimG

> I just bought and installed 12 AWG wires to go between the PS and the heatbed relay. I also forgot that I need to remove the glass and heatbed and cut out a hole in the corkboard where the thermistor is.  I think between the two of those I should be in good shape for heating my bed.  A cloth over the top of the bed is a good idea. slight fire hazard I would think.


If you are OK with the corkboard below the heater, then you should also be OK with the cloth on top ;-)  The biggest problem with the cloth, or anything else on the top, is that you have to be there to remove it when the bed is warmed up.  'Membering things like that when I am working in the "lab" is not my strongest skill.

I have cardboard below mine.  The piece of silicone foam rubber I bought for this turned out to be too thick.

Jim

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## usarmyaircav

> If you are OK with the corkboard below the heater, then you should also be OK with the cloth on top ;-)  The biggest problem with the cloth, or anything else on the top, is that you have to be there to remove it when the bed is warmed up.  'Membering things like that when I am working in the "lab" is not my strongest skill.
> 
> I have cardboard below mine.  The piece of silicone foam rubber I bought for this turned out to be too thick.
> 
> Jim


DOH!  I didn't really think about the cork underneath LOL.

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## printbus

One comment on the cloth idea - I'd only do that if I know the bed can (eventually) reach the temperature I want without it. If it can't, the heater may not be able to maintain the bed temperature when you remove the cloth.  

Seeing temperature characteristics change when the clips are moved doesn't really surprise me.  We all know these heater boards aren't all that flat or rigid, and changing the clip locations likely shifts where the heat bed is touching the glass and where it isn't.  If you happen to end up with even a very small gap between the thermistor area of the heat bed and the glass, that area of the heater circuit board will heat up faster than if the board is pressed against the glass and drawing heat into the glass.

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## usarmyaircav

so after changing the wires from the power supply to the relay my bed heated to 110c in 8 minutes.  I still need to make a small hole where the thermistor is in the cork but much better!

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## JimG

OK, reporting back with the results of the great wire swap of 2014.

Before starting the exchange, I measured voltages at the PSU and at the solder joints on the heated bed while the system was in its "stock" configuration:  12.06V at the PSU; 11.24V at the heated bed.  Total power loss from wire resistance around 13% (but remember I already had pretty heavy 16AWG wire for everything except the heater board leads).

I completely removed the 18AWG leads from the bed by unsoldering them.  Next time, I would NOT do this (see more below).  I soldered new 14AWG lead wires directly to the solder pads on the underside of the heater.  I ran the 12V side of the heater circuit from the bed to the relay board, and from the relay board to the PSU.  I ran the ground side of the circuit directly from the heater to the PSU.  All wires now 14AWG.

Result:  11.59V at the heater.  Approx. 7.5% loss of power due to wire resistance.

I don't know yet how this will translate into warm up times for 110C ABS printing.  Along the way I also discovered that the heater is very slightly warped:  the top surface is very slightly concave across the X direction.  It is most noticeable on "my" end of the bed.  I built a flexible shim from printer paper and pushed it in between the plywood and the underside of the heater.  This was just enough to bring the heater up into contact with the glass, but not enough to interfere with bed leveling.  Paper?  Well, my cardboard insulation hasn't caught fire yet so I figured why not.

If I did this again, I would proceed along my original mental plan, i.e., leave short pieces of the original 18AWG leads in place, and solder the new 14AWG leads to the remnant stubs of the 18AWG.  But I do a lot of soldering on PCB's, and the 14AWG wire is VERY flexible, so I felt confident and decided to do a complete leadectomy.  Mistake.

The physical thickness of the 14AWG poses some difficulty in securing the wires to the plywood bed because the little holes that Colin provided for a wire tie are too close together for 14AWG.  So I had to unsolder the new 14AWG leads and point them toward each other rather than 90 degrees to the back of the heater.  Even doing this left a wire bunch that was too thick for the small spacing between holes in the plywood.  I eventually got it all sorted out and got the wires secured well, but it took a bit of doing.

Did I mention the part about pulling the solder pad off of the PCB? Yup, applied a little too much heat on one of the new leads.  I had to scrape length of solder resist off of the main trace on the board, clean and tin the now-exposed copper, and resolder the new lead.

Did I mention the part about how well 14AWG wire conducts heat away from the tip of your soldering iron?  If you attempt this, dig around and find a nice heavy tip for your iron.  The little tips I use for most PCB work didn't stand a chance!

Jim

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## old man emu

I found that my heater pad was warped in a similar way to yours. I forget whether I did anything about it or not since I figured that I was printing on a glass sheet anyway and that would be flat as it appears to be. I didn't consider any effect that lack of contact with the glass would have. I was more concerned about getting a level print surface.

