CNC PCB Mill Status


#1

Hi folks, new member here. I’ve been lurking on the forums to try to get my bearings. I did have on question that I couldn’t find a complete answer to. What is the status of the PCB mill? Last I saw it was on the mend thanks to some charitable members. I sure would like to be able to bust out a sample PCB before sending the final to the board house. Hopefully to improve my success rate…which tends to drop the busier I get with my day job.


#2

I’m in the process of splicing in some extensions in the cabling. Have the limit switches left to do. This will allow us to set the miill off the cntrl box and put an enclosure of some kind around it. @JohnK has worked on flags for the limit switches. Once the splicing is done John and I will do some “torture testing” to make sure the extra length of cable has no ill effects.

Some notes:
Users will supply their own tooling - end mills, drills, etc. This may change later.
There will be a class required before using.
Need to build enclosure - similar to Shapeoko?
ChiliPeppr is the current sftwr being used. http://chilipeppr.com/tinyg
Small shop vac similar to that used on Shapeoko?
How to hold pcb while machining.


#3

As per my experience cutting good quality PCBs require good quality CNC machines. There are no short cuts or cheap alternatives available. If you don’t have the finances for a good machine then I would consider using the chemical etching process or a third party manufacturer.
If you do purchase a good machine then you will also be able to make so many other parts. I refer you to my signature. You can see on my photo sites what a good CNC machine will enable you to accomplish.


#4

In Dec give to Machine Shop chair - Nick Silva limit switches plate files that could be mill out. You will need to check with him how it is going & if their some one that could help do it if he is not able to get to it at this time.
PS Andy/aet if you need the stl files talk with me. I


#5

PCB hold down is the major impediment at this point. @AndyFrew if you have experience with hold down options i’d love to get some ideas from you.


#6

I used to work with some LPKF mills quite often, if y’all are looking for other opinions maybe I can offer some.

For our mills, having an enclosure was almost a requirement, to keep the dust out of the surrounding area and to keep the high pitched noises down (for isolation our spindle sat at 40krpm, drilling was 40-80krpm). The machine had some incredible dust collection and surfaces inside the enclosure would still be covered in fine slivers of copper from routing (the dust collection got most of the fine fiberglass dust, luckily).

I’d be concerned about using a small shop vac as dust collection, ours were similar but had HEPA filters as well. I used a canister style home vacuum to clean up once and the whole area started to smell like fiberglass. I assume the smallest dust particles just passed through and were blown into the air by the vacuum.

Our machines used a vacuum hold down system, the same dust collection vacuum would suck the material to the bed, through a fancy air permeable backer board. It was great but got to be pricey.

For yall’s use, I believe a more standard approach is to cut fixed size blanks and drill two holes on opposite edges, the holes can slide into two pins in the milling bed, you can also throw a thin piece of hardboard/mdf behind as a backer for through holes or routing (if you plan to route). The pins also allow you to flip and register the opposite side fairly easily. If you want to go crazy with it you could put multiple locations for pins in the bed, that’d allow someone to pick the blank best suited for their board. For reference, I believe this system was used on older LPKF mills with 9"X11" panels, and two ~3/16" pins (all metric of course…)


#7

@Dale_Wheat runs RBNO and has a cool PCB milling setup - - I would definitely ask for his advice…


#8

I’d defer to @JohnK for this. He has much more practical experience with milling PCBs than I do.


#9

What about something like this?


I could redesign it to fit the hold down screws on our bed and to hold down the spoil board at the same time. The idea would be to support 2 or 3 common PCB blank sizes.


#10

Update:
Cable splicing is done.
Stepper motors tested.

@JohnK and I did some testing to check if lengthening the cables had any impact on performance.
ChiliPeppr was used to mill a simple pc brd.
Some notes:
G Code and tooling were not optimized.
Z axis topo mapping was not used - pc brd did not lie flat -obvious in photos.


After 3 - 4 passes. .0625" end mill. Brd slopes downhill from upper left corner to lower right corner.
Spindle is at assigned home point. Repeat-ability appears to be excellent.


Middle and right cuts are done w/ .0250" end mill. 3 - 4 passes each.
Again repeat-ability appears to be excellent.

Flags for limit switches are being made.
Limit switches and Z topo have not been tested.

Need a base and removable enclosure to cntrl noise and dust.
Need a small shop vac w/ HEPA filter. Any recommendations?


#11

I’d recommend getting one that uses bags. Shop vacs with HEPA filters won’t save you from that very nasty fiberglass dust when it’s time to empty the thing.