I was quite intrigued by reports that piezoelectric disks would not be suitable at the temperatures of heated beds. The temperatures given in various data sheets were 85C for both operation and storage, but this is just the "industrial" temperature classification. RepRappers have used wirewound resistors and thermistors way beyond their datasheet values for years. Looking at the construction of pby leadinglights - General
I just looked at both Force Sensitive Resistor and Piezoresistance on Wikipedia and I stand corrected. Load cells would be nice but where can you get such a beast at a hobby price? Mikeby leadinglights - General
Thanks Roxy, that looks like it will work. I have almost no skills with high level languages (but was useful back in the day with assembler). I will try my hand at some tinkering. Mikeby leadinglights - Firmware - Marlin
With my fingers crossed to ward off Murphy and other malign spirits, the present setup looks good as-is with Delta printers and hopefully should work with Cartesian printers. Piezoelectric materials are a lot more sensitive than I thought before I tried the disks. Below is a table from Wikipedia showing a comparison between Peizoelectric and Piezoresistive (FSR) sensors. Mikeby leadinglights - General
I reduced the gain from 5:1 to 2:1 and incorporated a bit of hysteresis. Also added an extra capacitor to the comparator and changed the LED driver to a P channel device as it is harder to pick up a LED flashing off than one flashing on. PDF of schematic at . Mikeby leadinglights - General
QuoteMoriquendi .... This is what bothers me, any (ok, any sensible movement) movement on a delta requires moving three axis, tuning that out has been a headache in the past. I'm assuming that the false triggers are a mechanical (vibration) issue rather than an electrical interference one? ..... Moriquendi I eliminated electrical interference early on, the spurious triggering on a Cartesian prby leadinglights - General
First I must apologize for asking a question when I haven't yet tried Marlin and have spent only about an hour reading about it and viewing the source code. My question is, when Z probing, is there a way of having a short delay between each movement in the XY plane and the Z down movement? The delay would have to be something of the order of 100ms. The significance of my question is that I haveby leadinglights - Firmware - Marlin
Is there any way to introduce a short delay, perhaps about 100ms, between an X or Y movement and the down Z movement when Z probing? The significance is that the piezoelectric disk sensors that I am working on ( ) are sensitive enough that they sometimes trigger from the deceleration of the hot end between each Z measurement. Z_PROBE_START_SCRIPT applies only to the start of a a set like G29by leadinglights - Repetier
Can I gently point out that I was linking to a URL that showed a technique that many people don't know about. I didn't say that it was anything new - I first used it at least 25 years ago on injection molded parts. Mikeby leadinglights - General
I saw this on 3ders.org I thought that it was a nice clear explanation of how to put brass inserts into prints. I would add though that it is worthwhile having a long brass screw in the insert so that it can be tweaked to be upright to the print. Mikeby leadinglights - General
@Moriquendi. Higher frequency noise from the motors is damped by the amplifier filter cutoff and problems are almost purely with movement noise from the X and Y carriages. There are a bunch of false triggers at the end of each X or Y travel and even more if both X and Y are active. I am fairly sure that just reducing the sensitivity a bit (a mosquito cough will trigger it at the moment) and by inby leadinglights - General
QuoteMoriquendi I've been following this thread with interest, finding an accurate z-probe has been bothering me for as long as I've had my printer. I've been playing with some 20mm piezo transducers and I think you might get a cleaner response by flexing the disk rather than squeezing it. I tried mounting my transducers over a hole so they were only supported by the edge and pressing on the cenby leadinglights - General
I think that it is mostly mechanical. With only slow movements using a 3 point G29 I just got the following: 14:01:18.234 : Z-probe:9.63 X:40.00 Y:40.00 14:01:29.890 : Z-probe:9.68 X:140.00 Y:95.00 14:01:41.453 : Z-probe:9.58 X:40.00 Y:130.00 14:01:46.265 : Z-probe average height:9.63 14:01:46.265 : X:40.00 Y:130.00 Z:10.000 E:0.0000 14:03:11.109 : Z-probe:9.61 X:40.00 Y:40.00 14:03:22.718 : Z-pby leadinglights - General
I suspect that there is already a delay in the Repetier software between move and sampling but I want to understand the electrical and mechanical side as well as possible before asking Repetier for a tweak or software work. Mechanically, the false triggering could be from the judder on the end of movement. Electrically there could be oscillation in the comparator - it was clean on the bench but bby leadinglights - General
Having just done several hundred M30 commands from Repetier Host, I do know some things. Repeatability is tremendous - corners can vary up to ±20µm between runs in the same place but only quantization differences are found further in. There is either mechanical noise or electrical noise causing sequences like M32 or M29 to fail. This is announced in the log by . 11:31:08.046 : Error:z-probe trigby leadinglights - General
The three sensors are at:- P1 X=40, Y=50 P2 X=130, Y=90 P3 X=40, Y=140 Early on I did have a problem with the sensors which only happened because there was a bit of a mismatch, one sensor was giving nearly twice the output of the other two. Once I made sure the output was similar then the problem went away. I don't think that even unmatched piezo disks will give a problem if they are conby leadinglights - General
