Dangerous Prototypes

In development => Project development, ideas, and suggestions => Topic started by: nickjohnson on January 03, 2013, 03:09:33 pm

Title: A stencil8 PCB tooling block for doing solder paste stencils
Post by: nickjohnson on January 03, 2013, 03:09:33 pm
So, I've been converted to the stencil8 (http://http://www.hoektronics.com/2012/10/27/super-simple-smt-stencil8/) way of doing things, but I need a decent tooling block to do it on. Getting these commercially CNCed in small quantities is very expensive, but a bulk order - 10 or more - is a lot more affordable. So I've put together a fundraiser on Tindie (http://https://tindie.com/shops/nickjohnson/pcb-fixture-block-for-solder-paste-stencilling/) to get some made. Please do join in if you'd find it useful to own one of these.

For those who don't know, these are robust precision machined Aluminium tooling blocks. They've got a grid of precisely aligned holes, and come with matching steel dowels. You design your PCB (possibly panelized) and stencil with matching holes, and all you have to do to apply solderpaste is put the PCB, then the stencil, on the pins, and wipe paste over them. No more alignment hassles!

I'm not really making any profit on these - I just want to get enough orders together to make it cost effective.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: matseng on January 03, 2013, 05:38:08 pm
I've been thinking about having one of those made as well.  When looking into the costs I realized that a 3 kilo block of aluminium might be a bit of an overkill.  A sheet of 8-10 mm acrylic (or even better polycarbonate/Lexan since it's more resistant to chipping) with holes either drilled all the way or just part through would most likely be enough for most non-professional applications. And would also be far cheaper than an aluminium slab.

Too bad that laser cutting probably won't make holes with enough precision - otherwise $13 for 5 custom lasercut 20x20 cm sheets from Seeedstudio would be a nice option.


FYI -  200x150mm is not A4 as the fundraiser says, it's actually only a half A4 I.E. A5.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 03, 2013, 05:43:16 pm
[quote author="matseng"]I've been thinking about having one of those made as well.  When looking into the costs I realized that a 3 kilo block of aluminium might be a bit of an overkill.  A sheet of 8-10 mm acrylic (or even better polycarbonate/Lexan since it's more resistant to chipping) with holes either drilled all the way or just part through would most likely be enough for most non-professional applications. And would also be far cheaper than an aluminium slab.[/quote]

Actually, the Aluminium is only a small portion of the final price - machining is a significant cost. But postage is a significant WRT the weight.

Quote
Too bad that laser cutting probably won't make holes with enough precision - otherwise $13 for 5 custom lasercut 20x20 cm sheets from Seeedstudio would be a nice option.

I've put out a quote request for a 10mm acrylic option, just to see if it works. I'm not sure about the hole size precision either, but it's worth a try.


Quote
FYI -  200x150mm is not A4 as the fundraiser says, it's actually only a half A4 I.E. A5.

Oh crap, how did I get that wrong? I'll fix it immediately - and maybe take it down if that's too small to be useful.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: matseng on January 03, 2013, 05:56:06 pm
[quote author="nickjohnson"]I've put out a quote request for a 10mm acrylic option, just to see if it works. I'm not sure about the hole size precision either, but it's worth a try.[/quote]
Drilled or laser cut?  Even with a powerful enough laser the divergence of the beam would make the hole much wider at the bottom than the top.

If I would do it with a laser I probably cut 4 pcs of 2.5mm boards and sandwich them with a uncut board in the bottom, put in the dowels and glue/bond them together.

Just for the fun of it I'll order one of the 10x10 laser service the on Monday when I send for my weekly PAW project. And put a bunch of holes in increasing sizes from 2.3 to 2.6 mm in 0.025 mm steps and see what size that will be the best fit.  Of course I need to find a 2.5mm steel dowel as well :-)

Well, A5 seems a bit wimpy , but you could actually fit a eurosized board 100x160 mm on it with margins for the holes, so it might be enough.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 03, 2013, 06:07:39 pm
[quote author="matseng"][quote author="nickjohnson"]I've put out a quote request for a 10mm acrylic option, just to see if it works. I'm not sure about the hole size precision either, but it's worth a try.[/quote]
Drilled or laser cut?  Even with a powerful enough laser the divergence of the beam would make the hole much wider at the bottom than the top.[/quote]

I asked for a pricing with a laser; the place I asked for a quote from has a very good machine. I'm not sure how bad the divergence will be.

