High quality PCB mill

[jeremy]

Hi guys,

I'm over waiting for test PCBs to arrive. I'm over fiddling with etching chemicals. I'd really just like a PCB mill that can do 6mil track/space Basically, I want to be able to do QFN.

I don't need auto tool change or funky software, I don't need big boards or speed and I would rather spend only $2-3k. I am going crazy looking for them because all I can find is the LPKF gear (>$20k) which I have seen used before, and the software is a let down. I've been trying to look for just the mechanics (the electronics is easy peasy and I figure I could save some money), but all of these chinese machines use leadscrews or rack/pinion instead of ballscrews. I already have a 3 axes worth of servo motors and controllers from a previous project, so I'd really like to go down this road if it can save me from the LPKF 'user-friendly' cost.

Does anyone know where I can find a machine like this? I'm running out of ideas!

PS: If anyone has any experience in this area, I've been wondering if adding 5um linear encoders to a machine would improve PCBs, or if the error is more likely to be in runout, board levelling, etc? Any ideas?

[MacAttak]

Is this something you want to buy/assemble today? Or are you OK with waiting a few months for it, and then likely still needing some hand tweaking?

[jeremy]

Either is good, I really just want the 6mil. I've got a large wood CNC mill so I am no stranger to the process, but I imagine I would need a rather stiff frame and I don't really have metalworking tools handy.

[MatCat]

Pretty similar requirements to what I am looking for as well.

[johansen]

http://www.taigtools.com/mmill.html

1000 bucks gets you a pretty stiff system, there are a number of improvements i've made to mine to increase the stiffness of the entire machine.
I've also made a change so i can get 7 inches of travel in the Y axis. 5.5 inches is all it can do stock. 

If all you want is PCB milling you might call them up and tell them to ship it without the spindle, that should take 150$ off the price.
the stock spindle can't handle the 30,000 rpm you need to get 6 mill traces with adequate precision.

i've not measured the linearity but the 20-TPI leadscrews are ground and hardened, so there should not be any non linearity problems, but you can correct those in software

do you have the software and steppers and driver already?

.001" backlash is not hard to achieve with these machines.

[jeremy]

Thanks!

Yep I do have the motors and was planning on using EMC2. What do you think about using a seig x3 instead of the taig and upgrading the acme threads to ballscrew? I can't work out where to get taig units in QLD, Australia.

Edit: although the question still stands, I found them in AU for about $1900 shipped: http://taig.com.au/index.php?main_page=product_info&cPath=65_66&products_id=432

[MacAttak]

Probably huge overkill for what you are wanting (capable of milling steel/aluminum), but the frame on this system should be exceptional. It is also not quite shipping yet, so in reality it might not live up to the advertised specs... until some customers get them and try them out we won't know for sure.

$1999 for the base machine, + $899 for 1HP spindle

Base machine also supports 3D printing, and they expect to add other bolt-on options in the future (scanner, etc).

http://store.qu-bd.com/product.php?id_product=45

[westfw]

Good luck with that, since it's pretty much at the limits of what the professional $20k+ system from LPKF or T-Tech claim to be able to do, using tools that run $80 each.  And you still don't get PTH, or soldermask, or other things that help make fine-pitch SMT actually DOABLE...

[jeremy]

And you still don't get PTH, or soldermask, or other things that help make fine-pitch SMT actually DOABLE...

Well as far as this is concerned, I already do fine pitch SMD stuff on an LPKF for work. So it's no biggie for me

I really think that a good chunk of the cost for the LPKF systems is in it's "completeness" ie it has a USB port, it has software, LPKF provides you with all of the profiles and tools, etc. I am no stranger to building my own machines (I have an engineering degree.....) so if I can save a good chunk putting it together myself, I'd be more than happy to. The other benefit is that when it breaks, I know exactly where to get the parts or exactly where to look in the code, something which has been a problem for the systems I have used before.

Also fairly certain that they have a large markup on the tools, kind of like how accessories for game controllers are marked up like crazy as they represent repeating income for the business. You can get an US made 30 degree V cutter with a 1/8" shank from amazon supply for about US$30.

[johansen]

Thanks!

Yep I do have the motors and was planning on using EMC2. What do you think about using a seig x3 instead of the taig and upgrading the acme threads to ballscrew? I can't work out where to get taig units in QLD, Australia.

can you find a seig x3 in australia?
a TAIG without the spindle only weighs 80 pounds and i'm sure they do international shipping.
you would have to upgrade the SEIG to ballscrews, take a look at the acme threading and the methods by which they do backlash adjustment.
also, the gear drive on the Z axis spindle is going to have some issues with repeatability.
when doing a PCB the depth of the cutting tool is critical, as is the planity of the work area. the bigger table is going to help you out a lot if you're clamping boards right to the table (like i do) but that's about the only advantage i see.

[jeremy]

Yes, I can grab an X3 locally. But this taig looks like it is more of what I am looking for. Out of interest, why do you need such high RPMs for tight cuts?

[johansen]

Yes, I can grab an X3 locally. But this taig looks like it is more of what I am looking for. Out of interest, why do you need such high RPMs for tight cuts?

because in order to get a 6 mill wide cut, you need to understand that at 30,000 rpm, you need a cutting tool that is .005" wide, so that with .0005 inch run out, you get a 6 mill wide cut.
30,000 rpm divided by 60 is 500 rps. .005 times 3.14159 is 16 mills.. times 500 is 8 inches per second.

typical cutting velocities for cutting copper is 200 feet per minute... that's 40 inches per second.

also, if you're cutting traces with a legit .010" diameter end mill.. you can only take off .0001? inches of copper per revolution or you're going to break the bit.

I use a home made spade bit that doesn't have that problem, however, it can't get anything less than 15 mill cuts. it could be more described as smearing and scraping its way through the board.

[WarSim]

I looked for over a year and found nothing worth using for under 10k in North America. I ended up getting an over seas mill for 8k. I have done 0.004" boards on it but that is the extreme limit of the mill. 
Normally I stay to .25mm and .5mm isolation end mills are cheeper and last longer than 2.5mil end mills.  I tried the spades but I don't like them anymore. 

[mikeselectricstuff]

Chemical etching is easily going to give a better cost vs. quality tradeoff. With a cheap mill you're just swapping swapping "fiddling with chemicals" to "fiddling with the mill".

Why do you think you need 6 mik for QFNs? Most QFNs are 0.5mm pitch, for which 10mil is fine.
 

[WarSim]

Chemical etching is easily going to give a better cost vs. quality tradeoff. With a cheap mill you're just swapping swapping "fiddling with chemicals" to "fiddling with the mill".

Why do you think you need 6 mik for QFNs? Most QFNs are 0.5mm pitch, for which 10mil is fine.
 

I personally required milling because in my situation I don't have a safe and legal chemical control and disposal option. Even my current huge employer stopped making in-house boards because of all the restrictions, costs and rules. Instead boards are contracted out to another location outside the insanity zone.

No idea maybe he wants to rout traces between the QFM pads, or under 0402 resistors.