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Re: Timing belt Vs fishing line - 7 years ago

Has anybody worked out what the maximum error is in the simple case for a printer such as the Tantillus? Mike

Re: Timing belt Vs fishing line - 7 years ago

@cozmicray, I can't say that I completely understand what you are saying but I do get a better sense of it even though I reject what you are saying. The post that you quoted and seem to object to is four lines (on my screen) and one photo. It took less than an hour to do the test and write it up - no "long dissertation, thesis, monograph, opus, oeuvre, study, critique" I would rather check my kno

Re: Timing belt Vs fishing line - 7 years ago

@ggherbaz, I doubt that many on the forum are concerned about $5 one way or the other. Speaking for myself, I seldom take anybodies word for anything, be they Doctors, Politicians, Physics teachers or even honoured members of the RepRap community - it doesn't mean that I don't value their opinions.Once I have done some checks for my own satisfaction I feel that I am on firmer ground and yes, I w

Re: Timing belt Vs fishing line - 7 years ago

Re: Timing belt Vs fishing line - 7 years ago

If I knew that you wanted a scientific paper to get a feel for how they behave I would not have bothered. But to make a couple of observations on your observations: The lines didn't need to be the same distance apart at the door handle as the angle is very small, the difference between them at 40mm apart and together would be less than .0.0008% Yes, the load on each is 10N ,1.01971621kg for acc

Re: Timing belt Vs fishing line - 7 years ago

Never knowing what to expect with modern materials and having some very similar size steel and Spectra fishing line I checked them out. I tied a 5 meter length of each to a door handle with the other end on a cross piece made from a length of 3mm studding. The cables were 40mm apart and at the center point I had a 20N dynamometer (posh name for a spring scale) Starting with a preload of 2 Newton

Re: Timing belt Vs fishing line - 7 years ago

O.K., so fishing line stretches, but does it stretch enough to be significant on a print? As Viktor points out, the accuracy of a device with a cable drive can have an accuracy, resolution and repeatablility which are acceptable. Even Nylon monofilament should work quite well if that is all that is obtainable but something like Spectra ( ) would be better and just might be better than steel. Mi

Re: Timing belt Vs fishing line - 7 years ago

@ggherbaz, Precision will be worse on a fishing line printer, but more due to the angular bit that you mentioned - it may still be well within acceptable limits though. On the vibration side though you are completely wrong. A guitar string is plucked sideways, not along the length. In any case, the frequency would be much higher on a fishing line and would lead to fewer artifacts. Mike

Re: Ideal hot end design for PLA - 7 years ago

True, but the world conspires to stop us using the best materials. Conductivities of materials from Wikipedia ( ) Diamond, Natural 2200 Copper, pure 483 Aluminium 236 ( at 273K ) Brass Cu 63% 125 Steel, Stainless 16.3 But then I guess diamond is a bit tricky to machine. Mike

Re: Timing belt Vs fishing line - 7 years ago

Although I have never used fishing line or steel cable on a 3D printer I have used 0.7mm nylon coated stainless steel cable ( ) on precision instruments and I think it would work well on a 3D printer. Mike

Re: Ideal hot end design for PLA - 7 years ago

I have always made my heater blocks out of copper but I wouldn't use it for a nozzle as it tends to be too grabby - trying to drill holes less than 0.5mm would break too many drills. Aluminium is slightly better but both brass and stainless steel are pretty well behaved by comparison. Mike

Re: Got 7 minutes to change 3D education? - 7 years ago

Hi Martha, Firstly, please don't put requests in multiple places in the forum. To re-coin a phrase from LOTR " Geeks are subtle and quick to anger". Reprap is an outpost of the land of Geek, a fact that makes the questionnaire that you want members of the RepRap community to fill in less than useful. Perhaps I should clarify a bit: At the beginning of your survey you ask about the standard thing

Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago

The world is a happy place again. I just received some Murata 7BB-27-4 piezo disks. After soldering them on and putting them in the hot jig I got an output of 5V at 105 degrees flatlining just above 110 degrees. While I wouldn't use these directly under the heated bed, they will be fine for use at 80 degrees. Since my plan for fame and world domination† needed a small fully enclosed Delta printer

Re: New print surface material? - 7 years ago

I have seen enough recommendations for PrintBite that I will try it as soon as my printers are in regular use again from a prolonged maintenance period. Having tried most things and found nothing completely dependable for printing ABS I think it worthwhile to note down my partial successes. Note that your experiences may differ PLA is not a problem, 3M blue builders tape works consistently altho

Re: Filament measuring thingy - 7 years ago

Generally if the Q of the resonant circuit is too high then it is not good for a sensor: Temperature, humidity, dust getting in the chamber and just about anything else will all send it off resonance. As far as audibility goes, I did not have it very loud as I used my signal generator directly and it has an impedance of 50 Ohms, but the sound was a nice melodious note.