Quote
If I would do it with a laser I probably cut 4 pcs of 2.5mm boards and sandwich them with a uncut board in the bottom, put in the dowels and glue/bond them together.

That's also a viable option.

Quote
Just for the fun of it I'll order one of the 10x10 laser service the on Monday when I send for my weekly PAW project. And put a bunch of holes in increasing sizes from 2.3 to 2.6 mm in 0.025 mm steps and see what size that will be the best fit.  Of course I need to find a 2.5mm steel dowel as well :-)

Good idea!

Quote
Well, A5 seems a bit wimpy , but you could actually fit a eurosized board 100x160 mm on it with margins for the holes, so it might be enough.

I think I'll find a way to do it at A4 (a 10mm thick piece of Aluminium in that size would be under 2KG) or not at all.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: matseng on January 03, 2013, 06:18:13 pm
Just ordered "2.5 mm X 20 mm STAINLESS STEEL DOWEL PIN X 10 (SPN 110-069-10) 180827351774 - Price: GBP 2.99" from eBay. They will probably turn up before I get the acrylics from Seeed. ^_^
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 03, 2013, 06:20:44 pm
There's a lasercutter at my local hackerspace, and I'm going there this evening. I'll give it a try with different sizes of hole. I've ordered some dowel pins myself, but it'll take a couple of days for them to arrive.

-Nick
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: bearmos on January 03, 2013, 06:27:45 pm
nice idea nick.  I hope you find enough takers on this.  Maybe send it to a few different blogs as well (I know hack a day ran an article featuring this tooling method a while back).
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: bearmos on January 03, 2013, 06:30:02 pm
[quote author="nickjohnson"]There's a lasercutter at my local hackerspace, and I'm going there this evening. I'll give it a try with different sizes of hole. I've ordered some dowel pins myself, but it'll take a couple of days for them to arrive.

-Nick[/quote]

I use old micro drill bits (1/8" dia shank in my neck of the woods) - they work well (just don't put your hand down on top of them accidentally).  dowels would certainly be preferable, but you might be able to scrounge up some bits locally to try this out - can you tell I'm inpatient...:)
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 03, 2013, 10:21:24 pm
Okay, so I cut a sample out of 3mm acrylic on the lasercutter at the hackspace, with a variety of hole sizes from 2.5mm down to 2.2mm in 0.05mm increments. I don't have my 2.5mm pins yet, but I do have some 2.54mm ones. They fit a little loosely into the 2.35mm hole, and very snugly - a fraction too snugly - into the 2.3mm hole.

Even just one sheet of acrylic holds them fairly well, so I'm optimistic three sheets, with the bottom one blank, would suffice for a good jig. This would require figuring out a way to bond them together without the glue gumming up the holes. There's rather good 'water thin' acrylic solvent around which might do the job.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: dolabra on January 03, 2013, 10:39:53 pm
what if you sandwiched 10 PCBs from a cheap seeed order and just had them milled with holes?
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 03, 2013, 10:49:48 pm
[quote author="dolabra"]what if you sandwiched 10 PCBs from a cheap seeed order and just had them milled with holes?[/quote]

I suspect 10 A4 PCBs would come to a lot more than a couple of sheets of acrylic, unfortunately.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 04, 2013, 08:01:52 pm
I've fixed up the Tindie fundraiser: $85 will now get you an A4 block, 200 x 300 x 10mm, with 6mm deep holes.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 21, 2013, 02:23:55 pm
Well, the fundraiser is over (successfully!), but there's still two left if anyone wants one. The URL has changed, it's now http://https://tindie.com/shops/arachnidlabs/pcb-fixture-block-for-solder-paste-stencilling/.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: bearmos on January 21, 2013, 03:09:19 pm
congrats, nick!
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 24, 2013, 11:19:33 am
Now all sold out!
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 29, 2013, 06:11:38 am
Excited about mine! Stencil ordered, nice metal squeegee ($3) and solder paste ($9) procured.

