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I need to make some part molds which will be compound organic shapes and must have the final surface finish be very smooth.
If anyone has advice on how to get a smooth final surface finish, I would really appreciate it.
Also, if you have any pictures or process photos, I would love to see them.
Thanks
Nathan
I did. First of all, consider the PCNC 770, especially if the molds to be made are small. You will probably using a lot of small cutters and the much higher RPM of the 770 will save you a lot of time. Also, you will be doing a lot of hand finishing, don't expect to take the mold off the mill ready to go. I have spent many hours of sanding on each mold. If you have $1500+ to spare, you can buy a small ultrasonic polisher/sander (they make them for the jewelry and molding industry). I tried looking for cheaper alternative (tried dremels etc.) but couldn't find anything that worked better than just sanding by hand.
I agree with Cord, 2x faster parts for what you are doing if you get a 770.
Or get this - 31350 - Tormach Speeder Series 2
You can get the parts off perfect with around a .001" stepover and the right endmills. Feed 2x faster on finishing pass instead of 2x slower like you would with the side of an endmill (to keep from rubbing and conserve time) All the hand finishing after that would be maroon scotchbrite and wd-40. I want to experiment with walnut or corn cob in my sand blaster too, still haven't though. I'm going to be making alot of fishing lure molds for a local place.
There is a whole machinist community on Instagram, seems odd I know. Worth it to take a look though. You can learn alot in the info of machining pictures and how they did it. I'm on there, and some others on this forum are.
Quick Example - Instagram
Thank you for all of the feedback.
So basically, one can do everything on an 1100 that they can on a 770 but since the 770 has a faster spindle, it can work aluminum much faster hence saving time, right?
It sounds like I will need to pick my endmills carefully and set myself for minimal final finish endmill cleanup passes. I will most likely need to explore the use of ball endmills for my finish passes since the shapes I am working on will be more organic.
I can't afford an expensive ultrasonic sander yet but will look into less expensive alternatives like scotch brite and soft blasting techniques.
I may look into a vibration tumbler to get the mold parts closer. If anyone has a recommendation or link to more info on them, I am all ears.
Thanks again.
Thanks for the link Brad.
Best,
Nathan
Vibratory finishing with 1/4" green plastic pyramids would work well, if you can tolerate having the sharp edges removed. It will remove all the machining marks, and gently break all the edges, in about an hour, leaving the parts looking like they'd been bead-blasted. The Harbor-Freight 18 pound machine works well, and is cheap enough that even if you didn't like the result, you wouldn't be out much.Quote:
Originally Posted by CadRhino
Regards,
Ray L.
Well you know what I use for tumblers, I have a new one I haven't showed tho, but it's rotary.
I agree/disagree with Ray. I have 1 HF tumbler, and 1 Eastood tumbler. The Eastwood is the same design (seems to hold up better) only you get 2 bowls and some free media. I HATE Green Prymids, I have about 1.5 gallons of them I'll never use again.
Also there are adjustable offset weights in them, so you can tune it.
For soft metals, stick with Walnut and add metal polish. Takes longer, but comes out like a Mirror.
I have 2 Rotary and 4 vibratory tumblers total.
I don't see that on their website, in either 5 lb or 18 lb size, though they do sell extra bowls for a very reasonable price, which is nice. It's very nice having a separate bowl for each kind of media. Not an option with my 24"/1HP machine.....Quote:
Originally Posted by BAMCNC.COM
Why? Properly used, they do a fine job, and last forever. I've been using the same media for 5 years now. The only problem I have is they get lodged in small holes, and can be a real bugger to get out.Quote:
Originally Posted by BAMCNC.COM
Regards,
Ray L.
Sorry Ray, it could only be an eBay deal.
Green Pyramids leave a white film on your parts, and even an ultra sonic cleaner has trouble getting it off if it dries in crevices you can't get too. Also, yeah, them getting stuck in holes, but walnut is even worse for that. If you have threaded parts, put set screws in them before tumbling.
Scratch that, I have a HUGE professional vibrator that holds over 100lbs of media, so I guess I have 5 Vibratory :)
I have no problem getting the residue off with plain old soap and water. It's a lot easier if you do it as soon as you remove the parts from the finisher, and don't let the residue dry. But, even when dry, it comes right off with warm water and dishwashing soap. May also depend on what you use to keep the media wet. I use a cap-full of SimpleGreen and lots of water. Also, you pretty much HAVE to have a drain on the bowl, and keep a slow drip of water going through to flush most of the residue out as the machine runs. But that media will remove ALL machining marks in about an hour, which is tough to beat.Quote:
Originally Posted by BAMCNC.COM
Regards,
Ray L.
