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Skipsoaring
04-06-2015, 03:50 PM
Hi there!
I will be building a 4 axis CNC hotwire maching for cutting cores for Radio Controlled gliders.
I am just starting the serious research (when I am not being seconded into the real world) and so far I'm thinking that due to my current space constraints I will make it so that it holds the foam vertically against the garage wall.
The machine size is still up in the air and will depend on the size of the blocks I can source. The largest wing panel I can see myself making is 1500mm, although being CNC made (accurately compared to wire dragged over templates/fences) I could make the panels in 2 parts as the majority of the wing panels would be 750mm.

I have a LOT to learn as I am trying to teach myself CAD (Onshape and Sketchup), am yet to learn anything about CAM and have always been petrified by Electrickery!!

I have chosen to build a CNC hotwire as it should be relatively simple and I want to build a CNC router next, having learned some lessons along the way.

The basic idea of the CNC Hotwire machine is to enable me to cut eliptical wing panels which requires independent movement of each end of the wire along the x axis and z axis (hopefully got them right from a gantry machine perspective)

The x axis travel shouldn't need to be more than 500mm and the z axis travel should be similar. I do need to figure out if I would need more though. If, for example, I was to cut a 750mm panel with an elliptical shape and the posts were 1500mm apart, the x axis travel would need to be much greater than if the posts were 800mm apart. Perhaps I need to look at designing my machine to have relocatable rails for the x axis?

I understand that from a construction point of view, my two machines will be worlds apart, the lessons I'm hoping to take to the next build will hopefully be software, electrical and generic.
Anyway, gotta go do the school run.

Cheers
Clayt

Skipsoaring
04-06-2015, 06:00 PM
Just re read above and it read like i was planning to have the foam on the wall. I meant the machine BASE against (or leaning onto) the wall.

Skipsoaring
11-06-2015, 11:28 PM
After some computer issues, I can get going on the learning side of things again.
I found Autodesk Fusion 360 (thanks again to the info here) which integrates CAD and CAM so have started using it. I'm brand new to Macs so am still learning the in's and out's of screen shots etc.
I won't be having the foam cutter anything other than flat as it wouldn't be possible to keep the foam block and the cut part in the correct position at the end of the cuts and would cause damage to the parts. With the block flat, I can use double-sided tape and gravity.

Better keep drawing, hopefully have some info and pics for you soon.
Clayt

Boyan Silyavski
12-06-2015, 06:39 PM
Show us what exactly will be the final part. If its a 3d shape you will need a router, not wire cutter.

njhussey
12-06-2015, 09:13 PM
Show us what exactly will be the final part. If its a 3d shape you will need a router, not wire cutter.
Boyan, if it's for cutting RC plane foam wing cores then a hot wire cutter (4 axis) is the thing to go for. I'll be making one at some stage (10 years time at my current build rate! !!) For exactly the same use.

Skipsoaring
13-06-2015, 12:08 AM
Show us what exactly will be the final part. If its a 3d shape you will need a router, not wire cutter.

Normally cutting wing cores from foam requires passing a hot wire over 2 fences shaped with the aerofoil at either end of the foam block. CNC will provide the same service and remove timing errors and snags (getting stuck) giving a much more accurate wing core.

mitchejc
15-06-2015, 10:40 PM
Sorry can't help you with any info on the 4 axis hot wire but Silyavski may have a point depending on what you want to do. If you need to cut a lot of wing profiles rapidly the hot wire is obviously the way to go but if time is on your side then simple 3 axis milling is not such a bad idea as it gives you a lot of options that hot wire can't do. A relatively flimsy but fast 3 axis router dedicated to foam cutting should be easy to build.

