Tell us about the injection molding process for Mini end-plates
 
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Tell us about the injection molding process for Mini end-plates  

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MKEMike
(@mkemike)
Eminent Member
Tell us about the injection molding process for Mini end-plates

I love the idea of using injection molding and other processes for some parts, where it makes production sense.  Anything that allows you to keep your high quality, reduce waste, and shrink lead times is great.  I know that some things about your process may need to be closely held, but as an aspiring "plastics nerd" I'd love to hear as much as you can tell us.

What we know so far:

1. You're recycling less-than-optimal printed parts and filament.

2. You're saving loads of printing time (about half) on the printed parts for the Mini.

3.  You have two molding machines.  Are they the same?

4. You're not moving away from printed parts and you're still publishing the files so we can print and/or modify these pieces ourselves.

So Questions:

1.  These pieces are still PETG, but how are they different from the printed versions?  Stronger or weaker?  More or less shrinkage or warping? More glossy or more matte?

2.  How much do you have to grind up the recycled material to get a good melt going for injection in the molds? 

3. How much work did it take to CAD out the molds vs. the printed parts?   What special factors did you have to work with (number of injection inlets, wall slope, release agents, etc.)  Are the molds simple "sandwich molds" or are there additional mechanisms for some areas?

4. How hot do you have to get the material and how much pressure do you need to get it to flow into the molds properly?  

5.  Have you tried PLA?   How does it mold compared to PETG? 

6. What other factors have you seen influence quality when molding?  Material color or age? 

7.  Did you find much difference between using recycled prints vs. filament vs. raw material (before being made into filament)?  Is there much the prints would have been through the melting / cooling process one more time than filament or two more times than the raw material?

8. How much of your scrap black PETG are you using versus making?   Do you ever run out and have to wait for more scrap or use raw material?  

9.  You said you have two injection molding machines, is that one for each plate?  Or do the molds produce both plates on each cycle?  Does the molding operation just keep up with the rest of the production for the Mini, or does it run faster so you can stock up on parts and/or not run as many hours on the machines?   Have you tried making any other parts via injection molding?

10. How is maintenance of the injection molding machines and molds compared to the printers in the farm? 

11.  How often do you get a scrap part out of injection molding vs printing?

12.  How much does injection molding these pieces improve overall production time of the Mini's? 

13.  Given a flat top surface on the molded part, could you 3d print on top of it and have it adhere reliably?  Would you need to rough up the surface once out of the mold, or apply a texture to the mold?

14.  Do you see a market for a hobbyist injection molding machine?  Do you think Prusa would ever sell one?  While getting molds machined would be a bit pricey, more of us are getting into CNC machining as hobbyist-level mills are increasing in quality and decreasing in price.

 

Posted : 28/01/2021 12:16 am
cwbullet
(@cwbullet)
RE: Tell us about the injection molding process for Mini end-plates
Posted by: @mkemike

14.  Do you see a market for a hobbyist injection molding machine? 

Yes i do,  

--------------------
Chuck H
3D Printer Review Blog

Posted : 30/01/2021 3:56 am
Yveske
(@yveske)
Estimable Member
RE: Tell us about the injection molding process for Mini end-plates

I don't have a need for this but it was fun watching the build

Having problems with bed adhesion every morning...

Posted : 30/01/2021 6:38 am
3DALHEMIJA
(@3dalhemija)
Estimable Member
RE: Tell us about the injection molding process for Mini end-plates

You guys really think that a big company like Prusa with such order lead time will produce plastic parts with self-developed improvised injection molding machines??? Its not efficient and reliable, so waste of time, money.... everything. I bet they use some well known injection molding machines.

Posted : 30/01/2021 8:01 pm
cwbullet
(@cwbullet)
RE: Tell us about the injection molding process for Mini end-plates

@3dalhemija

You might be right, but they make their own printers.  

--------------------
Chuck H
3D Printer Review Blog

Posted : 30/01/2021 8:10 pm
3DALHEMIJA
(@3dalhemija)
Estimable Member
RE: Tell us about the injection molding process for Mini end-plates
Posted by: @cwbullet

@3dalhemija

You might be right, but they make their own printers.  

If they make their own printers, and some modified "MK printer-based" automated assembly lines, doesnt mean that they will make just about everything behind the scene (filament lines, laser cutters, CNC machines, injection molding machines etc....). They are not startup anymore, time is their/our money. 

We forgot that Joseph Prusa is economist, he knows what efficiency is. They chosen injection molding to reuse waste and to skip printing bigger models (such as mini plate) that occupy several hours of farm printers. Plus, these parts will not be redesigned very often. 

They actually farm inhouse parts mostly because of its production efficiency and long-term redesign sustainability, lastly because of its fancy "rEpRaP4LiFe" story that we think first off...

Posted : 30/01/2021 10:05 pm
Gordon W
(@gordon-w)
Reputable Member
RE: Tell us about the injection molding process for Mini end-plates

I saw a picture of the machines being delivered on the back of a lorry prusa posted on their discord channel, but can't find it at the moment! No home build machines for sure!

Posted : 31/01/2021 2:26 pm
cwbullet
(@cwbullet)
RE: Tell us about the injection molding process for Mini end-plates

@3dalhemija

I think it depends on if they intend to market them.  If they think it might be profitable, I am sure we will see it come to market.  

I have a friend that used to buy CNC'd aluminum parts for patient lifts.  He decided to start making them in house.  He researched commercial machines and finally engineered a machine to make the part himself.  He did that because he could make it cheaper than he could buy it and if he made it, he could fix it himself.  Not everyone can do that.  

--------------------
Chuck H
3D Printer Review Blog

Posted : 31/01/2021 2:32 pm
Fayoh liked
Gordon W
(@gordon-w)
Reputable Member
RE: Tell us about the injection molding process for Mini end-plates

Found it! Two fanuc presses being delivered in late December.

Posted : 31/01/2021 2:39 pm
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