Prometheus for Rapid Prototyping - Forget Everything You Know About PCB Milling

[fcb]

I've used an LPKF years ago - a real faff, long learning curve and a lot of baby-sitting (as someone else mentioned). The biggest PITA was stitching all the vias with this paste, very unreliable & time-consuming.

I can see the value of a PCB mill if you do RF/stripline stuff - but all other cases just a bit of organisation and wait a week for the boards to come back.  For example, I've got a 160x160mm PTH board going off this weekend: PCBWay will do 5 copies for $73 ($48+$25 shipping) total, if I can cope with no-solder mask and I need one in a hurry, then I use "PCB Train" by Newbury Electronics - proper PTH board, next day service for about £120+VAT, just send it to them by 9AM and they ship it out that evening on a courier.

And if you've tried assembling a board without solder-mask, it can be a nightmare.

[Mechatrommer]

And if you've tried assembling a board without solder-mask, it can be a nightmare.

i can finish assembling those before the masked pcb order arrives. and by the time the masked pcb arrived, i know my design is working on non-masked pcb and ready for mass production board order. my desk is only fit for one project, barely enough for 2 small projects. organization of 3 or more projects at a time just doesnt cut it. anyway, this is "you like blue i like red" problem, both are true.

if soldermask is important, i'll prefer this..


but since the material is not yet available to my place, i'll try this...

[G0HZU]

In house proto manufacturing IMHO absolutely worth it .
Every time the guy who is in charge of the machine is off, or the mill has some problems(wit our heavy use, it breaks time to time...), there this sense of impeding doom among electronics designers
We have team of cca 25 electronics designers, and most of the day the PCB mill is working all day long. Also our colleagues from mechanical department discovered that you can make nice stuff from plexi and POM, so the CNC is used for this as well. We have used it for qfn, and even some BGA no problems.
For vias we use rivets and wire stitching

I agree. At work we have been using milling machines for about 25 years. Mostly for RF prototyping but they can also be used for making front panels and other structures using various materials. Here at home I have an old T-Tech 7000S machine that I use quite regularly for RF PCB prototyping and for making various tools, spacers, panels etc. I've actually got two of them but the other one is really just for backup.

If you want to design and prove some novel RF filter designs on an exotic RF laminate and maybe do a few iterations over a couple of days then I'd be keen to know from the experts here how I could do this as efficiently as having a PCB mill sat next to me? It's going to be slow and expensive and highly irritating to have to keep waiting for the next batch of prototypes to arrive by courier if I do it all at a PCB house.

The Prometheus machine looks promising but it would be nice to see it do some isolation/rubout in order to make the PCB nicer to work with once milled. Also, it doesn't seem to use a stabilising foot or maybe I missed it in the video? My T-Tech machine is an early model with the very basic stabilising foot. This works well as long as the operator is knowledgeable and sympathetic of its limitations. So I sometimes have to mill certain parts of the PCB in a specific order to get the best results. Newer models are much better with a better designed foot. At work we moved across from T-Tech to LPKF many years ago and have had very good results.

[rocco]

In house proto manufacturing IMHO absolutely worth it .
Every time the guy who is in charge of the machine is off, or the mill has some problems(wit our heavy use, it breaks time to time...), there this sense of impeding doom among electronics designers
We have team of cca 25 electronics designers, and most of the day the PCB mill is working all day long. Also our colleagues from mechanical department discovered that you can make nice stuff from plexi and POM, so the CNC is used for this as well. We have used it for qfn, and even some BGA no problems.
For vias we use rivets and wire stitching

I agree. At work we have been using milling machines for about 25 years. Mostly for RF prototyping but they can also be used for making front panels and other structures using various materials. Here at home I have an old T-Tech 7000S machine that I use quite regularly for RF PCB prototyping and for making various tools, spacers, panels etc. I've actually got two of them but the other one is really just for backup.

If you want to design and prove some novel RF filter designs on an exotic RF laminate and maybe do a few iterations over a couple of days then I'd be keen to know from the experts here how I could do this as efficiently as having a PCB mill sat next to me? It's going to be slow and expensive and highly irritating to have to keep waiting for the next batch of prototypes to arrive by courier if I do it all at a PCB house.

The Prometheus machine looks promising but it would be nice to see it do some isolation/rubout in order to make the PCB nicer to work with once milled. Also, it doesn't seem to use a stabilising foot or maybe I missed it in the video? My T-Tech machine is an early model with the very basic stabilising foot. This works well as long as the operator is knowledgeable and sympathetic of its limitations. So I sometimes have to mill certain parts of the PCB in a specific order to get the best results. Newer models are much better with a better designed foot. At work we moved across from T-Tech to LPKF many years ago and have had very good results.