One thing I would consider is attaching the thermistor to the glass plate to obtain a more accurate reading of the temperature at the actual print surface. That could be difficult as it is hard to find a space between the heater pad and glass.

How have you secured your thermistor to the heater pad? There was a tip in relation to fitting the extruder thermistor of setting it in place in is hole with a blob of auto muffler putty. I wonder if that would work with the heater pad and be better that kapon tape.

Don't forget that going from 18AWG to 14AWG is like going from a fire hose to a garden hose. There's a mighty big constriction to flow. I think you did the right thing by struggling with the 14AWG all the way to the pad.

Old Man Emu

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## JimG

I applied some of that white silicone heat sink grease to the underside of the heater, then plopped the thermistor in and on top of the grease.  Taped it down with kapton.

The other thing I did was glue a very fine wire thermocouple to the underside of the bed so that I can independently monitor its temp.  Just to keep the thermistor honest.

I found that the thermocouple reading and thermistor readings never vary by more than 4C.  This would be very crude for a lot of applications, but I think is just fine for this one.

Jim

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## Stigern

> One comment on the cloth idea - I'd only do that if I know the bed can (eventually) reach the temperature I want without it. If it can't, the heater may not be able to maintain the bed temperature when you remove the cloth.  
> 
> Seeing temperature characteristics change when the clips are moved doesn't really surprise me.  We all know these heater boards aren't all that flat or rigid, and changing the clip locations likely shifts where the heat bed is touching the glass and where it isn't.  If you happen to end up with even a very small gap between the thermistor area of the heat bed and the glass, that area of the heater circuit board will heat up faster than if the board is pressed against the glass and drawing heat into the glass.


Yeah, the only reason I use a cloth is for faster heatup and evenly heating the glass plate. As for clips, I have added 3-4 more clips, some smaller ones.

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## rco3

If your heater bed isn't in contact with the glass plate, then you are depending on heat transfer across a layer of air which is a great insulator.  Glass is a poor conductor of heat, too (0.96 W/m-K; air is 0.02, copper is 400 W/m-K), so heating one region of the glass plate does little to heat the adjacent regions.  So what you really need is contact between PCB and glass all around the glass plate. Remember, that thermistor tells you what the temperature of the PCB is in that specific area of the PCB; the solid copper layer should do a pretty good job of distributing the heat, but you need to get that heat from the PCB to the glass evenly as well. 

When I assembled my 10" i3V, I noticed some warp in the heater PCB and corrected it by gently flexing it. I think that ideally, you want the PCB to be convex up so that the glass plate sits on a very slight hump in the middle, and then you use the clips to pull the edges into contact as well. The middle hump (or ridge, in my case) keeps some pressure against the middle to maintain contact (not too much, you'll flex the glass).  I find that clips on all four sides are usually needed to get good adhesion near the edges, too.  The LAST thing you want is for ANYTHING to be between the glass plate and the PCB. You might try a very small amount of heatsink grease to fill very small gaps, but that's a poor substitute for direct contact.  It's probably more useful as a visual to see where the glass isn't touching.  Where you have good contact, the grease should be squished thin enough to see the PCB through it.  Where all you see is grease… need better contact. 

The nice thing about this PCB / glass bed scheme is that you can replace the glass when it breaks.  Otherwise, I'd be tempted to simply glue nichrome directly to the glass.  

--Rob

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## JimG

Makes me wonder how much more effective, if any, a mirrored surface might be?  I like the idea of clips on all 4 sides.  Think I will give that a try.

Thanks.

Jim

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## JimG

Glass is actually not quite as bad a thermal conductor as I thought.  While metals like copper are hundreds of times more conductive, glass is more conductive than water, wood, and even salmon  :Big Grin: 

There does not seem to be much difference, conductivity-wise, between ordinary plate glass and borosilicate glass.  The thermal expansion of the boro, however, is only around 1/3 that of plate glass.

Glass is not quite as conductive as a thin sheet of rock, like slate, would be.  But it is pretty close.

Jim

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## Steven57

For what it's worth I used 12gauge for power and I used pipe wrap insulation (yellow fiberglass) under the glass. Cost about $5 at Lowe's/HD and three piece fit perfectly under the 10" bed. And there's plenty left over to share!

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## AbuMaia

> glass is more conductive than water, wood, and even salmon


Have you been cooking on your print bed? :-P

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## JimG

> Have you been cooking on your print bed? :-P


Now, there's an idea ....

Jim

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## old man emu

*​Bar-b-que at Jim's place this weekend! He's supplying the salmon.*

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## TechMasterJoe

i cooked 2 eggs sunny side up as a joke once on my schools Airwolf HD2x
it's about the only thing it's good for


i got a 12in i3v on the way and i picked up 12ga silicone wire for this reason 
I'm going to be using a .075in thick sheet of stainless steel that i machine polished at work for a bed at first just to try it out
i don't really like that mini relay that they come with so i got a 50amp SSR and heatsink.
another thing using relays and or mosfets it's always best to put them on the ground side in case of internal failure
they just stop working

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## JimG

The AC SSR's I use for controlling nichrome heaters drop around 0.6V across the switched terminals when conducting.  They are spec'ed at around 1.6V drop, but in my applications I only see around 0.6V.  

