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View Full Version : DIY Injection moulding by JR Hartley.



HankMcSpank
02-09-2010, 02:15 PM
Ok, so I started aquiring 'machinery for the home' about 18 months ago....

DIY CNC machine - check
Mini-lathe- check
PCB fabrication - check
Injection moulding - dammit, I've gots to gets me one of those.

Joking aside, I've now a burning ambition/need/want/blah blah to be able to make my own custom guitar pickup bobbins.

"Why Hank, why - injection moulding is for grown ups?"

Well, because nobody makes them in the size I need ...I presently make them out of acrylic on my CNC *but* even just making one bobbin, I end up with a beard like the guitarist in ZZ Top, so while my last beard was growing my mind began to percolate (never a good thing).

So what are my options...

1. Ask someone to make them for me .....pros - less hassle. cons - massive spondoolies. (for the mould)

2. Ponder how I can make them at home. So my immediate thought was,of "does such a beast exist", well this is 2010 so yes it does....

http://cgi.ebay.co.uk/Bench-Table-Top-Injection-Moulding-Machine-Repro-Minor-/230448510847?pt=LH_DefaultDomain_3&hash=item35a7cd377f .

but OUCH!

I think I've seen manual ones elsewhere (which clamp to the bench & where the operator is the 'compression element' lol!) ...smaller cost, but still at least one British Kidney in payment.


So I thought I'd throw this one out to the mycncuk 'massive'....what would you recommend?

My requirements are... a plastic bobbin which looks something like this...

http://ww.tinyurl.com/38jq75z (http://ww.tinyurl.com/38jq75z) (but to my own size - about 5mm long x 5mm high)


Any clever ideas about how I could make them in quantity....or how I could get them made in quantity without having to force my wife to work down Commercial road?

ecat
02-09-2010, 02:37 PM
No idea about the bobins but here is a DIY Injection Moulding machine :)

http://www.users.uswest.net/~kmaxon/page/side/mold_mach_137.htm

HankMcSpank
02-09-2010, 03:12 PM
No idea about the bobins but here is a DIY Injection Moulding machine :)

http://www.users.uswest.net/~kmaxon/page/side/mold_mach_137.htm

Intersting link ....but *way* above my skills (or needs).

this manual lever style is perhaps more of my accessibility level...

http://replicatorinc.com/blog/2010/02/desktop-injection-molding/

or if someone wants to go the "scrapyard challenge" route...

http://www.youtube.com/watch?v=v8oRzCvGFbw

it does make me wonder if I a standalone 1 axis (Z plane) CNC machine could be designed to do the compression aspect?

Robin Hewitt
02-09-2010, 03:17 PM
Now there's a subject close to my heart :rofl:

Here's a useful link...

http://www.dms-diemould.co.uk/

I started making an injection moulder because I didn't have room for the real thing in the garage. Then I suddenly got space and bought an old 25 ton Arburg, haven't plumbed it in to the 3 phase yet.

The point being, I have most of a home brew, fully automatic injection moulder about 6 feet behind me. All hydraulic, opens closes, ejects, injects from a hot pot a la Travin, measures plastic in, heaters all wired up with a digital thermostat, plugs in to a paralell port for all the critical timings etc.

I don't really want to sell it, but I can be arsed to finish it. If you are interested I am sure we can come to some arrangement :naughty:

NB70
02-09-2010, 04:08 PM
Anyone tried DIY iinjection moulding with a glue gun ? I think you can get nylon and polyethylene glue gun rods:

http://www.mutr.co.uk/index.php?cPath=56_19_57

Jonathan
02-09-2010, 07:58 PM
Aww I'd just finished typing a really long post then the webbrowser crashed :(.
Anyway....take 2

I've seen/used a 'manual' injection moulder at school. It requires a LOT of force to pull the lever to inject the plastic. As in hanging off the lever with my feet off the ground isn't enough (granted I was only about 15 at the time but you get the idea) .... so I'm not sure a Z-axis would be up to it. Then again you do get a huge mechanical advantage with a screw, but is it going to be fast enough? The machine you had a pot which you put the plastic pellets in, waited for it to melt... then squash so quite simple really. I could try and get a picture of it if you like?

I think your main issue might be making the mould. There are only two moulds for the one at school - both made by the teacher. He told me they were difficult and took a long time to make, especially since he used the surface grinder on the mating faces of the two parts. I guess it could be easier to CNC mill the mould, but still something to consider.

I don't mean to put you off, just thinking aloud that's all!

