good mold making system for making a dielectric copy of pliers? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: December 15, 2018, 04:43:06 am
content: The idea is to remake these pliers out of a dielectric material. I have seen youtube videos of how various molds are made (you would need to destroy a pair to make the master mold I think, maybe out of siliconeBut what would be a good suitable compound to use to make pliers that are1) non conductive2) non conductive for RF3) decently hardThe idea is to make a tool you can apply pressure to RF components like inductors and capacitors.I think a big part in safety would be to give it a very smooth surface finish with lots of sanding and final polishing so they wipe down well.Can human interface safety be given by the mold material, or should a tool rated for high protection be canibalized for its handles?

author: vk6zgo
author_rank: Super Contributor
timestamp: December 15, 2018, 07:24:24 am
content: Quote from: coppercone2 on December 15, 2018, 04:43:06 amThe only material I can think of that is reasonably hard as well as easy to mould is Epoxy, but it would have be good stuff, not just the Epoxy glue you pick up at the hardware store.I assume this comes from the earlier thread about RF safety, where someone got an RF burn by trying to adjust the dimensions of an inductor with the circuit live.I really think your idea is a "solution looking for a problem", as its "dielectric properties" may well detune the very component you are trying to optimise.Such things can be done safely without inventing a new tool, by following a sensible routine.Turn the thing OFF, tweak the inductor or whatever, turn the thing on, see if that did the job----if not turn the thing OFF, & so on.

author: coppercone2
author_rank: Super Contributor
timestamp: December 15, 2018, 09:11:00 am
content: I kind of want to take it a step further and try to study the dynamic behavior of denting capacitors and stuff in complicated circuits that are difficult to setup mechanical jigs for.I thought it would be the least intrusive material to useyes its not a normal request just to satisfy my sick curiosityWhat kind of epoxy would be good? Probably something from like 3M but would you do any additives to it like fiber or something?I also saw stuff like polyurathane molding kits for making prototypes of plastic parts.. they are expensive but I don't know how it will compare to pliers in this application.I think after the working mold is made most parts other then the jaw grip surface and the adjustment mechanism interior can be reinforced with fiber glass or kevlar or something (need to think about this).I wonder if the epoxy is dimensionally stable enough during curing to make the mechanism work, if only be needing to have pivot size adjustment (if the parts will shrink equally). Also no metal reinforced epoxy.

author: beanflying
author_rank: Super Contributor
timestamp: December 15, 2018, 09:35:35 am
content: This is not something that takes no practice and while youtube will help it is a skill set needing practice like all things. Silicone, Epoxy or plaster molds (easiest options), parting boards (mold splitting) and careful work and be prepared to fail several times and even then the accuracy needed will take more attempts to adjust. Silicone has issues with lack of stability but allows parts to be released easier. So you really need to go to Epoxy with fiberglass reinforcing and consider where you set you parting boards to split the molds to release the part.On shrinkage Epoxy is Best then Vinyl Ester and avoid Polyester Resins.How much force do you need on the jaws? For a one off and maybe 4 or 5kg clamping/crushing force and a 1-2kg load limit skip the molds and it could be done straight to a 3D printer. Care needs to be taken with the print to get the strength in the correct orientation and looking at the slip jaws you have shown the heads and handles would need to be a bit more deep in the vertical direction for your proposed use. This becomes a CAD job initially and then knowing the limits of the printing technology to judge dimensions.If these are skills you don't have the time to learn then best you pay someone to do it.Check out here for possible 3D printed designshttps://www.thingiverse.com/search?q=pliers&dwh=245c14cc84c04dd

author: coppercone2
author_rank: Super Contributor
timestamp: December 15, 2018, 09:43:19 am
content: nah no way I am doing cad, i was thinking about one of those engineering silicone molding kits. they say you can do it in like 2 days workcan you get the jaw grip done right with fiber glass? and the hole mechanicism??

author: beanflying
author_rank: Super Contributor
timestamp: December 15, 2018, 09:48:18 am
content: There is no shortcuts for close tolerance mold making. As above Silicone isn't stable.From the link I added above you could simply have a set of these made by a 3D print servicehttps://www.thingiverse.com/thing:745743but if the layer orientation isn't correct it will shear along the layer lines.

author: coppercone2
author_rank: Super Contributor
timestamp: December 15, 2018, 10:09:08 am
content: i am not going to do that in cad and pay people to do this. I also want that cobra design.How distorted will a silicone mold come out? Can you do it with less then 10% materials loss to sanding and filing?does anyone know the serious engineering company that was making tutorials and selling the mold making equipment? They had a pretty advanced youtube video showing you how to do it for corporate level prototyping of plastic brackets and stuff for like aerospace etc.

author: beanflying
author_rank: Super Contributor
timestamp: December 15, 2018, 10:11:08 am
content: There is a very good reason a Pattern makers apprenticeship is four years and after that they spend a lifetime learning new skills.