Thank you, G0HZU. Yep, a full copper rubout (exact Gerber duplication) is something I want to demo. I have some RF clients who use Roger's so this is high on my list.

You didn't miss it in the video - there is no pressure foot because Prometheus doesn't need one! Instead, ProCAM runs a ~90 second probing cycle before milling begins, where the tip of the tool moves down until it makes electrical contact with the copper-clad surface. When it does, it records the height with 1.25-micron resolution. After probing a grid of points, ProCAM forms a surface map behind the scenes and automatically tells Prometheus how to adjust the Z axis on the fly to keep a consistent milling depth. Basically, it follows the peaks and valleys of the board on its own. This has proven to produce fantastic results and users don't have to worry about pressure foot limitations or the pad wearing or snagging or anything like that. It just works.

[Pitrsek]

My recommendation was not aimed particularly at LPKF, but in house prototyping in general. 
LPKF - since I'm not the one the one taking care of the machine, I can't comment much about user friendliness. But my colleague is not complaining about it. We've had several warranty repairs and post warranty repairs, also local distribution is mediocre at best(delivery dates sux). So in general I can see that there is a place for quality competition...

@nctnico - Yes, and I believe it's well worth it. For lot of stuff I don't need silkscreen, when I do I order express from fab house. You can test an idea within a single day, that is priceless. Re-use value is very high. If I decide to use the design, the schematics is already drawn and I have first rough layout as well. So when time comes for proper layout, most of the stuff on board is already verified by means of simple small boards from CNC.
Also if project manager likes your new gizmo and needs 5more pcs to show off, its way easier to make more. For stuff we do, it's been really beneficial. Off-course there is a lot of areas where 2l board for prototype won't cut it.
 
@Roco - we do cool medical stuff  . The thing is we do develop and sell the devices as well. Basically marketing department is our customer. So there is a lot of going forth and back during the development before spec is frozen(that happens quite late in development). It's not like you have closed specification at the beginning. Branches, some dead ends, lot of experiments, circles, figuring out what market(ing) wants... So you come in on Monday morning and you hear PM "we've had a meeting, and I wanted to ask you would it be possible...." Its very fluid development, and I like it a lot. The way our company works has obviously effect on how we value the prototyping possibility.

[ebclr]

I like the idea of drone motor, I will try to set one on my delta 3 printer

[mrpackethead]

We run 2-3 proto boards a week and have 1 or 2 production boards as well.  Board sizes vary from tiny to A4 size.  Mostly boards are 4 layer. 4 layer often ends up cheaper as It's more compact and more importantly it's quicker and easier to design and gives a better result in general.  Low cost pcbs are only $100 for something I have in hand in 72-96 hours.   Milling also implys
Not having a stencil ( at least not a stainless one and plastic/Mylar laser cut just don't cut it at fine pitch ).

While I applaude what you have done I just don't see this being something that would be truely cost beneficial

[rocco]

While I applaude what you have done I just don't see this being something that would be truely cost beneficial

Thanks. I would never argue that it makes sense for everyone to have something like this on their desk, but I will absolutely say that there exists a segment of the population out there for which Prometheus or other high performance PCB mills do make sense, as we have seen from some of the previous comments. In your case, you pay $100 for something you get in 72-96 hours. It's safe to say that someone else would pay a certain amount extra to have that board in hand in say 48 hours... maybe it's only $5 more. Maybe it's $500. That depends on the end user. Almost every board house I've seen or worked with offers faster service if you're willing to pay more for it.

Quick cost analysis: I posted previously a snapshot from a PCB service price aggregator where I searched for the cheapest price for a 2-day turnaround in the US for a 2-layer board, and the result was $503.16. You are not one of the people doing this (and that's great if that works for you!) but they do exist. if you were ordering 2-3 boards per week at that price, you'd have Prometheus pay for itself in less than two weeks! Not to mention that you'd have the added convenience of getting your boards in minutes (or maybe an hour or so if it's a bigger job) - not 2 days.

Board houses will always be slower than Prometheus and more expensive as well, since you're also paying for a truck/plane to expedite it to you unless your board house is across the street. Or until teleportation is invented and they can beam it to you.

[usagi]

people will be cross shopping the othermill, which as a generic cnc mill can do pcb and everything else.

