What thickness acrylic are you using? I've been designing with 1.5 mm acrylic (which looks better to me for smaller enclosures). What slot-to-edge thickness are you using? I've been using 3.0 mm (or twice the 1.5 mm acrylic thickness). What width slots are you using? Probably nominal acrylic thickness plus 0.05 mm to 0.10 mm? What length slots are you using? Probably nominal 10 mm slot length plus 0.05 mm to 0.15 mm?
Some laser-cutter drivers adjust for the laser kerf automatically. For example, if a hole or slot is being cut, the laser-cutter driver may assume that the laser path should be shifted inward so the hole or slot dimensions are correct. Some laser-cutter drivers require that you adjust for the laser kerf manually in your design. Some experimentation is often needed to get the results you desire.
The assembly problems you are experiencing sound like the parts are too tight. Loose, but not too loose, is probably easier to assemble. Remember that the hardware will hold the case together.
I made my sides of my prototype long enough to overlap the ends (simple butt joint). I then inserted the case sides and case ends into the bottom window. I then squeezed the case sides slightly to keep the case ends in position while adding the top window. This was eventually accomplished. Which is not too bad if you're just assembling the enclosure once. But if one is opening and closing the enclosure a lot, you have a definite point. This is not a particularly user friendly case closure scheme.
The following files illustrate one of the problems that the Bus Pirate v4c layout may have with Scheme G. These acrylic top/bottom/end/side case parts are being fabricated to illustrate Scheme G. Notice that the 12-pin shrouded male header for the Bus Pirate v4c design comes fairly close to the 5.2 mm diameter magnet holder mounting holes [1]. The 6.0 mm diameter crown on the top magnet holder (intended to cover any minor defects in the magnet holder mounting holes) would have to be partially removed.
[attachment=0] [attachment=1] The IO connector opening is located at (51.5, 18.5) and defined to be
0.2 mm window-offset (X) + 2.032 mm left-shroud-offset (aka 0.080") 5.08 mm connector-without-shroud (aka 0.2") 2.032 mm right-shroud-offset (aka 0.080") 0.2 mm window-offset (X) = 9.554 mm in "X"
0.4 mm window-offset (Y) + 3.81 mm left-shroud-offset (aka 0.150") 15.24 mm connector-without-shroud (aka 0.6") 3.81 mm right-shroud-offset (aka 0.150") 0.4 mm window-offset (Y) = 23.66 mm in "Y"
This issue doesn't arise with the Bus Pirate v3.5e layout since that design uses a 10-pin shrouded male header. Using a relatively rare 12-pin shrouded male header for the Bus Pirate v4c layout has some drawbacks (link) (link).
Probably not. It sounds like you only started getting the first round of the new layout Bus Pirate boards back for debug recently. Private message sent.
[font=Georgia:]top and bottom acrylic window dimensions
[quote author="dsm"] Scheme G is generally compatible with the acrylic side/end window schemes that have been proposed.[/quote] Without acrylic side and end windows, the dimension budget for the top and bottom windows for Scheme G is
1.0 mm additional mounting-hole-to-edge (since mounting hole is 1.0 mm larger in radius) + xx.0 mm board + 1.0 mm additional mounting-hole-to-edge (since mounting hole is 1.0 mm larger in radius) = xx.0 mm + 2.0 mm
For example, for a DP6037-size board the overall dimensions would be 62.0 mm by 39.0 mm.
With acrylic side and end windows, the dimension budget of the top and bottom windows for Scheme G is
3.0 mm edge-to-slot (strength issue ~ twice 1.5 mm acrylic thickness) + 0.2 mm maximum laser-cut kerf correction (probably less for laser-cut slot edge against fixed tab thickness) + 1.5 mm nominal acrylic thickness + 0.2 mm wall-to-board margin + xx.0 mm board + 0.2 mm wall-to-board margin + 1.5 mm nominal acrylic thickness + 0.2 mm maximum laser-cut kerf correction (probably less for laser-cut slot edge against fixed tab thickness) + 3.0 mm edge-to-slot (strength issue ~ twice 1.5 mm acrylic thickness) = xx.0 mm + 9.8 mm
For example, for a DP6037-size board the overall dimensions would be 69.8 mm by 46.8 mm. The tabs [1] are assumed to be in side and end windows and no laser kerf corrections are made to these parts. The slots are assumed to be in top and bottom windows and all laser kerf corrections are made to these parts. The inside edge of the slots is nominally fixed, so all laser kerf corrections are made to the outside edge and ends of the slots.
Thanks for your time.
dsm
[1] For tabs and slots suggestions, see (link).[/font:]
I also really like Scheme G since it has the potential to be simple, cheap, flexible, and look good. There is a little retention ring (shown in yellow on the parts) that I need to improve (the retention ring should probably be a one-way retention barb) after some experiments with laser-cut acrylic holes. The top magnet holder could be made in various lengths (currently the space-above-board is set to 5.0 mm). For example, one obvious variant could accommodate the height of an Ethernet connector. Parts could also be made to accommodate thicker 3.0 mm acrylic. Scheme G is generally compatible with the acrylic side/end window schemes that have been proposed.
