RC Aircraft Hobbyist

[cambridge_cnc_stuart]

Hello to all,

I am new to the world of CNC Routering, if that's correct spelling / grammer. I have a few years experience on 3D Printing if that would help at all.
I would very much like to build a CNC router to use my Dremel with a bed size of approx 1000mm x 600mm. The bed being made of 18mm MDF. Ive been told that for a router of this length I should be looking to use belt drives. I am not looking for the land speed record for this router but neither do I wish for the "Escargot" of all routers

I am aiming to cut bulkheads and wing ribs for Large RC aircraft / Jets, Carbon Fibre Plates for Multirotors.
One that can cut Balsa Wood, Ply and Carbon Fibre sheet, Ideally Up to a MAX 10mm thick.

I have downloaded the plan pack from Bluurmax cnc but they would need adapting from imperial to metric. I have looked at some software and this does not seem unrealistic.

As for electronics I am open to suggestions. I have a budget around £600 / £1000 but naturally keeping the overall cost down would be advisable, as this year I have purchased three turbines, four jet airframes and made a Vacuum Former and modified my 3d printer three times.

I look forward to hearing from the knowledgeable on this matter

Happy CNC'in!

[m.marino]

How accurate and how fast do you want to be cutting? The design links to a gantry router that is acrylic and MDF. Not the greatest materials to work with. You might want to look at some of the designs here. There are a few designs that use ply laminate with epoxy that have a reasonable life span but it really depends on how long you plan on using your machine and what accuracy you are looking for and longevity. Acrylic doesn't like stress and MDF like's water a lot.

Design depends on what you are looking for and what you want out of it. Gladly help as I can.

Michael
MM0MSU

[cambridge_cnc_stuart]

Hi Michael

Thank you for the reply.

I hear what your saying. I don't mind making it our of square aluminium channeling and Plates. As for accuracy. As it would be used for making RC aircraft parts. I'd like it fairly accurate. I have zero experience of speeds when it comes to these sort of things. As I am a newbie. Any and all advice is welcomed

[m.marino]

Strongly suggest reading through 4 or 5 of the different build thread than and getting an idea of what different folks have done. I am in the process of getting things ready to move so my CNc gantry is currently down and when i bring it back online it will be using a 2.2Kw spindle to allow both a large range of tooling and reasonable cutting ability in all the materials I work with and be able to add some additional ones as well.

Best of luck and Your link points out that I really need to put up the design of my gantry router and how to set it up for different sizes and build materials.

Michael
MM0MSU

[A_Camera]

I think that rigidity and accuracy is CONSIDERABLY more important than speed, especially for aircraft. In your case, balsa is not an issue, but carbon fibre definitely is tough and demands a really rigid machine. I would not build a CNC from anything less than aluminium. Belt drive sound good in theory, but I think that in reality, if you want quality and accuracy and no backlash then you can't just take any belt... If I'd plan to build this machine I'd still use ball screws and ball nuts. I don't think you will have issues with speed, unless you have unrealistic speed dreams. With steppers you should be able to get about 7000 to 9000 mm/min maximum speed, at least if you are using fixed gantry moving table design (which is better regarding rigidity), and probably something between 4000 to 6000 mm/min if you go for moving gantry design. Remember that maximum speed is normally not the milling speed, that depends on the material and many other things, so in all honesty, I don't think there is any advantage in belt drive in your case, even if you are limited in top speed.

...but I think the biggest issue is your budget limits. I really think that you have to double that (or maybe even more) to get a good enough machine to mill carbon fibre.

[Zeeflyboy]

Belts would be fine, but you have to have them far thicker than you would have thought... that then eats into the cost saving. For the price of some c7 rolled screws from china these days I don't really see why you'd use belts. It's not like your axis is too long for screws.

Dremels are also a pretty bad choice in almost every regard, not least that when cutting carbon fibre they will blow the dust around even more than it already will be, and CF dust is nasty stuff for humans and machinery. My first machine had a proxxon router which is similar to a dremel but with better bearings, still blew through two of them in fairly short order once I asked it to start machining FR4/G10 and CF.

