Bed can't hit 100C?

[Noircogi]

I've got my V3 up and running, but I haven't been able to use my customary ABS settings.

It seems the bed will never hit 100C with the stock power setup. At around 96-97 degrees it slows to a stop.

Is this correct or do I possibly have a bad connection somewhere?

[Qdeathstar]

I can't speak specifically to the Rostock max v3 but the v2 takes about 30min to get to 100c

[KAS]

30min? ouch. Try covering the top with a folded towel, see if it will get to temp that way.

[gchristopher]

That's about the performance I saw from my V2 with the older-style PC power supply.

A towel will improve your heat time, but once you remove the towel, your max temp will probably go back to where it was.

A minimal enclosure, even a shower curtain, might raise the ambient temp enough to let the heated bed get a bit warmer.

[Noircogi]

What's the real fix here? A 24v supply for the Onyx and some sort of FET to switch it?
The bed heating seems pretty pathetic.

Edit: It looks like I need to buy a 24V 20A power supply and a solid state relay, put it all in the base controlled by the current bed heater wires.

[Xenocrates]

Couple solutions. First would be to make sure you're delivering at least 12V to the Rambo, using the trimpot on the power supply. Then if it still won't deliver the power you want, you can slowly and carefully turn up the voltage. It will increase the power available to the hotend and fans as well (Unless you install a regulator or resistor before those go to the Rambo, which is rather easily doable it seems with the V3). A chamber helps, as it keeps drafts off. The V3 should be able to use most of the existing designs (I haven't checked if my design will work, if someone could through a picture of the top of the towers my way with dimensions, or a CAD file that would be great). You could also play with the PID values some.

Beyond that, I think the V3 makes it pretty easy to add another power supply, although you'd need to make it less centered in the base, and have an SSR so that you can drive the bed using the original power wiring.

It may also be just environmental. I could get to 110 pretty well at first, as the area it was in was quite warm when I first started. Then I started seeing much slower warm ups as the temperature decreased (No environmental controls there). I got to a point where I couldn't get it beyond 97C. The Onyx shipping with it is the same version I have, and while it takes quite some time to get it to 100C (Although I think my ADC calibration is off, as it seems much warmer with the Duet than 100C did with the Rambo, so it may be even hotter. It seems hotter than even the 110C on a Taz 6). My power supply delivers a solid 12V, but only ever 12V. If you can get 13V or a little more, which the industrial supply should be able to do, you can decrease the time and increase power delivery.

[Noircogi]

I almost always print ABS and the current heating time is very slow.

There's quite a bit of room in the base. I think I could cram another power supply of similar size in there.

I was thinking of something like this:
https://www.amazon.com/gp/product/B01B1 ... NHWEFTZZNI

I'd need to build some new mounts for both power supplies.

[Xenocrates]

If you used that, it would be overloaded or need to be turned down. It is rated to supply 20A (And I trust it about as far as I could throw a Meanwell supply, which is a damned sight less distance than I could throw that at 2.7 pounds), and a Onyx has a rated resistance of 1-1.1 Ohms. At the high end of it's resistance, it's drawing ~21.8A. Low end 24. I suggest trying to turn it down to ~20V, which will still give you a lot of power (3X the current rated power of the Onyx,) and keep it with a bit of margin for amperage and power draw.

[Noircogi]

Thanks for the info. I read somewhere else that the Onyx was around 1.2 ohms.

I just measured mine and it's 0.92 ohm, much lower than I was expecting.

[Noircogi]

I fixed this problem by replacing the stock power supply with a 600W 24V supply which I turned down to 20V, a 12V regulator to power everything but the bed and a solid-state relay to switch the 20V going to the bed.

It heats up nice and fast now.

It does use about 7 more watts of power at idle though (18 instead of 11) due to the regulator etc.

On closer inspection it didn't seem feasible to get a second power supply in the base.

[Noircogi]

Just a note on this.

If you do the same, make sure you get a high-quality MOSFET-based SSR. Don't buy a Fotek or SHZE. They have huge internal resistance and will heat up and fail, even with a large heatsink, thermal paste and good airflow.