R.E. Bobbin making.
Couldn't you just cut them out of a sheet and use a T-slot cutter to do the undercutting? That way you could machine the lot in one go.....and tessellate lots onto a sheet of plastic.

Tom
02-09-2010, 08:07 PM
Another little teaser here... :)

http://www.cambam.co.uk/forum/index.php?topic=355.0

John S
02-09-2010, 10:07 PM
Which Commercial road ?

.

i2i
02-09-2010, 11:35 PM
funny you should mention a desktop stand alone plastic injection machine, i have the very same thing.:tongue:

HankMcSpank
02-09-2010, 11:35 PM
Now there's a subject close to my heart :rofl:
Here's a useful link...
http://www.dms-diemould.co.uk/
I started making an injection moulder because I didn't have room for the real thing in the garage. Then I suddenly got space and bought an old 25 ton Arburg, haven't plumbed it in to the 3 phase yet.
The point being, I have most of a home brew, fully automatic injection moulder about 6 feet behind me. All hydraulic, opens closes, ejects, injects from a hot pot a la Travin, measures plastic in, heaters all wired up with a digital thermostat, plugs in to a paralell port for all the critical timings etc.
I don't really want to sell it, but I can be arsed to finish it. If you are interested I am sure we can come to some arrangement :naughty:
Thanks for the mould mft link - Have you had a quote from them for a mould?
Your injection mould - being 3 phase would be a problem (I'm low-fi here!)...I'm also envisagening an unfeasibly large contraption!?



I think your main issue might be making the mould. There are only two moulds for the one at school - both made by the teacher. He told me they were difficult and took a long time to make, especially since he used the surface grinder on the mating faces of the two parts. I guess it could be easier to CNC mill the mould, but still something to consider.


I guess most people aspire to a nicely finished mould (so no machine marks are visible on the end result) - but since these puppies will not be visible, I could probably accept a rough & ready one! I'm hearing that Aluminium loaded expoxy might be the route for the mould for my modest requirements.



R.E. Bobbin making.
Couldn't you just cut them out of a sheet and use a T-slot cutter to do the undercutting? That way you could machine the lot in one go.....and tessellate lots onto a sheet of plastic

That's a reasonable idea...I might ponder. It'd certainly make the beard a little bit shorter (more Rolf Harris than ZZ Top), but I'd still prefer unshaven (I'm talking beards here - right?). Also, a quick skeg on the net shows they might be a bit hard to find? (ok, so Argios probably isn't the best! -joke ok!). BTW that second link - he rocks, talk about understated....legend!


Which Commercial road ?.
C'mon, You know the one (psst: you never heard of tipping?)



PS Not related to injection moulding at all, *but* hot off the press tonight - another 'machine for the home', after much trashing of plastic & flaying of switches & sensors - a 'direct to copper clad board' inkjet printer :-)
http://img836.imageshack.us/img836/5917/successe.jpg (http://img836.imageshack.us/i/successe.jpg/)


Edit: Just seen your post...


funny you should mention a desktop stand alone plastic injection machine, i have the very same thing.:tongue:


We need more details than that - a photo to prove it along with a scan of your driving license etc. Seriously...I need more details - I think I now need the opposite to viagra (flacidagra?)

Robin Hewitt
03-09-2010, 12:10 AM
Thanks for the mould mft link - Have you had a quote from them for a mould? Your injection mould - being 3 phase would be a problem (I'm low-fi here!)...I'm also envisagening an unfeasibly large contraption!?

That's not a mould manufacturer, they sell the bits to make moulds.

See also http://www.pmseurope.com/

The Americans make moulds from what they call 7075 T6 alloy

But Alumec 89 is available in the UK in cut plate and is wear resistant to a greater depth.

I have a book telling how to make a really crummy lever operated press you could knock up in a couple of days. I can find it if you're interested.

HankMcSpank
03-09-2010, 12:34 AM
That's proper hard core there Robin - I'm only after making a bobbin 50mm long! (the words crack, hammer & nut a bouncing around my head). A lovely looking machine though (every garage should have one)...but alas, everything I buy has to go into my workshop in the loft (this is London & not many have workshops!) - so anything/everything I buy has to go through a loft hatch!

Re the book ...thanks for the offer, but I'd probably buy something rather than make something - I don't trust myself to build a proper injection moulding machine - anthing over what my car foot pump produces (pressure wise) & I start trembling & having palputations.