Kinda wish Sick of Beige was on 0.1" centers so it would fit right in this. Something to consider for v2.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Kean on January 29, 2013, 06:29:04 am
Ian, can you tell us where you procured the metal squeegee?
I've been looking around for a while but haven't found anything suitable.
I typically use an old credit card :-)
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 29, 2013, 06:36:10 am
3rd floor of the "tool" building in huaqiangbei :) It's behind the international LED building, I'm sorry I don't know the actual name or stand number, but it is near the escalators. Should I get a few dozen next time and add to the store?
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Kean on January 29, 2013, 06:53:17 am
LOL, if only that was just around the corner... but I am in Sydney, and not sure when I'll be able to drop by Shenzhen.

I think this would be a great item to add to the store.  I imagine lots of people are looking for small & cheap ones for low volume work.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: matseng on January 29, 2013, 07:06:34 am
[quote author="ian"]Should I get a few dozen next time and add to the store?[/quote]
If you add non-electronics to the Seeed store don't forget the "Altoid"-style tins we looked at.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 29, 2013, 07:12:34 am
Will do. Was actually thinking of bringing them here and selling from our DP store because it's so low volume and Seeed is valuing their stock space pretty highly right now, but the tins are definitely for the Seeed Store.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 29, 2013, 08:52:41 am
[quote author="ian"]Excited about mine! Stencil ordered, nice metal squeegee ($3) and solder paste ($9) procured.

Kinda wish Sick of Beige was on 0.1" centers so it would fit right in this. Something to consider for v2.[/quote]

I'm hoping to hear back from the CNC place about progress today, and have them posted by the end of the week. Fingers crossed!

It's 10mm centers, not 0.1", by the way!
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 29, 2013, 09:21:42 am
Maybe I can whip up a SoB style one with the standard placement. However I figure I won't do much stenciling of prototypes, and the holes are easy to add to panels. I bought a pneumatic paste dispenser to do 1-off prototypes before running the passives by PnP.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 29, 2013, 09:22:00 am
Thanks for the update and arranging everything by the way!
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 29, 2013, 10:13:06 am
[quote author="ian"]Maybe I can whip up a SoB style one with the standard placement. However I figure I won't do much stenciling of prototypes, and the holes are easy to add to panels. I bought a pneumatic paste dispenser to do 1-off prototypes before running the passives by PnP.[/quote]

How much was the paste dispenser? I'd love one, but I get the impression they're expensive.

Quote
Thanks for the update and arranging everything by the way!

My pleasure! It'll be a load off my mind once they arrive and I see they're as-specified ,though.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Kean on January 29, 2013, 10:42:49 am
I also use a foot pedal controlled paste dispenser for most prototypes, but for the smaller pitch devices the stencils work better.

Nick, I got my paste dispenser on eBay for about $150, but you also need to buy tips and an air compressor.  The Chinese dispensing tips are a bit average, and you need to replace them often as they clog up if left a few days.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 29, 2013, 12:26:43 pm
I got a digitally set dispenser with lots of settings all the bits and bobs and tips (not a compressor, which I have to get) for 320rmb, about 50 bucks US. I saw some starting at $25 though, this was the most expensive one I could find. I don't have a pic, but it is scheduled for delivery Friday.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 29, 2013, 12:35:53 pm
[quote author="ian"]I got a digitally set dispenser with lots of settings all the bits and bobs and tips (not a compressor, which I have to get) for 320rmb, about 50 bucks US. I saw some starting at $25 though, this was the most expensive one I could find. I don't have a pic, but it is scheduled for delivery Friday.[/quote]

Wow, that's the price of two stencils. I have got to find me a place to get one of those.