[rocco]

people will be cross shopping the othermill, which as a generic cnc mill can do pcb and everything else.

I'd be happy to invite anyone to compare Prometheus and the Othermill Pro on specs and price. For Othermill specs, visit https://othermachine.co/othermill-pro/ and scroll to the bottom. For Prometheus specs, visit the bottom of the home page http://www.zippyrobotics.com/

In my opinion, there is a very clear winner.

[ebclr]

Othermill Pro
$3,199

239,99

https://www.amazon.com/Machine-Engraving-Milling-5-12x3-94-Effective/dp/B01LWBLVYS/ref=sr_1_1?ie=UTF8&qid=1492920412&sr=8-1&keywords=pcb+cnc

What one have that the other doesn't

[usagi]

people will be cross shopping the othermill, which as a generic cnc mill can do pcb and everything else.

I'd be happy to invite anyone to compare Prometheus and the Othermill Pro on specs and price. For Othermill specs, visit https://othermachine.co/othermill-pro/ and scroll to the bottom. For Prometheus specs, visit the bottom of the home page http://www.zippyrobotics.com/

In my opinion, there is a very clear winner.

can you do anything other than PCBs? e.g. can you mill aluminum or brass bar stock?
how much Z do you have?
do you support standard Gcode?

[mrpackethead]

Thanks. I would never argue that it makes sense for everyone to have something like this on their desk, but I will absolutely say that there exists a segment of the population out there for which Prometheus or other high performance PCB mills do make sense, as we have seen from some of the previous comments. In your case, you pay $100 for something you get in 72-96 hours. It's safe to say that someone else would pay a certain amount extra to have that board in hand in say 48 hours... maybe it's only $5 more. Maybe it's $500. That depends on the end user. Almost every board house I've seen or worked with offers faster service if you're willing to pay more for it.

Quick cost analysis: I posted previously a snapshot from a PCB service price aggregator where I searched for the cheapest price for a 2-day turnaround in the US for a 2-layer board, and the result was $503.16. You are not one of the people doing this (and that's great if that works for you!) but they do exist. if you were ordering 2-3 boards per week at that price, you'd have Prometheus pay for itself in less than two weeks! Not to mention that you'd have the added convenience of getting your boards in minutes (or maybe an hour or so if it's a bigger job) - not 2 days.

No, Promethues woudl never be cost effective to me.  The cost of using milled pcbs, that have no vias, are only 2 layer, and where i have no solder stencil would cause me a a massive increase in labour.  The 'time' benefit of having somethign in a few hour's would be negated very rpaidly, when someone had to put 200 vias in by hand.  And the two layer restriction is a big one.   

[/quote[
Board houses will always be slower than Prometheus and more expensive as well, since you're also paying for a truck/plane to expedite it to you unless your board house is across the street. Or until teleportation is invented and they can beam it to you.
[/quote]

But what a mill produces and what you get from a board house are not the same product.   

[rocco]

Thanks. I would never argue that it makes sense for everyone to have something like this on their desk, but I will absolutely say that there exists a segment of the population out there for which Prometheus or other high performance PCB mills do make sense, as we have seen from some of the previous comments. In your case, you pay $100 for something you get in 72-96 hours. It's safe to say that someone else would pay a certain amount extra to have that board in hand in say 48 hours... maybe it's only $5 more. Maybe it's $500. That depends on the end user. Almost every board house I've seen or worked with offers faster service if you're willing to pay more for it.

Quick cost analysis: I posted previously a snapshot from a PCB service price aggregator where I searched for the cheapest price for a 2-day turnaround in the US for a 2-layer board, and the result was $503.16. You are not one of the people doing this (and that's great if that works for you!) but they do exist. if you were ordering 2-3 boards per week at that price, you'd have Prometheus pay for itself in less than two weeks! Not to mention that you'd have the added convenience of getting your boards in minutes (or maybe an hour or so if it's a bigger job) - not 2 days.

No, Promethues woudl never be cost effective to me.

I think you misunderstood. I'm not trying to say that it would be cost effective for you. Just that entities do exist for which same-day prototyping is valuable, even with it's limitations. I get that you're not one of those people, and that's cool.

"But what a mill produces and what you get from a board house are not the same product."

True, but again the product that a mill produces still has value to some people (I understand that's not you) and more importantly, a board house doesn't produce any product that you can hold in your hand within an hour of ordering it.

