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Old Oct 15, 2012, 11:41 AM
skatun is offline
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CNC Mould


Hi
I am building a large scale glider, wingspan 10m. I am currently putting up up a cnc mill with 6m length and 1.5m width.

The problem is how can i make realtively cheap good mould for the fuselage and wings.

So here is 2 options i have considered:

1 Mill it out of styrofoam with 3mm to deep cuts, then add 2*160g glasfiber, then gelcoat, and then remill to accurate depth and then polish

2 Mill it out of POM directly to correct depth and then polish it

3: Other options

Regards Kim
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Old Oct 15, 2012, 09:49 PM
samc99us is offline
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Corian/LG Himac etc.
Old Oct 15, 2012, 10:13 PM
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How many parts are you expecting to produce from the molds?
Old Oct 18, 2012, 07:12 AM
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I'm just getting into RC mold making.
How would 6061 aluminum go?
Main problem would be warping whilst machining.
Price is quite reasonable.

Just checked out the Corian, very interesting have never heard of it.
Old Oct 18, 2012, 07:31 AM
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Hi
We want to make at least 10models.
Can you just polish corian and then laminate in it?
Kim
Old Oct 28, 2012, 02:07 PM
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6061 would make some amazing moulds I would think! And they can produce a lot of parts. I do know they are easily scratched and tough to repair.
Old Oct 28, 2012, 03:03 PM
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Quote:
Originally Posted by LOONY BOY View Post
I'm just getting into RC mold making.
How would 6061 aluminum go?
Main problem would be warping whilst machining.
Price is quite reasonable.

Just checked out the Corian, very interesting have never heard of it.
For aluminum, cast tooling plate is really nice.
Old Oct 31, 2012, 12:38 PM
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Corian


Corian is my choice but take good care of them as they are brittle and do brake.
It can be machined fast and is very easy to polish, especially if you do small step over.
Take a look at a finished cnc'd part, a sanded part and a polished part in the pics.
One thing to note is to build yourself clamps to evenly distribute the load.
Square tubing is perfect.

Regards
Orrin
Old Nov 01, 2012, 07:42 PM
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Say I wanted to build a cnc mould, and wanted to get someone to turn my sketches into a cad design, then pay a machinist to make my moulds from corian- where is most of the cost, the cad design or the machining? Id love to do this one day.
Old Nov 02, 2012, 06:16 AM
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Josh,
That's a hard question to answer. It all depends on the detail of the CAD work. The average CAD design is $40.us per hour. A simple design can be 1-2 hours. As far as mold making I charge $1.00us per minute run time. Again depending on the size of the mold you can get hundreds of dollars into a mold fast.
Hope this helps
Steve in Maine.
Old Nov 03, 2012, 03:53 PM
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Quote:
Originally Posted by orrinade View Post
Corian is my choice but take good care of them as they are brittle and do brake.
It can be machined fast and is very easy to polish, especially if you do small step over.
Take a look at a finished cnc'd part, a sanded part and a polished part in the pics.
One thing to note is to build yourself clamps to evenly distribute the load.
Square tubing is perfect.

Regards
Orrin
Could you tell me more about the preparation of the corian molds. How are you sanding and polishing them after finish machining?

I'm very interested I have a CNC and some corian.

Bill
Old Nov 05, 2012, 04:21 AM
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Bill here is the first part,
I'll add the next step for the sanding and polishing.

Part 1 - Preparation of corian before machining.
Hi,
First step is to check that the corian is the correct thickness and and has extra material for structural support.
It would be a good idea to mount it to a non-warping surface to give rigidity.
I would then place the piece that is slightly oversize onto the sacrificial board.

I have a sacrificial board at the bottom fastened to the surface bedof the cnc table.

I will sometimes mill two sides that are perfectly aligned to the zero of the cnc program.
This allows me to consistently machine the same place if I have need to.
You can make holes to take metal dowel pins that are used to align to your surface and them pull them out when the corian is mounted.

This gives me very little to no-error if I have to re-machine an area.
I would have programmed 6 holes that are used to hold the work peace down.
I drill 3mm holes for the screws that I use and then a countersunk hole approximately 7mm in diameter so that the screws are well under the maximum depth of the machine cut to be used.
After all this has been done I will fasten the corian work peace down.
I will then set my z-zero using a piece of paper under the front of the bit just touching the paper.
In other words it must hold the paper but not be all the way through. This will give you a very small space which can be measured with a vernier caliper, or you could start the spindle and move it very slow until you notice cutting.
Zero the z-axis.
Take the z-zero up to 10mm and re-zero, now do a dry run to ensure the tool path is doing what you intended.
If you are happy take down by 10mm and re-zero, now you should be able to run the program and not have any surprises.
This is the only setup that I use and is not necessary everyone’s choice.

Part 2 to come.
Old Nov 05, 2012, 06:28 PM
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Josh,

I tell people to estimate a thousand dollars plus materials and you'll probably be safe. You can probably get it done cheaper, and some will charge more.

Usable molds aren't always easy to make the first try though. I'm on my fourth or fifth set now and they get better every time... that's with me doing CAD, me doing CAM, and me doing machining through part manufacture. If you're having others do pieces and parts of the work, expect that some things will have to be reworked along the way.
Old Nov 05, 2012, 08:19 PM
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Thanks for the detail on the setup. I am familiar with the process you described but others may not be. What I was wondering about was the steps you went through after you had done your finish toolpath.

Please feel free to continue with part 2 as planned. I find I learn something from everyone. For instance your sacrificial board idea.

Bill
Old Nov 12, 2012, 10:00 AM
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Nice description of the process! - also looking forward to part 2
Just about to embark on some corian routing for some glider moulds - never worked with corian before.. How are you finding tool life? - is HSS enough or would you recommend carbide?
Haven't run across feed/speed info yet - if you have any recommendations, that would be great!...
Also, any pointers on toolpath generation with the amount of overlap/pass/finishing cutter size to get a nice result for sanding/polishing ?

Thanks in advance!


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