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Culvan
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PostPosted: Wed Feb 17, 2010 9:31 pm    Post subject: Reply with quote

LaughingCheese wrote:

Good gravy, why $280, can you cut aluminum too??? lol

Ijust want to be able to cut foam, like EPP, etc. I did want to cut aluminum but now I'm thinking about how I can save, and buying less powerful motors is one way.

Also, are those plans easily scalable?

For instance I was considering a 3' x 2' machine instead of the 4' x 4'.


As for Z height, do you think that's enough for cutting armor pieces, and RC aircraft airfoils?

Actually, I'm not sure how you'd cut an airfoil with that, I'd think you'd need it edge on or something.


Actually it probably could cut aluminum, but I don't know enough to make it do that. There are a bunch of considerations about how to get the chip load out of the machine so it doesn't get gummed up. I think they usually use a jet of lubricant to wash the chips away and keep the tooling cool.

The scale you are talking about is tricky. You will be increasing the weight that your steppers will have to handle. If you are looking at salvaging steppers out of printers then you will find that at some weight you cannot move your stuff. I'm not sure when that will happen. The second concern with long a long axis is that everything bends. keeping a 12 inch piece of MDF straight is pretty easy. Keeping a 12 foot piece straight is not. Taking an existing design and scaling it up may ignore significant mechanical design constraints. If you want my advice, start smaller. There are a lot of reasons, you can reuse all of the electronics you develop on the smaller system on a bigger system. You can re-use all the software on a bigger system. You will have a very good idea of the mechanics of how a system is supposed to work once you've done it once. I've noticed that a lot of people on CNCzone seem to take this approach. I opted to avoid CNCzone for the most part because I knew I would learn things that would make me want to spend more money. My goal was to do this inexpensively. I think you can do it. There are some good instructables for smaller scale machines, electronics and so forth. If you can get 3 dead printers then you can probably salvage 3 stepper motors that could certainly drive a "desktop machine." You might even find rods, belts, puleys and bearings in there that you could use too. I'm not the type to work off of salvage that way, but I believe it can work.

You asked about Z axis depth. I'd recommend you consider the length of the cutting surface of the tool you plan to use. I use rotozip bits mostly. They have a cutting length of about an inch and a half. It's really hard to cut more than 1.5 inches deep into something without having the collet hit the workpiece. I think my machine is supposed to have 4 inches of movement, but I'll never use all of it. If you look up 1/8" end mills you will notice that they rarely have cutting lengths of over 1 inch.

Mcmaster Carr has a lot of good terminology.
KBC tools has much better prices[/url]

There are a few ways to cut a 2-sided object like an airfoil. 1) cut the top, flip it over and cut the other side. It is tricky to get the alignment right, but if you figure that out then you can probably make something very nice. 2) If you look in Cazyfool's CNC thread you will notice he used a 4th axis module to flip the material for him. That solves many of the alignment problems. 3) You can cut two separate pieces and glue them together.

Andy
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LaughingCheese
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PostPosted: Thu Feb 18, 2010 12:28 am    Post subject: Reply with quote

[quote="Culvan"]
LaughingCheese wrote:

Good gravy, why $280, can you cut aluminum too???

Ijust want to be able to cut foam, like EPP, etc. I did want to cut aluminum but now I'm thinking about how I can save, and buying less powerful motors is one way.

Also, are those plans easily scalable?

For instance I was considering a 3' x 2' machine instead of the 4' x 4'.


As for Z height, do you think that's enough for cutting armor pieces, and RC aircraft airfoils?

Actually, I'm not sure how you'd cut an airfoil with that, I'd think you'd need it edge on or something.


Quote:

Actually it probably could cut aluminum, but I don't know enough to make it do that. There are a bunch of considerations about how to get the chip load out of the machine so it doesn't get gummed up. I think they usually use a jet of lubricant to wash the chips away and keep the tooling cool.


Cool!

Quote:

The scale you are talking about is tricky. You will be increasing the weight that your steppers will have to handle. If you are looking at salvaging steppers out of printers then you will find that at some weight you cannot move your stuff. I'm not sure when that will happen. The second concern with long a long axis is that everything bends. keeping a 12 inch piece of MDF straight is pretty easy. Keeping a 12 foot piece straight is not. Taking an existing design and scaling it up may ignore significant mechanical design constraints.