When they fail, they fail in the "on" state and could easily cause a fire.

I ended up eventually getting a 40A Crydom from digikey, but from doing some research, I think the 100A Auber http://www.auberins.com/index.php?main_ ... cts_id=288 has similar low resistance for much less money.

The Crydom doesn't even get warm in the same config where a 40A SHZE burnt up in 2 minutes.

Also, you cannot use a DC/AC SSR for this application. Those are much easier to find locally but won't ever turn off with a DC load.

[tim]

I am new at this and have yet to make my first print. I will be using ABS. How critical is it that the bed temperature be right on 100 degrees?

[Xenocrates]

I am new at this and have yet to make my first print. I will be using ABS. How critical is it that the bed temperature be right on 100 degrees?

From my experience, it isn't. I have printed on beds ranging from 90C to 110. I know some people claim ABS can be printed on an unheated bed, and in fact have gotten some success at it using judicious application of ABS juice. However, if your bed temperature is set to 100, it won't start before it hits at least 95C, as there is a range in which it will actually start. I suggest that you start with trying to get to 100C, and then play with the settings once you have some prints, and choose between speed and quality, and if it isn't enough for you, I'd go ahead and make sure you're delivering 12V, and if you are and still don't heat fast enough, research bed coatings (I suggest PEI and ignoring proprietary coatings like Geckotek and zebra plate, as they will get expensive fast or don't work well), and upgraded power supplies. There are a huge number of options, and you may find you prefer printing a different material that wants for lower (or higher) bed temperatures.

[Twac1]

What do you need your bed at 100 c for?

[gchristopher]

If you do the same, make sure you get a high-quality MOSFET-based SSR. Don't buy a Fotek or SHZE. They have huge internal resistance and will heat up and fail, even with a large heatsink, thermal paste and good airflow.

When they fail, they fail in the "on" state and could easily cause a fire.

I ended up eventually getting a 40A Crydom from digikey, but from doing some research, I think the 100A Auber http://www.auberins.com/index.php?main_ ... cts_id=288 has similar low resistance for much less money.

The Crydom doesn't even get warm in the same config where a 40A SHZE burnt up in 2 minutes.

Also, you cannot use a DC/AC SSR for this application. Those are much easier to find locally but won't ever turn off with a DC load.

Do you know if the rated switching frequency affects SSR reliably for this application? That was the only major stat I could find that seemed significantly difference for the more expensive Crydom.

What do you need your bed at 100 c for?

I found that with purple glue stick on glass, I could get good adhesion with ABS at 90C. I only needed higher temperatures once I switched to a PEI print surface.

With PEI for ABS, and found that a bit higher bed temperature (110C) gave me the best results. The biggest advantage of the PEI is that it is simple and reliable and doesn't require getting that fresh coat of glue stick at just the right thickness. PEI also releases more easily and reliably when it cools down.

[Noircogi]

If you do the same, make sure you get a high-quality MOSFET-based SSR. Don't buy a Fotek or SHZE. They have huge internal resistance and will heat up and fail, even with a large heatsink, thermal paste and good airflow.

When they fail, they fail in the "on" state and could easily cause a fire.

I ended up eventually getting a 40A Crydom from digikey, but from doing some research, I think the 100A Auber http://www.auberins.com/index.php?main_ ... cts_id=288 has similar low resistance for much less money.

The Crydom doesn't even get warm in the same config where a 40A SHZE burnt up in 2 minutes.

Also, you cannot use a DC/AC SSR for this application. Those are much easier to find locally but won't ever turn off with a DC load.

Do you know if the rated switching frequency affects SSR reliably for this application? That was the only major stat I could find that seemed significantly difference for the more expensive Crydom.

I don't think that's the issue here. The real problem was the "On" resistance. The SHZE 40A were especially bad. I had one burn up and latch on before the bed hit 60 degrees the first time, it had never switched off.

I think the Auber is probabaly fine and it's only $20. I actually bought one to test but I don't really feel like taking the Crydom out since it's working so well.