Author Topic: adhesives for Delrin/PTFE  (Read 4687 times)

Offline minerva

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adhesives for Delrin/PTFE
« on: August 28, 2012, 05:02:19 PM »
hi guys,
an odd query perhaps, but here goes anyway,
I am currently carrying out some experimentation in the manufacture and use of Solenoids for potential use in an EDM machine.
my first effort using a home-made solenoid was only partially successful, the mechanics proving to be adequate for the job in hand but over an extended period of usage the heat build up within the solenoid was detrimental to the Perspex spool core (slight melt down) Sooooo!, a rethink is necessary. the cheeks of the spool are of  Perspex and were undamaged but the Perspex core was not up to the job. The experts have suggested that a better material would be Delrin or even better PTFE which I intend to try but I pose the question, what if any adhesives will work with these materials - Araldite? Superglue?
I look forward to your thoughts
Terry T AKA Minerva

Offline Bluechip

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Re: adhesives for Delrin/PTFE
« Reply #1 on: August 28, 2012, 05:59:51 PM »
Terry
 
Most of the solenoids I've stripped had moulded, one-piece bobbins. No glue problem ....  :thumbup:
I would suggest turning one up from solid, otherwise use Kite brand SRBP, this glues very easily with Epoxy, better to rough the surface with a bit of coarse glasspaper first ..
This is the stuff:
http://www.directplasticsonline.co.uk/TufnolSheet/Kite/
Use the Whale brand for the rods ..
Dave

 
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Offline philf

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Re: adhesives for Delrin/PTFE
« Reply #2 on: August 28, 2012, 06:46:30 PM »
hi guys,
an odd query perhaps, but here goes anyway,
I am currently carrying out some experimentation in the manufacture and use of Solenoids for potential use in an EDM machine.
my first effort using a home-made solenoid was only partially successful, the mechanics proving to be adequate for the job in hand but over an extended period of usage the heat build up within the solenoid was detrimental to the Perspex spool core (slight melt down) Sooooo!, a rethink is necessary. the cheeks of the spool are of  Perspex and were undamaged but the Perspex core was not up to the job. The experts have suggested that a better material would be Delrin or even better PTFE which I intend to try but I pose the question, what if any adhesives will work with these materials - Araldite? Superglue?
I look forward to your thoughts
Terry T AKA Minerva

Terry,

PTFE is very difficult to stick with anything unless the surface is etched which involves seriously nasty chemicals. Machining a bobbin out of solid PTFE might be OK but PTFE isn't the most dimensionally stable of materials and winding the coils would tend to close up the bore. Delrin probably won't fare much better than Perspex as it's temp rating is similar (about 100 C). PEEK is a much better material which can easily handle temperatures of 200 C. What size do you need? - I have some offcuts in my plastics drawer.

Phil
Phil Fern
Location: Marple, Cheshire

Offline Noitoen

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Re: adhesives for Delrin/PTFE
« Reply #3 on: August 29, 2012, 08:52:02 AM »
For a DC voltage coil you can use a thin wall brass tube for the centre of the solenoid and brass sheet for the sides with a soft solder joint. Just insulate it properly on the inside before you wind the coil. You can use Nomex paper to do that.

Offline HS93

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Re: adhesives for Delrin/PTFE
« Reply #4 on: August 29, 2012, 10:30:31 AM »
Have a look on this site they do a primer that will suite you plus lots of different adhesives

http://www.fivestardistribution.com/


Peter


Primer 9770 clear surface primer for hard to bond plastics
 
A high power clear surface primer for use on plastsics such as: Polyethylene, Silicone, polypropylene, Teflon ( PTFE ), Delrin and nylons etc
 
In the past many plastrics have been hard to bond, this is due to the surface chemistry of the plastic not a defective adhesive, simply wipe this clear primer on and wait a few seconds and the plastic will then be fully bondable with most adhesives, we reccomend a cyanoacrylate for use with this product for plastic bonding.
 
