Machinists, need advice.

[abudabit]

I'm always inventing things but never building them. Decided to finally to take the step of making a light duty injection molding machine (plastics manufacture). Anyways, the molds needed for the parts you make need to be made of a solid block of metal (steel, alum, etc.) because of high pressure + 350-450 degree temperatures. Outsourcing mold making is very expensive, so I need to make them at home.

I have never machined parts. I'm not looking to spend a lot of money on this. Maybe a $300-700 machine / set up. What I need is a machine that carves into the face of a solid metal block with moderate precision (+-.025" at worst) the shapes I need to. Would that be a milling machine? And keep in mind since I only need to make each mold piece once (or rarely in the case of breakage) I can spend a good amount of time on each piece.

1. Is a vertical milling machine what I am looking for?
2. For this one and done machining need, would a manual be better than a CNC machine? If CNC is better, is that even possible in my price range?
3. Where do I find aluminum blocks that are at least 4" x 10" x 20"? I looked at ebay and all I saw were blocks less than 2" thick.

Thank you very much, I need to know what direction I need to look when making my machine purchase. Thank you for your time.

[Glenn Dandy]

next time my buddysover I'll ask him... but heonly made vinyll stamp tools, but hes pretty smart. I'll check on it...

I cant believe theres no machinists on here?

[Sct Ptersns Twn]

C&C is the way to go. Got any pics of what you want? I am the sales manager @ a Very modern and precise machine shop in Virginia. I have various sources for material as well. I would love to look @ the part/parts for ya. :action-sm

[Glenn Dandy]

SPT is the man...

[abudabit]

Cool guys, thanks.

I haven't made mock ups except in CAD. But here are examples of molds for plastic injection. My needs aren't nearly as complex / intricate as these, at least none of the things on my plate right now are as complex.

http://www.storesonline.com/members/530126/uploaded/injection_mold_with_8_internal_slides_image.jpg

http://img.alibaba.com/photo/50569112/Injection_Mold.jpg

That top one is especially complex because it uses slides, which I won't be using.

[Sct Ptersns Twn]

My needs aren't nearly as complex / intricate as these, at least none of the things on my plate right now are as complex.

That top one is especially complex because it uses slides, which I won't be using.

Gravy, right up our alley. We make shit that goes into space, in the depths of the seas, and everything in between. PM me if you need advise. I have a laundry list of machines @ your disposal.

[THE FEZ MAN]

Gravy, right up our alley. We make shit that goes into space, in the depths of the seas, and everything in between. PM me if you need advise. I have a laundry list of machines @ your disposal.

those parts are quite complex for a home machinest, i would go with SPT, your going to need a pro for that or use resin castings for your r&d

here's a few sites ive found

http://www.cnczone.com/
http://www.wttool.com/

[Dopie Opie]

Wow - you guys are really fucking smart. I always wondered how these type of things are invented and what the applications are.

I work for a trucking company and I amazed at the amount of freight that these companies produce. These seems to be much more plastic injected molds than metal. I had a customer who made aluminum extrusions and that was pretty cool, but they shut down about a year ago.

I also have another account that makes rubber extrusions and their business is booming. The biggest obstacle is still the fact that the chinks make this stuff for pennies.

Good luck.

[abudabit]

http://www.cnczone.com/
http://www.wttool.com/


Awesome, that cnczone has lots of advice. I'm going through it and the minimill reviews now.



Gravy, right up our alley. We make shit that goes into space, in the depths of the seas, and everything in between. PM me if you need advise. I have a laundry list of machines @ your disposal.

Awesome, thanks for the offer. Although I prefer to do the machining myself because of costs and because I start new projects on a pretty regular basis.

[THE FEZ MAN]

http://www.sears.com/sr/javasr/product.do?BV_SessionID=@@@@2039533442.1186943003@ @@@&BV_EngineID=cclkaddljljjegmcefecemldffidfko.0&pid=00921754000&cat=Bench+Power+Tools&subcat=Jointers,+Planers+%26+Shapers&vertical=TOOL&ihtoken=1

this thing is really neat too. i would love to take a class at the local comedy collage but they dont offer machine classes any more

[abudabit]

Isn't that wood only? That thing looks cool, might be a book out for machines like that.

