PP v4 Mold Standard
This topic contains 14 replies, has 5 voices, and was last updated by Anonymous 1 year ago.
Here are still open issues or problems to solve:
1. molds in bazar not really standardized, requires us to supply users with custom adapters.
2. extrusion/injection connectivity causes people to use a few adapter and then have problems with pressure due to heat transfer loss over the added length; i have seen this a lot
3. v3 System is using an outer thread but this cutter (150 Euro upwards) is rather hard to get and still, you have to make sure the end can be heated
4. brass seems ideal but hard to weld; also pretty expensive in some cases. also thread cutters are not available to everybody.
5. that is another story : but there safety problems coming with all that; rendering the machine near unusable for certain ages in an educational contexts.
I am no expert in this but the nozzle and sample adapter below proved well since the exit is very close to the nozzle heatband and the mold entry is getting heated as well; we use it for injection and extrusion. M20 Metric standard thread. I am opening another thread addressing this problem; also seeking for more standardization. We’re looking into the option to have a system where folks can put their mold inside; heated by cartridge heaters or similar and yet removes the need for gloves.
Any thoughts are welcome (@s2019)
@s2019 Stan you’ve right, but I forgot to explain that I would be missing the way to retain the plastic while it warms up, the people of @preciousplasticusa designed a knife valve system to avoid threading and unscrewing a plug before the injection. Maybe combining one of these designs we would avoid threaded connections.
I was just thinking of using a plate as a fake mold. It could be out of non-conductive material (wood, etc.) with just a metal insert to block off the nozzle. The toe block and the clamp interface probably need to be metal but the rest could be non-conductive with a relatively cool outer surface. You could potentially enclose most of the hot end in a similar manner. It would leave few surfaces where you could burn yourself. You could potentially encase even aluminum molds in a protective layer to keep the burns to a minimum.
You could use a spring loaded closure. During loading and compaction, you are not applying a lot of pressure. Though it does not keep a youngster from hanging on the compression handle. You could also do a closing bar/latch that is out of plane to the picture I posted.
One advantage to building up a hot end assembly block is that you can leave room for a cartridge heater and not have to worry about keeping geometry for a band heater.
hello people I was thinking the same. The threaded connection takes a lot of time so I was thinking of a quick coupler connection. Like the one in the picture Tell me what you think
Yeah, the drawer or ramped slide are tempting, but it gets a little more complicated. I think you want 1.5 to 2 mm penetration into the mold and some compression to minimize leakage. If you wedge it, then removal gets a little harder.
It will be interesting what your hardware ends up looking like. I have not worked through the details and dimensions.
Three plate molds should also work well where the middle plate defines an outline. Maybe the teacher can CNC rout the middle plate to the kid’s design.
Ok, we had a look on how this could go well for our commercial units in the edu sector where teachers currently can’t leave the kids on it because they burn their fingers so easily.
So for now I will go with your drawing as base, possibly more like a drawer just – details like the clamping (tapered guides), etc.. still to be figured. What’s great is that it’s like a cartridge then, wood seems tempting because it
is the more easy to make. And, there is space for a simple 2 plate mold and additional addons like heating if needed. When done, the instructor or student can take it of with no gloves and plug the next. This can be also done with backward compatibility for the devices already sent, lovely.
thanks again, it still needs some home work but it’s getting there 🙂 And sorry for the account confusion; i think the IT department is still a while busy fixings bugs 😉
great; just what i needed; i will need some time to compile and make something; another heatwave is slowing down things here drastically 🙂 thanks Stan. There is just one thing left; get the base connectivity to work for extrusion as well; thus the thread as base but more likely interior after all.
Thanks Stan; something like this, yeah. What you think about a spring loaded mechanism which closes the nozzle; pretty much as in your drawing, just smaller; with some luck it’s synced together and opens/closes it automatically. That would address usage problems for most educational clients. I am just thinking loud 😉
For me, having just a simple flat faced hole on the mold side was easy to implement. For my wooden molds I just put in a flanged bushing. As long as you have the flat on flat seal the diameter of the hole and the nipple don’t have to match. You could use a flare fitting https://www.grainger.com/product/AIRWAY-Male-Connector-1LNL8 or even a drilled out acorn nut to get a different interface, perhaps more tolerant of tilt errors.
nice; thanks a lot. this could also address the closing problem for the injector; i was about to swap the o-rings of a water valve for this… for the thread interface however i still hand out a cone adapter at the moment.
for now I’d say that’s a go and this looks easy doable on the Arbor version; great. let me try a few things.
I’m not sold on the threaded interface. In my machine, the pressed interface works pretty well and is quick to change between the blocking function for compaction and the mold itself. The wedges I use are a temporary solution but I think a general, self reacting approach could easily be done.
The picture below shows a cartoon of the concept. Think along the lines of a ski boot binding with a fixed toe retention and a heel clamp. The actual injection interface would be a hole in the mold and a protruding nipple in the cap of the injector. The toe and heel clamp geometries and mechanisms have a lot of options and need to be thought through. You could of course have clamping on both sides.
The mold design simplifies to a hole and two simple (bolt on?)features for retention/clamping
I have tried a similar thing sometime ago and as Stan said, it’s jamming easily that way, til a point you need a hammer…nothing we can use for commercial units, at least not in our case.
I build instead a nozzle from chromium, 12 mm ID, and 45 mm OD to get a heatband on it. Instead of threading a hole from the side, I am in good hope that 12 mm pin with air tight fit will do ok, driven by a thread outside of the nozzle. I will see how it goes in 2 weeks.
Thanks everybody. I am splitting the topic up in a few sub chapters soon.
That gate valve looks nice and for the standard PP hot end may be a good solution. I’ve had plastic squeeze out even through the clearance between a bolt and a threaded hole so I am cautious about putting any moving mechanism in contact with the plastic. I would lean towards an external cap that is retained with a cam type buckle or equivalent.
Lots of options for creativity.
Whatever the clamping mechanism, I would keep it away from the plastic. Under high pressure in the injection machine, it seems to ooze into even small gaps. It is worth trying, but I would be concerned that the two locking cams will get filled with plastic.
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