Standoff size and side height

Standard PCB templates and project cases

Re: Standoff size and side height

Postby dsm » Fri Feb 24, 2012 5:55 am

Scheme G "first article" DP6037-size case

The initial "-v1" top and bottom magnet holder prototype parts for Scheme G ordered 06Feb12 from Shapeways arrived back on 23Feb12. This was an unusually long delivery delay even for Shapeways and was probably caused by a catastrophic server failure Shapeways experienced earlier this month.

In fact, these parts took so long to arrive, that I have already updated the top and bottom magnet holder design and ordered new parts as described further on in this forum thread.

These initial "-v1" top and bottom magnet holder prototype parts were used to build a DP6037-size enclosure intended for the Bus Pirate v3.5e design. This enclosure provides 1.5 mm top and bottom acrylic windows [1] so that the circuitry on the top of the board and the pin usage legend on the bottom of the board can be observed. Neodymium magnets in the top and bottom magnet holders sandwich the board through the mounting holes in the corners of the board. For this prototype, the "north" pole protrudes from the bottom magnet holder parts and the "south" pole protrudes from the top magnet holder parts. Although I used cyanoacrylate glue to construct this initial Scheme G enclosure, my intent is to design the various constituent components so that the enclosure that needs no adhesives to hold it together.

IMG_0802_2.jpg
initial Scheme G case ~ top view

IMG_0803_2.jpg
initial Scheme G case ~ bottom view

IMG_0804_2.jpg
initial Scheme G case ~ edge view

IMG_0805_2.jpg
initial Scheme G case ~ exploded

Thanks for your time.

dsm

[1] The top and bottom acrylic windows had already been updated to "-v2" as described elsewhere (link).
Last edited by dsm on Fri Feb 24, 2012 1:40 pm, edited 2 times in total.
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Re: Standoff size and side height

Postby dsm » Fri Feb 24, 2012 6:18 am

Scheme G "first article" DP6037-size case (continued)

The DP6037-size Scheme G enclosure described above has no side walls. I believe that this Scheme G enclosure variant may be the best solution for many users since it assembles securely and comes apart easily.

In case someone does want side walls, however, there's an enclosure variant for that. 1.5 mm acrylic is used for the top, bottom, end, and side windows. There is an opening in the top acrylic window to allow an over-molded mini-USB cable to plug into the board and still hold the USB end window securely in place.

IMG_0798_2.jpg
initial Scheme G case with side walls ~ top view

IMG_0800_2.jpg
initial Scheme G case with side walls ~ bottom view

IMG_0801_2.jpg
initial Scheme G case with side walls ~ exploded

Thanks for your time.

dsm
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Re: Standoff size and side height

Postby dsm » Fri Feb 24, 2012 6:52 am

Scheme G top and bottom magnet holder comments

The initial "-v1" top and bottom magnet holder prototype parts for Scheme G (used for the above DP6037-size enclosure prototypes) were designed for 1.5 mm acrylic windows and had a retention ring (0.05 mm high by 0.5 long) scheme.
The redesigned "-v2" top and bottom magnet holder prototype parts have a one-way barb (0.15 mm high by 0.5 mm long).
In addition, I created variants for both 1.5 mm and 3.0 mm acrylic. These "-v2" top and bottom magnet holder prototype parts were ordered 13Feb12 and UPS claims that they should arrive later today.

If my intent is to design the various Scheme G constituent components so that Scheme G enclosures need no adhesives to hold them together, there are two critical dimensions...
  • The diameter of the magnet wells (under a range of SLS fabrication conditions) must allow the 3.0 mm diameter neodymium magnets to be held in place without adhesives (slight interference fit).
  • The diameter of the laser-cut holes in the acrylic windows must allow the one-way barb to securely and permanently capture the top and bottom magnet holders.

SchemeG-1x-v1-2x-v2.jpg
Scheme G "-v1" versus "-v2" top and bottom magnet holders

Thanks for your time.

dsm
Last edited by dsm on Fri Mar 02, 2012 12:36 am, edited 3 times in total.
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Re: Standoff size and side height

Postby ian » Fri Feb 24, 2012 7:21 am

Wow! Really amazing! With the pegs so inexpensive they could be a real alternative to the hex standoffs. Lighter to ship, easier to (dis)assemble, and custom colors too! Could even be sold as a kit with multiple color options.
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Re: Standoff size and side height

Postby tayken » Fri Feb 24, 2012 8:40 am

Loved it!
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Scheme G magnet holder pegs.

Postby arakis » Fri Feb 24, 2012 9:45 am

I converted DSMs magnet holder pegs from his scheme G to sketchup, and exported them as STLs.
I also used 2.55m for the acrylic width
I used these dimensions
base diameter 7mm,
base lenght, 1.5mm
shaft external diameter 5.2mm
shaft internal diameter 3.1mm (left 0.1 mm clearance)
shat internal length 3.1mm
shaft external length 2.55mm+5mm top, 2.55mm + 1.8mm bottom

Could someone plz check the STL files if they are the right dimensions, cause I am unsure if Sketchup exported them in inches or mm..or made the conversion properly, when I checked them in Meshlab they seemed ok.
Attachments
TopMagnetHolderSUmodel.rar
(16.95 KiB) Downloaded 166 times
bottomMagnetHolderSUmodel.rar
(16.89 KiB) Downloaded 187 times
TopMagnetHolder.rar
(5.78 KiB) Downloaded 191 times
bottomMagnetHolder.rar
(5.79 KiB) Downloaded 170 times
best regards FIlip.
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Re: Scheme G magnet holder pegs.

