search coil housings 3D printing

[bernte_one]

you could finish the surface, if you put your part into a Container with some acetone
take a kitchen paper, drop some acetone over it then fix it on the upper part of the Container (the cover)
maybe a metal box for danish cakes
the 3d printed part lays on the bottom of the box, wait some minutes

[The Urban Prospector]

you could finish the surface, if you put your part into a Container with some acetone
take a kitchen paper, drop some acetone over it then fix it on the upper part of the Container (the cover)
maybe a metal box for danish cakes
the 3d printed part lays on the bottom of the box, wait some minutes

Hmm interesting idea, I am not to worried about surface finish at this stage, more about function with me, my phone camera can see way better than my naked eye so tends to show up all the print lines and blemishes much more than I can see in the real world, the prints look quiet good in real life. I did try soaking some PLA in Acetone over night to see if it dissolved but it didn't, I also did the same thing with ABS and not much happened with that either, both plastics may have been a little softer but I am not sure, I did this because someone told me you could make a sort of paste with ABS and acetone to help 3D models stick to the print bed better. Models can be sanded and even painted to a really good finish I have noticed, lots of people finish there models off quiet well on thingiverse.com.
Will try what you said anyway with some small prints and see if it works.

[Qiaozhi]

Just posting the finished pics of my fully 3D printed Surf PI 1.2, it came out really good and functions as intended.

That's a really nice job. I'm impressed!

[6666]

Something strange I noticed is that when I snapped the 2 housings shut around the coil I lost 2" -3" inches in detection depth

Just for interest what do you read with your multimeter on high scale resistance around the housing ?

[Koala]

Great job. Very professional.

[The Urban Prospector]

That's a very good question 6666 which I haven't tried, I am very much an amateur with electronics and color blind to make things worse, I was also wondering if I should have had the detector coil housing earthed as well?, the Surf PI circuit board is as yet not properly pinned down and earthed in the board housing either, I was very surprised when my Surf PI actually worked when plugged in first time, even more surprised it seems very reliable, chirpy and fast, loves coins, gold, nails, hairpins, stubby tops and large iron chunks, lol, I have a cheap multimeter and I am considering purchasing my first oscilloscope. But how do I set the the multimeter to check the scale on the housing if you don't mind me asking?
Before putting coil in housing I was getting over 12 inches on Australian 50 cent pieces, 9 to 10 inches on most other Australian coins, 9 inches on a 9ct 3.5 gram gold ring and 3 inches on a 1/2 gram gold nuggets, after placing coil in housing about 9 inches on 50c, 6-7 inches on most coins and the ring, and about 1- 1.5 inches on the 1/2 gram nuggets.
I might add to this when I had a Faraday shield using aluminum tape the detector lost a similar amount of depth, but when using the shield I didn't noticed much further reduction in depth when placed in printed housing, I didn't do tests and take notes on exact figures then either though.

[Chet]

Great job on the housings.

The ohms scale is normally 200, 2000, 20k, 200k, 2000k/2m, 20m. Test the meter by setting it on 2000k; wet your thumb and first finger; place the two probes about a 5 mm apart and squeeze them between your finger and thumb. You should get a reading of around 500k it will vary with pressure and slight movement.

Wash off any sea salt that may be on the coil. Now place the two probes 5 mm apart anywhere on the plastic and see if you get a reading. Try several places on the plastic. If the meter doesn't get a reading then the plastic is non-conductive.

If you get a reading then turn the scale down one setting and measure again. Keep doing this until the meter no longer gets a reading. You can also vary the spacing between the probes. The final readings will indicate the conductibility of the plastic.

If it is conductive then earth/grounding will be required. And further testing will be needed to determine the effect on the detector.

Regards,
Chet

[The Urban Prospector]

Great job on the housings.

The ohms scale is normally 200, 2000, 20k, 200k, 2000k/2m, 20m. Test the meter by setting it on 2000k; wet your thumb and first finger; place the two probes about a 5 mm apart and squeeze them between your finger and thumb. You should get a reading of around 500k it will vary with pressure and slight movement.

