Vacuum forming coil housings.

[simonbaker]

Well I finally got everything ready for making some coil shells. One thing that was real apparent with the first two tries, is it is not as easy as Dfbowers makes it seem with his fine work. But then people who know what they are doing make it look easy even if it is not. My thanks to Don for taking the time to document and post his work with vacuum forming. This is what got me started in the first place. It will no doubt take a few more tries before I have the technique figured out.

A few things I have noticed:

1. Get the plastic hot enough so it sags several inches. Once it starts to drop, it goes fairly fast.

2. You need to move quickly after taking out of oven and placing on vacuum table. Pretty much have one shot at it. So I made side wall for locating frame so it is just a matter of stuffing it into a corner and dropping down onto the table/form.

3. When it is on the table, the heat gun does not provide enough heat for the vacuum to pull it the plastic tight to the form. I melted holes in the first two tries. I got better luck with using my hands (with gloves) to quickly work the plastic into tight spots. You only have a short time before the plastic gets hard.

4. It was easier for me to rough trim the outside of the shell and place it back on wood form and then use the heat gun on low power and heat a small area and hold it tight to the form until cool and then move to the next area. If you do not get into a hurry this works.

5. The area between the clevis ears does not form properly. I drilled a hole between the ears to put more vacuum in that area and it is better but now the vacuum makes a hole without completely pulling the plastic tight to the form. I can trim this once it is filled with epoxy but is not as neat looking as it should be.

6. I wonder if it is possible to have too much vacuum suction for a given hole size on the table. One two of the shells, the vacuum sucked plastic right through the hole. Thinking maybe smaller diameter holes and more of them. As I recall I used a .19 inch diameter drill when I made the table.

The first picture is vacuum table, form and the best of three tries.
Second picture is close up of best shell.
Third shows what happens with too much use of the heat gun.

I think I can salvage the first attempt. It should make a usable but ugly looking coil

Anyway that is my tale of coil making for today

Jerry

Thanks Jerry (and Don) for excellent report on this subject and the various subtleties.

It's too bad you can't put the form in the oven under the plastic and let it just melt down over the form. I guess that's what the really high-end plastic forming devices do, combine oven and vacuum table. I like the low-tech approach, but clearly takes skill and practice.

I have to go make a grilled cheese sandwich now...

-SB

[dfbowers]

Well I finally got everything ready for making some coil shells. One thing that was real apparent with the first two tries, is it is not as easy as Dfbowers makes it seem with his fine work. But then people who know what they are doing make it look easy even if it is not. My thanks to Don for taking the time to document and post his work with vacuum forming. This is what got me started in the first place. It will no doubt take a few more tries before I have the technique figured out.

A few things I have noticed:

1. Get the plastic hot enough so it sags several inches. Once it starts to drop, it goes fairly fast.

2. You need to move quickly after taking out of oven and placing on vacuum table. Pretty much have one shot at it. So I made side wall for locating frame so it is just a matter of stuffing it into a corner and dropping down onto the table/form.

3. When it is on the table, the heat gun does not provide enough heat for the vacuum to pull it the plastic tight to the form. I melted holes in the first two tries. I got better luck with using my hands (with gloves) to quickly work the plastic into tight spots. You only have a short time before the plastic gets hard.

4. It was easier for me to rough trim the outside of the shell and place it back on wood form and then use the heat gun on low power and heat a small area and hold it tight to the form until cool and then move to the next area. If you do not get into a hurry this works.

5. The area between the clevis ears does not form properly. I drilled a hole between the ears to put more vacuum in that area and it is better but now the vacuum makes a hole without completely pulling the plastic tight to the form. I can trim this once it is filled with epoxy but is not as neat looking as it should be.

6. I wonder if it is possible to have too much vacuum suction for a given hole size on the table. One two of the shells, the vacuum sucked plastic right through the hole. Thinking maybe smaller diameter holes and more of them. As I recall I used a .19 inch diameter drill when I made the table.