author: coppercone2
author_rank: Super Contributor
timestamp: December 15, 2018, 10:12:42 am
content: Quote from: beanflying on December 15, 2018, 10:11:08 amso does a engineering degree whats your pointno offense but I would not have had most of the skills I have if I listened to all the people telling me I need to be doing something for a decade to get it done. It means its hard but I don't really listen to that too much, but thanks for the warning I guess. With trades I noticed they can just get it done in faster time with less material loss and they can use cheaper equipment better (i.e. good wood worker with a knack can get it done with shit equipment) so they are commercially viable... they don't really become gods.I am not looking to like, close a production overload in record time because the quarter is ending and we got a order for 5000 space grade parts next month.

author: beanflying
author_rank: Super Contributor
timestamp: December 15, 2018, 10:24:03 am
content: Then why ask advice if you are going to ignore it? I have spent long enough making molds and using them to have an idea of what does and doesn't work. You have never made a mold is telling me you have most of the skills to do it and other skilled experienced tradespeople 'don't really become gods'Not sure if you are just arrogant, ignorant or if it is a translation thing? I am done regardless as you clearly know all you are going to.

author: coppercone2
author_rank: Super Contributor
timestamp: December 15, 2018, 11:04:29 am
content: your telling me to 3d print it. I am asking how deformed it will be (how much material will \I need to sand to align it correctly)

author: eKretz
author_rank: Frequent Contributor
timestamp: December 15, 2018, 11:07:43 am
content: Quote from: coppercone2 on December 15, 2018, 10:12:42 amPretty clear what his point is. An engineer doesn't do a mold or pattern maker's job. A pattern maker doesn't do an engineer's job. Just because they both learn for 4 years then continue to learn doesn't mean that theylearn the same thingsor that their knowledge is interchangeable. That is a nonsensical comment bordering on rudeness.Trying to make a semi-complex (i.e. with moving parts) tool that is nice and functional with a silicone mold is almost certainly going to be a Very Large Waste of Time. By all means if that's what you like to do, go for it.

author: eKretz
author_rank: Frequent Contributor
timestamp: December 15, 2018, 11:09:58 am
content: Quote from: coppercone2 on December 15, 2018, 11:04:29 amThere is no answer to this question that he can give you that will likely be correct - and he's already told you that. Your answer will have to come through trial and error. Plastics move as they cool, and with 3D printing as well as irregular shapes that can be unpredictable.

author: coppercone2
author_rank: Super Contributor
timestamp: December 15, 2018, 11:19:59 am
content: the quality shown of a youtube guy doing this on a mold pipe wrench seems adequate without serious industrial equipment or anything for destructive testing of partsforget the mold I will try to waste my money on that, but what should I use for the filler ? materials wise like what epoxy parameters do I want to hone in on>?ima put some epoxy putty on the original sample to make it thicker where I can too so it is more beefy with the reduced epoxy strenght

author: JonM
author_rank: Unknown
timestamp: December 17, 2018, 03:31:37 pm
content: A widely used family of epoxies in the US is West System:https://www.westsystem.com/Here is an application of molding using West System epoxy:http://www.cstsales.com/mold_fiberglass_fuselage_instr.html

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 17, 2018, 03:59:01 pm
content: Silicone rubbers used for molds come in a variety of grades. From soft and flexible, which allows removing very complex parts with undercuts and fine detail from the cured mold to relatively rigid varieties. The latter have pretty good dimensional stability. I don't have quantitative numbers, but in my opinion they would be good enough for your purpose. Unfortunately I am away from home and can't get you the specific references to the vendors and grades.I think you will need to have fiber fill to get appropriate strength, particularly in the jaw space adjustment area. You might get by with chopped fiber, which would be easier, but best strength would come with layed in fiber. Strength can vary widely with details of how the fibers are layed or distributed in the matrix. That is one of the knowledge bases the pros in this area get with their years of training and experience.The adjustment mechanism really should be modified to reflect the properties of the material system. Basically just make it thicker. That isn't easy to achieve in a molded copy. Leading to another recommendation for learning some basic CAD skills and then doing a 3D print. Either to use directly or to use as the pattern for your mold. I didn't have too much trouble learning the basic skills in FreeCAD and it only took a few days. I don't have any reason to believe that you would be slower.In addition to the thought and work mentioned in earlier posts about mold lines and the like, consider post molding processes in your planning. If I were doing this I would plan to file or otherwise work the faying surfaces in the joint, and probably also touch up the jaws. This approach is used in commercial production of similar devices.In all of this you will have to consider the electrical properties of the device. Carbon fiber would be best for strength, but probably too conductive for your purpose. The resins are intrinsically non conductive, but can easily develop conductive channels through contamination or humidity.Whatever your approach realize that this fun project is likely not to be a quick one. False starts and iterations are likely. And as you say the molding systems are not cheap. As I recall the smaller kits from the vendor I would recommend run around $35, and you will consume a large part of one of them for each iteration.