When dealing with mains voltages this is not a big deal.  I will be curious to know what kind of voltage drop you see across your SSR?  The relay, although a little noisy, at least does not drop much voltage when it is switching.

In AC heater circuits I have seen far more SSRs fail in a shorted condition than an open condition.  It would be a lot better if they failed open, but Murphy's Law is at work, I guess.

Jim

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## printbus

I agree on the voltage drop.  A 50A SSR will likely have more on-resistance than a relay.  The heat bed on the 12-inch printers is apparently lower watts-per-area than on the 8-inch and 10-inch, so I won't be surprised if we start hearing owners of the new 12-inch printers bemoaning long warm up times. Eliminating all the voltage drop you can could become real important on the 12-inch printers.  

I've also grown to appreciate the click of the relay.  It makes it easier to be doing something else while the bed is heating up. As soon as I hear the relay start to cycle off and on, I know I've got about a minute to get to the printer to check/wipe the priming of the extruder as the print starts.    

For anyone wondering, the Omron G8QN relay used on the MakerFarm heat bed relay is rated for 30 amps.

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## JimG

> For anyone wondering, the Omron G8QN relay used on the MakerFarm heat bed relay is rated for 30 amps.


According to the spec sheet for the Omron G8QN, the electrical contacts are rated for at least 100,000 operations.  Assuming around a 5 second time base for the PID routine*, then the relay would be good for at least around 70 hours of operation.  I guess I should have a plan for replacing mine at some point ;-)

Seems like a power MOSFET that uses the bed as a heat sink might be worth exploring?

Jim

* This was not immediately obvious to me in the Marlin code.  Does anyone know what the default value is, and where the code is located?

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## TechMasterJoe

i tested and i see .6103v drop and have sense built a mosfet board based on 
http://www.newark.com/international-...-7p/dp/28W1167
this will be a ground switching setup with a real mosfet driver feeding Gate voltage + opto-isolated
apx RDS will be under .0008ohm (test board .000691)
this i think will get the volt drop to stay under 0.02v at the switch
2 mosfets in parallel each rated for 260amps, 300amps pulsed
this will come with 10ga wire apx 3in long soldered on with XT60 connectors as i have tested them and see less then .01v drop at 30amps
i plan on making a few if anyone wants one PM me
test done with 200mhz Tektronix oscilloscope, Fluke 87-5 + i 410 amp clamp
I will include tested RDS with finished part and a thermal photo under 35amp load
test board is 1in by 1.15in 1.5oz copper PCB with 10ga wire soldered on temp on mosfet cases is 6.3c above ambient without a fan under 45amp static load
apx cost for each board will be around 11$ for 15$ i can include an extra 6ft of 10ga silicone wire (842 strands) + apx 3$ for shipping US only for now
this will cover just about any hotbed install i think 

hey if anyone is bored hook your hotbed to a audio amp and place a magnetic on on the bed (best to take the glass off so it don't get broken)
it plays music (act's like a voice coll)

i just did some numbers based on the wire i have 10ga silicone ultra flex and yes it's true 10ga but even true 10ga will net a 2.5~3.5% loss in only 6 feet
i can cut this in half if i drop down to 8ga but price might go up a buck

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## JimG

Very nice solution.

Jim

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## dacb

Here is a data point... On my 10" MF, when it was in the garage, and ambient was > 20 degree C, I could reach 110 without a lot of struggle.  Below that, it was constant on and problematic although I was well below the rated PSU wattage.  I don't print a lot of ABS anymore so it isn't much of an issue and the printer is inside where 22 C is pretty close to the norm.  Heats to PLA 70 deg by the time the extruder is hot.  I like that ABL lets the bed warm thoroughly while probing.  My sensor is mounted below the heater PCB per the directions.  I use a cardboard spacer which doesn't reflect heat upward as I'd like.  I tried (briefly) a silicon potholder and found it the same as cardboard.  So now we use the potholder in the kitchen.  I've wondered: How do Al beds do?  I occasionally come across a slice of Al that would work but I think about adhesion.  The sensor below doesn't really reflect what is actually going on at the glass surface.  Particularly hardware store glass like I run.  I always figured a drop in thermal transmission through the glass so the extra time lets the temperature penetrate and as glass is an insulator this can take some time vs. what the probe reads.

IIRC, some, like maybe clough42, don't use a heated bed for PLA?  I also recall 200mm bridges from his masterpiece, so I aspire.

