[smarbaga]

it is the techniks wet.

[samco]

This is done on our gantry mill.

http://www.electronicsam.com/images/KandT/cbottom.JPG
http://www.electronicsam.com/images/KandT/ctop.JPG
(The reason the holes don't line up towards the top of the of the circuit board (ctop.jpg) is we had not squared the gantry at that point)

Emc2 as the machine control. http://www.linuxcnc.org/
Using a "rotozip" as the spindle.
Eagle pcb software. http://www.cadsoft.de/
Pcb-Gcode http://groups.yahoo.com/group/pcb-gc...guid=148844392
engraving bits from here. http://thinktink.com/stack/volumes/v...e/mechmill.htm

The board was held down by a wood top vaccum box.

over all very powerfull.

sam

[pminmo]

samco, outstanding. Which specific bit do you use from thinktink?

[samco]

Thanks. I just have too many hobbies

60° tip, 1/8 in. shank, 1.42 in. (36 mm) long solid carbide mechanical etching & engraving bit - loose bits
Stock# EM2E8-0625-60V-001

samco, outstanding. Which specific bit do you use from thinktink?

[bkinman]

Nice results samco! Etching circuit boards on the mill I build is one of my end goals.

I finally broke down and bought myself some techniks press n peel blue... I read that this stuff is made out of mylar with some special coating on it.

I wonder how a plain sheet of thin mylar would work for toner transfer.

[bkinman]

Not only did I order technics press-n-peel blue, but I decided to go the full nine yards and order a dremel drill press along with some resharpened wire guage drill bits as well.

To top it all off I have decided to make my own stepper driver! I will be sending the stepping sequence out my parrallel port to a ULN2803A (darlington array).

I believe that I should be able to drive an 8 wire unipolar stepper or two 4 wire bipolar steppers with this setup.

The ULN2803A only supports 50@500mA per darlington pair, so I will not be able to driver very big motors.

I have attached the Eagle files for this driver, as well as a JPG of of the schematic.

Any response to what I have would be great. This is my first time using Eagle, as well as my first time designing a circuit (I have hardly even messed around on a breadboard! :violin

[ServoGuy]

I think you will like the blue film, just keep your boards super clean, and preheating can help. I have had my best results with an el-cheapo laminator. Harbor Freight sells those for <$25.00 I think.

About your design, I would recommend a couple of things in general.
1. Use decoupling caps for the power pins on all IC's, .1uF is always a good starting point.

2. Do the same for your power inputs, 1 - 10uF, ceramic.

3. Your traces to the motors are too thin; they will get hot and dissipate the power that should be going to the motors. The easiest way to check trace temp rise with Eagle is to use the "traceres.ulp" which can be downloaded from Cadsoft.de. For your application, try to shoot for a temp rise of < 10degC.

4. For a single layer board, if possible, you ought to have a ground plane on the top side of you board. It will help with electrical noise and thermal issues, and it save a lot of enchant.
• Use the Polygon tool draw a rectangular box around your board on the same layer as your traces.
• Now using the Name tool rename the box GND. At this point the box should become flooded.

5. Move traces around to ensure shortest signal path for the high current traces, and to allow the copper pour to get around without voids.

6. If you get a chance post the schematic, I may have some comments on that as well


For a 1st time PCB, I think your board is looking really good. It takes a lot of practice and patience to get where you feel confident about how a new board design is going to turn out. I still get surprised on occasion….

Not only did I order technics press-n-peel blue, but I decided to go the full nine yards and order a dremel drill press along with some resharpened wire guage drill bits as well.

To top it all off I have decided to make my own stepper driver! I will be sending the stepping sequence out my parrallel port to a ULN2803A (darlington array).

I believe that I should be able to drive an 8 wire unipolar stepper or two 4 wire bipolar steppers with this setup.

The ULN2803A only supports 50@500mA per darlington pair, so I will not be able to driver very big motors.

I have attached the Eagle files for this driver, as well as a JPG of of the schematic.

Any response to what I have would be great. This is my first time using Eagle, as well as my first time designing a circuit (I have hardly even messed around on a breadboard! :violin

[bkinman]

Thanks ServoGuy. I check into the changes you mentioned and post my results asap.

As for my scematic. Isn't that the schematic which was posted above? (in PNG format)

edit: it appears that traces.ulp is broken on line 22. I cannot figure out what the problem with the script is.

[PsyKotyk]

I've had hit-or-miss results with toner transfer, until I started using a power drill with an abrasive pad for roughing up the board before transferring. It made a huge difference to my success rate, and was much much faster than using sandpaper or steel wool. I'd still rather use my CNC to mill outlines, but it's not quite ready for that yet.