Of all the enclosure schemes that I've been posting, Scheme G probably has the most potential for being injection molded and sold through Seeed Studio.
I already ordered some test parts. They should arrive in about ten days from Shapeways. I'll also fabricate some top and bottom acrylic windows. But I'll also need some DP6037-size boards for photos and measurements...
In the mean time, more images...
[attachment=2] [attachment=4] [attachment=3] [attachment=1] [attachment=0] Thanks for your time.
Scheme G ~ magnetic attachment and acrylic window scheme
1.5 mm 3D printed SLS
top magnet holder + neodymium magnet + 1.6 mm top acrylic window + 5.0 mm space-above-board + 1.7 mm board + 1.8 mm space-below-board + 1.6 mm bottom acrylic window + 1.5 mm 3D printed SLS bottom magnet holder + neodymium magnet + = 14.7 mm [/list] Scheme G uses
3D printed SLS nylon bottom magnet holders are used to hold 3.0 mm diameter by 3.0 mm long neodymium magnets in position and provide feet for the enclosure.
Four bottom magnet holders are mounted in 5.2 mm holes in the 1.5 mm laser-cut bottom acrylic window to form the bottom assembly.
3D printed SLS nylon top magnet holders are used to hold 3.0 mm diameter by 3.0 mm long neodymium magnets in position.
Four top magnet holders are mounted in 5.2 mm holes in the 1.5 mm laser-cut top acrylic window to form the top assembly.
The target board is held between the bottom assembly and the top assembly.
Scheme G uses
Four bottom magnet holders. Four top magnet holders. Eight 3.0 mm diameter by 3.0 mm long neodymium magnets.
Due to the 1.0 mm magnet holder walls around the 3.0 mm diameter neodymium magnets...
The normal 3.2 mm mounting holes in the top and bottom acrylic windows are enlarged to 5.2 mm.
The normal 4.0 mm edge-to-mounting-hole distance is increased to 5.0 mm.
The normal 4.0 mm corner radius is increased to 5.0 mm.
The top and bottom acrylic windows are 2.0 mm longer and wider.
The 3D printed SLS nylon magnet holders are comparatively cheap because so little material is used. For example, $3.00 for all eight magnet holders in white SLS nylon (and $1.50 of that is a handling fee by Shapeways). The top and bottom magnet holders would be easy to injection mold for a few cents per unit. The top and bottom 1.5 mm acrylic windows are easy to customize with a laser cutter. The case holds together robustly, yet comes apart with no difficulty. The additional acrylic window length and width doesn't interfere the USB connector engagement.
You'll probably want to rename the USBIRtoy file names from v2.5_201202xx to v3_201202xx prior to release.
The three electro-optical components (TX, RX, and RX2) violate the 1.7 mm board edge component keepout. ian will have to tell you whether he feels the position of these components should be changed. I was thinking that a board edge style enclosure would be a natural choice for this type of design (which to me suggests moving the electro-optical components would be a good idea).
My recommendation was for a 1.7 mm board edge component keepout based on the following error budget calculation...
1.0 mm deep slot + 0.2 mm case-to-board (3D SLS printer) error budget + 0.2 mm board-edge-position (board routing) error budget + 0.1 mm component-placement (pick-N-place) error budget + 0.2 mm component-to-case margin (so SMT components don't touch the case) = 1.7 mm
As a practical matter, a 1.7 mm board edge component keepout would allow ordinary 0.1" (2.54 mm) wide headers to be placed 3.0 mm from the edge of the board. 1.7 mm + 1.27 mm == 2.97 mm => 3.0 mm (on a 0.5 mm placement grid).
I mentioned changing the board edge component keepout from 2.0 mm to 1.7 mm to vimark. In the 03Feb12 USBIRtoy layout, this feature appears to have been implemented for the USBIRtoy design. I am assuming that vimark has been propagating these changes to all Dangerous Prototypes board templates.
[hr:][/hr:] My comments on the bottom of page one of this forum thread had to do with the layout of the Bus Pirate v3.5e and Bus Pirate v4c boards. Since these board designs were updated before some specifications for the new Dangerous Prototypes board templates were proposed, some issues may remain.
Even with a 1.7 mm wide board edge component keepout, several components in these layouts violate this specification...
LEDS (4x) ~ 1.2 mm wide 0805 LEDs (aka 2012) should be 2.5 mm from the board edge (currently 2.0 mm). 1.7 mm + 0.6 mm == 2.3 mm => 2.5 mm.
push-buttons (2x) ~ 5.2 mm wide push-buttons should be 4.5 mm from the board edge (currently 3.5 mm). 1.7 mm + 2.6 mm == 4.3 mm => 4.5 mm.