Postby arakis » Fri Feb 24, 2012 9:46 am

update

I uploaded one to check if shapeways will accept this conversion, and all is ok, the dimmentions ar alright as well
best regards FIlip.
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Re: Scheme G magnet holder pegs.

Postby dsm » Fri Feb 24, 2012 1:35 pm

comment

arakis,

I tend to try to prototype my designs before releasing them into the world. This is my humble way of trying to reduce the amount of faulty data on the internet. Unfortunately, this development approach tends to take quite a bit of time if you are using a relatively slow vendor like Shapeways. In my case, I am probably at least one more redesign-prototype-review cycle away from releasing [1] the Scheme G top and bottom magnet holder designs.

As a general comment, however, I think your model may have some slightly incommensurate dimensions at the system level.
On the other hand, I might be entirely wrong.
You should get some parts built via Shapeways or i.materialise and see what results from your design efforts.

Thanks for your time.

dsm

[1] Plus there is always the difficult question about where to label such small parts with CC BY-SA 3.0...
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Re: Scheme G magnet holder pegs.

Postby arakis » Fri Feb 24, 2012 3:12 pm

dsm, I am sorry.
I assumed since you released your designs without mentioning any license, that it was public domain. If you want I'll remove my designs from the forum.
best regards FIlip.
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Re: Scheme G magnet holder pegs.

Postby ian » Fri Feb 24, 2012 3:39 pm

hey dsm - sorry about that, I asked Filip to make a initial mock-up in sketchup just to see what it would be like, and what was involved in exporting to a format shapeways could use. I'm sorry if I was overzelous, I was just curious what was involved.
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Re: Scheme G magnet holder pegs.

Postby dsm » Fri Feb 24, 2012 4:52 pm

comment

ian,

Producing an "stl" file for Shapeways using Google SketchUp is fairly simple if you are willing to add a plug-in.

While I use SketchUp for some projects, I've been using Autodesk Inventor Profesional 2012 for this design mostly because it has some interesting wizards for designing tooling for injection molded parts. One problem with Scheme G is that the one-way barb retention feature on the top and bottom magnet holders greatly complicates the tooling design compared to the design variant without the one-way barb. Obviously this is a non-issue with SLS 3D printed parts.

arakis,

My main objection is not about whether or not you wanted to design your own variant of Scheme G, but instead my main objection is about whether it was necessary to start another forum thread when an existing discussion on this topic was already available. It seems to me that spreading relevant information across several forum threads makes it easier to loose track of information and harder to communicate experiments and results. I am not a proponent of trying to censor the intellectual efforts of others. As a compromise, rather than deleting your work, is there any simple way to just append this forum thread to the SoB "standoff size and side height" forum thread?

Thanks for your time.

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Re: Standoff size and side height

Postby dsm » Sat Feb 25, 2012 1:32 am

custom spacers "first article" DP6037-size case

The custom spacers (link) prototype parts ordered 14Feb12 from Shapeways arrived back on 24Feb12.

IMG_0806_2.jpg
custom spacers ~ four sets

The custom spacer prototype parts were used to build a DP6037-size enclosure intended for the Bus Pirate v3.5e design. This enclosure provides 1.5 mm top and bottom acrylic windows [1] so that the circuitry on the top of the board and the pin usage legend on the bottom of the board can be observed. The intent of this design is to attempt reduce costs as much as possible (by using nuts & bolts) even if assembly is made absurdly more complicated.

There were two variants
    4x ~ M3.0 x 16 mm x 0.5 mm pitch zinc plated steel Phillips machine screws
    4x ~ M3.0 x 0.5 mm pitch zinc-plated brass knurled thumb nut
    4x ~ 5.0 mm OD / 3.2 mm ID / 5.0 mm long (e.g. space-above-board) spacers in SLS nylon
    4x ~ 5.0 mm OD / 3.2 mm ID / 1.8 mm long (e.g. space-below-board) spacers in SLS nylon
    ----------
    4x ~ M3.0 x 14 mm x 0.5 mm pitch zinc plated steel Phillips machine screws
    4x ~ M3.0 x 0.5 mm pitch zinc-plated steel nut
    4x ~ 5.0 mm OD / 3.2 mm ID / 5.0 mm long (e.g. space-above-board) spacers in SLS nylon
    4x ~ 5.0 mm OD / 3.2 mm ID / 1.8 mm long (e.g. space-below-board) spacers in SLS nylon
How cheap?
    4x ~ M3.0 x 16 mm x 0.5 mm pitch zinc plated steel Phillips machine screws ~ 92005A126 ~ 100 for $2.80 ~ $0.112
    4x ~ M3.0 x 0.5 mm pitch zinc-plated steel nut ~ 90591A121 ~ 100 for $1.39 ~ $0.0556
    4x ~ pair of 5.0 mm / 1.8 mm custom spacers in SLS nylon ~ (link) ~ $0.48
    ----------
    $0.6476
IMG_0808_2.jpg
initial custom spacers case ~ top view

