swill's minimal case design

[swill]

NEW: Launched a website to cover some of the prototyping and such...

blog.swillkb.com

PROTOTYPING...
These sessions are in reverse order.  The newest is at the top...


Back to business.  This is the most minimal case I have come up with so far.  It is simply a single sheet of acrylic with holes tapped for mounting the PCB.  I can get away with this because all the components are about the same height and acrylic is not conductive.  I may put a silicon sheet in between the PCB and the back plate, but I will put about 100 hours on this board like this before I decide what I want to do.  I added rubber bumpons on the back to add a little tilt and a strip of no slip tape along the front edge (not pictured).  It is pretty solid and a comfortable typing feel, so I may stick with it like this for a while...




Something for fun.  Here is what I did to my 40% board.  It is basically an all silicon case.  The PCB sits on the inside silicon layer and the PCB is hugged by the top layers.  This is a SUPER stable case because it is a full sheet of silicon making contact with the desk surface.  I was actually planning to put the backplate on, but I got this far and fell in love. 




In this second round of tests, I did not use any brass threaded inserts or any brass standoffs.  Instead, I just tapped the acrylic directly and put a silicone sheet between the PCB and the backplate.  I have not yet tested the solid core silicone sheets.  In this case I used a closed cell silicone foam sheet.  It has a very low durometer (I think its like 20A), but since there is so much surface area touching it has a pretty comfortable typing feel.  So far this is the best feeling setup.  On this one I also added rubber bumpers on the back and I wrapped the front edge with an aircraft tape that has a reasonably high coefficient of friction.  It sticks to the desk about as much as my Filco does with this setup, so that is pretty good considering it is a 60%.




The first prototype with an acrylic base plate, brass threaded inserts and male/female brass standoffs...  I am pretty happy with the initial result...


Tried tapping 5mm acrylic (just over 3/16") and I am super happy with the result.  I was able to strip the screw without any damage to the threads.  I will be doing more tests with 1/8" acrylic as I think that will be a really nice thickness.



Basic description of my case (images attached):
- 1/8" Aluminium bottom plate || 1/16" Stainless Steel || Wooden wedge
- 1/8"-3/16" Silicon pad; Thickness TBD based on max component height; Cutouts for taller components
- PCB + optional plate
- Rubber stick on adhesive feet to control the prefered keyboard angle.
- Bolts to hold the three layers together.

Motivations for my design:
- I want the solid feel of plate mounted switches, but without having to use a plate (can if you want to).  By having the PCB bolted to the back plate via the silicon pad, I should be able to get a very solid feeling PCB mount.
- I wanted to get some of the benefits of PCB mounted switches.  Easy access to open switches.  I also want the dynamic feel of a PCB mounted switch.
- By using the silicon, I hope to achieve lots of the benefits of the Trampoline Mod.  Basically, it will be quieter than most cases and should have a little bit of a bounce/spring/feedback on bottom out.
- I want a super simple and rugged design that can be easily adapted to different PCB layouts.
- I want a very low cost case that is very accessible for prototyping.  The total for this case should be in the ballpark of around $30.
- I want a relatively low profile, but with the ability to increase it by adding larger feet.  Gotta have a low profile for my new SA caps that are coming. 

I am targeting smaller boards with this case.  It could potentially work on a TKL, but I will be focusing on designing for boards in the size range of 40%, 60% and 75%.

Here are some very basic renderings (I am a noob with CAD so forgive me).  They are still very rough and none of the dimension are final, but I used the GH60 layout for the initial design.

Metal back plate and rubber feet:
(the holes in the metal plate will be threaded so the pcb will be bolted directly to the back plate.)





Wood wedge base:
(this would have threaded inserts mounted into the wood, like this)




Acrylic/Plexiglass base:
(this would have threaded inserts mounted into the plexiglass for the screws)




And a shot of the silicon pad.  This is what I currently have, but I have a supplier for this already because we use this at www.kiteaid.com to distribute iron pressure.