-Nick
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: sdixon on January 29, 2013, 05:52:49 pm
I did some experimenting with a sheet of acrylic and a laser cutter to create a stencil8 block.  It is hard to get a really tight fit on the 2.5mm pegs with a laser cutter since the holes are not nearly as precise as they would be from a mill.  So there is a little play in the pegs when you put them in the plastic block.  However, the 2.5mm holes which were milled into a test PCB were a more precise fit so when the board is placed onto the pegs the whole thing is very stable.  I also did some tests of cutting appropriate holes into a Kapton stencil with a laser cutter.  There is still a very small amount of movement in the stencil but overall I think the alignment is very good.  A metal stencil would probably work better since it would be more rigid.
I still have to do a complete board including putting the paste down and reflowing but I think that a laser cut plastic block and Kapton stencil is a reasonable, lower cost, way to do the stencil8 process.  It is certainly not going to be as precise as a milled aluminum plate or a metal stencil but I think it will work pretty well.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 30, 2013, 10:46:02 am
[quote author="ian"]I got a digitally set dispenser with lots of settings all the bits and bobs and tips (not a compressor, which I have to get) for 320rmb, about 50 bucks US. I saw some starting at $25 though, this was the most expensive one I could find. I don't have a pic, but it is scheduled for delivery Friday.[/quote]

So, they're a bit more expensive on aliexpress etc - about $100, but still not outrageous.

What did you get for an air compressor? All the options seem to be either 12v automotive ones, or huge expensive 20+ litre ones.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Kean on January 30, 2013, 11:02:20 am
You don't want an automotive tyre one - they run continously and are horribly noisy.  You need one with a pressure tank, and generally they are a few hundred dollars for anything decent, up into the thousands.  Not sure if the hobby size ones sold at model stores have enough pressure/capacity for dispensing, but they typically are sold at a premium price.  The cheap compressors for home garage use are bulky and also very noisy when running, but once pressurised you can just turn it off and use the stored pressure to complete a dispensing job.  Belt drive are quieter than direct drive, but again more expensive.  For my work, I went with an aluminium tank model that is lighweight and also rated to be pretty quiet - but pretty expensive for hobby use.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 30, 2013, 11:13:25 am
I'm looking at a few alternatives right now. One would appear to be air compressors designed for use with airbrushes. They're small, cheap, have a tank, and operate at up to 70PSI.

Another alternative is Scuba or paintball gun air tanks - though then the issue is getting them refilled.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Kean on January 30, 2013, 11:30:06 am
Yeah, the airbrush ones was what I was thinking of as "hobby size".  70psi should be OK, I think I generally have mine set around 60psi.  But the small tank means it will have to run more often, and when I looked at them I decided they don't look very solid.  In Australia they sell fo nearly $400 though at a hobby store, but maybe available cheaper online.  My 20L aluminium tank "light industrial" unit was a bit under $500.  You can get cheaper 12L ones for under $200.  Noise is the main issue with cheap ones, but of course you also need the space.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 30, 2013, 01:08:13 pm
Yikes. Just got back from looking at a few. 24L (20L?) is $150 at the brick and mortar. Googling I found the same with free delivery for $100, and a smaller 6L model with all the same pressure specs for $100 (both free delivery).
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Kean on January 30, 2013, 01:10:39 pm
And at that price they will be crap - you get what you pay for!
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 30, 2013, 01:21:25 pm
I'm currently looking into alternatives for stored gas - such as buying a CO2 or air cylinder. A scuba tank would last forever and costs a pittance to fill, but tanks are expensive and bulky.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 30, 2013, 01:28:05 pm
I don't mind crap, I only plan to do one-offs with dispenser, stencils for multiples for sure.

adding - will wait until the dispenser it is delivered so I know the exact specs I can get away with.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Kean on January 30, 2013, 01:35:29 pm
Fair enough!  :D

I actually started with a cheap/crap compressor many years ago, but upgraded last year once I was happy with the whole system, and wanted something that didn't require me to wear ear protection.  The compressor is also located on the other side of the workshop where I have the other machine tools, with a long pressure hose going to the electronics benches.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: blarson on January 30, 2013, 03:24:17 pm
In the US, the cheap, heavy, noisy variety are available at harbor freight.  I got one like this http://www.harborfreight.com/3-gallon-1 ... 95275.html (http://www.harborfreight.com/3-gallon-100-psi-oilless-pancake-air-compressor-95275.html) for $40 a couple of years ago on sale.  It's marginal at its primary job of 80psi tire inflation.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 30, 2013, 03:25:25 pm
Biggest shipment released from customs! :) probably too late for delivery today, but in time for workshop video tomorrow for sure.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on January 30, 2013, 03:33:18 pm
[quote author="ian"]Yikes. Just got back from looking at a few. 24L (20L?) is $150 at the brick and mortar. Googling I found the same with free delivery for $100, and a smaller 6L model with all the same pressure specs for $100 (both free delivery).[/quote]

