Text im Video
00:02[Music]
00:09hello and welcome to the master class
00:11this series of videos is all about
00:13giving you some practical advice to help
00:16you design better parts for digital
00:18manufacturing whether that part is
00:21produced by 3d printing injection
00:23molding or CNC machining we want to help
00:26you get it right this week we're going
00:28to take a closer look at the surface
00:30finish of a molded part and what you
00:33should be thinking about in theory there
00:36are a number of different surface
00:37finishings possible for anything from
00:40texture to a highly cosmetic smooth
00:42finish and of course putting that theory
00:45into practice is very different so there
00:49are a few things that you need to
00:51consider first what development or
00:54production stage is your part at is it
00:56prototype or is it a finished part
00:58second what material (Hersteller) is it being
01:01manufactured from and third what is the
01:04end use of the application we are going
01:07to deal with the number twos in this
01:09list and deal with some of the
01:11practicalities that you should be aware
01:13of before you begin your design let's
01:16start with plastics as these are the
01:18most common injection molded material
01:20there are of course hundreds of
01:23thermoplastic resins that are flexible
01:25strong and can give you fine cosmetic
01:28finish the finish will depend on the
01:31mold aluminium molds are processed using
01:33three axis milling and are easily hand
01:36polished or textured to any one of seven
01:38different finishings from anything from
01:40non cosmetic or textured surface to a
01:43high-gloss polish if that were it though
01:46this would be a very short video but
01:48life is never that simple there are of
01:51course more that needs to be considered
01:52than that the material that you select
01:55for your part can affect your surface
01:57finish generally the link is small but
01:59glass mineral or soft and high strength
02:01materials can produce parts with a
02:03different finish to what you are looking
02:05for these materials have unique
02:07properties that unfilled materials don't
02:10if you do an either cosmetic finish
02:13part you try to avoid them or at least
02:15be cautious about using them they can
02:17produce streaking making it difficult to
02:20distinguish between different finishings
02:22this isn't the case with all field
02:25resins but the best thing to do is to
02:27speak to injected molding supplier and
02:29get their advice a textured finish is
02:32different again in terms of what you
02:34need to know in this case your part may
02:37have more draft requirements than the
02:38polished surface would we deal with the
02:41topic of draft in a later video but
02:43briefly it means that you need to apply
02:45a slightly different taper to the face
02:47of the part so that it can be ejected
02:49from the mold if you don't then you may
02:52end up with scratches or drag marks the
02:55exact draft you need depends on both the
02:58design of the part itself and what
03:00surface finish you want a good example
03:02of a draft is taken look at an ice cube
03:05next time you're pouring that cider it's
03:07not a perfect cube it has rounded edges
03:10so that you can get it out of its mold
03:13but dragging you away from that cider
03:15it's almost worth noting that you may
03:18not be possible to get finishes or deep
03:21and thin ribs as they are very
03:23challenging to reach within the molds
03:25and if surface finishing is important to
03:28you then you must also think about
03:30gating this is where the liquid resin
03:32enters the mold
03:34unfortunately the gate interrupts the
03:36mold surface and that leaves an
03:38unavoidable cosmetic defect on your part
03:41ejector pins if needed to remove the
03:43part can also affect the finish these
03:46are all things that you need to think
03:47about at the design stage and just to
03:51add to the list you may find that your
03:53supplier can offer you custom finishes
03:56you might for example be able to order
03:58these different finishes apply to
04:00different sides of the mold plastics are
04:03the most common material used in
04:05injection molding but let's finish off
04:07by considering another popular option
04:09liquid rubber silicone the mold itself
04:12is produced and exactly the same way as
04:14plastic but the molding process is
04:16different it uses two liquids mix
04:19together which are then heat cured in
04:22the mold to produce the final part the
04:25big difference is that
04:26arts made from liquid silicone rubber
04:28are much more forgiving than plastic
04:30parts they can be manually moved from
04:33the mold so there's no ejector pins are
04:36needed liquid silicone rubber also needs
04:39extremely shallow gates so any
04:42imperfections from this area are almost
04:44invisible well that's it for this week
04:46we've hope you found of interest and we
04:49will see you next time
04:50[Music]
Letzte Änderung: 17.04.2020