Not a 12in so YMMV.

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## TechMasterJoe

V0.3.jpg
OK guys here is the finial PCB i will send out to the fab house
opto-iso + 500ma PNP driver for main mosfets makes sure both are in full saturation
made a foot print for the XT60's and put them on board
made it as simple as i can power on one end, hotbed on other..

if anyone is interested in whats really just a ground switch with a crazy low volt drop just PM me
i can safely say this will take 60 amps all day without fail. 
at 60amps total resistance comes up a tad to .00091ohms (.052vd) or about 3.5watts lost (mosfets rated for 200watts dissipation each)
this the size of the board and traces i think 60amps is a safe rating with spikes up to 100 amps the 
board and connectors are really more of the weak point. i expect the copper to go long before the mosfets
i will Tin the power traces (silver solder) to help with power limits.
Capture.jpg

official price is 20$ shipped and includes 6feet of 10ga silicone ultra flex cable
the two things will increase hotbed power by
20% over 14ga speaker wire and stock relay
16% over 12ga and stock relay
 37% over 14ga wire and ramps built in mosfet (yes ramps really eats that much power)

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## printbus

Looks like something with potential!  




> ...includes 6feet of 10ga silicone ultra flex cable...


IIRC, you don't have your printer yet. What is the concept for connecting 10ga wires to the smallish pads on the heat beds? Some people are going to need guidance on that.  




> ...37% over 14ga wire and ramps built in mosfet (yes ramps really eats that much power)


I'm curious - did the analysis factor the voltage drop through the 11-amp polyfuse on the RAMPS heat bed circuit?  I think that alone adds 0.1 ohm of resistance.

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## JimG

> at 60amps total resistance comes up a tad to .00091ohms (.052vd) or about 3.5watts lost (mosfets rated for 200watts dissipation each)


I'll admit to not having thought this all the way through, but .....

Can you arrange the new PCB in a way that would permit using conductive epoxy to bond the new PCB to the heater PCB?  If the portion of the new PCB that is bonded coincides with the copper pads for the MOSFET heat sinks, then you would not lose even the 3.5W.  I understand that there is a big loss in efficiency when trying to cool the MOSFETs with a heat sink that is already at 110C, but I am thinking it might still work OK?

Jim

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## TechMasterJoe

questions and answers 
as far as attaching 10ga to the hot bed i will have to try a few things and see how it worksyes that loss is with a unmodified RAMPS 1.4 board with a poly fuse that get damn hot with out a fani will look in to it driving mosfets at or near 110c will shorten the expected life but of the 2watts lost at the mosfets 5.8 watts is lost in 6ft 10ga cable


i can talk to my board house and maybe make a few hotbeds with everything on the hotbed but that can be drastically more expensive.
the piggyback option will work but it will take up apx 1/4in under the hotbed so some people might have to raise it up a bit.
the mosfets are really big compared to the Dpaks on most control boards  .131 tall and .6in wide .575 long monster mosfets i like to call them
i use them on a dual channel mixing speed controller i made for 15lbs combat robotics wight class. 4 mosfets form a H-Bridge and a AVR dose the talking
the board for that is 1.8in by 4.2in has 8 mosfets i have never burned one up and take them to 100 amps at 48volts with peeks over 400amps driving unfiltered DC motors.
the reason for using them is simple i have 2 full reels (1854) on hand and a mini pick and place machine to do the job + a DIY reflow oven that works

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## JimG

> as far as attaching 10ga to the hot bed i will have to try a few things and see how it works


One of the main advantages to locating the MOSFET PCB on or near the heater PCB is that you could use the light gauge OEM wires for a very short run from the heater to your new PCB.  This would avoid the need to desolder the OEM leads, and replace them with heavier gauge leads.

BTW, I am very jealous about the pick and place machine  :Stick Out Tongue: 

Jim

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## TechMasterJoe

> One of the main advantages to locating the MOSFET PCB on or near the heater PCB is that you could use the light gauge OEM wires for a very short run from the heater to your new PCB.  This would avoid the need to desolder the OEM leads, and replace them with heavier gauge leads.
> 
> BTW, I am very jealous about the pick and place machine 
> 
> Jim


i have FW and a program that will pull placement from eagle you just need a vacume pump, servo,and a small solenoid valve to make a 3d Printer into one
fw is for RAMPs (i do think you will need to change Z to a belted system)
i will need to clean up the code a little before i go handing it out
it will export files as a CSV and will work with the cheep china units as well

if you want to put the mosfet driver under the wood Y bed to isolate it from the heat and use the stock cable i don't see why not just keep it under 6in to take full advantage of it
i will still include the 10ga to run back to the psu but i guess twisted pair bell wire can be added of equal length to send control signal.
i can add a bright led to

i used a diy for a long time
but now own a used MC-385V2V this thing is fast......

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