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Re: Hotend overshoots - 10 years ago
What disturbance is initiating the cold-extrusion-prevention-triggering swings? Is it the fans coming on or is it the extrusion starting? Or reading again, does it only swing excessively on the initial stabilization after the M104/M109 S185 ? For the first, I'd add a G4 dwell after the fans to let the system accommodate the change in airflow. For the second, I'd experiment with the AUTOTEby DaveX - Reprappers
Re: Hotend overshoots - 10 years ago
Does it get back up to temperature with the current PID_MAX, or does running the fans max out the heater at PID_MAX and then then temp fades to some lower than setpoint steady-state? If the former, maybe try coming to temperature with the fans on. If the latter, rather than the PID not reacting fast enough, it may be more that the power in is less than the power required to hold temperature aby DaveX - Reprappers
Re: Annoying heated beds. Input on ideas - 10 years ago
If you put more watts in, or keep the watts from leaking away, it will heat faster and be able to maintain a higher temperature. If you aren't going to spend the $ to put more watts in, dual heated beds, or anything with more mass and surface area is just going to take longer to heat. $-wise, you could work on reducing the watts out and insulate the bottom (I think Nophead had good results fiby DaveX - Reprappers
Re: Heated Bed Stopping - 10 years ago
Did it ever work correctly? Is it still trying to heat? Could be insufficient power to the bed. I'd check the bed terminals for the expected voltage.by DaveX - Reprappers
Re: Inline Filament Dryer - 10 years ago
Are you running it at 28inches and 140F in the pic? Duh. It says so in your text....by DaveX - General
Re: MINTEMP triggered - 10 years ago
MINTEMP happens with high resistance on thermistors, so maybe you are having an intermittent open-circuit on your thermistor somewhere. Pronterface only polls every second or so, so it could miss a quick open circuit / infinite resistance / MINTEMP.by DaveX - Reprappers
Re: Virtual Axis - 10 years ago
Looks like that is Repetier around Speaking out of mostly ignorance, the way the Deltas work is that they break each cartesian line segment motion (e.g., G1 Z10, relative) into a number of steps along a "virtual axis" aligned with the motion, transformed into delta coordinates. For example, a vertical move (G1 Z10) would be an equal motion along all three axes, and require the same sort of cooby DaveX - Firmware - mainstream and related support
Re: Hotend overshoots - 10 years ago
Thanks. Another thing that is essential to understanding PID controllers is that once you finally reach steady state, all of the output power is coming from the kI term times the integrated error. At steady state, the MeasuredValue = SetPoint, so error=MeasuredValue-SetPoint=0C, and the error isn't changing, so the slope is 0C/s. If you need 8W to maintain temperature at the SetPoint, tby DaveX - Reprappers
Re: Hotend overshoots - 10 years ago
I edited my text above to add: "You also could reduce the maximum power by (ETA reducing BANG_MAX or PID_MAX from 255 (see around ) depending on whether you want to limit the behavior on the way up into PID_FUNCTIONAL_RANGE or within the PID controller." Quotedrmaestro Here's an update on what I did: I've checked PID_FUNCTIONAL_RANGE and it was set at 10 as DaveX mentioned. I've set it at 35by DaveX - Reprappers
Re: Hotend overshoots - 10 years ago
You using Marlin? And a heater cartridge? If you are using a cartridge and you are heating by 3-5C/sec near the operating point, which might be too much for the autotune. You also could reduce the maximum power by (ETA reducing BANG_MAX or PID_MAX from 255 (see around ) depending on whether you want to limit the behavior on the way up into PID_FUNCTIONAL_RANGE or within the PID controller.by DaveX - Reprappers
Re: PT-100 connection to J-head extruder - 10 years ago
Lots of boards already have 4.7K pullup resistors installed. You are basically making a voltage divider with the pullup connecting to the ADC reference voltage, and the ADC sensor pin connects to the junction between the pullup and the thermistor or PT-100, while the other end of the sensor connects to ground. On most boards, the circuit is like part of the the schematic on but without thby DaveX - Reprappers
Re: Tri Color Mendel Microswitch alternative - 10 years ago
I couldn't follow the link, but if you can get it in the right position, pretty much any microswitch will work. Even this one:by DaveX - Reprappers
Re: RFC: Marlin mod: extruder pid feed forward and lag - 10 years ago
Looks like there used to be a Kc term for adding a term proportional to the extruder speed: But the current_block->speed_e doesn't look like it is available any more. ETA: Duh. That's the functionality you are building off of.by DaveX - Firmware - experimental, borrowed, and future
Re: RFC: Marlin mod: extruder pid feed forward and lag - 10 years ago
This is what I'm imagining: You can have a noise-free signal that doesn't change very much if your process slews by maybe 0.5C/second at full power (or maybe full extrusion), and you are sampling a 0.5C/count ADC (100Kthermistor, with 4.7K pullup, operating at about 200C) with a fast 131ms/16=8ms sampling period. A perfect no-noise ADC would be changing state about once per second, so with Marliby DaveX - Firmware - experimental, borrowed, and future
Re: RFC: Marlin mod: extruder pid feed forward and lag - 10 years ago
Quotesvanteg Interesting, informative and I think we agree on most aspects. QuoteDaveX In Marlin there's an AUTOTEMP feature in the planner that increases the temperature SP proportionally to the highest E speed in the move buffer. I have not tried this yet so I might have misunderstood. However my understanding of it is not to regulate a desired set temperature but rather change the temperaturby DaveX - Firmware - experimental, borrowed, and future
Re: RFC: Marlin mod: extruder pid feed forward and lag - 10 years ago