Robin Hewitt
03-09-2010, 12:34 AM
I guess most people aspire to a nicely finished mould (so no machine marks are visible on the end result) - but since these puppies will not be visible, I could probably accept a rough & ready one! I'm hearing that Aluminium loaded expoxy might be the route for the mould for my modest requirements.

I think loaded epoxy may give you a couple of shots before flashing becomes a problem.

After machining the mould you get out your die grinding pencil and polish up the visible bits.

I do have a 4.25" diameter bar of 7075 T6, I could probably flog you a couple of slices off it if you have the means to cut it :naughty:

Robin Hewitt
03-09-2010, 12:45 AM
I will admit it is a bit agricultural :whistling:

spluppit
03-09-2010, 02:18 AM
I'm a bit curious why making these items seem to take you a long time to machine if you have a small cnc. Do you think it could be your approach to the way you are machining them? There are many methods that can be used to drastically reduce machining time, it is only plastic after all. If you want to give me a run down of the exact process you are using, may be I can help you reduce your machining time down to tolerable levels or even better than tolerable.



I think even on a home made basis injection moulding will be prohibitive cost wise unless you need to produce these in the tens of thousands. Of course where there is a will there is way, the time spent making the set up and the cost maybe better spent perfecting the machining process.




Kind regards,


Scott

HankMcSpank
03-09-2010, 11:34 AM
The main 'speed impediment' wrt my cnc 'output rate' is my spindle- basically I chose low noise levels over 'grunt', becuase I live in a terraced house, with no workshop - so I don't want to receive a neighbour induced an ASBO, but do want to be able to use the machine late (it's this one - http://www.google.co.uk/imgres?imgurl=http://www.rejon.co.uk/Products/Proxxon/bfw40e.jpg&imgrefurl=http://www.rejon.co.uk/proxxon_bfw40e.html&usg=__mrnvC_FbTfKrA2igCU4m1cphgH4=&h=396&w=400&sz=88&hl=en&start=1&zoom=1&um=1&itbs=1&tbnid=1pe_JP7d0WNHDM:&tbnh=123&tbnw=124&prev=/images%3Fq%3Dbfw%2B40/e%26um%3D1%26hl%3Den%26sa%3DN%26rlz%3D1T4GGIH_en-GBGB278GB278%26tbs%3Disch:1 - just the router part) it is *very* quiet, but being relatively low powered 250W & a max RPM of 6,00, the max I can push it at - even with feeble acrylic - is about a 3mm depth cut at about 80mm per minute (yes you read that right!)....else the tool wanders off course (I guess it can't get rid of the swarf at any higher rate & takes a path of its own)

So the average bobbin is about 120mm circumference - but being 2.5D it needs several passes ...and holes - plus I make two halves do everything need to be doubled (so tool changing involved...touching off etc)

Roughly the procedure is this (& you need to bear in mind, I'm wet behind the ears & proud!)...

1. cut a piece of acrylic stock to size (I have a mini table saw)
2. Scribe the centre point.
3. Double sided sticky tape to affix the acrlyic onto some spoiler/waste material beneath.
4. Clamp it.
5. Put 4mm drill into tool holder - align tool over acrylic centre, touch off etc.

About 8 mins has elapsed & I haven't started the CNC machine up yet!!

6. CNC machine drills twelve holes (I make two halves of a bobbin & join them in the middle, therefore twice the number of holes/cuts per bobbin!)
7. Tool swap - 3mm flat endmill into position, touch off.
8. Cut bobbin shape around holes to a depth of 2mm (i use 3mm thick material) - this leaves 1mm at the bottom (ie the edge of the bobbin)
9. Now move the cutter outwards a bit & cut the outer perimeter for the whole 3mm depth (ie completely cut the shape out from the acylic stock)

I now have two bobbin halves.

10. clean the parts up (wire wool the rough edges etc)
11. Glue the two halves of the bobbin together.

On a good day with the wind behind me (& no screw ups - which happens a fair bit!) - I can do in about 30 minutes from start to end. A high proportion of that 30 minutes is the tool moving oh so slowly on those numerous 2.5D cuts around the part perimeters!, at the minute this isn't a huge problem (as I don't make that many), but I'd like to be in a position where I could make 20-30 bobbins in 15 minutes or so.

therefore with a moulder...

1. Turn heater on
2. Load plastic granules.
3. Compress
4. Spit part out

About 30 seconds per bobbin?!! It's a compelling argument!