[Barry_ward]

I've been fiddling around with this for years.

The best results that I've gotten have been with Laser printing on Epson glossy inkjet paper.

Yes, toner on inkjet paper. I use an HP6550 color laserjet. It seems to slather the toner on nice and thick.

See http://www.barryfish.com click on the PCB Fabrication link

The only way to get a good transfer is with heated rollers like a laminating machine. An iron will only give sporatic results. Make absoultely sure that the board is clean and grease free.

If you cnc the holes, deburr them before transferring.

For double sided boards, tape the printed images face to face on light table or window (bright light used to align front and back holes)

Slide the (drilled) board between the aligned artworks and use the light again to align them.

Tape the edges.

Laminate.

Peel while boards are warm. All of the toner should transfer.

Etch with warm ferric chloride.
Use a pump to flow the ferric over the board sides. With good FeCl3, warmed and pumped you can have good boards in a couple of minutes. It's well worth the prep time to set up a pump and heat lamp.

Finish by using an SOS pad to scrub the toner off under warm water. Good cleaning of the board keeps them from ever turning green.

If you dont mind copper color, just use wax or Pledge (spray wax furniture polish) to buff and protect the copper. Or if you are finickey, solder plate the boards by coating them with flux then use an iron an solder wick to tin them with a scrubbing action.

I still don't have a good easy way to plate the holes so I use Z wires or have a service company do the whole job.

regards,

Barry

[smarbaga]

nice boards, berry.
if you really need your boards tinned :
1. solder all the traces, quick as not to let the heat from the iron lift them.
2. prepair a moleskin cloth folded about 4" x 4"
3. soak the cloth in lard for about 10 minuits.( let it cool and dry )
4. place some cooking oil in a pan and heat until it is hot enough to soften the solder on the pcb.
5. place the soldered board in the hot oil pan for a few minuits. ( 1 or 2)
6 pull it out with longnoze pliers and wipe the solder off with the moleskin cloth.
the traces will be tinned and as smooth as glass, the cloth can be used over and over.
in days gone by, i used to do pot wipping if communication cable splices.
this involved pouring molten led over the led sleeve ( from 2"-12"+ in dia) and wipe the lead at the seames and end so air would not escape.

[sswitaj]

I noticed that the subject of using an old HP penplotter for PC boards has come up.

I have one of these (a 7475A, I believe) sitting new, and apparently unused, in a box in my shop.

It came with some test equipment from a company we bought out some time ago, they apparently had a legacy application that used plotters, and kept one as a backup, I never had a reason to even take it out of the box. I know nothing about it's condition, nor do I make any guarentees, but if anybody wants it, it's theirs for the price of shipping.

Contact me at steve at stealthac dot com. (obviously, you have to de-spam the address)

[bkinman]

Yes Barry, Very nice results!

Hey sswitaj, I have emailed you regarding that plotter. I would be very interested.

[chad123]

I have been making boards on and off for the last 15 years and after trying about every method I have found the photo to be the best.

It can be a pain at first but when you get it figured out you can produce some stunning results. I regularly make double sided fine pitch (44 pin tqfp ) SMD boards. I still have to use wire for vias but I can easily get 8 mil traces.

I use presensitized boards, heated ferric chloride, and most importantly a UV fluorescent lamp. It takes me on average 7 min for exposure 30 seconds to develop 30 seconds to wash the board and around 10 min for etching.

I will never go back to doing it any other way, aside from having some pro made boards for things that have too many vias or really tiny smd stuff.

I have purchased stuff from web-tronics.com. They have good prices and have always come through. I got the UV kit and one of each low cost etchant tank kits. You can order the bulb alone for 8 bux and put it into any fluorescent holder from any home center. It makes a huge diff. While you are at the home center buy a piece of replacement glass to hold down the artwork.

I also like to flip and invert so the toner side on the transparency is in contact with the pc board, i find i get slightly sharper traces with less undercut. The photo method does take some time to get straight but when you get it it works great and you can bang out some nice boards.

here is the link to the pcb supplies.

http://www.web-tronics.com/printed-c...-supplies.html

Oh yea as for you building your own stepper driver with the darlington array don't bother. There are zillions of chips that will drive a stepper with just a couple of external simple components. As a bonus all you have to do is give it motor power and step and direction input (like from mach- from the parallel port).

Something like this would work well

http://www.allegromicro.com/sf/3967/

Just make up a company name and request some "evaluation samples" and they will send you a few for free!!

Chad