IMG_0809_2.jpg
initial custom spacers case ~ bottom view

IMG_0810_2.jpg
initial custom spacers case ~ edge view ~ knurled thumb nuts

IMG_0817_2.jpg
initial custom spacers case ~ edge view ~ steel nuts

Thanks for your time.

dsm

[1] The top and bottom acrylic windows had already been updated to "-v2" as described elsewhere (link).
Last edited by dsm on Mon Feb 27, 2012 4:06 pm, edited 4 times in total.
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Re: Standoff size and side height

Postby dsm » Sat Feb 25, 2012 1:53 am

custom spacers "first article" DP6037-size case (continued)

The DP6037-size custom spacers enclosure described above has no side walls.

In case someone does want side walls, however, there's an enclosure variant for that. 1.5 mm acrylic is used for the top, bottom, end, and side windows. There is an opening in the top acrylic window to allow an over-molded mini-USB cable to plug into the board and still hold the USB end window securely in place.

IMG_0813_2.jpg
initial custom spacers case with side walls ~ top view

IMG_0814_2.jpg
initial custom spacers case with side walls ~ bottom view

IMG_0816_2.jpg
initial custom spacers case with side walls ~ edge view ~ knurled thumb nuts

IMG_0819_2.jpg
initial custom spacers case with side walls ~ edge view ~ steel nuts

Thanks for your time.

dsm
Last edited by dsm on Mon Feb 27, 2012 4:00 pm, edited 1 time in total.
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Re: Standoff size and side height

Postby ian » Mon Feb 27, 2012 8:42 am

I did merge Filip's thread here as you suggested. That was also my fault, I asked him to post in a new thread.

Set of 8 spacers on own-holder for $0.50 - amazing!

Thumb screws also very nice. It means it can be built with a single bolt without using ugly, small nuts.

I notice you use red parts. On Shapeways' site they note that SLS nylon is porous can become discolored over time. Does the red dye help prevent that from happening?
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Re: Standoff size and side height

Postby dsm » Mon Feb 27, 2012 3:43 pm

comments

ian wrote:I did merge Filip's thread here as you suggested.

Thanks, no worries.



ian wrote:Set of 8 spacers on own-holder for $0.50 - amazing!

Given that each of the metal threaded standoffs proposed in the postings that started this thread are each roughly twice this amount (and there were eight of them), $0.48 is not too bad. You shouldn't be surprised since

ian wrote:Many of the combinations are very hardware intensive. My goal is cheap, so whatever is cheapest will make me happy :)

Absolute cheapness, however, is not always a virtue.
The real problem with the scheme shown above is that, unlike Scheme G, it is a nightmare to assemble and disassemble.

One could reduce the cost even more by replacing the upper spacer with two steel nuts (5.0 mm spacer => 4.8 mm) and the lower spacer with one steel nut (1.8 mm spacer => 2.4 mm). Use 16 mm bolts and 1.5 mm acrylic. The side and end acrylic walls would have to be modified slightly. The cost [1] would then be
    4x ~ M3.0 x 16 mm x 0.5 mm pitch zinc plated steel Phillips machine screws ~ 92005A126 ~ 100 for $2.80 ~ $0.112
    16x ~ M3.0 x 0.5 mm pitch zinc-plated steel nut ~ 90591A121 ~ 100 for $1.39 ~ $0.2224
    ----------
    $0.3344


ian wrote:Thumb screws also very nice. It means it can be built with a single bolt without using ugly, small nuts.

Unfortunately, the thumb nuts are also even more expensive than threaded standoffs.
    4x ~ M3.0 x 16 mm x 0.5 mm pitch zinc-plated brass round knurled thumb nut ~ 96115A420 ~ $1.11 each ~ $4.44


ian wrote:I notice you use red parts. On Shapeways' site they note that SLS nylon is porous can become discolored over time. Does the red dye help prevent that from happening?

I've been using red SLS nylon just because it looks nice with the red Dangerous Prototypes boards.
I don't have enough experience with the longevity of the SLS nylon material to answer your questions.
People who sell puzzles on the Shapeways site dye the pieces using bright dyes (link).
I just wish the SLS nylon surfaces were the hard detailed surfaces of injected molded parts.

You are close enough to the European home of Shapeways (in Eindhoven) or i.materilise (in Leuven) that it might be worth trying to arrange a tour of their facilities. Their respective cost structures mean that Shapeways is typically cheaper for small 3D printed objects, but i.materialise is cheaper for large 3D printed objects.

Thanks for your time.

dsm

[1] The prices I mention are relatively high since they are based on relatively low volume purchases.
Costs on the ground in Shenzhen will obviously be lower.
Last edited by dsm on Wed Feb 29, 2012 3:01 am, edited 1 time in total.
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