Thanks for the reality check!

I'm a total newb at this stuff, so that didn't even come to mind.

What about making it smaller? Like 2' x 2'?

Obviously that would reduce the load and make it not bend as much right?

Quote:
If you want my advice, start smaller. There are a lot of reasons, you can reuse all of the electronics you develop on the smaller system on a bigger system. You can re-use all the software on a bigger system. You will have a very good idea of the mechanics of how a system is supposed to work once you've done it once. I've noticed that a lot of people on CNCzone seem to take this approach. I opted to avoid CNCzone for the most part because I knew I would learn things that would make me want to spend more money. My goal was to do this inexpensively. I think you can do it. There are some good instructables for smaller scale machines, electronics and so forth. If you can get 3 dead printers then you can probably salvage 3 stepper motors that could certainly drive a "desktop machine." You might even find rods, belts, puleys and bearings in there that you could use too. I'm not the type to work off of salvage that way, but I believe it can work.


Thanks, I was debating whether or not to build the McWire machine, because it is 'desktop' size, or this other one, because 2' x 2' at least is the build size I would like for the X and Y axis, and I figured that would last me longer.

But like anything new its probably best to start out small.

Quote:

You asked about Z axis depth. I'd recommend you consider the length of the cutting surface of the tool you plan to use. I use rotozip bits mostly. They have a cutting length of about an inch and a half. It's really hard to cut more than 1.5 inches deep into something without having the collet hit the workpiece. I think my machine is supposed to have 4 inches of movement, but I'll never use all of it. If you look up 1/8" end mills you will notice that they rarely have cutting lengths of over 1 inch.



Interesting. So not only do I not need huge Z axis depth, I'll probably never get it?



Quote:

There are a few ways to cut a 2-sided object like an airfoil. 1) cut the top, flip it over and cut the other side. It is tricky to get the alignment right, but if you figure that out then you can probably make something very nice. 2) If you look in Cazyfool's CNC thread you will notice he used a 4th axis module to flip the material for him. That solves many of the alignment problems. 3) You can cut two separate pieces and glue them together.

Andy



Ah! I'd rather avoid gluing, sounds like it would be weaker.

The only other thing I could think of would be to make the software smart enough to recognize when its done on one side, to ask you to flip it over or something. Shocked Laughing



Thanks for the reply!


LC
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coffeehedake
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PostPosted: Sun Feb 28, 2010 6:46 pm    Post subject: Reply with quote

Stumbled across this today, got me very interested:
http://www.doughtydrive.com/index.html

Adds that 4th axis to an existing 3 axis machine. No idea on the prices. I'm tempted to rough one out myself using the 3 axis machine to build the parts. Being able to tilt the router 360 degrees in each direction would be invaluable for our purposes as a lot of the details for some models would be difficult to implement vertically.

I'm assuming that most breakout boards can accommodate the 4th axis, I'm fairly certain that Keling Inc C10 breakout board can, so adding it should be relatively easy.
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Culvan
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PostPosted: Mon Mar 01, 2010 10:18 am    Post subject: Reply with quote

Sorry, I didn't get back to you sooner here. I've been very busy recently.

LaughingCheese wrote:
What about making it smaller? Like 2' x 2'?

Obviously that would reduce the load and make it not bend as much right?


Correct, but I'd be thinking more on the scale of 5"x7"2" for a small scale machine. 2'x2' is still pretty large.

LaughingCheese wrote:

Quote:
If you want my advice, start smaller.


Thanks, I was debating whether or not to build the McWire machine, because it is 'desktop' size, or this other one, because 2' x 2' at least is the build size I would like for the X and Y axis, and I figured that would last me longer.

But like anything new its probably best to start out small.


That's an interesting design, I considered it too, but I thought it was too small and the instructions seem to leave a few gaps. I didn't see dimentions or what those stepper motos are. Also the comments people made seems to make me believe that there are a number of unanswered questions.

LaughingCheese wrote:

Quote:

There are a few ways to cut a 2-sided object like an airfoil.