[THE FEZ MAN]

makeing the machine its self is easy all you need is xyz motors, but getting it to work with the computer is way way beyond my ability's, you might want to check E bay for some used equipment.

[abudabit]

From that link you posted earlier they were talking about kits you can buy, not sure of the price of those. Tons of mods, too.

[Sct Ptersns Twn]

You have to be able to program the machine and determine what tools to use with those machines. If you can find a machine that is only 1/3 of the answer. You need to program it, get the material and tooling.

[d0uche_n0zzle]

Try here. (http://www.emachineshop.com/)

[THE FEZ MAN]

i added that one to my favorites

[grail]

How many tons force and how big of a shot are you looking to inject? Based on the pics you posted that would be at least a 50 ton machine for a single shot that size. (I don't know exactly how big a piece your looking to make). Are you looking into making mud tooling (interchangable in a base frame)? If so I would be looking at 17-4 stainless or aluminum bronze to allow the clamping pressure. Are you going to want cooling? What material are you wanting to inject? I just don't want you making something then going to do your first shot and having molten plastic and metal shrapnel everywhere. stp might be the way to go. If you were doing extrusion tooling I could definetly help more.

If you need a prototype and have a 3d cad file or solidworks file, I might be able to help.

This might help you find something as well.

http://www.thomasnet.com/nsearch.html?cov=NA&which=prod&what=Tooling%3A+Plastic+Injection+Molding&navsec=search&heading=86026044

[Fendbass22]

I use a Bridgeport at work all the time to replace parts that will take to long to order. Not a machinist at all tho. Good used bridgeports around here are about $1500. Just sucks you will have to use a VFD to get your 3 phase.

Tooling is expensive but will last a long time if used correctly. I don't know much about CNC.

[abudabit]

How many tons force and how big of a shot are you looking to inject? Based on the pics you posted that would be at least a 50 ton machine for a single shot that size. (I don't know exactly how big a piece your looking to make). Are you looking into making mud tooling (interchangable in a base frame)? If so I would be looking at 17-4 stainless or aluminum bronze to allow the clamping pressure. Are you going to want cooling? What material are you wanting to inject? I just don't want you making something then going to do your first shot and having molten plastic and metal shrapnel everywhere. stp might be the way to go. If you were doing extrusion tooling I could definetly help more.

If you need a prototype and have a 3d cad file or solidworks file, I might be able to help.

This might help you find something as well.

http://www.thomasnet.com/nsearch.html?cov=NA&which=prod&what=Tooling%3A+Plastic+Injection+Molding&navsec=search&heading=86026044

Those pictures aren't my molds, I was just showing people who didn't know injection molding what a mold looks like. But yes, I will need strong molds. And I will have a clear blast shield, I'm not stupid enough to put my life in the hands of something I made. :icon_mrgr I'll also put a safety in, where the blast shield has to be down before I can pump.

No cooling planned, no rapid yield needed. Hell, the pumping is going to be crank controlled most likely and I'll be using the antiquated plunger press method. I'm going to have heating elements in the feeder chamber, the press, and the injection tube. I'm just going for a simple, cheap design. Haha, maybe my version of cooling would be a nozzle to attach the garden hose to the outside of the mold.

Thanks for the advice on the materials, need to find out which would be the easiest to tool with a mini-mill yet would still hold up in the rigors of injection.

As far as the plastic, looking at ABS but I want to experiment. It will change from project to project but since this first project the plastic will be for the casing I'm thinking ABS.

[grail]

17-4 isn't bad to machine before heat treatment but can be a super bitch once it is. Aluminum Bronze is a uberbitch to machine but holds up really well. D2 steel might work as well and is fairly easy to machine.

As far as ABS goes and the application your describing. You might try CYCOLAC* MG34LGHF Resin. It's from GE. They might be able to send a sample to your business. Its fairly high flow, low gloss. You might be able to do a search for the material you want on http://www.ides.com/. If you want something that will flow like ABS and still stand up to sunlight and weather you might try an ASA like Geloy.


