footprint rotation for pick and place - Page 1
Forum section: electronics / general

author: m12lrpv
author_rank: Regular Contributor
timestamp: December 15, 2019, 07:16:59 am
content: I've been working on a board design in altium that I intended to get assembled by JLCPCB. It's my first non hand soldered board.When I submitted the design and BOM and the pick and place files I was shown a rendering of how everything would be placed.Unfortunately my polarised caps and a mosfet were out by 180 degrees and my regulators were out by 90 degrees. The diodes were also possibly out by 180 degrees but I haven't confirmed that yet.So the rotation of the component associated with the PCB placement did not align with the rotation needed for the pick and place.How do people normally handle this in altium???I'm hoping that I can just add a rotation to the part based on type for a given output job. I don't want to be redrawing footprints for a pick and place machine.

author: m12lrpv
author_rank: Regular Contributor
timestamp: December 16, 2019, 03:30:33 am
content: I was reading the other thread about JLCPCB assembly and seems the feature doesn't exist and people are manually editing the pick and place file to manage the rotations.

author: ajb
author_rank: Super Contributor
timestamp: December 16, 2019, 05:30:51 pm
content: A good CM should verify the orientation of all parts for you as part of their setup validation process. Does JLC not offer that level of service?

author: thm_w
author_rank: Super Contributor
timestamp: December 16, 2019, 08:54:34 pm
content: Quote from: ajb on December 16, 2019, 05:30:51 pmYou do know what they charge right? All responsibility for gerber errors/alignment/etc is rightfully upon the designer.

author: m12lrpv
author_rank: Regular Contributor
timestamp: December 16, 2019, 09:13:34 pm
content: Yeah they're cheap and in there defence they do let me review the placement myself.I've actually resorted to rotating the footprints I'll probably eventually end up with a library with each orientation. It's safer given that for some strange reason they also do their angles anticlockwise. The last thing i need to do is see that a part needs 90 degrees rotation and end up with it 180 degrees out.

author: Pitrsek
author_rank: Regular Contributor
timestamp: December 20, 2019, 07:47:10 am
content: Quote from: m12lrpv on December 16, 2019, 09:13:34 pmPersonally I would not do that. I would suggest to keep library in standard IPC orientation and do the rotation at the level of BOM. So export from your design SW is assembly house neutral.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 20, 2019, 10:07:59 am
content: Yes, despite the fact that the IPC standard came late, and not everybody else follow it, you should still try to follow the standard; it will be easiest in the long run.So just build your footprints according to the standards, and avoid importing libraries done by others - if you do, check the rotations.Some contract manufacturers follow the standards and are able to understand your data directly, only using your assembly picture as a tool for manual verification; others follow your assembly picture as the primary rotation data source, manually performing each rotation; and I guess, with the new JLCPCB low-cost service with built-in web preview, I guess it's up to you to do the manual rotation each timetheirsoftware fails to be standard-compliant.Make a copy of your P&P file and edit the rotation field, instead of modifying your Altium footprints. This way, your Altium files stay standard-compliant, and you are just making a working copy for this specific manufacturer.

author: m12lrpv
author_rank: Regular Contributor
timestamp: December 20, 2019, 07:55:44 pm
content: Probably good advice for people doing this for a living.For a hobbyist though I have to weigh up the pro's and cons because there are multiple issues.If there's an error I wear it and having to edit the pick and place file every time I generate it is insanely error prone. It was smarter to edit the footprint because I can now walk away from the design for 6 months and come back and it all still works.Having a library specifically for that manufacturer helps in that respect too. I can place the component on the schematic and then not touch it apart from rotation and position on the pcb.On topic of editing the footprints I did find it interesting that Altium outputs the center of the footprint as the mid point of the center of the pad centers. That was half of my problem for something like the TO-252. I had to offset the main pad's center by 2.2mm to get the center in the center so it would position correctly.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 20, 2019, 10:01:11 pm
content: Quote from: m12lrpv on December 20, 2019, 07:55:44 pmExcept that it probably won't work, because your library was customized 6 months ago for a single cheap manufacturer offering a then-brand new, probably still buggy service, against the standards, based on how their black box production software happened to work on that particular day. Chances are, when you upload the same file 6 months later, the rotations have changed. Besides, it's likely you are at least looking at competiting CMs in 6 months.The cold reality is that producing a working PCB with any CM involves a step of manually confirming each component rotation every time you submit the files (unless you can simply repeat the complete order as-is) . Usually they do it according to the supplied drawing. Apparently with JLCPCB, you are doing it by yourself, by modifying the files. Yes, this process is error prone; but no, you typically won't repeat exporting and re-uploading production files all the time.So while the standardized way is no silver bullet, and manual work is needed inany case, following the IPC is the way of least confusion. Yours will be the riskiest, and it seems it is providing you with the classical false sense of security.The hurdle is the same regardless of whether you do it for living or as hobby.