[usagi]

True, but again the product that a mill produces still has value to some people (I understand that's not you) and more importantly, a board house doesn't produce any product that you can hold in your hand within an hour of ordering it.

this market is going to be incredibly small.

businesses and universities serious about pcb prototyping will buy something with a commercial onsite support contract. if they are so dependent on 1hr turnaround, then they will want a support engineer on site to fix it NOW.

your average hobbyist doesn't need 1hr turnaround, and wants something like oshpark silkscreened PCBs with vias anyway.

[rocco]

people will be cross shopping the othermill, which as a generic cnc mill can do pcb and everything else.

I'd be happy to invite anyone to compare Prometheus and the Othermill Pro on specs and price. For Othermill specs, visit https://othermachine.co/othermill-pro/ and scroll to the bottom. For Prometheus specs, visit the bottom of the home page http://www.zippyrobotics.com/

In my opinion, there is a very clear winner.

can you do anything other than PCBs? e.g. can you mill aluminum or brass bar stock?
how much Z do you have?
do you support standard Gcode?

No to all of the above. I want to be clear here: Prometheus is only for PCBs. it's not a general purpose CNC mill (and neither are machines by LPKF or T-tech). Prometheus was engineered specifically for PCBs just like the other professional solutions that cost $8,000+. If you want a general purpose mill you should not buy Prometheus. Given the nature of this site, in my last comment I was referring to a comparison based on the desire to prototype PCBs, not other stuff. I feel like it's best to choose the right tool for the job. The requirements to do high quality PCBs are different than general purpose milling with the most important factor being the spindle. If you try to run a .007" square end mill with a hobby spindle, it will likely snap on contact with the copper-clad before you get any useful work out of it due to the large runout of those spindles. That's why you'll only see them run "V" bits (engraving bits) below a certain diameter. Also, when you go down to such small end mill diameters, the chip load necessarily needs to go down as well, which means that you'd want a high speed spindle to keep the feed rate reasonable without prematurely breaking the end mill. Prometheus's spindle is 50,000 RPM.

[mikeselectricstuff]

businesses and universities serious about pcb prototyping will buy something with a commercial onsite support contract. if they are so dependent on 1hr turnaround, then they will want a support engineer on site to fix it NOW.

..or if it's cheap enough, just buy two units.

However if you're so dependent on doing 1hr protos, chances are you're doing it wrong.
 

[Kjelt]

I do agree that a general purpose cnc mill is not good for pcbs, own one, tried that, and failed.
They usually have larger areas and lack the resolution on repeatability ( going back and forth and ending up in the exact position) due to the stepper resolution and backlash.
For normal milling jobs ending 0,02mm off track is not a big thing, you dont see it, with a small pcb it could ruin the entire design.
IMO you need better steppers and continuously calibration to pull it off.
The same way the other side up:  those affordable general purpose cnc mills also are not able to mill steel.
They dont have the weight, torque, power whatever, it just does not work.
Wood, aluminium are ok.
You need the special tool for the special job.

[mrpackethead]

I think you misunderstood. I'm not trying to say that it would be cost effective for you. Just that entities do exist for which same-day prototyping is valuable, even with it's limitations. I get that you're not one of those people, and that's cool.

who is it valuable to? Coudl you describe the use-case where it is valuable?

[mrpackethead]

IN summary,

The title of this post is quite misleading.  A PCB mill by itself does not provide 'everything' for rapid prototyping.   In fact it only provides a very small use-case for possibilitys.

[Mechatrommer]

For normal milling jobs ending 0,02mm off track is not a big thing, you dont see it, with a small pcb it could ruin the entire design.

you are out of luck then... seeedstudio can only do 6 mils reliably, thats 0.15mm. Thickness Tolerance: (t?0.8mm) ± 10% that translates to ±0.08mm error.
http://wiki.seeedstudio.com/wiki/Service_for_Fusion_PCB

jeez people you want to do physics package go find another tools, we know what a $2K (or $200) tools can or cant do, expecting it to do 6 digit priced tools is hilarious. if you can afford $100 in each iteration go for it, some people just dont have the luxury, or similar workflow/burden/profit as you are.

[Kjelt]

you are out of luck then... seeedstudio can only do 6 mils reliably, thats 0.15mm.

Messed up a digit should have been 0,2mm.

we know what a $2K tools can or cant do, expecting it to do 6 digit priced tools is hilarious.