[Photekq]

solidworks

[CPTBadAss]

I've seen files in Solidworks, AutoCAD, and Sketchup. You could use Inventor as well and it's free. I prefer and have Solidworks. AutoCAD was mostly for drawings. It's not good for a 3D visualization.

[metalliqaz]

I use librecad to do 2D designs.

[Melvang]

Solidworks gets my vote.  If you are a student you can get a copy for about $150 or if you are a veteran you can get the student version for $20.  Keep in mind that the student version is only a 1 year license and does not include updates or formal tech support.  The full version if I heard correctly when I was talking with one of their reps cost in the realm of $43,000.  But that includes free updates for life, and full tech support along with all the features available.  Some of the more advanced stuff is blocked on the student version to my knowledge.  But it is what I use being a vet.

[agodinhost]

Sketchup mainly, OpenScad for compositions and DoubleCad XT for 2d stuff.

[metalliqaz]

I thought Sketchup was mostly for making models of buildings and bridges and stuff like that?

[swill]

Thanks everyone.  There are definitely ones in here I did not know about, so I will have to go check them out. 

Not sure that I can afford solidworks right now.

When I drew up plans for my two level deck addition for my house to be submitted to the city, I used Sketchup.  It was pretty easy to use and that was what I was planning to use if there was not something that was obviously better.

Another question...
Is there a resource somewhere that describes the exact dimensions of the most common PCBs?  I am assuming there must be some common knowledge about that considering now many Poker cases there are.

For now I am most interested in the GH60 dimensions, but any specific dimensions would be welcome just so I have something to start from.  My design should be able to support many different sized PCBs very easily.

Thanks...

[Photekq]

http://geekhack.org/index.php?topic=34959.msg954124#msg954124

[jdcarpe]

This is the upcoming SmallFry 40% Keyboard:

[swill]

I love it. You guys are so fast.

Alright that gets me going for what I wanted to get done tonight.   Thx...

[swill]

Thank you for your input so far.  I have introduced my case design in my entry in Glissant's giveaway, so you can go check it out there.  I will be creating an actual thread specifically for this case design so I can field questions about it.

On that note.  Should I just change the title of this thread and change its intent to be specific to my case, or should I create a new thread specifically for my case design and leave this thread as is for people to discuss case cad topics?

[CPTBadAss]

On that note.  Should I just change the title of this thread and change its intent to be specific to my case, or should I create a new thread specifically for my case design and leave this thread as is for people to discuss case cad topics?

Rename the title and keep talking about your case here is my vote.

[metalliqaz]

Thank you for your input so far.  I have introduced my case design in my entry in Glissant's giveaway, so you can go check it out there.  I will be creating an actual thread specifically for this case design so I can field questions about it.

On that note.  Should I just change the title of this thread and change its intent to be specific to my case, or should I create a new thread specifically for my case design and leave this thread as is for people to discuss case cad topics?

Very interesting concept.  I've totally done that with a half-assembled PCB and a mouse pad.  It's a good idea.

[swill]

One thing that I am unsure about so far is if the PCB will be held in place well enough with just the mount points that are in the PCB.  I am assuming it will, but if not, I will have to do something around the outside edge to stabilize the pcb.  We will see, I will only add that sort of detail if the initial design does not work because my goal is to keep this as simple as possible.

I need to build some prototypes first to see how they feel.

I am going to start out with aluminium sheets because I think they will probably have the closest 'feel' for what I am looking for, but if I have problems with warping, I may have to switch to steel.  I have considered using wood as well (something like 1/4 inch russian birch), but I think a metal will be a better fit.  The great thing about the design is that the bottom plate is the only thing that needs to be machined and it is done with standard sheet material, so there is totaly room to play with different mediums.

A question I have to the machinists out there.  If I do the bottom plate in steel, I was considering just using a tap and die set to thread the holes in the bottom plate so no nuts are needed on the back side.  This way the bolts would go through the PCB and screw directly into the bottom plate.  If I use aluminum, will it be solid enough for me to tap and die the holes to thread them (sorry I can't remember which is the tap and which is the die right now)?

[CPTBadAss]

Yes you can thread aluminum with a tap and die.

