Precision alignment and cutting of plastic panels - Page 1
Forum section: electronics / projects

author: h_p
author_rank: Unknown
timestamp: April 24, 2017, 05:29:09 pm
content: All,I am working on building my first bench power supply and I am a bit of a perfectionist. I have 19 years of electronics experience so the building of it (electronically) isn't a concern for me. I am however wanting to ensure the holes in the front and back panels for knobs, power switches, fans, etc.. are precise in their placement and cutting. These panels are made of plastic that is about 1mm thick. Does anyone have tips for software that might help me in doing this? So that I can ensure my placement is accurate. My thought is to give it a go with the plastic panels that came with my housing and if that fails then to get metal panels cut the same size and have a water jet cutting company do the CAD work and cutting, the problem is that I called a few water jet cutting services locally and they wanted $160-200 to do the work which more than doubles the cost I am spending on this power supply. I am quite tempted to use their service though as they also do laser engraving and as I said I am a bit of a perfectionist. Any help would be greatly appreciated.Caveat (I use a Mac and do not have access to a Windows PC.)

author: CM800
author_rank: Frequent Contributor
timestamp: April 24, 2017, 05:36:41 pm
content: Hello!,What are the size of the panels, you might be able to do fine with a cheep 8060 cnc router from china, they are good enough for your kind of work!Equally their laser cutters too could be fine.

author: German_EE
author_rank: Super Contributor
timestamp: April 24, 2017, 05:44:30 pm
content: Find your local Makerspace or Fablab, they will probably have a laser cutter that will do a perfect job first time.

author: sokoloff
author_rank: Super Contributor
timestamp: April 24, 2017, 05:59:19 pm
content: Any old manual mill (even a Harbor Freight one) will hold tolerances close enough that a perfectionist's naked eye couldn't determine there was a variance from the desired.Faced with this task, I'd useOpenSCADto layout the panel and then cut it manually on the cheap Harbor Freight mill in the basement. I'm very familiar with OpenSCAD and fit it extremely quick to accurately model something where I know all the measurements. Others might use InkScape if the goal was just to get vector outlines for the cutter.You could laser print the design onto paper and cut it out manually with an Xacto knife (or a maker space vinyl or laser cutter) to check the fit against the supply.A $20 digital caliper and a few test sheets and you should be able to get the X, Y coordinates and sizing needed for a manual mill.

author: h_p
author_rank: Unknown
timestamp: April 24, 2017, 06:01:52 pm
content: The size of the panels is 83mm high by about 218mm wide in the middle and it tapers to 215mm at the ends.

author: h_p
author_rank: Unknown
timestamp: April 24, 2017, 06:03:23 pm
content: Unfortunately the local maker space is owned/run by a museum and unless you pay for one of their classes you can't use their equipment.

author: h_p
author_rank: Unknown
timestamp: April 24, 2017, 06:08:06 pm
content: What is a manual mill? I have never been a big tool guy. I use the tools I need/have to at work for maintaining the particle accelerators I work on and haven't ever really ventured outside of that realm when it comes to owning/using tools of my own.I only recently began acquiring tools for home repairs and am in the process of building my own home electronics workshop (Got my own O scope, multimeter, Agilent power supply, function generator and have found a place that sells used workbenches locally). So I am in stage 1 of setting up my bench at home.

author: sokoloff
author_rank: Super Contributor
timestamp: April 24, 2017, 06:17:35 pm
content: Think of a mill as a drill press with an X-Y table underneath it. (There are differences mechanically, but for a mental picture, that's good enough.)You will have a manual hand wheel for X with a known travel per rotation (and a vernier dial on the wheel) and the same for Y. This allows you to clamp the part to the table, and very precisely (0.01" is trivial to accomplish) locate the holes.That takes care of the physical cutting. Then, the logical design (how far does that post need to be from that other post) is a matter for the software design.

author: sokoloff
author_rank: Super Contributor
timestamp: April 24, 2017, 07:05:13 pm
content: Here's a decent intro to how mills work, both manual and CNC driven.

author: dave_k
author_rank: Frequent Contributor
timestamp: April 24, 2017, 08:04:53 pm
content: I've used this service/software before, and have never been disappointed.https://www.frontpanelexpress.com/Their designer software let's you very accurately place holes and cutouts, and supports OSX

author: h_p
author_rank: Unknown
timestamp: April 24, 2017, 08:06:02 pm
content: Oh that's cool!

author: clack
author_rank: Newbie
timestamp: April 24, 2017, 08:41:07 pm
content: Quote from: h_p on April 24, 2017, 08:06:02 pmYes I use this too, the best thing is being able to see exactly how much it costs to make the panel and make cost cutting changes. E.g if you use a colored panel and don't put infill in your text you save.In europe its Schaeffer AGhttps://www.schaeffer-ag.de/en/Great for one offs

author: langwadt
author_rank: Super Contributor
timestamp: April 24, 2017, 09:48:23 pm
content: Quote from: clack on April 24, 2017, 08:41:07 pmI used them years ago, it isn't exactly cheap but it is very nice quality. I really like how their programspecifices what each operation cost so you can decide what features are worth the cost.another option is PCBhttps://youtu.be/Yj0Bv4UEFSs

author: Zinger
author_rank: Contributor
timestamp: April 25, 2017, 02:03:43 am
content: Fusion 360 from Autodesk is a complete CAD system. It's free for hobbyists. It's easy to learn and there are a ton of instructional videos on YouTube.http://www.autodesk.com/products/fusion-360/overviewYou could design your control panel as a 2D sketch in Fusion 360, then export the sketch as a DXF file. Most laser cutters will take a DXF file.It's very common (universal even, maybe) for Maker Spaces to require training before you can use their equipment. They are safety and liability concerns. Also, they have a lot of very expensive equipment that can be easily broken if you don't know what you're doing.

