Custom Quantum/Hadron PCB Heated Build Plate

Electronics related to CNC

Final design, do you like?

Postby frob » Tue Feb 28, 2012 3:38 pm

HadronTOP2.png
Hadron side


QuantumBottom2.png
Quantum side


HBPdeets.png
connector / config closeup
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Re: Custom Quantum/Hadron PCB Heated Build Plate

Postby bdring » Tue Feb 28, 2012 4:08 pm

How tall are the components under the board? I assume those tall components on the Quantum footprint are not there for the Hadron setup. Are those lugs used as an alternate to the flex cable?
Bart
"If you didn't build it, you will never own it."
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Final design: Notes

Postby frob » Tue Feb 28, 2012 4:15 pm

A few explanations about the current layout:

This is a prototype, so to save cost the Hadron & Quantum heaters are both in the same board, on opposite sides, to save cost on proto boards.
The production boards will probably be separate boards/designs, assuming i get more than a couple requests for Quantum sizes.

Though the picture shows all parts mounted, only those relevant to the version requested will be installed;
- the threaded bosses and connectors in particular would get in the way otherwise

Note the threaded bosses selected are M3 thread, 3mm high, but 4 or 6mm are available too, if that's more convenient to leave room for insulation,
however its probably best to add extra insulating washers if you want it higher off the carriage plate.

There is a surface-mount thermistor connected to the center standoff mount ring; the center standoff wont be installed unless you specifically request one- it should not be connected electrically to the carriage plate if the built-in thermistor is used. There is an additional thermistor about 1/4 of the way in from the edge if you prefer that and then you can cut the tracks to the center one to use that as a mounting point instead. The center standoff is there mainly to support the Hadron side, it cannot be mounted on the opposite side at the moment.

For the Hadron there are 4 red LED's along the front edge under the board; this will reflect off the carriage plate and i expect it to produce a nice visual effect.
For the Quantum the LED's are in the 4 corners on top;
the board is made a little longer in this case to allow a square piece of glass to fit between the LED's, which could
serve double duty to help keep the glass in place.
The LED's are powered from VIN and switched to ground using a separate signal; i may add a transistor switch & constant current regulator in the final layout to make it easy to interface to any MCU. i prefer this option so you can have the MCU flash the LED's the entire time while the plate is reading above a certain temperature threshold, rather than only while the heater is energised. If you prefer the latter you need only connect the LED signal to the heater switch input.

The extension on the back of the Quantum heater on one side allows the connectors and config solder shunts to be accessible on the top side, which is necessary to allow both boards to be combined into one. If i get at least a dozen orders for Quantum, i will adjust the layout to place the connectors etc on the back side like the Hadron.

The different voltages are configured by adding or removing solder blobs on special shorting "shunt" pads; they will come pre-blobbed for 12V unless you specifically request otherwise. The production units will have an easy to read chart printed on the underside showing which locations to make short or open for each voltage.

The flex cable "experimental" option uses standard 1mm pitch x 30 FFC cable. In theory it should not act as a heater as well :P but i will test that thoroughly before recommending others to try it. The regular 1/4" FastON tabs are the primary connection mode. these are nice and cheap and work well as a surface-mount connector, and you can pick up crimp-on female connectors cheap from any hardware / automotive store in every cable size. The Hadron shows some extra power connectors on the front edge, but those are for 5V only and wont be installed.

On detail missing in these renderings is the connector for thermistor /LED control, which will probably be a regular right-angle 4-pin 0.1" header, surface-mount-style.
I would have liked to use screw terminals or such but since all connectors will eventually be on the underside of the board, that would require taller standoffs, and those are more expensive anyways. if you have any opinion on this its not too late to change that.
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Re: Custom Quantum/Hadron PCB Heated Build Plate

Postby bdring » Tue Feb 28, 2012 4:34 pm

A lot of people like one side to be all unconnected copper. It is smoother, acts as a heat spreader and less likely to get shorted. The shorting might not be a problem on your design since you use only one side for each application.

I like the SMT thermistor. I don't know why I have not seen that before.

I like the SMT screw fittings. I see a lot of Prusa machines where they had to nip the glass around the screws. They always looked rough.

I love the grid and the color :D
Bart
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Re: Custom Quantum/Hadron PCB Heated Build Plate

Postby frob » Tue Feb 28, 2012 4:37 pm

bdring wrote:How tall are the components under the board? I assume those tall components on the Quantum footprint are not there for the Hadron setup. Are those lugs used as an alternate to the flex cable?