The first picture is vacuum table, form and the best of three tries.
Second picture is close up of best shell.
Third shows what happens with too much use of the heat gun.

I think I can salvage the first attempt. It should make a usable but ugly looking coil

Anyway that is my tale of coil making for today

Jerry

Good work Jerry! There is a learning curve but you are most of the way there!! I can suggest a few things that may help. It sounds like you have everything pretty much figured out. Here is how I got around some of the problems that you ran into:


1. Time/temp is so critical. Too hot and it melts. Too cold and it does not form. I have been erroring on the side of too cold lately. I have a stopwatch and pay close attention to exactly how long it stays in the oven. Also, I always start with a cold oven, preheat, and then put my plastic frame in the oven. I have been doing them one at a time lately as the second one I put in the oven will generally get hot much faster.

5. I did not elaborate on the ears that much, but I did the same thing with drilling a hole on the form between the ears to help get the air out. I have a small wooden tool that just fits between the ears. While the plastic is still soft, I just press the tool down between the ears. It comes out perfect most of the time.

Don

[Jerry]

Third time is the charm....... sort of.

Well I finally got everything ready for making some coil shells. One thing that was real apparent with the first two tries, is it is not as easy as Dfbowers makes it seem with his fine work. But then people who know what they are doing make it look easy even if it is not. My thanks to Don for taking the time to document and post his work with vacuum forming. This is what got me started in the first place. It will no doubt take a few more tries before I have the technique figured out.

A few things I have noticed:

1. Get the plastic hot enough so it sags several inches. Once it starts to drop, it goes fairly fast.

2. You need to move quickly after taking out of oven and placing on vacuum table. Pretty much have one shot at it. So I made side wall for locating frame so it is just a matter of stuffing it into a corner and dropping down onto the table/form.

3. When it is on the table, the heat gun does not provide enough heat for the vacuum to pull it the plastic tight to the form. I melted holes in the first two tries. I got better luck with using my hands (with gloves) to quickly work the plastic into tight spots. You only have a short time before the plastic gets hard.

4. It was easier for me to rough trim the outside of the shell and place it back on wood form and then use the heat gun on low power and heat a small area and hold it tight to the form until cool and then move to the next area. If you do not get into a hurry this works.

5. The area between the clevis ears does not form properly. I drilled a hole between the ears to put more vacuum in that area and it is better but now the vacuum makes a hole without completely pulling the plastic tight to the form. I can trim this once it is filled with epoxy but is not as neat looking as it should be.

6. I wonder if it is possible to have too much vacuum suction for a given hole size on the table. One two of the shells, the vacuum sucked plastic right through the hole. Thinking maybe smaller diameter holes and more of them. As I recall I used a .19 inch diameter drill when I made the table.

The first picture is vacuum table, form and the best of three tries.
Second picture is close up of best shell.
Third shows what happens with too much use of the heat gun.

I think I can salvage the first attempt. It should make a usable but ugly looking coil

Anyway that is my tale of coil making for today

Jerry

[dfbowers]

Just thought I would mention that my Hays Electronics coil housing came with a strain relief marked Hummel PG7. It looks just like the Heyco model. It seems they do sell it separately for $1.90.
http://www.hayselectronics.com/parts.htm

Merc

Yes, that looks familiar. I have been ordering 3237. PG7 is just the thread size.


http://www.heyco.com/products/sec_02/ltf.html

[Merc]

Strain Relief

Just thought I would mention that my Hays Electronics coil housing came with a strain relief marked Hummel PG7. It looks just like the Heyco model. It seems they do sell it separately for $1.90.
http://www.hayselectronics.com/parts.htm

Merc

[bernte_one]

@ satdaveuk
for the procedure it is not necessary to take an industrial oven or vacuum cleaner.
For my projects i only use standard home tools- i want to show that eveybody can do this by his own at home. My oven works most time on 180 degree celsius (pizza ).
And i tried this too for my plastic sheets it works. My vac cleaner has 1200 watt (middle class).
But if you have professionel parts and tools why do not try them. But pay attention more is not even better. When i write this i must think of tool time with tim taylor