[Melvang]

Aluminum will be fine.  Taps very easy just don't over tighten the screws.  I wouldn't go with anything thinner than 1/16".  I believe this is pretty close to 16 gauge.  I don't usually work with stuff that thin at work aside from precision shim stock which comes down to .001" and is exactly what they say it is.  For the most part I work with 1/8" up to 2" plate.

[metalliqaz]

One thing that I am unsure about so far is if the PCB will be held in place well enough with just the mount points that are in the PCB.

I think it will.  Once that thing is snug against the foam, it isn't going to want to move.  There is also the issue of catching the corners, though.  It would be easy to lift it and break things.

[swill]

Aluminum will be fine.  Taps very easy just don't over tighten the screws.  I wouldn't go with anything thinner than 1/16".  I believe this is pretty close to 16 gauge.  I don't usually work with stuff that thin at work aside from precision shim stock which comes down to .001" and is exactly what they say it is.  For the most part I work with 1/8" up to 2" plate.

I got a quote from a local place for $6/piece of .09" (~3/32) of 6" x 12" cut offs.  I picked that thickness originally because I thought it would be thick enough, but I was really just guessing.  Maybe I will start out by getting a piece at 3/32 and one at 1/8 and see which I prefer.

When I tap, I should probably try to use a higher thread count in order to minimize the possibility of stripping the threads, is that right?  Or should I just try to get as much thread depth as possible?  I am not sure which is more durable.  Higher thread count makes it easier to know that you are tight enough without putting too much pressure, but the threads are usually not as deep in the plate walls.

[swill]

One thing that I am unsure about so far is if the PCB will be held in place well enough with just the mount points that are in the PCB.

I think it will.  Once that thing is snug against the foam, it isn't going to want to move.  There is also the issue of catching the corners, though.  It would be easy to lift it and break things.

I agree, I was thinking of doing corner caps, but I have not looked into how feasible that is yet...  Please link anything you think would help solve that problem.  I have a couple ideas, but I am still undecided how I would attach them..

Edit: Maybe even just a non-structural vinyl cap could work to keep the edges protected: http://www.dgpcaps.com/ENG/ENGcnc.html

[metalliqaz]

I would probably just go with whatever is easy to find, for example 4-40

[Melvang]

Aluminum will be fine.  Taps very easy just don't over tighten the screws.  I wouldn't go with anything thinner than 1/16".  I believe this is pretty close to 16 gauge.  I don't usually work with stuff that thin at work aside from precision shim stock which comes down to .001" and is exactly what they say it is.  For the most part I work with 1/8" up to 2" plate.

I got a quote from a local place for $6/piece of .09" (~3/32) of 6" x 12" cut offs.  I picked that thickness originally because I thought it would be thick enough, but I was really just guessing.  Maybe I will start out by getting a piece at 3/32 and one at 1/8 and see which I prefer.

When I tap, I should probably try to use a higher thread count in order to minimize the possibility of stripping the threads, is that right?  Or should I just try to get as much thread depth as possible?  I am not sure which is more durable.  Higher thread count makes it easier to know that you are tight enough without putting too much pressure, but the threads are usually not as deep in the plate walls.

I would use a coarse thread for this purpose.  I realize that this isn't a high strength application but fine thread doesn't usually stand up as well in softer materials.  Plus fine thread is a lot easier to cross thread in these smaller sizes.

[swill]

Aluminum will be fine.  Taps very easy just don't over tighten the screws.  I wouldn't go with anything thinner than 1/16".  I believe this is pretty close to 16 gauge.  I don't usually work with stuff that thin at work aside from precision shim stock which comes down to .001" and is exactly what they say it is.  For the most part I work with 1/8" up to 2" plate.

I got a quote from a local place for $6/piece of .09" (~3/32) of 6" x 12" cut offs.  I picked that thickness originally because I thought it would be thick enough, but I was really just guessing.  Maybe I will start out by getting a piece at 3/32 and one at 1/8 and see which I prefer.

