RC Aircraft Hobbyist

[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.

[A_Camera]

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

It does not sound good at all to my ears. 30x60 and 30x30 is for 3D printers, not for a CNC. Rigidity and mass are important even if you give up on milling CF. My machine is mainly built using 45x90 extrusions and is definitely not overkill, not even for plastics which I mainly use it for. Wood is not different. I am also milling aluminium but would not start milling CF with it, I think that would be too painful. You should not use any NEMA17, again, they are good for 3D printers or other things where forces are considerably less. Even the Z requires a lot of force and pretty high mass to move up and down at a fast speed, so don't go for a weak solution. There is no advantage in using a small motor, the price difference is negligible.

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.

Good luck. That's what most people chose because it is the sexiest design. The only advantage it has over a fixed beam type is that it looks more impressive when you show it to your friends and that it takes a bit less space. Fixed beam is easier to build, easier to square and align in every angle, AND provides better rigidity. A 2.2kW spindle is pretty heavy, even the 1.5kW I am using is too heavy for NEMA17.

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

To answer your three questions:

1. Yes, the electronics in principle the same, but a CNC requires much more powerful motors and better drivers. Also, the 3D printers I looked at, are not driven directly from any software, you generate an STL file and transfer that to the printer using a memory card or some other means and print that specific file. A CNC uses a PC which generates G-code and sends that code to the motion controller. The software can be Mach3, Mach4, UCCNC and so on, some are more expensive than others, but they all communicate with the CNC using the parallel port or through a motion controller using USB or Ethernet, like the UC300USB or UC300ETH or others. Those motion controllers require a driver utility, a plugin, which the software you are using uses to communicate with them. As an example, all the UCx00 from CNC Drive have a Mach3 plugin but no Mach4 plugin. Of course, all can be used with the UCCNC software, since it is made by the same company.

2. Yes. It is a very bad idea to leave those out from the design because they are actually protecting your machine. I don't think there is anyone on this earth who never hit the limit switches. My machine runs at 9000mm/min and smashing into the sides at full speed is a pretty nasty thing. Even with limit switches it means a sudden stop and a loud bang, so it is scary, but it saves the machine from committing suicide.

3. Yes and no. The heat depends on your drivers. Some drivers get very hot, others not at all. My drivers are never hot and I don't have a fan in my electronics box. I do have a large fan spinning at low RPM in my PSU box and that fan is temperature controlled, the sensor is on the rectifier. At normal temperature the fan can't be heard, at 35 degree Celsius the rpm is increased to 60% and then gradually if the temperature continues to rise. I don't think I ever had the fan at 100% rpm. The VFD has a fan as well, and that is also spinning at low RPM unless the heat is increased. I have never had the fan at 100%, so that is also pretty quiet. Steppers can get hot, up to 60 degrees, but that's normal. I have no cooling on those. Note that I have all those in three separate pretty large boxes. The VFD has it's own, delivered by the factory, but the PSU and the electronics is my own design, so those use the boxes of my choice. Many people build everything in a smallish box, which I think is a bad idea, but it is up to each to decide what they prefer. In those cases there is probably a need for fans because the air inside will be heated and the lack of natural air flow is prevented, so you must have a fan (at least one) to generate air flow and cool the contents. Also many people use cheap Chinese switching PSUs and all those have a small fan which is spinning all the time, generating high noise. Also, if you have a powerful machine you may need individual PSUs for each stepper, generating even more noise. So, in short, there are always fans involved somewhere, but the number of them and how much noise they generate depends on the design.

A CNC is much more complicated than a 3D printer, so don't underestimate the challenge you are facing. While a 3D printer works in principal the same way, I don't think they are actually comparable in any other way than both apply synchronized axis motion on 3 axes.