Correct, and vice-versa. The standoffs are slated to be 3mm high, but that can be made 4 or 6mm as well. The power tabs for the Quantum are chosen to allow surface mounting in the center of the board, before cutting out the Quantum size from it. If you're careful you can probably bend the rear tab down with 2 pairs of pliers to have it point horizontally instead of vertically. Personally i'll just use 90-degree cable connectors instead. If / when the 2 boards get separate into independent designs, i'll convert the Quantum version to the same arrangement as the Hadron.
Because of the presence of the carriage plate, i had to place the flex cable connector (2mm high) along the rear edge. it is pointing forward on the Hadron so the cable will be folded back over it to exit the rear - this is necessary to allow the other end to mate with either Quantum or Hadron with the same cable pin-out and orientation. it should also help prevent the cable from coming accidentally unplugged.
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Re: Final design

Postby frob » Tue Feb 28, 2012 5:05 pm

bdring wrote:A lot of people like one side to be all unconnected copper. It is smoother, acts as a heat spreader and less likely to get shorted. The shorting might not be a problem on your design since you use only one side for each application.
I like the SMT thermistor. I don't know why I have not seen that before.
I like the SMT screw fittings. I see a lot of Prusa machines where they had to nip the glass around the screws. They always looked rough.
I love the grid and the color :D


Thanks Bart!

I dont know what exact shade of blue the boards will turn out as, there's not much choice in that, i just hope it comes close enough to the color of the anodizing :)
The initial prototypes will be green since its cheaper though-

About the heat spreader /smooth copper question -
i actually mulled this over quite a lot and came to the conclusion that its better to have the heating element itself on the top side.
FR4 is a really lousy thermal conductor (really more of an insulator) especially of you don't riddle it full of vias and fill them with metal.
That partly explains why it takes so long to heat up some of the existing designs.

One key aspect of the design i came up with is to make maximum use of the available copper, with only a 7mil gap between traces, for 2 reasons:
- because the solder mask is sprayed on, narrow gaps fill up more and produce much less of an uneven surface.
- More importantly, to avoid hot spots which can degrade the FR4 under the copper traces. This more than anything limits the power and heat you can get out of it.

And it seems most people use either a glass plate, kapton tape, or other surface on top, so in that case its less of an issue. i hope :)
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Re: Custom Quantum/Hadron PCB Heated Build Plate

Postby mhensen » Tue Feb 28, 2012 9:24 pm

This heated bed looks extremely good and a good addition to the Hadron printer, which I hope will come soon :-)

Do you have any indication on pricing and timeframe? And in pricing I mean the complete working heatbed, pre soldered and tested.

With kind regards,

Michael
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Final design: please reserve now (pm me) if interested

Postby frob » Tue Feb 28, 2012 10:08 pm

Hi Michael,
thanks!

Well i'm still hoping i can sell it for $25 ea. for the first batch, as a special for buildlog members ordering the first ORD-bots. (not including shipping)
Worst case it would not be more than what others are selling similar ones for.
It all depends on the quantities. so far i have baker's dozen "reservations" - to be able to make that price i have to order at least 100 boards.
i was hoping to see at least half that many reservations by the time i'm ready to order a production batch, which should be in a couple of weeks if all goes well.
Thus time-frame for production units would thus be end of March. Every unit will be assembled and tested.
If the ORD bot kits haven't shipped by then and enough people reserve in advance, (assuming this is ok with Bart)
it might be possible to ship a bunch to him for inclusion in the kits, which would cut down the overall shipping costs for those.
I rather not promise too much though before i have a working prototype in my hands.

mhensen wrote:...Do you have any indication on pricing and timeframe? And in pricing I mean the complete working heatbed, pre soldered and tested.
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Proto PCB extra space: ArduinoMegaRAMSpololu4 all-in-one any

Postby frob » Tue Feb 28, 2012 11:49 pm

Looking at my options for low cost prototype boards for this- options are limited due to size,
so my normal preferred source isn't a good value here - looking at other options,
The option i'm considering has a set price for anything between 20x20 and 30x30 cm... and not much extra for blue SM...
hmmm.... that leaves a lot of unused pcb space.... what a waste.... wait a minute...
So i started working on a respin of Arduino Mega + RAMPS + Pololu's as a low cost, all-in-one single pcb (all-smt of course) tailored for ORD bots (ok and similar 3D printers too..) with a few extras, like maybe thermocouple support...

Stay tuned for more in another thread, i'll have more to post on that in a couple of days...

can you say....
ORDuino?
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Re: Custom Quantum/Hadron PCB Heated Build Plate

Postby mhensen » Wed Feb 29, 2012 7:40 pm

I hope I did my reservation for the heated bed..
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