silicon rubber heater bed -120 Deg celsius in 1 minute (Page 2 of 4)

I will post pics as soon as I have mine working,  the 150mm size + a bulge forced me to craft a shim out of AL foil otherwise I can't see a way to fit this w/o a whole new bed/mounting position.  I do believe I have mine flat enough as to not have issues; this may or may not be easy for everyone else, nevertheless it was cheap. Ideally you would want a 2nd AL plate with a relief cutout for the heated beds raised areas. You obviously can't just go cutting holes in this bed, but one day maybe we could setup a group buy for a custom pcb that has our bed screws taken into account; if the hack proves to hard to be leveled or has other unknown issues...AL foil is cheap and I needed only half a roll or so.

I was thinking of getting oversized glass as well. Since the printer can currently extrude "off bed" why not extend the print bed and make use if all the travel.

Also have sorted out a bigger power supply. I took some power supplies from som dell power edge 2560 before they were scrapped at work. 12 rail with 45 amps available.

These old server supplies can be picked up on eBay for probably cheaper that the average arx supply. Or black box switch mode supply like the unit originally shops with.
(They are cheap because companies change the form factor all the time. And searching around online for almost any server supply finds some rc forum with the pinouts where someone already made a battery charger with one. Pretty much regardless of that supply you have.

Relay coil driven from the control board (small terminal +/- usually on the relay) and high current through the main contacts- take your pick which side you want to switch. Out from power supply through relay and back to power supply.

Don't forget to wire a diode in parallel with the relay to eliminate back EMF.

Nice relay. 

For wiring just take your existing bed wires and terminate on the input side of relay.  From PS output + hooked to heater, other heater line hooked to relay output +, Relay output - hooked to PS - 

You won't need diode protection on the activation side of the relay as there should not be an actual coil, so you won't get and induced spike back on the driver.  Personally- it never hurts to add one anyhow in case of other events

To protect the relay itself, you can put a diode across the load.

I didn't read the early posts so I assume you are not using the original heater anymore?  If so, above should work out for you.

*Edit* just looked at your PS- that wouldn't be my first choice.  You may want to get something a bit more "beefy"

I may be missing something here but I saw the specs at up to 11.5amps on the 6x6 unit.  Just from personal experience- the laptop type power supplies are not intended for continuous high load situations.  They may be able to supply high current for short times- but they are usually designed to provide small current over longer periods.

On initial heat from cold your heater is going to draw hard and as the temp comes up the internal resistance will as well- and the current will lessen.  My crystal ball says that once we have a bed that heats up crazy fast- we will be tempted to shut it off more often- whereby running your power supply hard again. 

The unit u have may be ok.  I'd probably do some current measurements just to see what the heater actually draws.

Yes- by using to power supplies you have completely removed all the heater load from the original source and put it on the new power supply you got.  The load doesn't get "shared".  The only load on the original source is the current required to operate the relay "gate" which is tiny since you got a solid state relay. Hence the whole purpose of a relay- use a very small current to control a much larger one.

The bed is heating now 80), but it is only getting 3.7 volts when I check the relay on the other side and is heating more slowly compared to before. 10 min to or so to hit 100. Ya I don't know why I decided to buy this Laptop PSU, I have tons of PSUs sitting around;  I repair PCs so I have lots of spare parts. Now I just need to go get some dang superglue and I will be printing again!!! wooohooo!!! I will post pictures of everything tonight.  Now I just need to get rid of this nasty z-backlash I have developed and I will be back to 100%. I can print well enough to craft a support, it should be easy to design something adapted what the other forum and thread have came up with.

Thanks for the help! I am sure this relay is defective.  Why?  Its not properly gating the voltage when in a off state. Great tech, but I am glad I watched https://www.youtube.com/user/CrydomSSR..

Q:  M304 seems to do nothing...How do I use this and do I  have to use the formulas since BED PID is without auto-tune?  I know the resistor folks were using BANG-BANG (PWM now).  Do I need to just remove a comment in the firmware to use this vs the resistor?
A: configuration.h  changes+ "M303 E-1 C8 S90"  e.g. to run autotune on the bed at 90 degreesC for 8 cycles.

// When temperature exceeds max temp, your heater will be switched off.
// This feature exists to protect your hotend from overheating accidentally, but *NOT* from thermistor short/failure!
// You should use MINTEMP for thermistor short/failure protection.
#define HEATER_0_MAXTEMP 210
#define HEATER_1_MAXTEMP 210
#define HEATER_2_MAXTEMP 210 <------------I went ahead and changed H1, H2, & BEDMAX to safe solidoodle 2 number; yes I know we don't have 3 extruders 80)...never know what "bugs in software" could occur so this is just to be safe)
#define BED_MAXTEMP 110 <----- 150 was pointlessly high; 110 is the heating limit for the resistor anyway really...might even consider 100 at the limit to increase life)

Here is the part that needs to be edited.