When I tap, I should probably try to use a higher thread count in order to minimize the possibility of stripping the threads, is that right?  Or should I just try to get as much thread depth as possible?  I am not sure which is more durable.  Higher thread count makes it easier to know that you are tight enough without putting too much pressure, but the threads are usually not as deep in the plate walls.

I would use a coarse thread for this purpose.  I realize that this isn't a high strength application but fine thread doesn't usually stand up as well in softer materials.  Plus fine thread is a lot easier to cross thread in these smaller sizes.

Thank you. I was a bit concerned about that too. I will try to stick to a relatively standard thread. I have to check what I have in my tap and die set.

[swill]

Anyone know the length and width of a 75% PCB?  Thx...

[metalliqaz]

Anyone know the length and width of a 75% PCB?  Thx...

A 75% doesn't have to be a specific width/height.  However, the numbers you are looking for are these: 12" width x 4.5" height.

[swill]

Anyone know the length and width of a 75% PCB?  Thx...

A 75% doesn't have to be a specific width/height.  However, the numbers you are looking for are these: 12" width x 4.5" height.

Thats perfect, thanks...  I putting together some sourcing for the silicon and I want to reduce waste as much as possible, but still be able to support both 60% and 75% with my initial order for prototyping.

I need to play with a few different durometers as well so I can try to produce a really solid typing feel.  We will see what I come up with...

[Leslieann]

Thanks everyone.  There are definitely ones in here I did not know about, so I will have to go check them out. 

Not sure that I can afford solidworks right now.

Try Tinkercad.com
It's free and easy, you can do almost anything with it given enough creativity (except compound curves). I've designed a whole 3d printer with it.

[metalliqaz]

I've designed a whole 3d printer with it.

Mega geek-cred.

Also, Solidworks can be had for the low-low price of free if you know where to look...

[Oobly]

I've designed a whole 3d printer with it.

Mega geek-cred.

Also, Solidworks can be had for the low-low price of free if you know where to look...

IMHO, Solidworks and a lot of other commercial software should change their model a bit. Free for personal use, pay for commercial is how it should be (with different prices / packages depending on shop size perhaps). That way you learn how to use a good package as a hobby and if you ever go commercial, you pay for it. They'd get a whole lot more users that way and people wouldn't have to learn some other free (and often inferior) package for hobby use. You could perhaps have a limited number of plugins / feaures for the free version (over and above the basic design package), but the user can choose which ones.

Anyhow, back on topic: Great idea! I suspect 3/32 aluminium will be a little thin to hold a good thread without nuts (unless you're very careful tightening the bolts), but 1/8 should do very well. I'd go for 1/8 for rigidity, too, but it all depends on the feel you want. 3/32 will be more "springy".

[Melvang]

I've designed a whole 3d printer with it.

Mega geek-cred.

Also, Solidworks can be had for the low-low price of free if you know where to look...

In my experience any free version of solid works is a pirated copy.  However, if you know a veteran with a dd-214 (discharge paperwork) it can be had legally for $20.  I don't feel we should be condoning illegal activity.

[swill]

Anyhow, back on topic: Great idea! I suspect 3/32 aluminium will be a little thin to hold a good thread without nuts (unless you're very careful tightening the bolts), but 1/8 should do very well. I'd go for 1/8 for rigidity, too, but it all depends on the feel you want. 3/32 will be more "springy".

Ya I am planning to go with 1/8 for aluminum. Less if I use steel.

I want the bottom plate to be rigid. I will play with the durometer if the silicon to match the typing feel I want.  I am not going for 'springy', I want solid with a subtle dampening on bottom out. A bit like how a topre board feels when you bottom out. I know that is not realistic, but I want to see how close I can get.

[swill]

Added some wood wedge renderings as a potential base material...

[akikun]

I really like this idea, and I think the wood base would be gorgeous. What do you guys think would be the best way to cut that slant, though? Bandsaw with a tilting table, maybe?

[swill]

I really like this idea, and I think the wood base would be gorgeous. What do you guys think would be the best way to cut that slant, though? Bandsaw with a tilting table, maybe?

A band saw with a jig is probably the best option. 

[swill]

added plexiglass renderings and launched swillkb.com...