Ah! I'd rather avoid gluing, sounds like it would be weaker.

The only other thing I could think of would be to make the software smart enough to recognize when its done on one side, to ask you to flip it over or something. Shocked Laughing

Thanks for the reply!

LC


If you use the right glues it is frequently stronger than the stuff it's holding together. However it's not uniform and usually adds weight and could change the center of gravity. All of which could be a concern.

The easy way to do this is to have two G-code programs with the same zero point. Have it run the first to cut one side and move the cutter to the zero point that is out of the way. Flip the piece while the cutter is off then run the second program. The trick will be to line everything up when you flip it. You will also probably need to leave some sort of sprue so the part stays in place while it's being cut. Then you'll have to manually remove it after the machine is done.

coffeehedake wrote:
Stumbled across this today, got me very interested:
http://www.doughtydrive.com/index.html

Adds that 4th axis to an existing 3 axis machine. No idea on the prices. I'm tempted to rough one out myself using the 3 axis machine to build the parts. Being able to tilt the router 360 degrees in each direction would be invaluable for our purposes as a lot of the details for some models would be difficult to implement vertically.

I'm assuming that most breakout boards can accommodate the 4th axis, I'm fairly certain that Keling Inc C10 breakout board can, so adding it should be relatively easy


I had a similar idea. I've been eyeing a rotary clamping table from harbor freight for a while. I wasn't planning on rotating the cutter with it though. It seems akward to me trying to keep everything aligned. I was going to mount it sideways to the table and put parts on it more like a lathe. Otherwise I'd probably need to increase the Z-axis travel. I guess it depends on what you plan to cut with it.

My electronics have the space for a 4th axis, but I didn't buy the components. I could probably upgrade without too much difficulty.

Andy
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coffeehedake
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PostPosted: Mon Mar 01, 2010 10:26 am    Post subject: Reply with quote

Culvan wrote:
I had a similar idea. I've been eyeing a rotary clamping table from harbor freight for a while. I wasn't planning on rotating the cutter with it though. It seems akward to me trying to keep everything aligned. I was going to mount it sideways to the table and put parts on it more like a lathe. Otherwise I'd probably need to increase the Z-axis travel. I guess it depends on what you plan to cut with it.


I've seen a couple machines set up with something like that... even using the motors from a satellite dish! I was considering that too, as for milling round / cylindrical parts (like prop gun barrels) this would be perfect, but I'm not sure how it would do with things that are oddly shaped (like a TK helmet).

I'm sort of divided about this right now... as I'm fairly certain that the price for the pre-made, double-axis, cutter mount is probably astronomical in comparison to the rest of the machine. I also think that for doing cylindrical parts, your solution is far superior, especially (as you mentioned) in planning the tool path.

Well, it's always good to have options!
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Culvan
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PostPosted: Mon Mar 01, 2010 10:58 am    Post subject: Reply with quote

I'd like to do some lightsaber hilts and it seems like the easiest way to make something like that for custom shapes. I've done quite a few hardware sabers.

coffeehedake wrote:
I'm not sure how it would do with things that are oddly shaped (like a TK helmet).


Perhaps this will help you visualize how a helmet might work: http://www.youtube.com/watch?v=ZP57SrWCJj4
I am directing you to the section between 1:35 - 2:05.

Andy
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coffeehedake
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PostPosted: Mon Mar 01, 2010 11:05 am    Post subject: Reply with quote

Well... I think you just sold me on it. That was awesome.

If you do implement the Rotary Table, let me know... I'm practically giddy with excitement.

Link of Note: http://www.cnczone.com/forums/showthread.php?t=39588&page=27 This guy built his own 4th axis out of MDF. I bet we can too.

Even better:

http://www.crankorgan.com/4thaxis.htm
http://modularcnc.flyingcart.com/index.php?p=products&req=dept&id=21 This one is listed as an indexer, looks like it's a vertical table rather than a horizontal, could be adapted.
http://www.cncinformation.com/cnc-forum/gorilla-cnc-wood-routers/added-4th-axis/view
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LaughingCheese
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PostPosted: Mon Mar 08, 2010 12:24 am    Post subject: Reply with quote

Culvan wrote:
Sorry, I didn't get back to you sooner here. I've been very busy recently.