// If your bed has low resistance e.g. .6 ohm and throws the fuse you can duty cycle it to reduce the
// average current. The value should be an integer and the heat bed will be turned on for 1 interval of
// HEATER_BED_DUTY_CYCLE_DIVIDER intervals.
//#define HEATER_BED_DUTY_CYCLE_DIVIDER 4

// PID settings:
// Comment the following line to disable PID and enable bang-bang.
#define PIDTEMP
#define PID_MAX 255 // limits current to nozzle; 255=full current
#ifdef PIDTEMP
  //#define PID_DEBUG // Sends debug data to the serial port.
  //#define PID_OPENLOOP 1 // Puts PID in open loop. M104/M140 sets the output power from 0 to PID_MAX
  #define PID_INTEGRAL_DRIVE_MAX 255  //limit for the integral term
  #define K1 0.95 //smoothing factor withing the PID
  #define PID_dT ((16.0 * 8.0)/(F_CPU / 64.0 / 256.0)) //sampling period of the

// If you are using a preconfigured hotend then you can use one of the value sets by uncommenting it
// Ultimaker
    #define  DEFAULT_Kp 22.2
    #define  DEFAULT_Ki 1.08 
    #define  DEFAULT_Kd 114 

// Makergear
//    #define  DEFAULT_Kp 7.0
//    #define  DEFAULT_Ki 0.1 
//    #define  DEFAULT_Kd 12 

// Mendel Parts V9 on 12V   
//    #define  DEFAULT_Kp 63.0
//    #define  DEFAULT_Ki 2.25
//    #define  DEFAULT_Kd 440
#endif // PIDTEMP

// Bed Temperature Control
// Select PID or bang-bang with PIDTEMPBED.  If bang-bang, BED_LIMIT_SWITCHING will enable hysteresis
//
// Uncomment this to enable PID on the bed.   It uses the same frequency PWM as the extruder.
// If your PID_dT above is the default, and correct for your hardware/configuration, that means 7.689Hz,
// which is fine for driving a square wave into a resistive load and does not significantly impact you FET heating.
// This also works fine on a Fotek SSR-10DA Solid State Relay into a 250W heater.
// If your configuration is significantly different than this and you don't understand the issues involved, you proabaly
// shouldn't use bed PID until someone else verifies your hardware works.
// If this is enabled, find your own PID constants below.
//#define PIDTEMPBED
//
//#define BED_LIMIT_SWITCHING

// This sets the max power delived to the bed, and replaces the HEATER_BED_DUTY_CYCLE_DIVIDER option.
// all forms of bed control obey this (PID, bang-bang, bang-bang with hysteresis)
// setting this to anything other than 255 enables a form of PWM to the bed just like HEATER_BED_DUTY_CYCLE_DIVIDER did,
// so you shouldn't use it unless you are OK with PWM on your bed.  (see the comment on enabling PIDTEMPBED)
#define MAX_BED_POWER 255 // limits duty cycle to bed; 255=full current

#ifdef PIDTEMPBED
//120v 250W silicone heater into 4mm borosilicate (MendelMax 1.5+)
//from FOPDT model - kp=.39 Tp=405 Tdead=66, Tc set to 79.2, argressive factor of .15 (vs .1, 1, 10)
    #define  DEFAULT_bedKp 10.00
    #define  DEFAULT_bedKi .023
    #define  DEFAULT_bedKd 305.4

//120v 250W silicone heater into 4mm borosilicate (MendelMax 1.5+)
//from pidautotune
//    #define  DEFAULT_bedKp 97.1
//    #define  DEFAULT_bedKi 1.41
//    #define  DEFAULT_bedKd 1675.16

// FIND YOUR OWN: "M303 E-1 C8 S90" to run autotune on the bed at 90 degreesC for 8 cycles.
#endif // PIDTEMPBED

I will be switching to PID today, and I bet I see even faster heating.  The accuracy is great atm on Bang-Bang Hysteresis though I will say. http://www.youtube.com/watch?v=Vn_LtGAv52A here is a video for using AC power on the BED which would be even better 80)!  Same concept as I have done with the dc-dc relay just dc-ac...wish I would have seen this first as I am not really that happy with the thickness of the qu-bd bed (it is not flat, having ridges and bumps around the power line input for the power and thermistor).

I think the quoted time would be for just the silicone hater by itself. As soon as you strap it to the bed assembly and and a piece of glass/aluminium the thermal mass with go up and the performance will come down.

Finally got the pieces in to complete the installation of these beds.  I used a 12V 12.5A power supply from Digikey.  I would post a link to it, but it appears I cann't put links in my posts.

I also used the Crydom D1225 Solid State Relay.  I bought them locally for $39 a pop.. not cheap, could get it cheaper from Korea or China, but I didn't want to wait.  Grainger carries them, as well as many other supply shops.

I ran into a snafu after installed just one bed, and spent the rest of the weekend fixing the other printer.  But I can tell you that I am in love with these beds.  The bed reaches 100C almost as quickly as the extruder hits 200C.  It is so shocking to realize that I'm not waiting for 12-15 minutes to wait on the bed to heat up!  All told, its about $100 per printer to upgrade the bed, but well worth it in gained productivity.

I took the piece off the back of the printer that can hold the PVC pipe for spools.  I created my own system and didn't need it there anyways.  I drilled holes and reused the same screws to screw the power supply and the relay to the back of the case.  It's nice, neat and stays out of the way.

Overall, a really great mod.  One thing to note, the back of the silicone bed is going to be raised up higher than the front.  While you could adjust the bed with the screw heads on top of the aluminum, I chose to print out Ian's great thumbscrews.  One other thing I had to do is stop using the binder clips to hold the glass on.  They could not open enough to fit onto the back of the board, and the stress of the ones on the front caused the glass to crack once it reached printing temp.

The solution was to make new custom clips out of Stainless Steel sheet metal.  We purchased a small sheet of it at 6mil, then cut and bent it by hand to create just the right amount of tension to hold the glass onto the bed, while making sure to leave as much build area as possible.  I've attached a picture of the final setup.