@ simonbaker
in times of emancipation and women are superior because of quote (not because of skill)
it is good that there are some places we can be among us

but if there are any women in forum i love you (because of technical interest)

[simonbaker]

Im I right thinking that the vacum is assembled to the box after its been taken out the oven
I got to talk the mrs round letting me use the oven first.
Ive got a industrial wet dry cylinder vac will that be ok or to powerful?
Thirdly the temperature deflower states is 400f will it melt Lead within the 2 mins its in the oven? or am i pushing the boat out.
The reason why I ask I have skills in sand casting from old, and it would be easy for me to make a lead casting of a 10" DD minelab coil, I cant use alloy etc because I have no means of getting the temp need to melt It, unless you clever folk have a DIY way of doing it.
And I also like to add how greatful and privilaged I am to be part of this team, and once ive sorted my coil maker out which is almost finshed, and got my detector built and up and running , I will able to contribute some more worthwhile information for you all as a big thankyou.
If you were girls i would give you all a nice big wet kiss
Warm regards
Dave

Brings up question: are there any girl members of this forum? If not, why? Are we all missing gene from X chromosome that would bring us to our senses?

[dfbowers]

Don, I would like to produce housings for a model differential sensing head. My loop configuration is DOD as shown below.
My question is how to form robust ears for clevis tube? With your former they will be hollow and will have thin walls.

Mike,

Yes, the "ears" for the clevis are hollow and have thin walls but once filled with exopy they they become extremely rigid. I have not broken one yet. I sometimes even mix in short strands of fiberglass. It is easy to make them as strong as needed.

I think that might be the way that Hays makes theirs as well.

Don

[satdaveuk]

nice! How thick is plastic that you used? What was your form/mold? Which detector is that ?

Im I right thinking that the vacum is assembled to the box after its been taken out the oven
I got to talk the mrs round letting me use the oven first.
Ive got a industrial wet dry cylinder vac will that be ok or to powerful?
Thirdly the temperature deflower states is 400f will it melt Lead within the 2 mins its in the oven? or am i pushing the boat out.
The reason why I ask I have skills in sand casting from old, and it would be easy for me to make a lead casting of a 10" DD minelab coil, I cant use alloy etc because I have no means of getting the temp need to melt It, unless you clever folk have a DIY way of doing it.
And I also like to add how greatful and privilaged I am to be part of this team, and once ive sorted my coil maker out which is almost finshed, and got my detector built and up and running , I will able to contribute some more worthwhile information for you all as a big thankyou.
If you were girls i would give you all a nice big wet kiss
Warm regards
Dave

[taliesin]

nice work

they look strong lugs.all you need now is "bernte_ one" stickers on there .

[bernte_one]

nice! How thick is plastic that you used? What was your form/mold? Which detector is that ?

I used Polystyren best 1,5mm( tried 1mm too but it is critical but possible for coil cover)
the form was cutted by 18mm strong wood plate
this is the surf pi single sided pcb with external battery pack
ond only on off switch all pots are on pcb ( or my little nephew)

[habitbraker]

Here my first vacu formed coil form:

https://fotoalbum.web.de/gast/bernd....Vacuum_Forming

thx to dfbowers and forum for inspiration

nice! How thick is plastic that you used? What was your form/mold? Which detector is that ?

[bernte_one]

Here my first vacu formed coil form:

https://fotoalbum.web.de/gast/bernd....Vacuum_Forming

thx to dfbowers and forum for inspiration

[bernte_one]

as little childs i was a joke to jump into glaswool ahh autsch

no imean this for housing

[taliesin]

tip for fiberglass

strenghten the sensible parts with epoxy and glasfibre
1 liter can 10euro in hardware store in the corner with yacht or boat articles and paints

rub hands and arms with talcum powder to prevent itching ( if you are affected)