In Marlin there's an AUTOTEMP feature in the planner that increases the temperature SP proportionally to the highest E speed in the move buffer. Part of the lag might be in the transfer function from the tip temperature to the thermistor temperature, but a significant part of the dead-time/process time constant is in the heater to tip/thermistor. It does seem like a feed-forward term should leaby DaveX - Firmware - experimental, borrowed, and future
Re: Hot end and bed not getting hot enough... - 10 years ago
I'd check the voltage delivered to the bed when the bed is on. The "12V, 20A, 120W" spec does not make sense, since 12V at 20amps means 240W. 120W at 12V would mean only 10A.by DaveX - Reprappers
Re: Thermistor and pull up reisitor - 10 years ago
The firmware-enabled resistors are different than the possibly higher-precision resistor used in the thermistor circuit. is a good reference for how the pullup resistor and the thermistor works. In Marlin, you can enable the endstop pullups individually around In Teacup, it isby DaveX - Reprappers
Re: Best print bed design for Prusa - 10 years ago
Three point support/leveling is good. If you like your screw mechanisms, I'd move one of the front ones towards the middle and then you could use it for back-front leveling, and do the side-to-side leveling by adjusting the ends of the x-axis. What's the problem with the Al bead or heater? I'd add a bunch of cardboard filler as insulation.by DaveX - Reprappers
Re: Openbeam rigidity for larger frames? - 10 years ago
QuoteMrDoctorDIV So in an attempt to understand that simply, 1.7X thickness = 2X the length? Yes-ish... since the 1.7 factor depends on the doubling of the length. If you quadrupled the length, the thickness would need to be 1.7*1.7, not 1.7*2. The basic formula is from , with the I values based on the thickness from the rectangular entry on Ohminarus, I guess I'm not precisely sureby DaveX - General
Re: Openbeam rigidity for larger frames? - 10 years ago
In general, profile-ignoring terms, square beam deflection or rigidity goes down with the third power of length and up with the fourth power of thickness, so if you wanted the same deflection with twice the length, you'd need 2^3=8 times the area moment of inertia, which would mean 8^(1/4)=1.7 times the thickness. In other words 20mm versus 15mm would get you (20/15)^(4/3)=145% more length.by DaveX - General
Re: Ramps drawing to much current? - 10 years ago
The pic you sent looks like a mechanical relay. It might work OK with bang-bang control, but you would need a solid state relay for reliable, long lasting PID control. RepRap's PID control uses a Pulse Width Modulation (PWM) process to rapidly switch the power completely on and off for an amount of time proportional to the control. Mechanical relays aren't set up for cycling at the many-Hertzby DaveX - Reprappers
Re: Marlin firmware: add custom button, is possible? - 10 years ago
In pronterface, I'd experiment with a macro with '';@pause' and ';@resume' perby DaveX - Firmware - mainstream and related support
Re: Using custom thermistor - 10 years ago
QuoteOhmarinus QuoteDaveX See http://hydraraptor.blogspot.com/2012/11/more-accurate-thermistor-tables.html if you haven't already. I think nophead uses a Fluke meter with a small thermocouple pushed down through the filament path into the melt chamber to do his calibrations. I use a thermocouple attached to a cheap PID controller, but I'm not tremendously confident in the controller's calibratiby DaveX - General
Re: I just smoked my Melzi electronics! - 10 years ago
With 12V, by Ohm's Law, I=V/R, that would mean 12V/1.7ohm=7 amps through the circuit you are measuring. That is a good picture of the measurement. From the earlier picture I can see that you've got a dual power board, and from this picture, it looks like this half of the board is 1.8Ohms. If terminals 2&3 aren't shorted together, as would be normal for regular 12V use per the table printedby DaveX - Reprappers
Re: Heated Bed at 37C? - 10 years ago
You can reduce the maximum power in software as well. Reduce MAX_BED_POWER in Marlin at https://github.com/ErikZalm/Marlin/blob/Marlin_v1/Marlin/Configuration.h#L223 I think you'll need some reduction to make the heating response curve match the cooling response curve better around 37C so that the PID controller isn't adversely affected by the asymmetry. IOW, if it takes 180 seconds to cooby DaveX - Reprappers
Re: Using custom thermistor - 10 years ago
See http://hydraraptor.blogspot.com/2012/11/more-accurate-thermistor-tables.html if you haven't already. I think nophead uses a Fluke meter with a small thermocouple pushed down through the filament path into the melt chamber to do his calibrations. I use a thermocouple attached to a cheap PID controller, but I'm not tremendously confident in the controller's calibration. Still, measuring theby DaveX - General
Re: I just smoked my Melzi electronics! - 10 years ago
Yes, take the warranty of you can get it. On the other hand, if you are stuck with the smoked board, and the other functions seem to work, replacing the MOSFET might be worthwhile. If it doesn't do anything at all, you might try unsoldering the burned up MOSFET and maybe the capacitor and see if the rest of it works. From the pic it looks like the MOSFET burned up, which it can do if there iby DaveX - Reprappers
Re: cheap-o end stop? - 10 years ago
Quotecnc dick In my mind there is only a couple things that could do that one is you are running them normally open and you have a bad wire so it doesn't get the signal. Second your acceleration rates are so low that when it's trying to decelerate it actually taking all the over travel out of the switch and bottoming out before the can stop Teacup is working on (see ) using ACCELERATION and ENDby DaveX - General
Re: I just smoked my Melzi electronics! - 10 years ago
An FDD 8580 is rated for 20V, 35A per Were you putting 24V through it? At 12V & 10A, an Rds of 0.009 ohm would mean 10^2*0.009=0.9W of heat at the MOSFET to dissipate. Replacing it with a better TO-252 N-channel MOSFET with half the Rds would require only half the cooling at the same load. Maybe look for something like to replace it with.by DaveX - Reprappers