No worries!

Quote:

Correct, but I'd be thinking more on the scale of 5"x7"2" for a small scale machine. 2'x2' is still pretty large.


Ok, so I guess I want medium! Laughing

Actually, I just want something that could fit on top of my desk like a printer; last time I checked the platform was like 18"x15" and maybe 5" Z height.


Quote:
If you want my advice, start smaller.


Indeed.

Quote:

That's an interesting design, I considered it too, but I thought it was too small and the instructions seem to leave a few gaps. I didn't see dimentions or what those stepper motos are. Also the comments people made seems to make me believe that there are a number of unanswered questions.


That's what I'm struggling with and its the main reason I haven't begun building yet.

One I want to know the cost of each one precisely.

I can't afford the other one if it costs $600, which is why I like the McWire design, but as you said, it has unanswered questions. XD

The main thing holding me back from building is a cost estimate and deciding which motors I need.

I suppose Nema 17 would be more than adequate for mere foam? Laughing

Oh yeah, the other thing is the electronics. That's usually where the meat of the cost lies, and so I want to see if I can keep that as small as possible, like $100 max for electronics, by using breadboards and/or Arduino controllers.



Quote:

There are a few ways to cut a 2-sided object like an airfoil.


Cool, I'll look into them.

Quote:

The easy way to do this is to have two G-code programs with the same zero point. Have it run the first to cut one side and move the cutter to the zero point that is out of the way. Flip the piece while the cutter is off then run the second program. The trick will be to line everything up when you flip it. You will also probably need to leave some sort of sprue so the part stays in place while it's being cut. Then you'll have to manually remove it after the machine is done.


Interesting.

So many terms, makes it difficult at best for a guy like me with zero machining experience to get into this.


I'm considering other alternatives now; like Pepakura for tracing and then cut out a mold to be vacuum formed or something.


Oy.
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coffeehedake
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PostPosted: Tue Mar 09, 2010 2:56 pm    Post subject: Reply with quote

LaughingCheese wrote:
So many terms, makes it difficult at best for a guy like me with zero machining experience to get into this.


I'm glad I'm not the only one! I've been keeping wikipedia and Mac OS's dictionary handy when working on this stuff... not everyone uses the same terms for everything, and some terms are also interchangeable... argh! I find myself learning new terms almost daily... which isn't necessarily a bad thing. (Bouncing around on different forums, how-to sites, manufacturer's sites, material distributor's sites, omg.... it's crazy the amount of information...)

LaughingCheese wrote:
I'm considering other alternatives now; like Pepakura for tracing and then cut out a mold to be vacuum formed or something.


After seeing some of the stuff the 405th has come up with, and therpf.com using Pepakura, I'm not counting that out either. I'd still like to have the CNC machine, regardless, as the skill some of these guys have with paper is unbelievable... and I can't see myself being as good.

By the way, if you get a chance, check out TMP's Iron Man progress threads (he has an additional one at thedentedhelmet.com) his stuff is absolutely amazing.
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Talon
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PostPosted: Wed Jun 09, 2010 3:37 pm    Post subject: CNC Reply with quote

I have a sidewinder cnc, if ya want to drive to TN you can have it i upgraded toa 10 ooo dollar cobra.
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PostPosted: Thu Jun 10, 2010 7:22 am    Post subject: Re: CNC Reply with quote

Talon wrote:
I have a sidewinder cnc, if ya want to drive to TN you can have it i upgraded toa 10 ooo dollar cobra.

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danipe70
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PostPosted: Wed Feb 09, 2011 5:34 am    Post subject: Reply with quote

I did the next stage. After two layers of epoxi resin with aluminum dust. I was so impatient than quickly made my firsts vacuum pulls, this is the result. The helmet is made of three parts.

Some conclusions:
- In some parts of the mold the foam probably reduce because the heat and the pressure brake the layer of resin, look the nose.
- It is necesary to rework and sand very much the mold because is hard to separate the plastic from the mold, the dome (upper part) is imposible and have to break it.

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