Also, have you checked out air compressors intended for airbrushes? I'm not sure, but I think they may do the job.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on January 30, 2013, 03:35:39 pm
yeah, gonna wait to get the dispenser so I know exactly what pressures it wants.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: neslekkim on February 06, 2013, 09:31:57 pm
[quote author="ian"]Will do. Was actually thinking of bringing them here and selling from our DP store because it's so low volume and Seeed is valuing their stock space pretty highly right now, but the tins are definitely for the Seeed Store.[/quote]

Do you have an store here?, I think you have mentioned an DP shop before also, but I cannot find it?, or is it future plans?
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on February 07, 2013, 11:01:24 am
We have the free PCB store and occasionally put stuff for sale in there too.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Zuph on February 08, 2013, 02:59:47 am
Well, I though I could get this thing milled for cheap, but the mill I have access to just can't cut the mustard with aluminum.

(http://http://i.imgur.com/XOL7yUY.jpg?1)

So, I've got some Delrin on the way, and I'm going to give it another go.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: bearmos on February 08, 2013, 03:24:39 am
Too bad it didn't work out (yet).

I thought the main attraction of acetal (delrin) was that it machined about hte same as aluminum (in my experience it tends to flow a little bit when trying to cut though)?

I'm guessing it's one of the home-brew type mills?  What kind of bit are you useing, feed, spindle speed.  Are you trying to use an end-mill and do a hellical path along the inside wall of the hole, or are you doing this with a standard drill bit?

in my limited CNC milling experience - primarily with wood, MDF and FR4 - i've found the solution to most of my issues was solved by using lighter (less agressive cuts).  With Al, most of the manual machining I've done - a bit of cutting fluid goes an awefully long way - helps to reduce heat quite a bit.

After using some HSS bits, I decided that all i wouldn't waste time with steel anymore - I only use carbide cutters now - helps out tremendously - the difference in cutting quality and tool flex is incredible.

Also, if your spindle has limited run-out, you may be able to get a bit that's of the proper diameter (or maybe a fraction under) and just do some drilling operations.  Pretty much no matter what your setup is - i would think that you'd be able to get away with peck drilling and cutting fluid.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Zuph on February 08, 2013, 01:35:01 pm
In my (also very limited) experience, Delrin is quite a bit easier to cut than aluminum.  This is a homebrew mill setup, designed and built by someone with a lot more experience in machining than I'll ever have.  The bit I used for aluminum was a coated HSS, 2-flute end mill recommended for drilling operations.  Feed speed was 5 IPM, spindle speed was ~10k RPM.  I was using a peck drill cycle, going 1/32" at a time.

The biggest problem is that the mill has a bit of slop in the Z-carriage when placed under high thrust loads. The result is that bit would skip around on the surface when penetrating.  With the delrin, I ordered a bit which claims superiority in drilling plastic.  Hopefully the reduced hardness of delrin (compared to aluminum) will mitigate this problem.  If that doesn't work, I'll order some center-drills, and indent the surface before the drilling operation.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: bearmos on February 08, 2013, 02:15:41 pm
[quote author="Zuph"]The bit I used for aluminum was a coated HSS, 2-flute end mill recommended for drilling operations. Feed speed was 5 IPM, spindle speed was ~10k RPM. I was using a peck drill cycle, going 1/32" at a time.

