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View Full Version : Benchtop Injection Molders - do they work?



GammaWill
03-08-2007, 07:24 PM
I'm looking at milling my own mold inserts for the Mini-Jector Wasp #45 Bench top injection molding machine. However, the machine is spendy, and I don't want to commit to something that won't work for my needs.

So far, it looks promising, since it can mold using an insert, which will allow me to "experiment" with the miniature toy weapons I sell, until the design is perfect and ready to be committed to a real production mold.

Has anyone used a Mini-jector machine, or can you recommend a good bench top injection molding machine under $10K?

---Will

MrMold
03-08-2007, 09:21 PM
Hi Will,

I thought a benchtop molder would work perfectly for you. They make models that are completely automatic, but the tooling is similar to any other production mold and the cost of these machines is a bit high. I think I'd go with one of the hand plunger models about $1500. I built your first production molds so you realize the cost involved, can't beat the cost of the parts off that mold. I'd think I'd use the bench top as a "bridge tool" where you would build some demand for some of your figures. It'll be easy for you to tell when to justify the cost of a production tool, you're arm will start to double in size. Just keep it simple and outsource when the demand justifies production tooling. You might try your hand at being a mold maker but unless you have some previous experience I wouldn't take it lightly. An aprenticeship can be 8 years long or 4 years with 4 years of college. If it were that easy everybody would be doing it. Good luck.

GammaWill
03-13-2007, 02:43 PM
Sage advice, Mark. Thanks! I'll look into the hand-crank version, and see if it can produce what I need, with sufficient quality to test the parts before committing them to a production mold.

Do you know of anyone that has used them to mold ABS? Most of the literature I read describes them using higher flow resins (recyclable plastics, PE, PP, PS) as a material source. Is ABS too "thick"?

Mark, your full-size mold quality is excellent. Have you produced molds for these kinds of machines, for ABS? Did you use aluminum blocks? 6061-T6, perhaps?

---Will

UPDATE 3/16/07: I called one of the hand-crank vendors, and he said he has not tested his machine with ABS. I'm sending him some sample triple-five ABS for him to try and I'll report any news I receive.

GammaWill
05-18-2007, 04:39 PM
Well, it looks like the $1500 benchtop injection molder (hand-crack) model does work with ABS resin :(

So, it looks like I'm going to have to expand my search to the AB series, Minijectors, and Gluco benchtop models. All are capable of injecting ABS - for about $10,000. Ouch!

Harryman
05-19-2007, 11:29 AM
I've seen these used in the jewelry industry but I don't know if these will work with ABS.

http://www.abplasticinjectors.com

Pres
05-19-2007, 11:56 PM
Well, it looks like the $1500 benchtop injection molder (hand-crack) model does work with ABS resin :(
Which "ABS" resin? There is a wide range of melt flows available with ABS.
For example: GE GPM-5600 ABS has a melt flow of 10-13 (that's pretty "runny")
Usual ABS is around 3-6 melt flow, although I've injected ABS with a 0.9 mf(extrusion grade) - about like thick putty. (hard to push - but a tough ABS when molded)

It primarily depends on your gate/cavity size, runner length to get a complete fill for a particular resin.

You need to provide specific mold/part dimensions to determine what machine size and material is needed.

Good luck,
Pres

GammaWill
05-23-2007, 11:34 AM
Which "ABS" resin?

He used these 3 types:

CYCOLAC KJW (melt flow: 4 g/10 min)
CYCOLAC T (melt flow: 1.7 g/10 min)
CYCOLAC MG38 (melt flow: 3.7 g/10 min)

He was able to get them to inject, but with some discoloration. All were injected at 480-500 degrees farenheit, which seems much too high IMHO.

He was also able to inject an ABS derved from grind-up Lego bricks which worked much better.