While they do change a little, the 'bad' squares do seem to be in the much the same pattern. There are quite a lot of possible sources of the randomness, slop in any of the linear bearings, sticktion in the Z carriage, dynamic movement in the frame caused by movement of the X and Y carriages and movement from the outside world - not to mention electrical noise. I am planning to put in a patch panby leadinglights - General
I don't think that the contact time is a problem. Generally the output will go low on contact and remain low for some hundreds of milliseconds or until the pressure falls - which only happens when the nozzle is lifted. Looking carefully the height map shows amazing repeatability, within ±10µ over many clean runs but variations of as much as ±300µ on a few spots. This behavior almost shouts mechanby leadinglights - General
It now all works very well and is exceptionally sensitive. Maximum deflection of the build stage at the corners is less than 0.05mm and contact pressure is less than 50gf maximum. Repetier firmware reports an occasional "g29 leveling failed!" which I am investigating. Most likely causes are the mechanical or electrical noise. The STL for the printable parts and a description, construction notesby leadinglights - General
I think that I will keep the three channels separate to get over the "three legged table" effect. Three comparators with open collector outputs can be "wired or" together. I seem to remember such a beast with powerful built-in input protection. A bit more speculative is to use a single sensor on only one leg but with an active full-wave circuit so that upside-down pulses from the side furthest fby leadinglights - General
The peak and is reached only after about 100ms. Ideally the first couple of milliseconds should be used where it may be only a few 10s of millivolts. There is also three sensors connected in parallel and this attenuates the signal to about 33% of the single transducer value. The amplifier is actually a voltage amplifier with a gain of about 5 and a bandwidth from <1Hz to 2kHz followed by a cby leadinglights - General
Piezoelectric sensors seem to be a good candidate for bed leveling and Z height setting as they have a exceptional output, they are very cheap and quite rugged. I saw the Youtube video of Njål Brekke piezo sensors and thought that it may be worth trying these in the opposite sense that he uses them: sense the release of pressure under the bed adjusting nuts rather than the increase in presure thby leadinglights - General
Most PCB heaters give out an even amount of heat over the whole area of the bed, but heat is removed unevenly - more at the edges where air rises round them. To make matters worse, the temperature is measured only at one point - if that point is covered by a print then it will get hotter for the amount of heat energy and un-insulated areas further from the thermistor will be cooler. If the printby leadinglights - General
If you re-read what I said, I referred only to the claim that your BLTOUCH was the end of story. As I said, this is an insult to those who are working in the field to try to get better answers. I would suggest that you take lessons in reading and attempting to comprehend what was written. Mike Quotetjnamtiw Quoteleadinglights When tjnamtiw says that the BLTOUCH is stupid simple, light and easyby leadinglights - General
When tjnamtiw says that the BLTOUCH is stupid simple, light and easy to set up then that is marketing but "End of story" is unhelpful and even plain insulting.by leadinglights - General
I have tried DC42s mini differential height sensor and found it accurate and relaible. The only problem I have with it is that there is an additional step needed if you change your nozzle - the height difference between the sensor trigger point and the true nozzle height needs to be set if there has been any change or adjustment. I have been doing some trials on the piezoelectric disk method - tby leadinglights - General
Just to pick up on one point - there are too many to address everything. If colour is the object in having more than one head then an external machine that cuts lengths of filament and welds them would be a good start. However, I am not too artistic and multicoloured Yodas are only of passing interest. When it comes to multiple material printers however, you would have my full attention. Considerby leadinglights - General
Back when I made my first Prusa Mendel printer with Wades extruder I made a jig from a block of nylon to hold two 608 bearings with a groove for the boltI held this in a vice and used an M2 tap to hob the bolt. I have now made a dozen or more hobbed drive gears both on bolts and on 8mm ground shaft and have not found any need to replace it. To make the jig I did need a lathe to cut the holes forby leadinglights - General
One problem with using designs from the CNC world is that there may be a number of swaps between heads on a single layer and these may need to be rapid. An example is in laying down support material where a layer may involve two heads for perhaps the larger part of the print. Mixed materials like building flexible hinge material into a rigid part are another example - adding a different colour anby leadinglights - General
I have been trying for some time to do make just such a mechanism to swap working heads for a printer. Like you I think that the next logical direction for an FDM printer to go in is to have additional functions - such as placing components - e.g. nuts into cavities, electronic components etc.. The approach I decided upon was to have the bed moving in both the X and the Y axis while a bunch of hby leadinglights - General