Man you really missed my point, probably my English. My point was that Prometheus is excellent for these kind of pcb jobs and that general cnc mills are not.
You have different tools for different applications, as soon as your cnc has to travel more than 300mm on any axis the backlash and all is going to mess it up unless you have optical decoder or other ways of continuous knowhing where you are which are costing lots of $$$.
They are different beasts, a pcb routing cnc is a total different design than a generic <5k$ cnc and different from the cnc's that do steel, that is all I am saying.

[Mechatrommer]

Man you really missed my point, probably my English. My point was that Prometheus is excellent for these kind of pcb jobs and that general cnc mills are not.

my comment is not specifically directed at you. its more to general conclusion to what is being discussed here.

You have different tools for different applications, as soon as your cnc has to travel more than 300mm on any axis the backlash and all is going to mess it up unless you have optical decoder or other ways of continuous knowhing where you are which are costing lots of $$$.

i think you misunderstood backlash and manufacturing imperfection. backlash only happened when you reverse direction. manufaturing imperfection is something like a 1mm thread should move 1000mm in 1000 turns but its not, maybe 1001mm or 999mm. it can be easily fixed in FW but... who cares perfecting the FW if the margin is too small? and it produced in super mass volume with varying tolerance. what users (consumers) can do for cheap stuffs like this? they compensate in CAD if someone doesnt want to bother with this compensation mess, they should save 6 digits for a machine, or pay 3 digits to  someone who has 6 digits machine, if that is 6 digits, probably 5 digits tops with very good compensating skill personnels in the house. or maybe a 5 digits 2nd hand of a used 6 digits machine they have to refurbish to you dont know what happened in behind.

[janoc]

My recommendation was not aimed particularly at LPKF, but in house prototyping in general. 
LPKF - since I'm not the one the one taking care of the machine, I can't comment much about user friendliness. But my colleague is not complaining about it. We've had several warranty repairs and post warranty repairs, also local distribution is mediocre at best(delivery dates sux). So in general I can see that there is a place for quality competition...

@nctnico - Yes, and I believe it's well worth it. For lot of stuff I don't need silkscreen, when I do I order express from fab house. You can test an idea within a single day, that is priceless. Re-use value is very high. If I decide to use the design, the schematics is already drawn and I have first rough layout as well. So when time comes for proper layout, most of the stuff on board is already verified by means of simple small boards from CNC.
Also if project manager likes your new gizmo and needs 5more pcs to show off, its way easier to make more. For stuff we do, it's been really beneficial. Off-course there is a lot of areas where 2l board for prototype won't cut it.
 
@Roco - we do cool medical stuff  . The thing is we do develop and sell the devices as well. Basically marketing department is our customer. So there is a lot of going forth and back during the development before spec is frozen(that happens quite late in development). It's not like you have closed specification at the beginning. Branches, some dead ends, lot of experiments, circles, figuring out what market(ing) wants... So you come in on Monday morning and you hear PM "we've had a meeting, and I wanted to ask you would it be possible...." Its very fluid development, and I like it a lot. The way our company works has obviously effect on how we value the prototyping possibility.

Seriously, if you are doing that sort of volume, why don't you buy a proper etching tank/machine and UV exposure box? Way less maintenance and babysitting needed and likely faster to produce those boards as well, especially if you use precoated boards or the dry film. The exposure box will be also useful for solder mask application if you decide to do it.

CNC is good to have for cutting materials to shape and perhaps drilling holes if you are doing a PTH design, though. But for that you don't need any super-duper high precision machine.

[Kjelt]

i think you misunderstood backlash and manufacturing imperfection. backlash only happened when you reverse direction. manufaturing imperfection is something like a 1mm thread should move 1000mm in 1000 turns but its not, maybe 1001mm or 999mm.

I am not sure, let me explain you what I mean.
At my 5k$ cnc mill if the sw tells to move 100,0 mm it moves 100,0 mm no problem.
BUT if I tell it to do the same move lets say 50 times go back and again, in the end the mill will fail around few tenths of mm.
That is because it does not have linear calibration guidance on its axis and depends on the stepping motor accuracy.
I don't know the exact english term, we call it "speling" on the bearings probably slack or backlash.

Anyway if you want to keep the exactness of the work the mill should recalibrate on a known X,Y,Z position every few minutes at least or very delicate jobs go wrong.
That is what I am trying to say that for normal cnc jobs that is perfectly ok, but for a job like pcb milling even 0,1mm deviation could cause a trace to be severed or damaged.
Then there is another thing and that is that in my experience going to a bit with a diameter <1mm on these $5k machines also does not work that well.
You end up spending more money on bits than on the pcb. Just my own experience.