Re: Filament measuring thingy - 7 years ago

@JamesK, I tested this with a signal generator and a multimeter and found that there was the greatest response at 160Hz but this fell to about 25% both at 100Hz and 200Hz and to about nothing by 400Hz. The output plotted on a usably straight line from a 0.78mm² filament (a 1mm drill bit) to 4.16mm² filament (a 2.3mm drill bit). It is possible that the peak is caused by a resonance effect, the res

Filament measuring thingy - 7 years ago

I have been trying to reduce the number of projects I am working on as they seem to be getting a bit out of hand. One of them seems to be too good to just forget so I am trying to offload it on anybody who wants to pick it up. The device is intended to measure the the filament as it is being passed to the extruder, measuring not the thickness but the cross-sectional area - a slightly flattened o

Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago

The Thingiverse entry has been updated with latest PDF having a newer circuit diagram and enlarged appendix covering the temperature behavior of the piezoelectric disks. I have ordered a bunch of Murata 7BB-27-4 discs to do a thermal comparison. The Murata disks are £0.43 instead of the £0.18 than no-name piezo disks can be purchased for. Mike

Octoprint needs support - 7 years ago

The single sponsor of Octoprint has withdrawn - no reason given. Mike

Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago

The ebay store I got it from was These are obviously offcut prices Mike

Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago

I used about 1/4 of a block of PEEK that cost me £11 from ebay. The big white chunk in the photo is cuttlefish bone which I often use as a cheap high temperature insulator. The sensitivity recovers completely on cooldown. I will do some trials cycling both temperature and pressure to check that there are no more unpleasant surprises. I have tried it both before each print and just to check that t

Re: Piezoelectric disks for Z contact detect and bed levelling - 7 years ago

I have been following up some earlier trials I did with piezoelectric disks at higher temperatures and the results are not as good as my earlier "thwack with the blunt end of a screwdriver" tests seemed to indicate. I made a jig with a heater block to heat the disk up, a spring to preload the disk and a solenoid to release the pressure. The pressure pad and parallel mechanism from the present de

Re: heatmap of the heatbed - 7 years ago

The biggest single thing that influences the temperature of various points on the bed is how well insulated it is on the top - by what is being printed. A large object covering the center of the panel (and presumably the temperature sensor) will hold the heat in there so that the temperature towards the edge of the piece will be much lower. What would be nice is a multi-zone heater so that each

Re: LCD controller board - 8 years ago

There are a lot of LCD controllers on Thingiverse. My own contribution is I think that I have put all of the info that you need in there along with layouts for the PCBs, wiring, STL files for the enclosure etc.. Mike

Re: Piezoelectric disks for Z contact detect and bed levelling - 8 years ago

@Moriquendi, Although the lower value resistor across R6 would lower the sensitivity, it will also increase the lower cutoff frequency, particularly as the smaller piezo sensors will also have a lower capacitance. My guess - and is is just a guess - is that you need a frequency response <1Hz to >500Hz. I found it necessary to reduce the gain to only about 2:1 and also incorporate some hyst

Re: Piezoelectric disks for Z contact detect and bed levelling - 8 years ago

I have been on holiday for the last couple of weeks and am pleased to see that this thread hasn't died. @Moriquendi, Nice job. How sensitive is your setup? (light finger tap or rap with the blund end of a screwdriver?) @Ralf, Thanks for putting up the leaded circuit. I used SMD as I thought it may be an idea to put the amplifier close to the piezos (not necessary) and selected the semiconductor

Re: Another reason not to use a glass bed - 8 years ago

The failure mode for glass is catastrophic - it does not get a little gouged or have a tiny bend. I ran two of my printers for years with only a heater directly under a 3mm glass plate without trouble until I changed the cooling of another part of the printer which was directed over the build stage and got a whole series of broken glass plates My guess is that the failure reported by DD is cause

Re: Piezoelectric disks for Z contact detect and bed levelling - 8 years ago

A quick passing note. I noticed this on a forage for information I don't know how well such a direct input would work but if it does then using piezo disks for bed leveling is potentially the cheapest accurate bed sensor around (about £2 in parts) Mike

Re: Piezoelectric disks for Z contact detect and bed levelling - 8 years ago

The piezo disks are now working very sweetly on my Mendel Prusa. In order to get it immune to the crosstalk from the X and Y movements I had to reduce the gain of the amplifier from about 5 to 2 and put a bit of hysteresis on the comparator. The red trace below shows the output of the amplifier op-amp showing the deceleration noise. The small sineywave stuff from about half way is Z motor artifa

Re: Piezoelectric disks for Z contact detect and bed levelling - 8 years ago

One of the things I looked at was a Murata document at . There is a bunch of graphs on page 9 - although the aging is at 85 degrees I assume that they had no interest in looking higher for their needs. I did find something in Wikipedia about time dependent dielectric breakdown, but that implies a sustained applied voltage but no voltage is applied in this kind of sensor. I am fitting both my De