[regack]

Nice.  I like this idea, trying to figure out how to adapt to to board where I have stuff stuck to the bottom.  Maybe some cutouts in the bottom plate in strategic places.

[swill]

Nice.  I like this idea, trying to figure out how to adapt to to board where I have stuff stuck to the bottom.  Maybe some cutouts in the bottom plate in strategic places.

This is why I asked you about the profile of the bottom of the board in the GH60 thread. 

The great thing is that there is a silicon sheet between the bottom plate and the PCB, so yes, I will be doing cutouts in the silicon sheet for the components that are taller than average.  For example, the USB connector and the reset switch, etc...  For something like the reset switch, I may even do a cutout in the bottom plate as well so it can be accessed without removing the case at all...

[regack]

Nice.  I like this idea, trying to figure out how to adapt to to board where I have stuff stuck to the bottom.  Maybe some cutouts in the bottom plate in strategic places.

This is why I asked you about the profile of the bottom of the board in the GH60 thread. 

The great thing is that there is a silicon sheet between the bottom plate and the PCB, so yes, I will be doing cutouts in the silicon sheet for the components that are taller than average.  For example, the USB connector and the reset switch, etc...  For something like the reset switch, I may even do a cutout in the bottom plate as well so it can be accessed without removing the case at all...

Yes, Komar answered in there with some measurements, but I have some one-offs with daughterboards sticking ~7mm off the bottom, but I'd guess they're unique to me, and not really a problem for anyone else.  I just have this (probably unwise) fascination with the idea.

[swill]

Nice.  I like this idea, trying to figure out how to adapt to to board where I have stuff stuck to the bottom.  Maybe some cutouts in the bottom plate in strategic places.

This is why I asked you about the profile of the bottom of the board in the GH60 thread. 

The great thing is that there is a silicon sheet between the bottom plate and the PCB, so yes, I will be doing cutouts in the silicon sheet for the components that are taller than average.  For example, the USB connector and the reset switch, etc...  For something like the reset switch, I may even do a cutout in the bottom plate as well so it can be accessed without removing the case at all...

Yes, Komar answered in there with some measurements, but I have some one-offs with daughterboards sticking ~7mm off the bottom, but I'd guess they're unique to me, and not really a problem for anyone else.  I just have this (probably unwise) fascination with the idea.

 We can definitely do cutouts in the bottom plate, with the non-wedge design, to accommodate for the daughter board.  Probably easiest to prototype with 1/4" acrylic, but if the cutout is large we may want to go with aluminum or steel to make sure we don't lose too much structure...

[regack]

 We can definitely do cutouts in the bottom plate, with the non-wedge design, to accommodate for the daughter board.  Probably easiest to prototype with 1/4" acrylic, but if the cutout is large we may want to go with aluminum or steel to make sure we don't lose too much structure...

They're pretty small: 46mm x 17mm and 38mm x19mm... even with the wedge made of wood, I could just chisel out some space I suppose.  Anyway, I like your ideas!

[swill]

 We can definitely do cutouts in the bottom plate, with the non-wedge design, to accommodate for the daughter board.  Probably easiest to prototype with 1/4" acrylic, but if the cutout is large we may want to go with aluminum or steel to make sure we don't lose too much structure...

They're pretty small: 46mm x 17mm and 38mm x19mm... even with the wedge made of wood, I could just chisel out some space I suppose.  Anyway, I like your ideas!

I have a couple wood wedge ones being made for me by The Beast and nubbinator.  I am about to start prototyping with 1/4 plexiglass soon.  The metal ones are going to be a bit more expensive, so I will wait till I have PCBs in hand and have tested with plexiglass first before I do any metal ones. 

I am basically waiting on getting my first PCB before I start doing real prototyping.  I expect to get Sprit's in probably about a month, so that will probably be the first. 

I am stockpiling quite a bit of material for these cases while I wait for the PCBs.  I am going to try a lot of different mediums, so I will be making a bunch right away.  Once I start prototyping I will probably start selling them at cost or giving them away so other people can try them and give me some feedback...