Had to dig around to find the model but several years back I did cut a few gliders for a friend on my router. He asked me to cut two wing profiles and I suggested we cut the whole aircraft in one go. The entire model including the fuselage was cut from one big piece of foam with a two sided strategy excluding the wing tips which were glued on afterwards. The screenshots below shows the model I drew using his wing profile. I know sh%t about aerodynamics so I just went with a sort of a teardrop shaped thing for the fuselage so he's got somewhere to put the battery and receiver:-) The white round bits you see on the wings are just supports used when I turned it over to cut the bottom profile. The piece of foam was bigger than the model so it was supported at the wingtips as well.

http://www.mycncuk.com/attachment.php?attachmentid=15559&stc=1http://www.mycncuk.com/attachment.php?attachmentid=15560&stc=1

Don't think I have any pics of the actual cut models but apparently they flew very nicely :-)

Skipsoaring
15-06-2015, 11:03 PM
Nice work on the glider Mitchejc. I agree that a router would be much more versatile and I will be making one to go along with the hotwire. One of the crucial things with supplying wing cores for people to finish is to also supply the beds. A router cuts the beds into little bits that are really hard to put back together ;-)
I'm aiming to produce 3 types of glider from foam as kits and hopefully the funds from them will help me to make my 'aluminium capable' router for making parts and moulds for composite gliders.
Prototypes for the composite gliders will be routed as you suggested above, especially the fuselages.

jregholdsworth
16-06-2015, 02:33 PM
I've built both if you call and eshapeoko strong enough to cut ali ..so if you do need any advice pleased to give it..and I just live down the road in Chestow.. Ok its the M4 ..I've programmed my own arduino based hotwire controller which is compatible with mach3 and GMFC, which I'd be glad to share and I've tried quite a lot of the software out there such as Mach3, and most of the devcad stuff including profili

Skipsoaring
16-06-2015, 09:02 PM
I've built both if you call and eshapeoko strong enough to cut ali ..so if you do need any advice pleased to give it..and I just live down the road in Chestow.. Ok its the M4 ..I've programmed my own arduino based hotwire controller which is compatible with mach3 and GMFC, which I'd be glad to share and I've tried quite a lot of the software out there such as Mach3, and most of the devcad stuff including profili

Thanks mate, I'd be glad to get some help, especially with the program bits.
Clayt.

jregholdsworth
16-06-2015, 09:55 PM
no probs..if you really do want to cut wings 1500mm long have a thought for the volts required ( its probably gonna be 50v +), which of course depends on the wire your using ( its probably gonna be 50v +),

Here is an interesting web site re wire choice http://www.jacobs-online.biz/nichrome/NichromeCalc.html

I use rene 41 wire, its strong and doesn't really weaken or stretch when it gets hot.

Again a site worth looking at is http://www.jacobs-online.biz/nichrome_wire.htm , http://jacobs-online.biz/rene_wire.htm and http://www.skykingrcproducts.com/accessories/foamcutterwire/renewire.html

Skipsoaring
17-06-2015, 08:41 AM
Thanks for that. Some rene on its way. Power supply is going to take some thought. It will need to be adjustable as the foam types and sizes will differ regularly.
Design of the machine is coming along slowly (the drawing is the slow bit, the design is evolving in my head)

jregholdsworth
17-06-2015, 07:53 PM
I built an arduino controller that uses PWM to control the wire heat...others use dimmers and transfromers...bit dubious about the safety of that though. The original idea was from Ufoman

http://diydrones.com/profiles/blogs/pulse-width-modulated-pwm?id=705844%3ABlogPost%3A92907&page=2#comments

I improved on this to give a heat read out and manual control mechanism, the option to drive it automatically from Mach3 or GMFC

Skipsoaring
18-06-2015, 08:28 AM
Arduino sounds pretty useful, but I think it might be one too many things to learn from scratch for this project. I'll see how expensive an appropriate power supply and heat controller are and then decide if I need to take the Arduino learning route.
Thanks again

njhussey
18-06-2015, 09:41 AM
I'll be following this with interest as I want to build a cnc hot wire cutter to make my own wings...

