Micromolding (Small parts such as small lense)

[iautry1973]

Well maybe not micromolding, but definitely small parts. I have been having some issues with a small lense. Total shot weight is 3.36g for a 4 cavity tool. Part weight is .07g. We have a larger barrel we are running it on (20mm). The shot size is fairly small and therefore hard to control the process. I was wondering if anyone had used a micromolding machine to shoot smaller parts like this and any advice on brands of machines?

[JayDub]

I've had good luck with Nissei machines. Ran a .12g part weight single cavity tool on a 30 ton vertical with a 14mm (as best I recall) screw. I've also run parts with weights down to around .02g (damn things floated around like snowflakes till we put a vacuum picker on the press) on a horizontal with a similar size screw. Where I am now we have a couple of Sodicks, which are also very good machines, but I haven't worked with them much.

Nissei currently makes a very small (7 ton?) press that I would definitely look at if I was going do to do a lot of micro-molding.

[iautry1973]

Thanks JayDub. Problem I am having is that the actual parts are being filled under hold pressure. So not the best process.

[Jason S.]

I just picked up a Nissei NEX15III equipped with a 14mm screw. I've had the machine since January and it has been fantastic, (I call it my little Asian princess). I also have a couple Battnefeld microsystem 50 machines that were actually designed for micromolding, I would replace both of them with Nissei's if I could. Its just a much better and repeatable machine.

[iautry1973]

JayDub, do you know how the service has been on the Sodicks and how reliable they have been?

[JayDub]

JayDub, do you know how the service has been on the Sodicks and how reliable they have been?

Keep in mind our machines don't see very heavy use - typically running low volume insert-molded parts with long cycle times. Our vertical hasn't been used much at all. That said, the older horizontal machine (of two) was purchased in 2010. I've only been here 2 years, but I asked our maintenance tech if we had ever had problems. Nothing but routine (planned) maintenance. So I can't tell you how service is as we've never had to call them.

[chrisprocess]

12x Nissei hm7 mini presses in house. These are great little machines with only 8 ton clamp.. They run molds with shot sizes around 2g.

Are you able to get a 15mm screw in your press? This option might work for you (3.36g shot weight) because if you go much smaller your residence time would be very short!

[chrisprocess]

Are you able to get a 15mm screw in your press? This option might work for you (3.36g shot weight) because if you go much smaller your residence time would be very short!

Maybe spoke too soon.. I suppose this depends on your needs and the resin you're molding.

[iautry1973]

Jaydub, thanks for the reply. Seeing as that machine is 7 years old and no real issues that is good, I know it is light use. We aren't going to be using ours super hard, but it won't be gathering dust either.

[iautry1973]

Chrisprocess, I looked at some of the smaller presses, but the issue I have is the molds aren't small and the EOAT they use is fairly large. I looked into a smaller screw, but they only go down to an 18mm with the next size down injection unit. So not worth replacing both of those. Might be able to get a custom barrel, but not sure how well that would work with the controller and injection unit. We are shooting PC and it is an optical prism. So tolerances are uber tight. like as in +/- 0" to make it work. I am talking to them about getting the mold rebuilt with a smaller runner. The machine has a nozzle body adaptor on it, the mold has a huge runner compared to the part, and a very long heated sprue. So I am having to transfer pressure into a very small part with a very large system that the material can be compressed in. Just not an ideal situation.

[chrisprocess]

Difficult situation because you'll need to balance screw-control with residence time..

What % of barrel usage are you using now? shot size/max dosage
What's estimated cycle time?

Info I have says 2 minutes residence time for PC (seems rather long..) I'd shoot for minimum 45 seconds residence time with a reverse barrel profile

You might be okay with that 18mm screw if your injection unit is downsized.. (shot size - machine manufacturer should help with this)

And I agree.. smaller screw would be nice, and hot sprue and/or hot-runner manifold would help.

Colleague of mine worked for a company that made custom lenses. They had to build their own 'modified' injection molding machine to produce them.
He mentioned they would inject plastic, and use the mold halves to 'press-fit' the part.

[chrisprocess]

Something like this (18mm) might work depending how capable your machine is:

206

[rickbatey]

How about an all electric add on injection unit to run this job? Check out Plasdan as those guys could build you one with a very small screw diameter.
Rick

[Jason S.]

You can get a nissei NEXIII 15 ton, all electric with a 14mm screw.

[iautry1973]

Thanks for all the info, sorry been on vacation and got back late this week to a lot of catching up to do on the floor.

Chrisprocess,

The specs show a 26g shot weight possible (GPPS). The part is 3.32g. The cycle time is about 30 seconds. The residence time I ended up calculating was a lot longer than 2 minutes. Two manufacturers are quoting me a 15 or 16mm screw which seems more manageable. We are looking at a Sodick which the sales guy said was originally intended for optical parts in Japan. The other is an Arburg. So far haven't seen another one that fits the specs we have for daylight/barrel size combination. We thought about getting the barrel downsized, but we have been having major issues with the service from Sumitomo. Had to get the battery on the board replaced last year. Started the process in Feb 2016 and still waiting for all the issues from the install in Dec 2016 to be finished. Numerous calls, emails, frustration, run arounds, failed promises, and face palm moments for 18 months. Doesn't leave management or I feeling great about keeping the machines seeing as we don't have any spare capacity.

Rick,

It is an electric injection unit. Might be able to run an 18mm screw with some work by a supplier. Just not sure about the machine however being the right one for us.

Jason,

I looked at the Nissei 15 ton, just not enough daylight for the EOAT/mold combination.

Thanks everyone!