[regack]

The 40% designs could really take advantage of this, I imagine.  I'll make sure you get one to play with when I get some prototypes made.

[mkawa]

we DO NOT condone illegal activity or software piracy here. please remove references or the mod team will do it for you.

swill? what does pricing look like on those silicone sheets? those are really nice. what dimensions (thickness in particular) can your provider supply? i have a particularly cool application for them

[swill]

we DO NOT condone illegal activity or software piracy here. please remove references or the mod team will do it for you.

swill? what does pricing look like on those silicone sheets? those are really nice. what dimensions (thickness in particular) can your provider supply? i have a particularly cool application for them

What reference are you referring to in regards to software piracy?  I don't think I have promoted software piracy, at least I never intended to.

I am going to see if I can get away with 1/8th thickness. The height difference between the average and tallest component will be my limiting factor.

For testing I am just getting from eBay cause my supplier likes quantity.  On eBay it is priced in the ballpark of $20/square foot.  I am also getting it with an adhesive backing and with high temp rating.

[swill]

The 40% designs could really take advantage of this, I imagine.  I'll make sure you get one to play with when I get some prototypes made.

I appreciate that. Jdcarpe is going to build me one when it goes to GB as payment for a keyboard I sold him on credit.

If I could get a prototype I could hopefully get a run of these sorted out by the time the GB hits. 

[mkawa]

we DO NOT condone illegal activity or software piracy here. please remove references or the mod team will do it for you.

swill? what does pricing look like on those silicone sheets? those are really nice. what dimensions (thickness in particular) can your provider supply? i have a particularly cool application for them

What reference are you referring to in regards to software piracy?  I don't think I have promoted software piracy, at least I never intended to.

I am going to see if I can get away with 1/8th thickness. The height difference between the average and tallest component will be my limiting factor.

For testing I am just getting from eBay cause my supplier likes quantity.  On eBay it is priced in the ballpark of $20/square foot.  I am also getting it with an adhesive backing and with high temp rating.

mod team cleaned up the piracy reference (except for my reference to their reference)...

you should be fine at 1/8". that is pretty thick compared to the average passive component and far thicker than anything but a very large bga IC. people have been using those mesh PU sheets for shelf lining for quite a while now under pcbs here and those are more like 3/32" thick

what kind of quantities does your supplier need?

[swill]

we DO NOT condone illegal activity or software piracy here. please remove references or the mod team will do it for you.

swill? what does pricing look like on those silicone sheets? those are really nice. what dimensions (thickness in particular) can your provider supply? i have a particularly cool application for them

What reference are you referring to in regards to software piracy?  I don't think I have promoted software piracy, at least I never intended to.

I am going to see if I can get away with 1/8th thickness. The height difference between the average and tallest component will be my limiting factor.

For testing I am just getting from eBay cause my supplier likes quantity.  On eBay it is priced in the ballpark of $20/square foot.  I am also getting it with an adhesive backing and with high temp rating.

mod team cleaned up the piracy reference (except for my reference to their reference)...

you should be fine at 1/8". that is pretty thick compared to the average passive component and far thicker than anything but a very large bga IC. people have been using those mesh PU sheets for shelf lining for quite a while now under pcbs here and those are more like 3/32" thick

what kind of quantities does your supplier need?

The shelf liners are not being used as structure to support the board though. They are just used to reduce noise.  We will see once I start bolting pcbs to it.

Last time I had to order 100 sheets from my supplier.  I found a new supplier in the US that does not require a minimum which I can send you the details for.

[mkawa]

please do

[tjweir]

I plan on making my own cases for Sprit's internals. 

This looks interesting. 

[swill]

I plan on making my own cases for Sprit's internals. 

This looks interesting.

Shipping should not cost much to you. What size pcbs did you get?  I got 60 and 75, so I will be making cases for those.  Once I get prototyped together I will take some pictures/videos. I would send you one for the cost of materials.

I am trying very hard to make sure the cost of this case is VERY affordable. That is one of the main reasons for this design. There will be more expensive versions done in nice wood and metal, but I am hoping to have a super inexpensive version as well.