I use CLR in my tumblers now, but don't use the slow drip method which would be ideal - however I used them in Rotary tumblers aswell with no way to do that. Also my tumblers are set on timers most of the time, and I may be sleeping or not home. So I've moved away from them and never had the issue again.
I have a better and faster way to do what you want in Aluminum, and less lodging of media, however I haven't perfected it, but will in a week or so and have a YouTube video showing it.
I've never had a problem with a white film on my parts after using a few ounces of VF-77T from C&M Topline (Tumbler Media | Plastic Media | Ceramic Media | Polishing Media). It works wondersQuote:
Originally Posted by BAMCNC.COM
Sweet! Thanks! Didn't know there was such a thing.
You should carefully compare the 1100 and 770. The 1100 is more powerful and has a bigger table among other things. The big advantage of the 770 is its high spindle speed which will allow you much higher feed rates with small cutters (in your case you might use small ball endmills and do a lot of very shallow passes with a tiny step over, so high rpm is your friend). About tumbling your molds: if you are doing injection molds a tumbler might be of limited use. There are many mold components that need to fit together with very tight tolerances. Tumbling your parts would break all the edges and mess with your tolerance, unless you somehow protect the areas you don't want to be messed with. I recently created a camera accessory (easygimbal.com) that consists of a lot of injection molded parts. All I can say is that it was a huuge undertaking and took a lot of patience. I had no prior knowledge of cnc milling or injection molding before I took the project on. Getting a grasp of the milling was the easy part but the injection molding drove me almost nuts. There are so many variables that impact the outcome (like ambient temp in your shop etc.) that it can become very hard to trace the errors. Prepare for a bumpy ride if you start getting into injection molding, it will take quite a bit of patience.
Sent from my iPhone using Tapatalk
Ray - do you have a company name or link for those green plastic pyramids or do you use the same brand that FuriousGeorge linked to?Quote:
Originally Posted by SCzEngrgGroup
Mike
Eastwood are most famous green pyramids
I thought about making my own, making a mold, and just using fiberglass resin and an abrasive powder.
Cord - I didn't know you did a Kickstarter - congrats, my TKSP Pen project ends in an hour!
Harbor freight has them: 5 lb. Rust-Cutting Resin Abrasive Tumbler MediaQuote:
Originally Posted by MichaelHenry
I believe you can find them on MSC/McMaster as well.
Mike,Quote:
Originally Posted by MichaelHenry
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.
I bought my green pyramids from ZORO. I have a HF vibratory finisher and initially had the white "goo" that was a PITA to remove. I found a constant flow of liquid prevents the build up and I just wash with water and they are fine. The trick is to have fluid flow without excessive fluid in the bowl. The HF plastic bowl has a small inlet and outlet drain port and the outlet can easily get clogged, so the outflow is was less that the inflow and you end up with a huge mess. I solved this by placing the finisher in a plastic container offset from the bottom about 4". I put about an inch of water in the container and use one of those cheap 12V bilge pumps in the bottom. This creates a fixed volume of water to circulate through system and it "self regulates". I put a 1/4" zip tie from the inside of the bowl pointing toward the exit of the fitting to prevent the triangles from clogging the outlet port. The bilge pump fills the bowl with the volume in the container. The fluid can drain back out in its own time and the cycle repeats itself, so no overflowing and the mess is contained in the large container. The impeller type pump can run dry between cycles (if the flow gets restricted) without issues.
Thanks for the insight Cordavision and congratulations on the successful Kickstarter campaign. Very cool. What injection molding setup did you use with your molds? Again, very well done. I hope you get lots of business.
-Nathan
Quote:
Originally Posted by cordvision
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 :/ )
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
Quote:
Originally Posted by cordvision
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
Quote:
Originally Posted by SCzEngrgGroup
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?
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.Quote:
Originally Posted by CadRhino
Regards,
Ray L.
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
Thanks George (and Ray). HF is close so I'll probably try theirs first. Interesting tips downthread on the water flush, too.Quote:
Originally Posted by FuriousGeorge
Mike
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.
Quote:
Originally Posted by CadRhino
Thanks Lakesnake. This was educational to me. I appreciate the photo too. It looks great.
Quote:
Originally Posted by LAKESNAKE
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 :()
Quote:
Originally Posted by cordvision
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
Quote:
Originally Posted by CadRhino
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.
I was using a carbide 3 flute,.125" ball mill from discount tool as I recall.
Thank you.
I take it you have a 770.
Did you buy an expensive polisher?
- - - Updated - - -Quote:
Originally Posted by cordvision
Thanks
Quote:
Originally Posted by LAKESNAKE