You can also try www.watlow.com for your heaters and controllers. Also you can try www.ppe.com for some supplies.

[abudabit]

Awesome dude, thanks! Are you in plastics?

[grail]

Yep, that's pretty much all I do. Mostly extrusion though, not so much on the injection molding, but most of the principles apply. The offer stands on the prototype if it's not too big. I just need a 3d cad file or an stl file. Thats what my company does is make machines and prototypes out of ABS, PC, PC-ABS, PPSF.

Look at this thread for http://www.wackbag.com/showthread.php?t=68992&highlight=stl some examples.

[Biking Mexican]

I build plastic injection molds. You could try S-7. That and H-13 are pretty much all the company I work for uses. S-7 is easier to machine, before heat treat, and easier to grind after. I would stay away from aluminuim bronze, that shit is awful to machine and the dust can cause cancer. Sounds like the other baggers have got you headed in the right direction.
Good luck buddy :action-sm

[Dave _from_Kiev]

I am a master machinist ( journeyman with 18 yrs experience in the Detroit area). with all due respect for the price you are looking to invest you can purchase a good bridgeport ( manual milling machine) or a horrible piece of shit cnc. problem with a horrible piece of shit cnc is that if you are not very adept at close tolerance machining the mold will not bolt/ mate properly to the injection machine nor to itself ( male and female halves) I ceartainly do not want to be the dave downer here but you need to know a few things :

1) how to cut high temp steels

2) how to program or at least ( if u get a bridgeport) basic machining skills

3) how to properly bench (finish sand) a mold.



If your willing to be a little more precise about what your trying to inject (plastic, metal) your options may be a bit more appropriate.

as far as cheap material goes. go to yopur local scrap yard. despite the recent boost to raw prices you'll probably find a good deal and the piece your looking for ( nitters have been stealing billets 500 + lbs around here.)


Again I dont want to be a downer but you need to be realistic if you are going to make a product that sells.


feel free to pm me with any help in any area.

good luck.

[grail]

abudabit what's the lastest on your project?

[abudabit]

Didn't have time to get started yet, been busy. Gonna start building the injector Sunday.

[abudabit]

Building the injection machine now. Now I have 2 more questions for the mechanically inclined:

1. This is a stupid one, but if a check valve is rated at 6000 psi is that the max pressure that can be applied from the inlet or outlet? I will be dealing with lots of pressure at the outlets but little at the inlets.

2. Anyone know of a good online place to get the parts to make gear assemblies? I need a crank that turns a worm screw which turns a 'screw' style press. The screw press will have to handle a ton of force (50,000 lbs).

Already bought almost all the tubing, just need these two things and I will be 50% done with the parts shopping.

[THE FEZ MAN]

hmmm thats way more pressure than ive ever dealt with

[abudabit]

Just remembered the gear name - lead screws. Found a place that sells ones that can handle that.

[grail]

Check valves have two ratings. The cracking pressure and the back pressure. The back pressure is the 6000 psi one you listed. This is the one that where the valve will fail and that's at the outlet. The cracking pressure is the inline and is the amount of pressure to open the valve.

[abudabit]

Gonna have to go with a lower pressure (150 psi) hot mold slow cooling method, these high pressure parts are too expensive or large. It will have a 10 minute cycle time instead of a 1 minute cycle time and will be limited in the plastics I can use but will have the advantage of being cheap to build, portable, and more leniency with the mold materials.

[abudabit]

Ok, got another problem. I need something that can "lock" with 30,000 lbs! It needs to have minimal backlash too.

The largest amount of force, even with these lower pressures, will be pushing against the 2 mold halves. I need to clamp them together. Lead screws that can handle that are too expensive and inefficient, and ball screws are even worse when it comes to the cost.

So basically it needs:

Low Backlash
High Clamp / Locking (the load bore while staying closed / locked / stationary)

But on the plus side it can have weak jacking ability (the load bore while closing / opening)

Thanks for your help everyone, I think this will be my last question (yeah right)

[abudabit]

U-Bolts and a latch bar, figured it out. There'll be a little leaking but not much if I engineer it right.