If Carbon fibre is on the menu, you really need to think about dust management which really ultimately ends up with cutting underwater. For that, a spindle that doesn't blow air everywhere (ie a water-cooled spindle) is really ideal... bonus is that they are also far more quiet. Even HEPA filters on Vacs can't guarantee you'll trap all those pesky CF fibres. A company I did some work with had no end of problems with their prototype electronics for months, eventually traced it back to them having a new CNC machine that they had been using to prototype CF frames for drones - despite the vac shoe and hepa filter on the shop vac, enough still escaped to settle on their PCBs and components to cause serious misbehaviour. They switched to cutting underwater and had a top to bottom clean of the lab, no problems since.

[cambridge_cnc_stuart]

Wow A_Camera & Zeeflyboy
Thank you so much for your reply and information. Very informative and the more information I get the better informed decision I can make. I am still at the design stage. Had come to the view I shall be using aluminium extrusions.
I have also been looking at a dust shoe.
I have also looked at the maximum size I need. This has been reduced slightly to a working area of 750mm X 450mm but taking into account losses I'm still thinking an overall footprint of 1000x600???
Also I have been looking for designs and have found it difficult.

Now this maybe the wrong at round, but to look around the software I have purchased Mach software......

Realistically, I think the majority of projects will use Balsa wood or Ply too 5mm thickness. I can't really imagine needing too cut CF. I already have 8 Multirotors. For the sake of safety, I think the safest way I'll be too outsource CF cutting.

Regards

[A_Camera]

Zeeflyboy is right, you should be getting a better spindle than the Dremel. I have a Dremel tool also, but I think the air flow is not the worst with that, but the extreme noise and the crappy bearings. They are also pretty weak. So, my opinion is that you should add a real spindle and a VFD to your budget. Of course, even if you give up on carbon fibre, adding a dust shoe is a very good idea, regardless which sort of spindle you use or which material you mill. Regarding dust and carbon fibre milling, one way of avoiding the dust is milling in a water bed. Have seen some people doing that, but you need to build the rig, so it may not be that simple to do.

Personally I gave up on Mach3 and using UCCNC from CNC Drive. I am also using their UC300ETH, which works also with Mach3. My drivers are DQ542MA and they work very well.

[cambridge_cnc_stuart]

Thank you Guys for your replies and information. I am getting an idea on what I should and shouldn't do.

How does this sound? I will make the frame from aluminium extrusion of say 30mmx60mm long sides y-axis and 30mmx30mm X-axis. I'm thinking of using two 23nema Steppers on the y-axis unless this is overkill for the length. A 23nema on the X-axis and a 17nema on the Z-axis
I am leaning more towards a moving gantry design. What is the best design / way to allowing the gantry to move.?
A Spindal of around 2.3kw That's as far as I have gotten so far.

A few questions now that I wonder about!

1, Do CNC routers use similar electronics to a 3D Printer?
2, Do the need microswitches for end stops?
3, I see a lot of electronics in boxes with fans?? Do they produce that much heat?

Any opinions/ advice greatfully received

Thanks once again

[Clive S]

I will make the frame from aluminium extrusion of say 30mmx60mm long sides y-axis and 30mmx30mm X-axis. I'm thinking of using two 23nema Steppers on the y-axis unless this is overkill for the length. A 23nema on the X-axis and a 17nema on the Z-axis

45x90 is a better size as the slots fit nicely with the BK and BF bearing etc. (assuming you are going with ball screws)

nema 17 are not good enough for the Z with a 2.2kw spindle.

1, Do CNC routers use similar electronics to a 3D Printer?
2, Do the need microswitches for end stops?
3, I see a lot of electronics in boxes with fans?? Do they produce that much heat?

1. Yes but need more power suggest, using drives AM882 run at 68v
2. its always a good idea to use limits and homing switches sensor type are cheap.
3. It is usual to put a fan in the box to get the heat away

It will be difficult to build on the budget you have stated I would estimate about £1500 to get a decent machine built by yourself.
I take you have read through some of the build logs on here. Also its never a good idea to buy kits of electronics as they are never matched.

You would be doing yourself a favour if you could draw the machine out in cad first.