Benchtop Injection Molders - do they work?

[GammaWill]

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]

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]

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]

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]

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]

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]

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]

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-su...88094QQfrsrcZ1

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

[Mite E Copter]

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). 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!

-Ken

[Pres]

.... 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]

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 . 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 ).

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]

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