Skipsoaring
22-06-2015, 09:25 PM
I've been playing with fusion360 and have come up with a bit of a design.
I've designed it so that when I'm not cutting cores I can utilise a flat surface for other projects so have gone a bit over the top with regards to the structure.

http://www.mycncuk.com/attachment.php?attachmentid=15611&stc=1

The idea is that the runners are interchangeable on the supported rails to enable some flexibility in the length of the cutting wire and it will be tensioned with a weight over a pulley.
The vertical axis will have a little bit of lateral force applied to them as the bases move independently. To deal with this, I am aiming to use hiwin rails for the vertical block.
There is hardly any force required to pass the wire through the foam, so I am planning on running belts and pulleys to control the axes (as per printer).
My drawing isn't very good and doesn't allow me to change and modify things (still learning CAD on the fly) but I am also aiming to do some epoxy levelling to the frame before mounting the rails and plates.
The way it is drawn at the moment gives a max effective cutting area of 2100mm long x 550 wide x 170mm high.
Just looked at the clock and I am about to be late for work! Gotta go! Sorry if it's a bit disjointed (The post) hopefully you get a little bit of an idea about my project.

rckeith
21-07-2015, 01:26 PM
I've built a 4 axis hot wire machine you can see my build and plans at http://www.rckeith.co.uk (http://www.rckeith.co.uk) and have used it to produce wings and fuselages. I don't really have a limit to the size of wing as the two towers can just be moved further apart. I usually secure them to a board to prevent them moving. I've found the best result are obtained with really thin wire( I think the size is on my website). If your wire is long then you may need to experiment with feeds and current as it may vibrate a little and give poorer results. The biggest challenge I've found is the software. Not much around for 4 axis hot wire so tends to be more expensive. I've spent more on software than hardware. I use Profili2 Pro and Dev Fus Foam but its a bit of a learning curve. Straight wings are fairly easy but tapered are bit more challenging. If you don't have positioned correctly in the machine according to the distance specified in the software the wing comes out larger or smaller. My first flying wing came out a bit smaller than I expected but it was a bonus because if flies absolutely fantastic. Hope that helps

Keith


Hi there!
I will be building a 4 axis CNC hotwire maching for cutting cores for Radio Controlled gliders.
I am just starting the serious research (when I am not being seconded into the real world) and so far I'm thinking that due to my current space constraints I will make it so that it holds the foam vertically against the garage wall.
The machine size is still up in the air and will depend on the size of the blocks I can source. The largest wing panel I can see myself making is 1500mm, although being CNC made (accurately compared to wire dragged over templates/fences) I could make the panels in 2 parts as the majority of the wing panels would be 750mm.

I have a LOT to learn as I am trying to teach myself CAD (Onshape and Sketchup), am yet to learn anything about CAM and have always been petrified by Electrickery!!

I have chosen to build a CNC hotwire as it should be relatively simple and I want to build a CNC router next, having learned some lessons along the way.

The basic idea of the CNC Hotwire machine is to enable me to cut eliptical wing panels which requires independent movement of each end of the wire along the x axis and z axis (hopefully got them right from a gantry machine perspective)

The x axis travel shouldn't need to be more than 500mm and the z axis travel should be similar. I do need to figure out if I would need more though. If, for example, I was to cut a 750mm panel with an elliptical shape and the posts were 1500mm apart, the x axis travel would need to be much greater than if the posts were 800mm apart. Perhaps I need to look at designing my machine to have relocatable rails for the x axis?

I understand that from a construction point of view, my two machines will be worlds apart, the lessons I'm hoping to take to the next build will hopefully be software, electrical and generic.
Anyway, gotta go do the school run.

Cheers
Clayt

Skipsoaring
22-07-2015, 11:40 AM
Thanks Keith. Things are a bit stop-start at the moment, with more stopping than starting.
This affects my focus and I find myself drifting off-target and 'considering' getting a cnc converted Mill (or converting one). Imaginations hey? Where would we be without one!

Blackrat
22-07-2015, 01:29 PM
550mm travel is a little tight imo ... when doing high taper cuts the one side can travel alot more than you think

just a thought :D

Skipsoaring
29-07-2015, 05:26 PM
Thanks for your inputs so far guys.
I have had a re-think and decided that I am not going to ruin my RC Hobby by trying to make any money out of it and therefore won't be needing to make large quantities of wing cores. So I won't waste my time, effort and money on building a CNC hotwire machine.

I will however, be building a CNC router although I think I need to build a shed/workshop first. Integral garage directly below my son's bedroom and attached to the living room will restrict the noises I can make.