PCB Router advice.

[EvilBarry]

Hi all, sorry if this is in the wrong forum but theres so many sub-forums that i'm a little lost.

I'm after a little advice on PCB routing. Basicly i'm after a small home build engraver to do PCB able to take euro card size boards 160x100mm and accurate enough to do moderate SMD componet pabs.

Any one have any suggestions?

Many thanks

Barry

[kreutz]

Barry;

I have been helping a friend build a machine for the same purpose. We are doing tests on it and I will probably hang a video on Youtube. Our experience so far:

-Z axis does not need to travel more than 4 inches, but extra travel will be of help when replacing bits.

-Z axis does not need to have high accuracy and backlash is not a problem if you use a "floating head".

-A floating head is needed in order to precisely control depth of cut, independent of the PCB clad conditions. We are allowing 0.1" float on the software, setting zero to the top side of the PCB, but our floating head will allow to float a few inches if required for other purposes.

-For X and Y look for the best lead-screws/nuts with NO backlash, we used grounded ball-screws and zero backlash nuts (they came with the donor machine).

- Spindle: 30000 rpm DeWalt DW660.

-Steppers are 425 Oz-in driven by Mardus-Kreutz micro-stepper boards.

-Tested cutting speeds are 120 ipm X and Y, 25 imp Z. We haven't tested beyond that, rapids are 330 ipm.

-Depth of cut or drill adjusted by a 0-2 inches micrometer.

-For the floating shoe (the part that slides on top of the PCB) we used a turned PVC irrigation pipe, that also serves as a vacuum cleaner tip. The floating head "floats" on a short linear rail with 4 inches of travel, mounted on a Z axis with 9 inches of travel. There is a weight compensation spring on the floating head used to control the drilling force.

We used two 1/8" pins for accurate registration of the two sides, each pin about 0.5 inches outside the board contour at exactly half of the X dimension, Bottom side is mirrored on the X axis. The two pins are flush with the top of the PCB, in order to avoid collision with the floating shoe.

In our tests we have been able to control depth of cut to 0.001" and draw 0.002" ( 0.002" deep) annular rings around all 0.032" drill holes in a test board 2.5" x 3.0" approx. using a 60 degrees V carbide bit. Bottom side registration is also perfect.

My friend is working now on a vacuum clamp fixture in order to avoid taping the PCB to the MDF board we use as a disposable back.

His router is also used for aluminum, and wood milling. He has a Porter Cable 2.5 HP (10000-23000 rpm) router mounted on the Z axis for those jobs (non-floating) and the linear rails for Y and Y axes are mounted on granite slabs. The whole structure weights probably around 700- 800 lbs and the working area is about 24" x 36". Such a beast is not necessary for PCB routing only, but a solid structure is required to avoid vibration when doing fine SMD pads milling.

By the way, we are open to new alternatives for the routing bits, the ones that we are using now (Bits&bits part number 815-HF60 with 0.003" tip) don't last more than a few pcbs.

Regards,

Kreutz

[djh82uk]

Hiya

i use my taig mill for pcb engraving, although I have hit a few problems.

I have come up with an alternative to vacumn clamping and double sided tape, i will post up details when it's done.

For engraving bits i get the best finish with 85 degree or 90 degree engraving bits, it completley eliminates the swarf. But if you cut to deep then your traces are too big, so you reall need good tolerances on the dpth which is my problem, I am trying to come up with a floating head design if anyone has any ideas?

DJH

[bunalmis]

I build small pcb engraving machine. X and Y axis competed. Z travel is only 2 mm therefore I dont want to use stepper motor for the Z axis.

My favorite is solenoide. But solenoid motion is too fast. How can i reduce this motion?

[bunalmis]

Z drive Electromagnetic solenoid with hydraulic damper

What type material this hydraulic damper?


LPKF ProtoMat® M60

Part # 108002
Working Area (X/Y) 21” x 15” (540 x 375 mm)
Resolution (X/Y) 0.3125 mil (7.0937 µm)
Repeatability ±0.2 mil (±0.005 mm)
Precision of front-to-back alignment ±0.8 mil (± 0.02 mm)
Milling motor Max. 60,000 rpm, software controlled
Tool change Manual, quick release
Tool collet 1/8” (3.175 mm)
Drilling speed 90 strokes/min.
Travel speed (max) 1.575” (40 mm)
Depth Adjustment Mechanical depth limiter
X/Y positioning system 2-phase stepper motors
X/Y linear drive Precision linear bushings and dual shafts
Z drive Electromagnetic solenoid with hydraulic damper
Machine table base Precision milled aluminum bed
Dimensions (W/H/D) 23.6” x 16.5” x 35.4” (600 x 375 x 760 mm)
Weight 95 lbs (43 kg)
Power supply 115/230 V, 50-60 Hz, 200 W
Compressed air supply None required

[Aurbo]

Originally Posted by EvilBarry Hi all, sorry if this is in the wrong forum but theres so many sub-forums that i'm a little lost. I'm after a little advice on PCB routing. Basicly i'm after a small home build engraver to do PCB able to take euro card size boards 160x100mm and accurate enough to do moderate SMD componet pabs. Any one have any suggestions? Many thanks Barry

Barry, any luck with this? I too am looking for a SMALL desktop pcb mill.

I'm looking at 6"x6" milling area maximum and a very small plunge depth, 1/2" max with maybe a bit more room to change the bits.

I've built the HobbyCNC system as well as a "Pipe Dream" but I want something more specific to circuit board milling.

Perhaps I'll have to design my own, but I'd rather not re-invent the wheel or pay hundreds of bucks for a more generic mill.

I'm hoping someone out there has a set of plans that will make this go quicker.

Cheers
Steve

[djh82uk]

Hi Guys

Have a look at my first post in this thread:

Is anyone willing to make me a spring loaded tool holder?

It has a picture of my engraving tool prototype (needs improvement).

As I said im using a taig mill as I also do metal work.

I am however still bit of a newbie

Im thinking of starting a big pcb routing thread for everyone to dicuss and pass ideas, what do you think?

DJH