The biggest problem is that the mill has a bit of slop in the Z-carriage when placed under high thrust loads. The result is that bit would skip around on the surface when penetrating.[/quote]
That certainly sounds reasonable. So was the issue getting the bit centered when starting the hole (which the center drill should help greatly) or actually drilling it? Also, 10k at 5IPM will probably generates quite a bit of heat because of the super light chip load - (not so good for the HSS bit)?  I would say cutting fluid would certainly help this (but it looks like you were using some based on the picture).  Using a lower speed would as well, (you can't really go with a higher feed rate if the z-axis is already having trouble with the load).  The other approach you might consider is to use the mill to accurately place your centers - then a nice sturdy drill press for actually drilling the holes (possibly having more rigidity and lower speeds than what the mill has) - this is assuming you have a nice drill press available.

[quote author="Zuph"]
 With the delrin, I ordered a bit which claims superiority in drilling plastic. Hopefully the reduced hardness of delrin (compared to aluminum) will mitigate this problem. If that doesn't work, I'll order some center-drills, and indent the surface before the drilling operation.[/quote]
This sounds like a great plan - excellent bits can make a world of difference.  Also, like I said before, the Delrin will tend to flow a little when cut, so that will help keep the holes the correct size, even if the spindle does have some run-out.  I haven't tried milling acetal for quite a while - maybe I'll have to give it another shot sometime ( I was thinking about trying to make some better anti-backlash nuts).

The inline picture is pretty small - is sounds like the main issue is that the holes are too large in diameter?
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Zuph on February 08, 2013, 03:15:08 pm
[quote author="bearmos"]That certainly sounds reasonable. So was the issue getting the bit centered when starting the hole (which the center drill should help greatly) or actually drilling it? Also, 10k at 5IPM will probably generates quite a bit of heat because of the super light chip load - (not so good for the HSS bit)?
[/quote]

Unfortunately, the mill was built for milling wood, so I don't have a reliable way to get the spindle speed below 10k RPM.  I did use cutting fluid.  On all the holes, the drill hit was sloppy, but as it drilled down, it approached the "true" diameter.  Unfortunately, the holes are shallow enough that this still allows some play in the dowel pins.  A bigger problem is that the drill hit would occasionally skip all over the face of the block, resulting in even higher thrust loads, resulting in skipped Z-axis steps.  This happened on 2 holes in the block shown.

The drill press idea is interesting.  I may give that a go if milling delrin goes down-hill.  I do have access to a fairly nice (if ancient) drill press.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: bearmos on February 08, 2013, 03:59:04 pm
[quote author="Zuph"]Unfortunately, the mill was built for milling wood, so I don't have a reliable way to get the spindle speed below 10k RPM. I did use cutting fluid. On all the holes, the drill hit was sloppy, but as it drilled down, it approached the "true" diameter.[/quote]
This sounds a lot like my home setup (http://http://twilightrobotics.com/cnc/cncnot2).  I found that the best way of making accurately sized tooling pins (in MDF) was to use a 1/16" end mill and use a helical pattern to create 1/8" diameter tooling pin holes.  Many attempts at the tooling holes can be seen about half way down the page.  Cambam supports this type of helical drilling operation natively.  There's a free edition at the bottom of this page (http://http://www.cambam.info/downloads/) that I use a lot.  If I start getting more serious about milling, I'll probably spring for the paid version ($150) - it seems to make basic operations really fast.

EDIT: The most important point for the helical drilling operation is that it allows you to tune the "ideal" diameter of the hole iteratively until you get a snug fitting tooling pin.  For example, if you have 2 mils of runout in your spindle you can still get a hole that will snugly fit your 1/8" tooling pin when using a 1/16" end-mill, after making the diameter of the "ideal" hole smaller in CAM.  This method can also be used to compensate for tool wear (as cutters get used their diameter changes ever so slightly) - but there are also other methods of dealing with tool-wear compensation.

[quote author="Zuph"] I do have access to a fairly nice (if ancient) drill press.[/quote]
If taken care of, these are often times better than a lot of the inexpensive newer presses.  The idea is that centering holes (accurately placed with the CNC) will help guide the bit to the precise center once it's on the drill press.  Since the press is better at drilling through metal than the CNC - you get the best of both worlds.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on February 22, 2013, 02:50:38 pm
Mine arrived!  Thanks again!

