[R-390] Silk screen

[Bob Camp]

Hi

Here's a basic explanation of the process. I'm sure others can 
elaborate further.

The basic equipment is pretty simple. You need:

1) A "nest" to hold the panel you are going to silk screen. Usually 
this is a piece of plywood with a couple of pegs in it to position the 
panel.

2) A screen to do all the work. Industrial screens are made out of 
wire, often stainless steel. For light weight work like panel screening 
you don't have to get very fancy. Local suppliers will probably have a 
range of screens for you to pick between. For this kind of work go with 
one that is not very expensive.

3) A negative to coat the screen with. The screen material is often 
coated with photographic emulsion. You scan the lettering on a good 
panel and use it to generate a graphics file with the data in it. The 
file goes out to the shop that generates the screen and they do the 
photographic process that converts the data in the file to a finished 
screen. They send you the finished screen in the mail.

4) A frame with the screen on it. The frame normally is attached to the 
nest board with some common hardware store hinges. The panel goes in 
the nest and the frame brings the screen down on top of the panel. The 
hinges and pegs on the nest are there to keep everything in good 
alignment.

5) Ink (paint) and something to push it around with (a squeegee). 
Normally on the stuff I do we use an epoxy ink that comes in two parts. 
You mix them up and screen them on. You then bake the finished part at 
125C for about an hour to cure the ink. The ink that is left on the 
screen you clean up with normal solvents.

The odd thing about all of this is that the only thing that costs very 
much is the screen. Everything except the screen probably costs less 
than $25. The screens we use at work are a couple of hundred dollars, 
but they are pretty etched stainless steel screens.

The hard part in the whole process is coming up with the image of a 
good panel. Usually this involves doing a scan of the best panel you 
can find and then playing with a good graphics editor for quite a few 
hours to clean up the result.

FInding a good clean panel to scan can be tough. Simply doing a good 
scan of the panel is harder than it sounds. You may be better off just 
using the scan as a guide and generating new lettering from scratch. 
Matching the type face used is the main challenge. If you can get close 
enough the result will be much better done this way.

Once you have the stuff set up for your first panel you are also set up 
to do lots more of them. I suspect that the original panels were done 
almost exactly by the process described above. With a bit more work and 
a CNC machine you could turn out brand new panels from scratch this 
way.

The other way to do a panel is using lithography. This is a more 
precise process than silk screening and will give better detail on the 
finished product. In order for it to work properly the panel you are 
printing must be absolutely flat. It also takes more equipment to do. 
There may be some panels out there that were done this way but I doubt 
it.

	Take Care!

		Bob Camp
		KB8TQ






On Oct 9, 2004, at 5:30 PM, Francesco Ledda wrote:

> Hi,
>
> I am bebuilding an MRC-108.  The control heads needs to repainted and
> silk-screened.  I would like to do the silk-screening myself.  Would 
> it be
> possible for anybody on the list to describe the  process of 
> silk-screening
> from start to end?
>
> Regards,
>
> Francesco Ledda
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Dan Arney
> Sent: Saturday, October 09, 2004 12:16 PM
> To: Bob Camp
> Cc: R-390 HF Receiver List; K2CBY at aol.com
> Subject: Re: [R-390] Calligraphy Pen for Non-engraved Front Panel
> Lettering
>
>
> Bob, I have both master silk screens for the R-390-A front and rear.
> I also refinish the panels by commercial stripping, cleaning, run
> through a time saver to eliminate surface scratches, powder coat and 
> the
> silk screen. $150.00 exchange plus UPS.
>
> Hank
> KN6DI
>
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