So, Pres, should I be looking for an ABS resin with a higher melt flow? Could you point me to a place that sells a higher melt flow ABS in small quantities (10 pounds or so)?

firetrkfxr
06-09-2007, 11:23 AM
I have some ABS that flows at 11g/10min as well as some that flows at 4.5g/10min. IM me if you are interested. I am currently making my own machine and have a good cheap source for band heaters on eBay. He's very well to work with and prices are reasonable.

http://stores.ebay.com/industrial-supplies-ptg_Band-Heaters_W0QQfsubZ9588094QQfrsrcZ1

He also sells cartridge heaters if you want to try that method.

Mite E Copter
09-14-2007, 06:03 PM
Hi Will,

Sorry for the late reply, but I just found this forum and saw your thread. To answer your initial question. YES. The Mini-Jector benchtop molders do work, and quite well. They are a bit pricey for a hobbyist but can quickly pay for themselves. I own a Mini-jector 55 and use it to mold all of the parts for my r/c helicopters (www.miteecopter.com (http://www.miteecopter.com)). Before I got it, I bought a 'drill-press' molder on ebay and tried a couple of things with it. It was too small (1/3oz) but, more specifically, it couldn't do the things that the Mini-Jector can. There was a short list of plastics that I could realistically use with it, it was slow and there was no way to be consistent.

My Mini-Jector is a real molder and can thusly use any type of thermoplastic I see fit, regardless of melt flow, so my parts are made of the same materials that would come from any other big plastics molder.

The downside was that it's hydraulic (messy) and required me to install 3-phase power in my garage!

The upside is that in the niche that I'm in, I'll probably never have to move production out of my garage! :D

-Ken

Pres
09-14-2007, 11:45 PM
.... The downside was that it's hydraulic (messy) and required me to install 3-phase power in my garage!
Ken, first off congratulations on getting a "real" injection molding machine.
(unfortunately, it's about the only way to get a consistent quality molding - but it's lottsa $$)

Secondly, their website (http://www.mini-jector.com/model55.html) states the following:
"The Model #55 requires only 230 volt single phase power..."

Perhaps you needed 3 phase for some other machinery?

Just wondered.
Pres
p.s. how did you get the utility company to put 3ph in your home garage?

Mite E Copter
09-15-2007, 09:11 AM
Ken, first off congratulations on getting a "real" injection molding machine.
(unfortunately, it's about the only way to get a consistent quality molding - but it's lottsa $$)

Secondly, their website (http://www.mini-jector.com/model55.html) states the following:
"The Model #55 requires only 230 volt single phase power..."

Perhaps you needed 3 phase for some other machinery?

Just wondered.
Pres
p.s. how did you get the utility company to put 3ph in your home garage?

Hi Pres,

I bought a used '55 at a STEAL :eek: . It's a ten year old model that has split 120/1ph and 220/3ph power. The hydraulic pump uses the 3ph, while the heaters, solenoids, relays and timers use the 1ph. The great thing about mini-jector is that the newest model 55 is mechanically the same as the one I have, so support and replacements are no problem (even though wiring isn't :rolleyes: ).

As far as the 3ph power, I bought and installed a phase converter and now use the 3ph to run a granulator along with my IMM.

-Ken

billfrissell
10-17-2007, 03:33 PM
Currently the Mini-Jector machines are manufactured by Miniature Plastic Molding located near Cleveland, Ohio. We offer the Model 55 with both 230 single and three phase as well as a CE and 460 power.

Please note the more current web site is www.minijector.com

Also we will be introducing an all electric version in 2008.

Regards,

Bill Frissell

ratrace2
11-09-2007, 05:31 PM
At one time, I too was in search of such an item. I looked all over the place and found a lot of used stuff here and there, mostly industrial auction sites. Consequently, not knowing a thing about what I was about to buy, I gave up the chase. Now, however, one might consider this a viable source of, albeit used and heavy industrial surplus, a good place to look for the "function" you require.:)

leppya
02-10-2008, 11:05 PM
Ever settle on anything? Still looking? I'd love to hear an update.
Leppya

MAGEDS
03-26-2008, 07:18 AM
Can anybody tell me if this machine is good
http://www.injectionmolder.net/index.htm