author: m12lrpv
author_rank: Regular Contributor
timestamp: December 21, 2019, 02:11:33 am
content: It will work for me quite well.I must have exported the files 20 times already in the last week. I'm not editing an xls file each time to just to satisfy someone elses desire to have me have footprints that conform to a standard that I need to pay money just to look at.When I did try editing the file I missed the occasional component. I don't have that many that are impacted... mostly caps, regulators some diodes and one mosfet but if I have say 20 diodes and I miss one that's a fail.The way i decided to do it means that I only need to do a quick glance at one of each of the components that are impacted to confirm that it's ok and from that I can deduce that the rest are ok too. I would rather check 1 component of each type than all of them.Doing what i am doing has already been proven to be the right way to do it. It's the least riskiest.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 21, 2019, 10:55:34 am
content: Why are you asking a question when you have decided your "correct" answer beforehand, and accuse experienced and well argumented tips of being someone else's "desires"?Please just go away and stop wasting our time. Thank you for your consideration.BTW you have serious fundamental issues going on if you need to regenerate P&P files and upload them to a CM 20 times. I strongly suggest you try to find the root cause for having such difficult time, to make the process easier for you. But if you insist on modifying your library to match the CM preview, you indeed do generate yourself the issue of needing the regeneration of the files. The correct place to adjust for this is in CAM, not in CAD.

author: Pitrsek
author_rank: Regular Contributor
timestamp: December 21, 2019, 02:36:57 pm
content: Center of component can be defined manually.IPC orientation is parroted on so many places, you do not have to buy the standard... just google for IPC component orientation.As a bonus Altium library wizard does conform to the standard.Use your favorite scripting tool to write a simple script that will process your BOM. You can do it in excel.Your solution is not flexible, does not scale and eventually will blow into your face (if you keep using it long enough).

author: m12lrpv
author_rank: Regular Contributor
timestamp: December 22, 2019, 09:52:20 am
content: Quote from: Siwastaja on December 21, 2019, 10:55:34 amI asked the question quite some time ago and when I do have to ask on a forum I don't just sit back and wait for answers... I keep researching.In the meantime I found what others were doing (editing the P&P) and I tried it myself and discovered that it was not practical and insanely error prone.In the end I drew a conclusion that editing the footprint was the best given that I already had both a component library with part numbers and a footprint library that was paired with it. Editing is not a great stretch.You put forward your suggestion and made a few points and I happened to disagree and provided valid real world reasons why I disagreed.As for generating the files many times there are plenty of valid reasons. One was testing out your process for it's sensibility.Another was to get a valid idea of cost which leads to what modifications I can make to the board to reduce the cost or to enhance it and stay within a budget.Another was parts availability given they are also supplying the parts I needed it to process cleanly. Also they have some bugs in handling the costs for some of their parts so I needed to work around that.So I don't have any fundamental issues and such insulting behavior is not necessary.Quote from: Pitrsek on December 21, 2019, 02:36:57 pmThe documentation claims that but any attempt to find out how led nowhere. When I determined how it was calculated I realised the documentation was stretching the truth a lot.Quote from: Pitrsek on December 21, 2019, 02:36:57 pmtrue. The wizard does do quite a nice job.Quote from: Pitrsek on December 21, 2019, 02:36:57 pmMy favourite scripting tool is not to have one.I've been programing for a living for a very long time and have to switch between enough languages as it is.Quote from: Pitrsek on December 21, 2019, 02:36:57 pmIf I'm producing 1000 boards a month for the next 10 years I might eventually encounter a problem. But a one off run of 25 is not going to be an issue. This project will never ever ramp up to high volume. It's a project I've been working on for a decade so I understand it well. I won't be looking at any other fab house I can guarantee you that. It's way outside of my budget. It's only due to this service that I am looking at having them assembled.