It came so much faster than I expected. I had no idea what this heavy block of a package was :)
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on February 22, 2013, 02:59:49 pm
That was fast! Please do let me know what you think.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: doub on March 12, 2013, 09:55:52 am
I finally decided to invest in one of these blocks, but they are sold out :-(

Anyone know if there will be another batch?
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on March 12, 2013, 10:05:36 am
The CNC shop who made the first batch gave me a huge amount of trouble and eventually gave up and sent most of the stock back unused. I'm still trying to get a refund out of them, and I had to refund most of the buyers.

I have found someone with much more experience with Aluminium who has offered to do the remainder for a very reasonable price. So I'll be offering them up again on Tindie once they're actually finished this time. If one of the original purchasers doesn't buy again, you might be able to snap one up.

I'm also exploring the possibility of making ones out of polycarbonate (lighter, so cheaper to ship) with a reduced hole count for substantially less than these ones cost.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: ian on March 12, 2013, 11:24:17 am
Sorry it turned out like that, I really appreciate the trouble.

Someone mentioned delrin (?) or some other very hard and stable material too.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on March 12, 2013, 11:33:45 am
Yup, I considered Delrin too, but according to the new CNC guy, Polycarbonate has better dimensional stability. He's going to knock together a sample for me when he does the Aluminium blocks.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: Kean on March 12, 2013, 11:36:13 am
Yes, I'd also strongly recommend polycarbonate over delrin for this.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: bearmos on March 12, 2013, 12:43:05 pm
[quote author="nickjohnson"]I have found someone with much more experience with Aluminium[/quote]
Wow, sorry to hear this was so miserable for you, Nick.  With all of machinists I deal with Al is the preferred material - I would have never imagined something so straight-forward would become a headache.

Good luck with the future revs, I'll be curious as to how the polycarbonate turns out - I've always seen things machined out of Acetal.  I might have some reading to do ;-)
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: neslekkim on March 12, 2013, 05:03:45 pm
Anyone tried this for stencils?
http://hackaday.com/2013/03/11/pcb-stencils-for-200/ (http://hackaday.com/2013/03/11/pcb-stencils-for-200/)
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on March 23, 2013, 07:45:10 pm
The tooling block's back in stock (http://https://tindie.com/shops/arachnidlabs/pcb-fixture-block-for-solder-paste-stencilling/)! With all of 3 units available, heh.

And I've been working with a CNC shop to make a polycarbonate version (http://https://tindie.com/shops/arachnidlabs/polycarbonate-pcb-fixture-block/). The reduced hole count makes it cheaper to produce, while still being as capable as the original, and polycarbonate being lighter, it's cheaper to post too. Plus, it just looks really cool.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: doub on March 23, 2013, 08:23:20 pm
I just ordered an aluminium one, thanks for the update :-)
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: RasmusB on February 05, 2014, 10:23:57 pm
[quote author="nickjohnson"]And I've been working with a CNC shop to make a polycarbonate version.[/quote]

I might be a bit late to the party, what happened to the polycarbonate version?
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: nickjohnson on February 05, 2014, 10:37:01 pm
[quote author="RasmusB"][quote author="nickjohnson"]And I've been working with a CNC shop to make a polycarbonate version.[/quote]

I might be a bit late to the party, what happened to the polycarbonate version?[/quote]

I put it up on Tindie for a fundraiser, and nobody backed it - the aluminium version is more expensive, but far more popular.
Title: Re: A stencil8 PCB tooling block for doing solder paste sten
Post by: RasmusB on February 05, 2014, 10:45:15 pm
Ok, thank you.
Title: Re: A stencil8 PCB tooling block for doing solder paste stencils
Post by: forrestv on November 19, 2019, 12:14:02 am
(Sorry to resurrect a long-dead thread, but I think that this is useful enough to justify it.)

Ever since nickjohnson's stock ran out, there hasn't been any way to get Stencil8 fixture plates. I've started manufacturing them and selling them at a similar price and intend to do so indefinitely.

One of these links should always work:

* http://forre.st/stencil8
* https://www.amazon.com/dp/B081NYLXD3

Hope this helps somebody!