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Topic: Sestos Controllers and maintaining stable temps...

So I have my control set to auto run the motor when the temp hits 180 and to cut off when it drops below. Im having ALOT of issues even after multiple auto tunes getting the controller to maintain a stable temperature. Ususally within 30 seconds of the motor switching on the temperature drops by 3 degrees triggering the motor to cut back off. repeat the pattern every minute or so and it become a bit annoying. So here are my thoughts... 1. move the heater closer to the nozzle, 2. move the temp sensor closer to the heater, 3. Play with settings on the Sestos to improve heat stability/cycle. So to those of you who have been playing with these longer what do you think my best bet would be. I have great tolerances and filament quality as is, i just need to maintain temperature so i have a steady extrusion without frequent stops and starts.

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Re: Sestos Controllers and maintaining stable temps...

Set the motor on setpoint a little wider. When the motor turns on, the system dynamics change in two ways:

The 12v bus sags a little
Plastic starts flowing, meaning more heat is needed to melt the incoming plastic.

When you're autotuning, you're tuning for the steady state dynamics of the system - the motor being on. The transient dynamics are different, so you're seeing some tracking error. You can optimize for one condition or the other, but not both (without gain scheduling, which can't be done on the price range controllers we're using). Just set the motor on/off setpoint a little wider, or don't use autostart.

Also if I remember correctly, you have an additional fan pointed at the nozzle. You might be running out of control authority (heat). If you tap the  SET button once when it is running, what do you see?

Try it without your auxillary fan. I have no trouble holding +/-1C.

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Re: Sestos Controllers and maintaining stable temps...

I am trying to program Sestos but I have problem with sensor. PV is always at 22 C. If you can describe what route you took to program Sestos I will appreciate it.

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Re: Sestos Controllers and maintaining stable temps...

alexcheve wrote:

I am trying to program Sestos but I have problem with sensor. PV is always at 22 C. If you can describe what route you took to program Sestos I will appreciate it.

Out of the box, there is no programming to do for it to display temperature correctly. As discussed over email, you most likely have a bad temperature sensor.

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Re: Sestos Controllers and maintaining stable temps...

digitydogs wrote:

So I have my control set to auto run the motor when the temp hits 180 and to cut off when it drops below.


This is a low mass system, with a small heater.  In order to heat up what mass there is, a long "soak" period is required.  As stated, when fresh pellets are moved into the pipe, the heater is not powerful enough to immediately overcome the sudden thermal demand.  Eventually, however, the system will find equilibrium.  Once it is in this state, you will be able to use the type of operation you describe, but really not until.  In all honesty, it's really not necessary, nor especially useful, to run it this way, and it would actually work against you while trying to auto-tune the heater control. 

I've made several modifications to my setup, but none related to the basic operation methodology.  My last run was 12 hours straight, which produced nearly perfect filament.  The key is a good preheat, monitor / tweak the temperature once it is running consistently, and when the filament size is where you want it, let it go for as long as you can.  There's no reason to start and stop the motor as this introduces an inconsistency which will make it harder to control.  The more useful modification is one which actually does the opposite of what you are attempting, and that is to get a second power supply and separate the motor from the heater.  This will allow the motor speed to be more consistent, as it will not slow down when the heater kicks on.

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Re: Sestos Controllers and maintaining stable temps...

Orb wrote:

The more useful modification is one which actually does the opposite of what you are attempting, and that is to get a second power supply and separate the motor from the heater.  This will allow the motor speed to be more consistent, as it will not slow down when the heater kicks on.

That is true, though currently shipping power supplies have more robust regulation than the first few hundred. Ideally they'd be on separate circuits, but you can still get great quality filament without doing so.

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Re: Sestos Controllers and maintaining stable temps...

Orb wrote:

nearly perfect filament.

Resin? Filament diameter? Variance? I love data. smile

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Re: Sestos Controllers and maintaining stable temps...

elmoret wrote:

Resin? Filament diameter? Variance? I love data. smile

ABS, 1.75mm

Worst case variance was .05mm, but this was a rarity.  The vast majority of that run was within .02 with much of it dead on.  Of course, the larger nozzle diameter, and the ability to tweak the motor speed a bit helped a lot in dialing it in.  Extrusion rate was approximately 1" every 4 seconds, or about 900 feet in that time period.

I've run about 3/4 lb of it through an Up! printer, and it's been working perfectly.

Previous runs were about the same, but I would get ramen at some point, thanks to a tiny burr I left when enlarging the orifice.  The plastic would collect on it a tiny bit at a time, but eventually became large enough to attach itself to the filament.  When this happened, it would get stuck in my modified guide and start wadding.  A tiny bevel on the orifice solved this, and it happily extruded, with no kinks, wobbles, etc,  until I decided to turn it off.

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Re: Sestos Controllers and maintaining stable temps...

So reading the thread here is what i now have to add.
I have since managed to get my temperatures to remain stable with autostart and stop functions. I went into the settings and made a few adjustments to the default cycles and heating settings (def not recommended and i will not post those changes as i wont be responsible for someone screwing or shortning the life of their extruder) followed by two autotunes once the system was up to temperature and extruding again.