Wash off any sea salt that may be on the coil. Now place the two probes 5 mm apart anywhere on the plastic and see if you get a reading. Try several places on the plastic. If the meter doesn't get a reading then the plastic is non-conductive.

If you get a reading then turn the scale down one setting and measure again. Keep doing this until the meter no longer gets a reading. You can also vary the spacing between the probes. The final readings will indicate the conductibility of the plastic.

If it is conductive then earth/grounding will be required. And further testing will be needed to determine the effect on the detector.

Regards,
Chet

Thanks for that advice Chet, I tried this and I am not get any reading on the coil housings so it must be non conductive, so why I loose several inches is still a mystery to me.
I still would like to try some different shielding materials after being unsuccessful with ally foil tape, like carbon or something, but not sure this will fix the problem or not, until I work it out I can't really seal the coil up and take it into the water.

[Chet]

Try to backtrack on what you may have done to change the characteristics of the coil circuity. Such as compressing or loosening the coil windings will change the inductance. Modifying or changing the cable between the coil and the detector will change the capacitance across the coil. Its also possible that the damping resistor is at critical value that is allowing the circuit to slip into a less sensitive operating point.

For shielding some have had good results with a conductive graphite spray paint that is used on farm equipment and truck beds. It has been discussed in some of the other threads.

Regards,
Chet

[Qiaozhi]

I am not get any reading on the coil housings so it must be non conductive, so why I loose several inches is still a mystery to me.

Take an object that you've 3D printed, and wave it in front of the coil. If it's detected, then the material supports eddy currents. In that case, when you wrap it completely around the coil, the signal will be reduced.

Looking at the following link -> http://www.matterhackers.com/3d-prin...lament-compare
I don't see a mention of any metallic content added to PLA.

[WM6]

Great job. Very professional.

Agree, excellent.

Now we can even skip design of a detector, and go directly to 3D-printed finds, as desired.

[The Urban Prospector]

Take an object that you've 3D printed, and wave it in front of the coil. If it's detected, then the material supports eddy currents. In that case, when you wrap it completely around the coil, the signal will be reduced.

Looking at the following link -> http://www.matterhackers.com/3d-prin...lament-compare
I don't see a mention of any metallic content added to PLA.

Yeah thanks I just tried waving a PLA coil in front of the detector and not even the slightest whisper signal, I even tried rubbing it on fabric to see if I could build up some static in it but nothing, so I think it would be safe to assume PLA does not support eddy currents nor is it conductive, so maybe some of the other things chat spoke about need looking at next, will try making a completely new coil and housing soon and see if the same thing happens, maybe when I pushed the wires inside the coil radius to fit them through the housing hole that caused the problem, but I thought re-tuning may have overcome this, but it didn't.
There is no metal in PLA, PLA is non toxic, made from corn starch and designed for human body implants that break down inside the body so they wouldn't put metal in it. There is however a conductive ABS that was released recently that was designed for printed circuits (bottom of that page you linked me to), I have been considering buying a roll of that and seeing if I could actually print a spiraled coil onto a flat thin printed disk and then print another flat disk over the top sealing it up, that would make water proofing a lot easier and it would be ultra light weight and a revolutionary way of making coils, I only wonder how I would solder the wires on, or maybe I could print tiny plug holes in it to.

[The Urban Prospector]

Conductive ABS Filament is a modified version of our standard ABS filament which has a resistance of 1200 ohm/cm.
Maybe printing a coil from this stuff was a bad idea after all, way to much resistance, but shielded housings maybe?

[Chet]

Conductive ABS Filament is a modified version of our standard ABS filament which has a resistance of 1200 ohm/cm.
Maybe printing a coil from this stuff was a bad idea after all, way to much resistance, but shielded housings maybe?

It might work well for a shielded housing although conductive paint shielding is usually much lower in resistance. On your sensitivity problem make sure your batteries are still up to full voltage when the detector is on.

Chet

[The Urban Prospector]

Yeah I put a freshly charged set of 3 PCB protected 18650 batteries in after I finished tuning and snapped the case shut, new batteries only cycled once, tested with volt meter after charging and all 3 were at about 4.14 volts.