Temperature control questions

[Leithan]

Is it required for the Rambo to control the temp of the bed and hot end? It seems that a lot more accurate temp control could be had by using a separate PID and RTD sensor to control the temps. From reading I noticed that some people were using a separate power supply controlled by an SSR to heat the bed, one would only need to add a RTD sensor and PID to have allot more accurate setup. I built my own Home Brew rig a few years back and I used PIDs to control my hot liquor tank and mash ton temps. They are very easy to set up and control. Just wondering if this has been tried, what would be the downsides to divorcing temp control from the Rambo or if it's even possible? It just doesn’t seem like thermistors are the best answer and allot of print performance is dependent on accurate temperature settings.
The type of controllers I am referencing, you would need 2 one for the bed and one for the hot end http://www.auberins.com/
There are others, to include ones that can be had on fleebay for under $20.00, but I used Auberins in the past.

[Captain Starfish]

The Rambo and thermistor are a PID and RTD and the sample rate is well over the impulse response time. You will get zero improvement in accuracy by doing this.

Some do it on the bed to run higher power than the RAMBo can drive for fast bed heating times and that's reasonable but the hot-end is well within the capacity of the RAMBo to drive. So, yes, you can do it. But there's not a lot of advantage. Personally I'd be throwing my spare cash at other enhancements.

Things to watch out for: you'll either need to continue running an RTD for the bed and hot end(s) on the RAMBo or change the firmware to remove the interlocks at the start of a job (within 1º typically) and to extrude (I think default is >150º). Apart from that, so long as you don't want the ability to change the temp mid-flight in code or anything, no problems at all.

[Leithan]

soooooo......the only reason to attempt then is because I can't figure out any other constructive way to blow $150. I should of known better, I made my own RTD probe for a fermentation vessel.......step #1 insert thermistor into metal tube.......I just reread your tutorial on calibrating, and after rereading it two more times, it doesn’t look as scary as I initially thought.

[Captain Starfish]

With your fermentation vessel, you didn't already have a PID controller sitting as an integral part of it to begin with so adding one made lots of sense. In this case, yeah: you've already got everything you need.

I'm still working (too many projects, not enough time) on a thermocouple upgrade which should stabilise the temperature reading a lot, but in the meantime the RTD aka thermistor will do the job.

[Generic Default]

The thermocouple will be useful once we start getting into higher temperature materials in the future.


For now, thermistors and heater cartridges are more than enough for our hotends. My Tri hotend heats up to 260 degrees from room temperature in about 80 seconds, and it maintains within +- 0.5 degrees at that temperature. Thermocouples won't be any better than that.

Your PID values are the most important part for maintaining consistent temperature. If they are going over and under in a wave pattern, you need to change them until they are steady.
The hardware is important too. You want a small thermistor with a fast response time in contact with a very conductive metal very close to the heater cartridge.

[RegB]

The prices if some of those temperature controllers "suggested" that I could build a sous vide thingie for a lot less than I could buy a commercial one for.
Then I found a few kickstarter projects that had bin there done that and now have units on the shelf.

Mash tun ?
Nahh, I gave up home brew a long time ago -
& eventually gave up booze {several times, but the most recent time has lasted a while (-: }