ExtPwr (1x) ~ 2.54 mm wide male header should be 3.0 mm from the board edge (currently 2.0 mm). 1.7 mm + 1.27 mm == 2.97 mm => 3.0 mm.
The package was sent via USPS first class parcel post on Monday, 30Jan12. I should have added tracking so I wouldn't have to ask this question, but did the package arrive?
[font=Georgia:]Bus Pirate v3.5e layout Issues Bus Pirate v4c layout Issues
ian,
The USBIRtoy v3 (neé v2.5) board layout process updated some specifications for the new Dangerous Prototypes board templates that affect the previous Bus Pirate v3.5e and Bus Pirate v4c board layouts.
For example, several components in these layouts now violate the 2.0 mm wide board edge component keepout.
LEDS (4x) ~ 1.2 mm wide 0805 LEDs (aka 2012) should be 3.0 mm from the board edge (currently 2.0 mm). 2.0 mm + 0.6 mm == 2.6 mm => 3.0 mm.
push-buttons (2x) ~ 5.2 mm wide push-buttons should be 5.0 mm [1] from the board edge (currently 3.5 mm). 2.0 mm + 2.6 mm == 4.6 mm => 5.0 mm.
ExtPwr (1x) ~ 2.54 mm wide male header should be 3.5 mm from the board edge (currently 2.0 mm). 2.0 mm + 1.27 mm == 3.27 mm => 3.5 mm.
I was working on an updated DP6037 case design and noticed the discrepancy.
See the 1.7 mm board edge component keepout update to this comment on the next page.
Thanks for your time.
dsm
[1] Although 4.5 mm would probably also work in a pinch[/font:]
Sorry. I didn't express myself clearly. I was not suggesting that you add more GND vias. My suggestion was about your existing GND vias and was almost entirely about board layout esthetics. My main point was that the layout would look slightly better (at least to my eye) if your existing GND vias were tucked out of the way.
I had seen the existing GND vias at the locations on your list above. As an experiment, I moved them to the locations on my list above and kind of liked the result. In addition to esthetics, since the proposed GND via locations couldn't be used for components due to the board edge component keepout, moving the GND vias would slightly free up the amount of board available for future components.
I do like the way your USBIRtoy layout is turning out. My suggestion was optional.
I looked at the USBIRtoy.v2.5.brd [01Feb12] board layout and have a few comments.
The following comments are driven by the new Dangerous Prototypes board templates.
The origin of the board... Nice.
The overall dimensions of the board... Nice.
The 3.2 mm non-PTH mounting holes... Nice.
Mounting hole locations... Nice.
Corner radius... Nice.
There is a 6.0 mm Layer 41 tRestrict and Layer 42 bRestrict centered on the four corner mounting holes. See 31Jan12 comments.
There is a 2.0 mm board edge component keepout implemented via Layer 39 tKeepout and Layer 40 bKeepout. See 31Jan12 comments.
The origin of the mini-USB connector is at location (54.75, 18.5)... Nice.
The following comments are driven by the specific USBIRtoy v2.5 board design.
The center of component TX is at location (6.0, 11.0). Nice.
The center of component RX is at location (4.0, 18.5). Nice.
The center of component RX2 is at location (2.0, 26.0). Nice. I like that that the optical components are back from the edge of the board and symmetrically spaced in the "Y" dimension. ----------
The center of the LED component is at location (29.0, 6.0). Nice. ----------
The center of the ICSP connector is at location (18.5, 32.0).
The center of the UART connector is at location (28,5, 32.0).
The center of the JP1 connector is at location (40.0, 32.0). [quote author="ian"]I also think the ICSP to be aligned with the other header block, I use a single row of right angle pin header on mine.[/quote] I believe
ian meant for ICSP, UART, and JP1 to be next to each other with ICSP aligned with the top row of UART and JP1 in order to reduce assembly issues for these optional connectors. See 31Jan12 comments. ----------[li] The center of the push-button component is at location (24.0, 6.0). Thanks for moving this component to the top of the board. Nice. ----------[/li] [li] The center of the Q1 component is at location (39.27, 10.0). Layer 43 vRestrict is present, but only around the crystal. Included because the crystal is comparatively tall. Minor.[/li][/list] The Eagle "info" command was used to determine some component and connector locations. I suggest a 0.5 mm placement grid for all components that interact with the enclosure. But some components that interact with the enclosure will be off-grid (e.g. mini-USB connector) for other reasons. Other components on the board might also benefit from being on a 0.5 mm placement grid, even if they don't interact with the enclosure.
The overall USBIRtoy v2.5 layout is looking very good.
[hr:][/hr:] I have one additional minor comment.
The GND "ears" around the mounting holes are generally not useful for other components, but they seem like a good place to symmetrically tuck in your top/bottom GND vias. For example...
(1.5, 8.0) (1.5, 29.0) (or maybe not due to RX2) (8.0, 35.5) (52.0, 35.5) (58.5, 29.0) (58.5, 8.0) (52.0, 1.5) (8.0, 1.5)