The points i will add about my mod testing extruder...
I already had my motor on its own power source, to me the slight power drops and miniscule drop in rpm is unacceptable when aiming for industy quality filament, for most however the very brief .01+- variance this can cause is fine for home printing and will not cause any issues at all. 
My fan is also set to come on along with my heater, i prefer the fan to be active from the start as activating it with the motor cause a slightly larger drop in power as they kick in, and the heating unit is better able to regulate when it has the airflow from the start not suddenly once up to temp.

Heater core and thermocouple placement.
Ive found that moving the heater core towards the back of the pipe coupler, and placing the thermocouple at the front, allows you more stable melting temps with the added bonus that it keeps your nozzle slightly cooler which helps which maintaining size on your filament as some heat is actually being pulled by the nozzle as its shaped and extruded. This is especially useful for pla until we get a combo water cooling and winding solution out into the wild and out of testing.

Coupling the auger to the motor... I am looking into alternate ways of achieving this as to me this is currently the weakest point of the extruders design. washers tend to slip or warp no matter how well or tightly fitted you have them. My current line of thinking is that squaring off the motor peg and using a socket wrench coupler may be the best bet for a snug fit.

Feed System for pellets/powders

For anyone who wants a more unattended feeding setup and isnt satisfied with a printed hopper extension.... You local Plumbing/Hardware store is perfect for this.. I am currently using a PVC plumbing pipe distribution system to feed my extruders from a large tank (can be built out of plexi, acrylic, and material that wont cause contaminents or you can use a fish aquarium) For powders i suggest a low rpm motor with fan blades attached installed in the piping in order to help facilitate flow of the powder and prevent clumping. This can also be used for pellets but so far hasn't seemed necessary.

Hope all this helps someone, and sorry for the run on sentences. Also anyone that wishes to add anything please do as this has been based off my experiences and im sure others have even better ideas and tips!

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Re: Sestos Controllers and maintaining stable temps...

digitydogs wrote:

Coupling the auger to the motor... I am looking into alternate ways of achieving this as to me this is currently the weakest point of the extruders design. washers tend to slip or warp no matter how well or tightly fitted you have them. My current line of thinking is that squaring off the motor peg and using a socket wrench coupler may be the best bet for a snug fit.

You can replace the washer with a 3/32" diameter stainless steel dowel pin, but then you lose the stall protection functionality. No drilling or grinding of either shaft is needed.

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Re: Sestos Controllers and maintaining stable temps...

digitydogs wrote:

For anyone who wants a more unattended feeding setup and isnt satisfied with a printed hopper extension.... You local Plumbing/Hardware store is perfect for this.. I am currently using a PVC plumbing pipe distribution system to feed my extruders from a large tank (can be built out of plexi, acrylic, and material that wont cause contaminents or you can use a fish aquarium) For powders i suggest a low rpm motor with fan blades attached installed in the piping in order to help facilitate flow of the powder and prevent clumping. This can also be used for pellets but so far hasn't seemed necessary.

Pictures?

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Re: Sestos Controllers and maintaining stable temps...

Tim ill post some pics in a day or so as im redoing my arrangement to accomodate all four systems rather than just the testing one.

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Re: Sestos Controllers and maintaining stable temps...

Sounds great!

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Re: Sestos Controllers and maintaining stable temps...

With any luck the mail will have delivered those thrust bearings and ill be able to actually have all four running and it tested before i show pics lol.

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Re: Sestos Controllers and maintaining stable temps...

Tim,

Just dropping an update i got those bearings the next day, had to alter my feed design as glass is just too easy to shatter and lets leave it at that... Switched over to wood and plexi.... with luck pics to come tonight before i get sidtracked with the spool winder assembly and then rigging a water cooling solution inline...

Ian,
Kit looks good... I will need three more of these as soon as we are sure all the bugs are worked out!

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Re: Sestos Controllers and maintaining stable temps...

Sounds good!

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Re: Sestos Controllers and maintaining stable temps...

Tim,

Finally got around to uploading a pic, still adjusting my pipe lengths before i mount it and fill it.

http://rcubedcreations.com/feedbox.jpg

And here are the extruders. 2 Stock fan for ABS 2 mod fans for PLA. I had started to disassemble for implementing a few mod ideas and remembered the pic so i threw them back together half @$$ed, so please pay no attention to random missing or off center parts, and yes they all work great.

http://r3screations.com/exarmy.jpg

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Re: Sestos Controllers and maintaining stable temps...

!!!

I would not recommend feeding from that wood, at least not without melt filters. One splinter will clog your printer's hotend.

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Re: Sestos Controllers and maintaining stable temps...

as i said not done yet... im actually going to be lining it with a high strength clear plastic after i paint it to prevent this very issue.  I am working on 1000 things at once these days so everything is in stages and a bit behind schedule thanks to that eye injury last week. But i've got three days off the real job coming up this week and i plan to get stuff finished up. Plotting out a pellet pre-cleaner as well, between that and the melt filters i can feel confident i wont have any contaminants.

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Re: Sestos Controllers and maintaining stable temps...

Ah okay. Just didn't want someone to have trouble.

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Re: Sestos Controllers and maintaining stable temps...

I know tim, your awesome at making sure no one screws up if there was anything you could do to help prevent it. I was just trying to clarify, sorry if it came off at all offensive.