StarLoc
03-26-2008, 06:28 PM
They look like they will work fine, but i would change the plastic feed, its easy enough to change it to some type of hopper, if you look at the onw in the link below you will see how you can add a funnel type to keep the top bit fed with plastic, if you keep the top fed with plastic, its easier as the top preheats the plastic before it drops into the barrel when you raise the plunger, making the heating of the plastic continuous so you dont need to wait between mouldings

http://www.travin.co.uk/tp2.html

MAGEDS
03-27-2008, 02:13 AM
They look like they will work fine, but i would change the plastic feed, its easy enough to change it to some type of hopper, if you look at the onw in the link below you will see how you can add a funnel type to keep the top bit fed with plastic, if you keep the top fed with plastic, its easier as the top preheats the plastic before it drops into the barrel when you raise the plunger, making the heating of the plastic continuous so you dont need to wait between mouldings

http://www.travin.co.uk/tp2.html
What I need is a small plastic injector to produce about 100 10 150 small plastic jar (capacity of 100 gm) for my samll business....is a Benchtop Injection Molder good enough??I cannot afford an expensive machine now!

StarLoc
03-27-2008, 05:03 PM
100g size jar sounds a bit too large for it, you may be able to do it though as the shot size should be ok,

they always measure the shot size of machines in polystyrene weight and the weight of a polystyrene jar 100ml is usualy less than the shot size of the machine, the problem i see is the presure being high enough to get the plastic round the shape of the jar with the presure from a handle, air powered ram it should be no problem for pressure

a problem with larger parts like jars is the mould, the size of it, you need to get it quite hot to mould successfully so you would need to heat the mould, but then it will become too hot and need cooling, so you will probably need some sort of mould temperature controler, because of the internal mass of the core part that forms the internal dimension of the jar it will hold a lot of heat

Why do you need to make the jar?, is it to customise it? , if not its far cheaper/easier/cost effective to buy the jars (from experience),

if just for a brand on the packaging, it would be best to form the lid with a name on and buy the base of the jar

Have you tried ebay for used injectors, you can get machines slightly larger than that, with air power, they will form parts much better , usualy a used machine will cost you less for a better machine and you often get to pick up extras like bags of plastics when you pick it up, if you have the space, you can buy fully auto machines often for low price if you can get them moved, with a larger/industrial machine such as a boy or arburg (they are too slow for most modern production) you can buy a ready made alloy mould to fit you just cnc the cavity out, a machine like the boy will auto mould all day and make jars at a very low cost, but the machine takes up a lot more space.

Kevin R
01-10-2009, 08:56 AM
I haven't really been part of the discussion but if you are looking at a low cost injection molder with varying amounts of downward pressure. try http://www.backyardengineer.com the site offers a fully completed package and a listing of all the parts. The machine costs less then $500.00 If you were designing your own and needed cylinders and or heating parts, those are sold individually at the site as well.

dancer
02-26-2009, 09:38 PM
Bench top injection moulding machines are widely used in India for regular production. They vary in size and shot capacity and the smaller ones are usually hand operated and use electricity only for the heater band. Maybe you can find them on the net somewhere.

tpmx57
02-28-2009, 03:19 PM
I am working on a machine for homeshop use for small production runs.
You can check out my website at:
http://www.hitechhobbies.com/
I just started machining parts and some assembly work and hope to have the first working model in the upcoming week.
I plan on selling kits or complete units and parts to build your own.
All frame parts are cnc machined.
Feel free to email me with questions.

KOS
05-23-2009, 12:29 PM
I know this thread is a little old, but just wanted to chime in and say I just recently purchased an Emco 2/3 oz pneumatic injection machine...has a few molds that come with it, but I will begin testing it soon.

Need to make a few changes or mods to it:
pre-heated hopper to reduce cycle times
possibly adding an air powered mold clamp (including ejector pins), but I may hold off as I also have a machine half built right now. If i do then...
hooking it all up to run off mach 3 (since this is what i have for my mill) and use a breakout board to see if I can set up automated runs.