Robin Hewitt
03-09-2010, 12:12 PM
I got the idea when I was hanging around Travin's shop, they were making some moulds for me

They do two small machines, both close the mould with a glorified G clamp, no ejectors. One air driven, the other using a lever.

They used to do the Travin Eagle which was a fully automatic, air driven, hot pot moulder but they seem to have discontinued it. They usually had one running and it seemed to work well.

http://www.travin.co.uk

i2i
03-09-2010, 12:24 PM
Thanks for the mould mft link - Have you had a quote from them for a mould?
Your injection mould - being 3 phase would be a problem (I'm low-fi here!)...I'm also envisagening an unfeasibly large contraption!?



I guess most people aspire to a nicely finished mould (so no machine marks are visible on the end result) - but since these puppies will not be visible, I could probably accept a rough & ready one! I'm hearing that Aluminium loaded expoxy might be the route for the mould for my modest requirements.



That's a reasonable idea...I might ponder. It'd certainly make the beard a little bit shorter (more Rolf Harris than ZZ Top), but I'd still prefer unshaven (I'm talking beards here - right?). Also, a quick skeg on the net shows they might be a bit hard to find? (ok, so Argios probably isn't the best! -joke ok!). BTW that second link - he rocks, talk about understated....legend!


C'mon, You know the one (psst: you never heard of tipping?)



PS Not related to injection moulding at all, *but* hot off the press tonight - another 'machine for the home', after much trashing of plastic & flaying of switches & sensors - a 'direct to copper clad board' inkjet printer :-)
http://img836.imageshack.us/img836/5917/successe.jpg (http://img836.imageshack.us/i/successe.jpg/)


Edit: Just seen your post...




We need more details than that - a photo to prove it along with a scan of your driving license etc. Seriously...I need more details - I think I now need the opposite to viagra (flacidagra?)it's made by the small power machine tool co, and is an sp1.

HankMcSpank
03-09-2010, 01:07 PM
Thanks (I've heard of it...but they're a bit rare!)

an interesting lo-fi solution to making repeatable, low resolution, small plastic parts...

http://www.instructables.com/id/How-to-make-artificial-fishing-bait-for-little-to-/

It has all the elements, ie melted plastic squeezed into a mould under pressure!

i2i
03-09-2010, 01:12 PM
this one has a hopper with plastic granules that are heated and pressed into the mould.

Robin Hewitt
03-09-2010, 04:10 PM
Hmmm. Have you considered simply pouring Polymorph in to a silicon rubber mould?

Suppose it rather depends on the operating temperature.

Could use potting compound if you vacuum degassed it.

i2i
03-09-2010, 07:19 PM
here you go, something for the attic

http://cgi.ebay.co.uk/DASSETT-CNC-vertical-plastic-injection-moulding-machine-/280544377692?pt=LH_DefaultDomain_3&hash=item4151bf7b5c

Jonathan
03-09-2010, 08:29 PM
That's a reasonable idea...I might ponder. It'd certainly make the beard a little bit shorter (more Rolf Harris than ZZ Top), but I'd still prefer unshaven (I'm talking beards here - right?). Also, a quick skeg on the net shows they might be a bit hard to find? (ok, so Argios probably isn't the best! -joke ok!). BTW that second link - he rocks, talk about understated....legend!

I've got 5 of them and I've never used them...so if you want one they're going cheap :P

deisel
03-01-2013, 06:57 PM
That's not a mould manufacturer, they sell the bits to make moulds.

See also Home Page (http://www.pmseurope.com/)

The Americans make moulds from what they call 7075 T6 alloy

But Alumec 89 is available in the UK in cut plate and is wear resistant to a greater depth.

I have a book telling how to make a really crummy lever operated press you could knock up in a couple of days. I can find it if you're interested.
Some work gone into that robin,:thumsup:did you ever finish it? or did you move it on?ive been slowly gathering the parts to knock one up.

Robin Hewitt
03-01-2013, 11:16 PM
Some work gone into that robin,:thumsup:did you ever finish it? or did you move it on?ive been slowly gathering the parts to knock one up.

Finish what? The home brew? Just gathering dust. You could have that really cheap but you'd have to collect it and I'd want to keep the pump :beer:

HankMcSpank
04-01-2013, 12:40 AM
13,300 views for this old thread of mine - whacky (though the stats spike the interest of the lazy entrepreneur in me & illustrate there's a phenomenal amount of interest in desktop injection moulding machines)

deisel
04-01-2013, 12:41 AM
ive sent you a message robin,i hope it got through:nightmare: