Which sensor are you using? I'm asking because I learned the hard way that you should make sure that you can trust the data from the sensor before making any assumptions.

I am using two different sensors one  (see http://www.thingiverse.com/thing:699308) taking a measurement as the filament exits the extruder  and another (http://diy3dprinting.blogspot.ie/2014/0 … ensor.html) taking a final measurement once the filament has hardened before it is wound on the spool. I have checked these sensors and am confident they are reading correct. I am also using the the ATtiny85 filament sensor on my printer to compensate for variations on my DIY filament. It is a similar sensor to Flippers one but using an micro processor that can be programmed using the arduino software.

wardjr wrote:

Ggalisky wrote:

I used these: http://www.amazon.com/Inch-Digital-Cali … l+calipers

Both lengths of filament were about 100g, and I took 10 measurements per 100g coil of filament. Both coils are on their way to wardjr for testing, since I do not currently have a 1.75mm printer.

Would you like me to verify your measurements?

Yes for sure!

Pretty well verified at this point.  I measured both rolls at 12" along the entire length and in only one spot (on both rolls) did I find the tolerance to be +.02 out of spec so I would say the + or - .01 statement to be absolutely correct.

Do not worry about asking too may questions, I would not have learned as much as I have with out asking questions.  The only time questions become problematic is when the answers can be found on a google search.

Pre-Drying
Many different types of plastics need to be pre-dried in order to get good quality filament and prints. The plastics that encounter frequently that need pre-drying are PLA, Nylon, TPU, and PC (polycarbonate). There are several more plastics that need to be pre-dried, but for simplicity I only listed a few. I used a food dehydrator I bought off of Amazon to dry all of my pellets. http://www.amazon.com/Presto-06300-Dehy … dehydrator . The dehydrator comes with mesh plates, so you need to find a way to stop the pellets from falling through. I use this: http://www.amazon.com/National-Presto-D … ZNA913RBA. I usually let the pellets dry for about 10-17 hours. After drying I seal the pellets in a zip lock bag with a silica gel packet inside, and add a label so I know what plastic it is.

Sorry for keeping asking questions but really trying to learn as much and as fast as possible   Do you use the heater when drying and at what temperatures? The datasheet for the ABS I'm using says 2-4 hours of drying is needed at 80C.  At this site http://www.ptonline.com/knowledgecenter … pic-Resins they state that for ABS "•Internal moisture can not be removed with hot air alone"

Does anyone have links to this sensor by Fillip?

http://www.thingiverse.com/thing:454584

I was not impressed because a piece of steel rod that was a uniform 1.58mm in diameter, checked with calipers, registered 1.53-1.63mm. It was not repeatable enough to be useful.

Thanks!

The BOM for version 3 of the sensor includes a drill rod (1/16) and during the calibration routine it will correctly measure the diameter...(well it did each and every time I tried) Only issue I see is that it's rather slow/lagging. When placing the drill rod only from the 3th measurement forward the value is correct and stable, same when removing it, only from the 3th measurement onward the value reaches 0 and stays 0.

Fillip sent me one of those sensors as well. It is definitely not as reliable as calipers. I was not impressed by it.

Can you explain in a bit more detail why you were not impressed?

it's one of the things I'm trying to find out if that is indeed the case, by changing the software a complete audit trail for an extruder run can be generated and then some calculations can be made how large that chance really is.

If you measure several dozen times along a length, statistically you'll catch at least one of those + or - widths. That's the whole idea behind simple random sampling.

In this case all that really matters is repeatability. Most $10-20 calipers are good to +/-0.01mm repeatability. If he takes 20 samples and they're all +/-0.01mm, then the filament itself is at least that good.

I beg to differ :-)  in this case repeatability is not a an "property" of the caliper but an indication of how consistent the user is using it when doing it's measurements.

The filament I extrude is measured using the sensor that [fillip] build for the lyman v5 extruder. First thing I noticed is that the behavior of the fluctuation is in the form of <long same width><short under or above width><long same width>  Sometimes those under/above widths were so short that I missed them while watching the sensor data on the lcd screen. So I rewrote the mackerel software to keep track of the min and max values and display them every 5 second. 

If I would take the filament produced and re-measure it by hand because of the cadence in which the "blobs" appear it's not likely that I will be measuring at exactly the same spot where those "blobs" are and hence would report better results for the filament then it in reality has.

Ggalisky wrote:

I used these: http://www.amazon.com/Inch-Digital-Cali … l+calipers

Both lengths of filament were about 100g, and I took 10 measurements per 100g coil of filament. Both coils are on their way to wardjr for testing, since I do not currently have a 1.75mm printer.

Would you like me to verify your measurements?

Yes for sure!