My new toy and project

Re: My new toy and project

Postby Rob M » Sat Jun 28, 2014 2:38 pm

I've been lookng into low pressure injection molding. It is basically done with a glue gun. Not sure how big of parts you can do and if the material is paintable.

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Re: My new toy and project

Postby Marquette » Sat Jun 28, 2014 5:55 pm

Rob M wrote:I've been lookng into low pressure injection molding. It is basically done with a glue gun. Not sure how big of parts you can do and if the material is paintable.


Paintability depends on what plastic you use. You can use any plastic you want.
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Re: My new toy and project

Postby Rob M » Sat Jun 28, 2014 9:47 pm

Marquette wrote:You can use any plastic you want.


Not for the low pressure injection molding. It uses a lower melting point plastic then say ABS. This process is design for encapsulating electronics so the plastic has to melt at a lower temp to keep from melting solder. The plastic is called a polymid and when I Google that it gives results for nylon.

I just need to buy some and try it. I can't find it now (away from home and on a laptop) but I found a starter set (glue gun and 5 sticks) for around $120.
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Re: My new toy and project

Postby Marquette » Mon Jun 30, 2014 8:16 am

I'm curious about what that setup is like then... because one can build a low pressure machine with regulatable temperature, and one can use it for any plastic...
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Re: My new toy and project

Postby areibel » Mon Jun 30, 2014 8:38 am

Actually it's interesting, I hadn't heard of the glue gun method but wayyyy back in ancient times I had one of these-
http://www.samstoybox.com/toys/HotWheelsFactory.html

It used some sort of low melt plastic and some die cast molds to create Hot Wheels cars. There's a newer 2013 version but they say the material is some sort of wax now instead of plastic. I'll have to go digging out at my Dad's and see, it's probably still in s box out there somewhere. I can remember I ran out of the wheel/ axle sets and couldn't find any more at the time, but it was a favorite of mine back about 45 years ago!
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Re: My new toy and project

Postby ConnRiver » Tue Jul 01, 2014 8:29 am

Bernd wrote:Brian, still learning MeshCam. Their instructions and tutorials left a bit desired. Would love to get some 3D software but that turns into another hobby. . . . My idea of using the CNC machine is to make individual parts and put together a master from them. Casting is much faster than trying to do a production run on CNC.

Have you looked into the table top injection molding machines yet? . . . One of the two links I'm including show that a mold can be made out of a resin epoxy. This would be great for small short runs. Bernd


Bernd, so MeshCam isn't a full-fledged 3D program?

Visited the Rhino 3D site, I see I can upgrade to 5.0 (my version is a decade old) for $495, but the CAM programs aren't cheap.

I'm with you, CNC cut individual parts and assemble. I machined the short hood roof for the GP7-9 project by offsetting the toolpaths in .001" increments and the results were terrific. With my fingertip I could not feel ridges on the 5-3/8" roof-to-side contour and neither could I see ridges. I little light "polishing" anyway and it would be ready to reproduce.

Thank you for mentioning resin epoxy moldmaking. I will explore it. I want to compare it with Devcon, a metal epoxy (if that's the correct description) that is used to make mold tooling.

I'm going to get into injection molding one way or another (used machinery, or "simple" custom-built machinery). I've got the bug. For some weeks now I've been reading a great deal about injection molding processes, machine components, and processing control. I haven't paused to run the numbers, but I would guess I'll need a universal-type machine with a clamping force in the 30 ton-50 ton range, which, I understand, is on the small size as machines go.

-Brian

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Re: My new toy and project

Postby Rob M » Tue Jul 01, 2014 3:43 pm

Bernd wrote:
ConnRiver wrote:Bernd, so MeshCam isn't a full-fledged 3D program?


No it's not. They call it a 2 1/2D, what ever that is. I'm getting better at using it. Learned a few more things about it here last week. The program is called MillWizard. It lets you use individual programs such as milling a circle, a slot, an arc and so forth and then combine them in anyway you want. You can make a very complicated cutting program. And like I think I've mentioned, I can hand code pretty good, so I can make the parts I want.


MeshCam does have support for a 4th axis so it can get close to 3d, closer than you get with 3 axis's.

2 1/2D means being able to cut along the X & Y axis at different heights. Great for cutting rectangles and circles but can't to side profiles or spheres.

I am currently working on making a manually indexed 4th axis to be able to do more complicated parts. I should be able to rotate a 3d model in Sketchup around a set axis and then output it to an STL file for 3d profiling in CamBam. More on that on it progresses.
Last edited by Rob M on Tue Jul 01, 2014 3:49 pm, edited 1 time in total.
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Re: My new toy and project

Postby Rob M » Tue Jul 01, 2014 3:48 pm

Here is a link to the polyamide glue gun sticks I mentioned earlier. Toward the bottom is the offer for the gun & sticks for $113. http://www.gluegun.com/collections/electrical-and-potting-glue-sticks/products/power-tec-bond-7718-polyamide-glue-sticks
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Re: My new toy and project

Postby ConnRiver » Wed Jul 02, 2014 8:03 am

My CNC software path is AutoCAD > Vector CAD/CAM > FlashCut. I draw 2D in AutoCAD (and, for complex objects, proof the drawings by re-creating them 3D in Inventor to check for fit), import drawings into Vector to create tooling paths and generate G-code, and import that into FlashCut to run the CNC machines. I have a rotary table that, if I add a stepper motor, can be used as part of tool path creation, too. So, I guess I'm good for four axis milling, then?

I'm in such a groove with what I'm doing that I can't see the forest for the trees. My nomenclature knowledge sucks (can I say that here? ;-) Maybe I can do more with my machines than what I'm doing. That's a problem with being self-taught, maybe, not having a solid overview of the capabilities / possibilities sitting in front of you.

Vector CAD/CAM has a 3D module available for purchase, but I have big problems with the American vendor of that program. . . .

Life is a process, which includes human activities like machining, I guess. . . . (sigh) Live and learn.

-Brian

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Re: My new toy and project

Postby Rob M » Wed Jul 02, 2014 12:14 pm

ConnRiver wrote:.... So, I guess I'm good for four axis milling, then?


Sounds like it. Do you have a 4th output on your controller board? Mine does but I don't have a breakout board for it.
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