author: theatrus
author_rank: Frequent Contributor
timestamp: April 25, 2017, 04:50:55 am
content: I can also suggest the PCB route. If you keep the copper pours it acts as a nice shielded cover to boot, and the one color printing is included in the priceI have a laser cutter in house and acrylic is very easy to work with, and cast acrylic engraves nicely. Ponoko is an option.

author: h_p
author_rank: Unknown
timestamp: April 25, 2017, 12:46:32 pm
content: I don't have any issues with training. I fully support that. The problem is that you can only use the equipment if you are taking a paid multi week course from the museum. That's not really a maker space. And the courses are as expensive as a semester long community college class. If I wanted to learn how to use a CNC or do something of that nature for that price I would take the CC class before I'd pay a volunteer at a museum the same price.

author: jolshefsky
author_rank: Regular Contributor
timestamp: April 25, 2017, 01:18:01 pm
content: Is it too inaccurate to print a 1:1 scale version and use it as a template? I center-punch the centers of holes and use a drill press for round holes. Although I bought a set of dies for cutting other sizes, I nearly always use a manual nibbling tool to nip out the square holes (e.g. the old Radio Shack one good for <1/8" <2mm or so).

author: h_p
author_rank: Unknown
timestamp: April 25, 2017, 01:31:29 pm
content: It'd be cheaper right now to have a metal shop punch the holes $1 per hole than for me to acquire all the necessary tools.

author: h_p
author_rank: Unknown
timestamp: April 26, 2017, 03:43:50 pm
content: Alright so I downloaded all the spec sheets for my power supply parts and have entered the cutout dimensions for the various parts in to front panel designer and placed them where I think they would work best. If anyone has tips or ideas on placement of these things let me know The only issue I am having is that I need the panels to taper from 218.9mm at the center to 216.1mm at the edges and the folks at FPD aren't being very helpful. I quickly annotated the front panel parts in paint so people would know what's what. The rear panel just has a 3 prong AC receptacle cut out and a 12 Volt 60mm fan cut out. I am not sure if the banana jack cutout size is correct so I have a micrometer coming in the mail so I can measure them tomorrow and adjust the size accordingly. Attached are the files if anyone could tell me how to taper the edges that would be greatly appreciated.I have the DPST power switch on the front panel but am not averse to moving it to the back. I put it on the front as I like being able to quickly turn the PS off if something were to go wrong. I have another DPST switch that I thought about putting on the back panel but that might be a bit overkill.

author: sokoloff
author_rank: Super Contributor
timestamp: April 26, 2017, 04:14:03 pm
content: You have a "volt/amp meter" without any means to switch between those two functions (which need fundamentally different cabling).I would consider either adding a switch or (better) adding a dedicated amp meter and dedicated volt meter, each centered above the control pot for the respective function.I would consider adding an indicator LED for power-on.I would consider adding another banana terminal which is earth grounded. (I would also consider the same with a screw post on the back panel for earth ground.)

author: h_p
author_rank: Unknown
timestamp: April 26, 2017, 04:51:15 pm
content: Hi,The meter measures and displays volts and amps at the same time. It is a two part digital display. They have separate wiring for each function. The DPST switch is illuminated when in the on position. I was thinking about adding an earth ground terminal. I will add that to the drawing. The distance between the positive and negative banana jacks is 12.70mm. Should I make the distance from the negative jack to the earth ground jack the same distance?See attached pic

author: rdl
author_rank: Super Contributor
timestamp: April 26, 2017, 04:56:35 pm
content: Quote from: h_p on April 26, 2017, 03:43:50 pmJust use the other DPST switch as a load switch. This would disconnect the output without having to turn the device completely off.

author: h_p
author_rank: Unknown
timestamp: April 26, 2017, 05:14:48 pm
content: If anyone is familiar with front panel designer and can help me taper the ends from 218.9mm to 216.1mm in that software it would be greatly appreciated.

author: h_p
author_rank: Unknown
timestamp: April 26, 2017, 05:17:28 pm
content: This was my original thought and is why I purchased the switch. I will have to think on this for a bit.

author: james_s
author_rank: Super Contributor
timestamp: April 26, 2017, 06:33:07 pm
content: I use Inkscape to draw up templates for this sort of thing with crosshairs in the center of holes. Print them on paper and used double sided tape to stick them to the panel. Drill a small pilot hole and then use a step bit to drill out to the correct size. For square holes I drill a round hole in the middle and then use a file to square it up and fine tune the size.

author: h_p
author_rank: Unknown
timestamp: April 26, 2017, 09:59:42 pm
content: Well here's Revision 2 of my power supply front and back panels. I got out the case and put the DC power supply, buck boost converter and the fan inside and noted I needed to move some things around. I also added the DPST switch to the back panel.

author: h_p
author_rank: Unknown
timestamp: April 27, 2017, 06:03:20 pm
content: Well here is revision 3. I figured out how to import a DXF file I got from the case manufacturer so that I had the correct angles on the edges of the front and back panels. I also added a 4-40 ground stud to the inside of each panel, changed some layout stuff and got the barrel jack holes sized up correctly. I am probably going to order these today unless there is something I find drastically wrong with them.**The little green circle is the ground stud. It is on the inside of the panel and won't be visible externally.

author: David Hess
author_rank: Super Contributor
timestamp: April 28, 2017, 01:16:48 am
content: I print out a punch-out diagram at a 1:1 scale on paper or sometimes projector film, tape that to the front panel, and then use an automatic center punch to mark the holes.

author: cncjerry
author_rank: Unknown
timestamp: April 28, 2017, 02:22:42 am
content: Contact me offline and I'll mill then for you for the cost of shipping if you haven't found someone. They look pretty simple.