Need a custom plastic spacer / gasket  - Page 1
Forum section: electronics / general

author: nali
author_rank: Frequent Contributor
timestamp: January 03, 2024, 12:10:27 pm
content: I need to find a source for a custom thin non-metallic plastic spacer about 100 x 50mm in size and about 0.5mm thick. Not a simple rectangle but a complex shape with cutouts for components, mounting holes etc. This is to act as a PCB standoff and will let me use an off the shelf IP68 enclosure, as one of the components on the rear of the board is a slight interference fit and I don't really want to go the route of custom enclosures or machining right now.I'm not sure which route to go: 3D printed parts or laser-cut parts from sheet material, so would be interested if anyone has done anything similar, and/or knows any companies in the UK who can help? Quantities are maybe low-hundreds and lead time is more sensitive than cost. I already have CAD files.

author: Kean
author_rank: Unknown
timestamp: January 03, 2024, 12:29:40 pm
content: I've cut gaskets from sheet rubber up to 1.0mm thick using my Silhouette Curio. It can be a bit tricky to keep the material stuck down and not be ripped up by the moving blade, so I certainly wouldn't want to be doing anything with really fine detail (<2mm holes), or be cutting too many of them.I now have a laser cutter, which can apparently cut certain types of rubber - but I've not tried it. Typically for larger quantities you'd want to be getting them die cut, but that would be a much longer lead time.

author: beanflying
author_rank: Super Contributor
timestamp: January 03, 2024, 12:42:07 pm
content: 3DP compared to Laser for thin 2D sheets would be painfully slow and comparatively a poor option as it would be 2 (maybe 3) layers thick.You could cut thin cork on a Laser Cutter but rubber is going to get you a gooey mess typically these get die or knife cut in industry for gaskets.What I would look at would be PETG (Coke Bottle plastic) as it is tough softish and fairly cheap in roll or sheet form. It Laser cuts well and anyone with a decent bed size Laser would be able to crunch some out for you for for not a lot. You could also look at thin Acrylic but below 1mm is a little harder to source.

author: Kean
author_rank: Unknown
timestamp: January 03, 2024, 12:47:58 pm
content: As you only really need a spacer, not a sealing gasket... another option could be FR4 PCB material.I've had 0.8mm thick FR4 (without copper) made up as insulating spacers via the usual PCB suppliers. I expect you could get thinner if needed.

author: thm_w
author_rank: Super Contributor
timestamp: January 03, 2024, 10:30:57 pm
content: 3D printing doesn't make sense for hundreds of parts here, laser cut or PCB as suggested above.Quote from: Kean on January 03, 2024, 12:47:58 pmJLC does 0.6mm for less than $0.5 per PCB, or 0.4mm for $0.8.

author: langwadt
author_rank: Super Contributor
timestamp: January 04, 2024, 01:14:31 am
content: https://www.cut-tec.co.uk/materials/other-plastics?

author: Kean
author_rank: Unknown
timestamp: January 04, 2024, 02:44:24 am
content: Keep in mind that many plastics are not ESD safe.

author: nali
author_rank: Frequent Contributor
timestamp: January 04, 2024, 11:12:50 am
content: Thanks all. The cut tec looks interesting, I think I can work with the +/= 0.5mm tolerance. (Google wasn't really doing it for me as I was getting loads of arts & craft type pages)I hadn't thought about FR4, although mousebites may be an issue with fitment here. Plus it seems a bit wasteful unless they can supply it sans copper (it will run close to a 2.4GHz SMD chip antenna)ESD shouldn't be an issue. The only part of the board which would touch would be ground fill, and it is going into an ABS enclosure anyway. Assembly will be by a CM and once the board is in it won't be touched.Or maybe I should just get the enclosure milled..? Hmm... can't decide

author: Kean
author_rank: Unknown
timestamp: January 04, 2024, 11:26:18 am
content: No reason for any mousebites - you can have them fully routed as they don't need to be in a panel for assembly. Of course the practicality depends on how much material you want to cut away.This type of insulator PCB seems to be common enough. I am pretty sure the PCB house just puts the bare FR4 core material through the drilling & milling processes and skips all other steps.It might not be orderable or give the cheapest prices via automated quoting systems, but almost any PCB house should be able to make them.

author: beanflying
author_rank: Super Contributor
timestamp: January 04, 2024, 11:26:21 am
content: Properly setup and kerf compensated getting a Laser under 0.2mm and into 0.1mm is possible. .5mm is either covering their ass or just being sloppy.This box from 1mm Acrylic was 'tight' off my small Laser which I know runs a kerf between 0.15 and 0.18 across most plastics. Typically I massage the design if I want an easy fit for glue so I will push say those tab and slots another 0.1 over the kerf value the cut software looks after.Much more recent job with the extra clearance in the tab and slots.

author: nali
author_rank: Frequent Contributor
timestamp: January 09, 2024, 11:36:10 am
content: Just thought I'd post a follow-up to this. The box is from Hammond, who offer a custom machining service according to their site, so I thought I'd ask for a quote anyway to have a recess machined into the inner surface of the case.Pricing was pretty good I'd have to say. It wouldn't be fair to disclose their actual pricing but for a MoQ of 25 their price for the customised part was about the same as Mouser's price for x100 of the standard part. There is a one-off fee of £95 for drawing creation which again I find pretty reasonable.As for the spacer.. for other reaons it's ended up at 1.5mm thick now which is a bit more managable so for my trial run I'll knock them up at home and either look into a supplier later or use it as a reason to justify buying a laser cutter

author: thm_w
author_rank: Super Contributor
timestamp: January 09, 2024, 11:11:51 pm
content: I don't see any problem disclosing their pricing for something like this... but yeah that seems very reasonable.