[CadRhino]

Thanks for the insight. I looked at the Boy 50T and that is quite a machine. I had no idea that one would need such a large setup to do a 3 oz shot of ABS. Must of cost more than your Tormach.
I hope you were able to use the molds you made on the Tormach. Did you use 7075 aluminum or 6061? Did you find any good references/books on making your mold or just hopping around on the internet?
I love Kickstarter. I helps build innovative companies like yours.
Best,
Nathan

We started with the Medium Machinery injection molder. Having not much experience with molding at all, we thought that we would be fine as long as the injection volume of the machine would be large enough for our parts. We learned quickly that there is much more to it. The two major limitations (among others) of this machine are clamping force and injection speed. Having only 12t of clamping force means you are limited to parts that have a projected area of about 3.5 in3 or less (for ABS). If your part has a larger projected area, you might not be able to keep your mold clamped shut. Also, those hydraulic jacks are pretty slow so you often wont be able to fill larger molds unless you very accurately pre-heat your molds to just the right temperature (not as easy to do as it sounds). We spent countless hours making the first batch of parts and then decided that our parts are just too large, thin walled, or complex to mold efficiently on this machine. Not saying that it is a bad machine, it just wasn't right for what we were doing. For smaller parts and hobby injection molding it might just be perfect. I eventually decided to get a Dr. Boy 50T2 which makes life a hole lot easier (and my wallet lighter :/ )

[CadRhino]

Ray, Thanks for your advice yesterday. It had me go to my local HF and buy an 18# vibrator and several bottles of their green pyramid plastic/resin grit.
I will try LakeSnakes detailed advise if I get the goo on my parts.

I wonder if the double stack Greenfield drums will work. Both machines look identical and it would be nice to get double duty for small part finishing.

Does anyone know, in my owners manual it alluded to the fact that one can do 'powdered' finishing of parts. Is that a process like a rock polisher where one can put a finish coat on aluminum for example?

Thanks
Nathan

Mike,

I don't recall who I bought mine from, but they are available from literally anyone selling abrasives. Google is your friend: "vibratory finishing media". You'll rarely see a brand name, but green plastic pyramids are basically the same no matter who you buy them from. They're plastic infused with silicon carbide. You will find WIDE variation in pricing depending on where you buy them.

Regards,
Ray L.

[BAMCNC.COM]

You can double stack the drums on the 18lb tumbler, just get some all thread. Artisan Dice on YouTube did it, he says it takes longer, but in the end is faster.

Cord - how much was your Injection Mold Machine?

[SCzEngrgGroup]

Ray, Thanks for your advice yesterday. It had me go to my local HF and buy an 18# vibrator and several bottles of their green pyramid plastic/resin grit.
I will try LakeSnakes detailed advise if I get the goo on my parts.

I wonder if the double stack Greenfield drums will work. Both machines look identical and it would be nice to get double duty for small part finishing.

Does anyone know, in my owners manual it alluded to the fact that one can do 'powdered' finishing of parts. Is that a process like a rock polisher where one can put a finish coat on aluminum for example?

Thanks
Nathan

Yes, you can use powdered abrasive as well. That is typically used dry with non-abrasive ceramic media, or walnut shells. I spent a LOT of time years ago trying to find a process to take machined aluminum parts, and then de-burr and polish them. I finally gave up and did them by hand. It can be done, but it's not easy, and the polishing step can take several days.

Regards,
Ray L.

[AUSTINMACHINING]

I Made this low pressure core/cavity injection mold (liquid silicone "Dragon Skin") using an 1/8" ball mill at 6000 RPM. It came out very smooth and I used it without any post processing. The finish is way smoother than the photo would indicate, but aluminum is very easy to finish to a polish IME using a hand drill and Mothers aluminum polish. They make various applicators (cone, ball etc.). I've used a company called Protomold for soft tool injection molds(aluminum). They offer different grades of finishes from "straight off the CNC" to bead blast and polished. I guess it depends on how much time you want to spend machining vs hand finishing. Protomold has been great (If you got the $$) and they can deliver molded parts in a week. The on line injection mold flow analysis is fantastic providing feedback on potential "show stoppers" in the design process. The aluminum molds (they say) are good for several thousand pieces. My steel molds cost about 3x more and 8 weeks to produce. You can however, make a gazillion parts with a steel mold.

Attachment 254886

[MichaelHenry]

Harbor freight has them: 5 lb. Rust-Cutting Resin Abrasive Tumbler Media

I believe you can find them on MSC/McMaster as well.

Thanks George (and Ray). HF is close so I'll probably try theirs first. Interesting tips downthread on the water flush, too.