10ml
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Offline minerva

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Re: adhesives for Delrin/PTFE
« Reply #5 on: August 29, 2012, 11:48:01 AM »
Hi guys, many thanks for the instant replies,
the bobbin in question is  42mm in dia and about an inch between the cheeks with a core dia of 15mm this has a 10mm through the centre to take the armature.
Dave
the srbp route seems a viable option and I think this is the way I shall most probably go
phil
thanks for the offer I will willingly pay the postage if you have an off-cut suitable.
Where does one purchase PEEK?
Noiten
another option I wouldn't have considered thanks
Peter
these adhesives seem to be a bit special and not overly expensive if they are all they claim to be

This morning I had a go at resurrecting  the original coil,  increasing the clearance between the armature and the bobbin and remounting on the jury rig for my EDM prototype (which started life as a portable drill stand.)  It seems to work fairly well but as I have no experience of this type of machine only time will tell how efficient it is. Suffice to say it sank a 3/32" hole about an 1/8" deep in about 1/2 an hour but again the temperature in the region of the solenoid is not good and I know it will have to be replaced sooner rather than later.
Once again many thanks for your input.
Terry T


Offline Bluechip

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Re: adhesives for Delrin/PTFE
« Reply #6 on: August 29, 2012, 01:27:54 PM »
Hi Terry
 
PEEK ??? Here ...http://www.directplasticsonline.co.uk/#
 
Click on the top row... PEEK Rod & Sheet
 
PREPARE TO BE TERRIFIED AT THE PRICE   :lol:
 
Can you pie wind the solenoid. ie in sections with a small gap between. There will be less heat build up, you could even fan the thing. Or rewind with a larger CSA wire ??
 
Dave
 
 
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Offline BillTodd

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Re: adhesives for Delrin/PTFE
« Reply #7 on: August 29, 2012, 01:47:56 PM »
Hmmm  More turns & fewer amps required perhaps?
Bill

Offline David Jupp

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Re: adhesives for Delrin/PTFE
« Reply #8 on: August 29, 2012, 01:59:16 PM »
One way to 'prime' many plastics for adhesives is to briefly 'wash' them with a gas flame - obviously not for too long!  Note that the primed surface can deteriorate over time, so glue it as soon as possible.

The bond strength may never be fantastic.    Of course take extreme care with regard to fumes - even plastics as simple as Polyethylene can give off noxious fumes if overheated, the likes of PTFE can be fatal !

Offline philf

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Re: adhesives for Delrin/PTFE
« Reply #9 on: August 29, 2012, 03:06:32 PM »
Hi Terry,

I'm currently on holiday - I'll look what I have in the way of PEEK when I get home. I may have had some 40mm dia but can't be sure.
 
As Bill has already said, can you not get more turns of smaller diameter wire in at a lower current to reduce the heating effect?

Cheers.

Phil.
Phil Fern
Location: Marple, Cheshire

Offline HS93

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Re: adhesives for Delrin/PTFE
« Reply #10 on: August 29, 2012, 04:34:03 PM »
I have been using there products for 10 years Plus they are local to me so know a bit about them , they do a lot of trade work and his hobby is modeling ,so he started to sell some to modelers direct it is good stuff they do tings like flexi superglue with rubber in and the same for epoxy it is great for fiberglass hulls and  prop shafts . a bit of flex instead of cracking.they will also mix specials for you .

peter
I am usless at metalwork, Oh and cannot spell either . failure

Offline minerva

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Re: adhesives for Delrin/PTFE
« Reply #11 on: August 30, 2012, 05:24:28 AM »
Thanks again for all your replied.
 I take it all on board. The blinkers have certainly been removed and valuable knowledge gained.
Bill
 as to the turns and current the original coil was a bit empirical increasing the number of turns until the required lifting force was achieved. I have since read another article which suggests that a different set up might achieve the same result.

kindest regards
Terry T

Offline BillTodd

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Re: adhesives for Delrin/PTFE
« Reply #12 on: August 30, 2012, 06:20:49 AM »
Quote
Bill
 as to the turns and current the original coil was a bit empirical increasing the number of turns until the required lifting force was achieved. I have since read another article which suggests that a different set up might achieve the same result.

Nothing wrong with that approach :)

 Now you know the ampere/turns required you could double the turns, half the current and quarter the heat generated :)


If you have a complicated bobbin or one that needs square holes etc. , 3D printing is an option (I've used it in the past for mic transformer parts)

Bill
Bill