PDA

View Full Version : Injection Mold Project



BridgeportBill
04-28-2013, 09:30 AM
Here is my latest project, a mold to do my own injection molding for a product I will be selling. I started off buying some 9x13x3" aluminum blocks and used my horiz. band saw to cut into my blanks.
Here is what the mold blanks looked like before I started profiling.
http://i241.photobucket.com/albums/ff162/skyboltiii/P4272094.jpg (http://s241.photobucket.com/user/skyboltiii/media/P4272094.jpg.html)
Here is an inprogress on the rotary table..
http://i241.photobucket.com/albums/ff162/skyboltiii/P4272098.jpg (http://s241.photobucket.com/user/skyboltiii/media/P4272098.jpg.html)
And here is the bottom half complete before polishing. Still have to make the top half.
http://i241.photobucket.com/albums/ff162/skyboltiii/P4272099.jpg (http://s241.photobucket.com/user/skyboltiii/media/P4272099.jpg.html)
Check out my web site LEDwaterfx for the kind of product we sell.

BridgeportBill
04-28-2013, 04:22 PM
Well here is the latest work done.
http://i241.photobucket.com/albums/ff162/skyboltiii/P4282101.jpg (http://s241.photobucket.com/user/skyboltiii/media/P4282101.jpg.html)
All I have to do is figure on how to bring all surfaces to touch at the exact same time. I have some experience with scraping, but never with aluminum. Any sugestions out there? Is it the same but lighter pressures? You can see the 3d printed part on the right mold cavity.

Glug
04-28-2013, 04:49 PM
Thanks for sharing those.

This is something I'd like to learn more about. I've done some searches, and watched some videos of the injection process and the machines. I'm still in the dark about the particulars of mold making, and also what it would cost to do smallish parts runs. I'm sure making your own molds really lowers the costs, though it does not seem to be trivial.

I've read that some of the larger maker shops have their own injection molding equipment.

Jimmer12
04-28-2013, 04:50 PM
Do you have access to a surface grinder? that's how we finished our moulds when I used to design and build moulds. Do you have a side view of the part you are trying to mould?

BridgeportBill
04-28-2013, 09:00 PM
Do you have access to a surface grinder? that's how we finished our moulds when I used to design and build moulds. Do you have a side view of the part you are trying to mould?

I do have a surface grinder but I do not know what wheels I need for aluminum. Also looking at the cross section I do not see how it will help on the lower surfaces.

http://i241.photobucket.com/albums/ff162/skyboltiii/turbineimpellerlightringdie611.png (http://s241.photobucket.com/user/skyboltiii/media/turbineimpellerlightringdie611.png.html)

Jimmer12
04-28-2013, 10:36 PM
Thanks for sharing those.

This is something I'd like to learn more about. I've done some searches, and watched some videos of the injection process and the machines. I'm still in the dark about the particulars of mold making, and also what it would cost to do smallish parts runs. I'm sure making your own molds really lowers the costs, though it does not seem to be trivial.

I've read that some of the larger maker shops have their own injection molding equipment.
One of the mould shops I worked in had 2 moulding machines for testing and short run production.

I do have a surface grinder but I do not know what wheels I need for aluminum. Also looking at the cross section I do not see how it will help on the lower surfaces.

http://i241.photobucket.com/albums/ff162/skyboltiii/turbineimpellerlightringdie611.png (http://s241.photobucket.com/user/skyboltiii/media/turbineimpellerlightringdie611.png.html)

Have to do some research on what wheel to use. We just did very careful measuring of the depth of the cavity to the height of the core and would grind accordingly. After wards we would spot them similar to scraping to confirm contact. Of course scraping would work too. Do you have a shop to do the moulding for you? How are you gating the part, ejecting etc?

mc_n_g
04-28-2013, 10:48 PM
Injection mold for what size machine, plastic and tonnage?
I forsee some freezes (spokes), sinks (thick radials) and no draft in the part to allow for ejection (if that is the the cross section is representing).
I don't see any runner or gate planning. This may lead to warping or cold welds of the final part.
Where are your ejection pins going to be located?
Are you planning on using locating pins or rings for mold closure?
Did you account for shinkage of the plastic? or are there no critical dimensions?
Just a few concerns.
Not being a smarta$$ but you may have spent time and money on an unusable mold.

Jimmer12
04-28-2013, 10:55 PM
What plastic is being used and what sort of run of production are you thinking? Some plastics will destroy an aluminum mould in literally dozens of shots let alone hundreds or thousands.

Jaakko Fagerlund
04-28-2013, 11:50 PM
Your mold is missing the guides or pins that will guide the halves together. If you have them, then the final thing to do is to spot it. Apply engineers blue to the other half, bring the mold halves together, open it up and file/grind/scrape away. And repeat until you get good sealing.

Jimmer12
04-29-2013, 12:00 AM
Your mold is missing the guides or pins that will guide the halves together. If you have them, then the final thing to do is to spot it. Apply engineers blue to the other half, bring the mold halves together, open it up and file/grind/scrape away. And repeat until you get good sealing.

To be fair I have designed prototype molds for proof of concept or very short run production that had no leader pins. They were doweled or keyed together and manually separated for each shot. Certainly no good for long production but ok for one offs or a few dozen parts.

BridgeportBill
04-29-2013, 06:04 PM
Well all I do appreciate the interest in my project. Some of the details are...
ABS will be used for the plastic, I am interested in doing about 1,000 pieces to prove marketability. I did put 1/2deg draft on the short sides and will put 1 deg on the longer sides. I know that I need a spru, runners, gate and possibly vents. Also I will install guide pins when I manage to get the surfaces to mate properly. I do have a cusin assisting in the design as he is in the business for another company and he also said we could have issues with the spokes and beyond. We will adjust the mold as needed. I plan on purchasing a injection press from http://www.mediummachinery.com/index.html. I know nothing about the company but it is technically big enough to handle the part and cheap enough to try it out.