Mike

[cordvision]

Unfortunately I can't use the molds that were made for the Medium Machinery Injection molder on the Boy 50 because the M.M. Injection Molder is mostly operated manually and it can't accept "tall" molds. I believe the mold needed to be no taller than 6 inches or so or it wouldn't fit. The Boy 50 can't even clamp such small molds. The minimum distance between the clamping plates is like 10 inches. I read a few books, the one I felt was the most useful was "Spritzgiessen für Praktiker" (german book. I'm Swiss so I can read german). It's not really about the making of the molds but about the injection molding process itself. I also read "How to Make Injection Molds" but it is very, very technical and felt it was only of limited use to me.
I bought the Boy 50 used and I got a pretty good price, but there's a lot more to it than just the price of the injection molder itself. You need other accessories (like a water cooler etc.) that add to the price. Also, transportation for such a big machine isn't cheap, and then you also need a pretty beefy electrical outlet (cost me $1400 to get one installed). On top of all that, it takes over 200 liters of hydraulic oil which isn't cheap either. I hope it all pays off but it is a little early to tell.

Thanks for the insight. I looked at the Boy 50T and that is quite a machine. I had no idea that one would need such a large setup to do a 3 oz shot of ABS. Must of cost more than your Tormach.
I hope you were able to use the molds you made on the Tormach. Did you use 7075 aluminum or 6061? Did you find any good references/books on making your mold or just hopping around on the internet?
I love Kickstarter. I helps build innovative companies like yours.
Best,
Nathan

[CadRhino]

Thanks Lakesnake. This was educational to me. I appreciate the photo too. It looks great.

I Made this low pressure core/cavity injection mold (liquid silicone "Dragon Skin") using an 1/8" ball mill at 6000 RPM. It came out very smooth and I used it without any post processing. The finish is way smoother than the photo would indicate, but aluminum is very easy to finish to a polish IME using a hand drill and Mothers aluminum polish. They make various applicators (cone, ball etc.). I've used a company called Protomold for soft tool injection molds(aluminum). They offer different grades of finishes from "straight off the CNC" to bead blast and polished. I guess it depends on how much time you want to spend machining vs hand finishing. Protomold has been great (If you got the $$) and they can deliver molded parts in a week. The on line injection mold flow analysis is fantastic providing feedback on potential "show stoppers" in the design process. The aluminum molds (they say) are good for several thousand pieces. My steel molds cost about 3x more and 8 weeks to produce. You can however, make a gazillion parts with a steel mold.

Attachment 254886

[CadRhino]

Thanks Cordvision,
This was really helpful info.
I am sure you will be doing more successful kickstarters and the Boy will be the first of many machine.
Now I need to learn German so I can read that book )

Unfortunately I can't use the molds that were made for the Medium Machinery Injection molder on the Boy 50 because the M.M. Injection Molder is mostly operated manually and it can't accept "tall" molds. I believe the mold needed to be no taller than 6 inches or so or it wouldn't fit. The Boy 50 can't even clamp such small molds. The minimum distance between the clamping plates is like 10 inches. I read a few books, the one I felt was the most useful was "Spritzgiessen für Praktiker" (german book. I'm Swiss so I can read german). It's not really about the making of the molds but about the injection molding process itself. I also read "How to Make Injection Molds" but it is very, very technical and felt it was only of limited use to me.
I bought the Boy 50 used and I got a pretty good price, but there's a lot more to it than just the price of the injection molder itself. You need other accessories (like a water cooler etc.) that add to the price. Also, transportation for such a big machine isn't cheap, and then you also need a pretty beefy electrical outlet (cost me $1400 to get one installed). On top of all that, it takes over 200 liters of hydraulic oil which isn't cheap either. I hope it all pays off but it is a little early to tell.

[CadRhino]

Hi Lake Snake and CordVision,

What brand, size and model of ball end mills did you use for roughing and finishing passes to make your molds?

Thanks,
Nathan

Thanks Lakesnake. This was educational to me. I appreciate the photo too. It looks great.

[cordvision]

I actually use just whatever brand I can get my hands on from local resellers and since I often use very small and long endmills I can't be too picky. The smallest I use are 1/32 ball endmills with 1/8 flute length. The largest is a 1/2 endmill with 2.5" flute length. However, cutting any deeper than .08 with a long 1/2" endmill results in excessive chatter on my Tormach.

BTW, you might get away without polishing when low pressure molding, but if you injection mold, you will see even the smallest tool marks. If you can see tool marks on your mold they most likely will also be visible on your molded product. You really have to polish the mold to get a really shiny surface on your plastic parts.

[AUSTINMACHINING]

I was using a carbide 3 flute,.125" ball mill from discount tool as I recall.

[CadRhino]

Thank you.
I take it you have a 770.
Did you buy an expensive polisher?

I actually use just whatever brand I can get my hands on from local resellers and since I often use very small and long endmills I can't be too picky. The smallest I use are 1/32 ball endmills with 1/8 flute length. The largest is a 1/2 endmill with 2.5" flute length. However, cutting any deeper than .08 with a long 1/2" endmill results in excessive chatter on my Tormach.

BTW, you might get away without polishing when low pressure molding, but if you injection mold, you will see even the smallest tool marks. If you can see tool marks on your mold they most likely will also be visible on your molded product. You really have to polish the mold to get a really shiny surface on your plastic parts.

- - - Updated - - -

Thanks

I was using a carbide 3 flute,.125" ball mill from discount tool as I recall.