CNC/3D too ambitious?

[xtrcom]

hello everyone

Mark here from Ireland.
Im planing on building a CNC which I am later on planing to convert into a 3d printer.
Any ideas on how i should alter my design to suit both? My plan is to build one that has a working are of 50x50cm and the budget is around 1000-1500 euro.

Any ideas and recommendations welcome :)
cheers

[brumster]

I don't have any experience on the CNC side, but from a 3D printer perspective, it could depend greatly on what you want to print with it. PLA should be fairly easy but keeping the print bay warm enough for ABS at that size might be a challenge. The structural rigidity and accuracy I expect you're sticking in for the CNC side will be more than enough for any 3D printing (I'm assuming the generic PLA/ABS plastics for now)... it's a big old print area though :) lots to heat up!

[xtrcom]

the 50x50 area will mostly be for the CNC. I will get a smaller heated bed and mount that to the base for the 3D.
Yes that is what i am hoping also that if a CNC is accurate then it should be good enough for a 3d printer conversion.

[brumster]

I would think so. Like I say, I'm new myself to the CNC machining side so no experience there, but I've run a RepRap Ormerod 2 for over 12 months now and love it. You're not talking massive requirements in terms of resolution; your average layer height with PLA on a 0.5mm nozzle is around 0.24mm, with the first going down thinner at maybe around 0.15mm... so pretty easy resolutions for your Z axis to make. The X and Y are in a way less critical because obviously you're laying material down, so you're just trailing the filament out onto the bed or previous layer. The tuning is really to do with extrusion and axis speeds, temperatures and so forth, but again by CNC standards you're in easy territory... you're unlikely to push more than 40 to 60mm/s on print moves (depending a lot on nozzle size, temperature, material, etc)...

[xtrcom]

I'm in the process of designing the 3d model of if... i shall upload and get some opinions and then i shall build :)

[cropwell]

Hi Mark,

I can understand that, if you are building and XYZ mechanism, you might want to make it all things to all men, but you are running into areas of conflict with the different requirements of CNC cutting and 3D printing. 3D printing needs to be fast and light but CNC cutting needs to be robust and accurate. You will end up being none of these for more cost than separate machines unless you are some sort of engineering genius. Ask on the forum if anyone has done this dual purpose machine, but more importantly, ask them how it panned out.

Cheers,

Rob

[xtrcom]

I'm still drawing out the model in CAD then i will do some simulations and upload here to get some feedback.
Hopefully with some better performing stepper motors i can achieve the comfortable speeds to do some 3d printing. (i'm not too bothered about the speed as long as it is not stupid slow).

Thank you for the input. I'm very happy that I joined this forum

[Neale]

With due respect to Rob, I have to say that my experience is that 3D printing needs much lower speeds than routing. My shockingly slow router will easily reach 900mm/min while my 3D printer seldom does more than a tenth of that - assuming that you are extruding plastic, you just can't get it out of the nozzle fast enough to need much higher speeds.

[cropwell]

With due respect to Rob, I have to say that my experience is that 3D printing needs much lower speeds than routing. My shockingly slow router will easily reach 900mm/min while my 3D printer seldom does more than a tenth of that - assuming that you are extruding plastic, you just can't get it out of the nozzle fast enough to need much higher speeds.My 3D printer extrudes at 40 mm/second (2400mm/min) and rapids at 150 mm/second (9000 mm/min). These are the manufacturers settings for ABS. My router is much slower than that.
Cheers,
Rob

[Clive S]

With due respect to Rob, I have to say that my experience is that 3D printing needs much lower speeds than routing. My shockingly slow router will easily reach 900mm/min while my 3D printer seldom does more than a tenth of that - assuming that you are extruding plastic, you just can't get it out of the nozzle fast enough to need much higher speeds.I think the acc is an important part of the equation and needs to be quite high

[Neale]

I put my hand up - confused minutes and seconds. Never was very good at time-keeping...

What also made me wonder, though, is that when I'm sitting watching the wheels go round on the printer, it doesn't seem that fast and I think Clive is right - acceleration is very important as 3D printed components are generally fiddly little things and the extruder is changing direction a lot. I found the same effect doing some fairly fine engraving with the router - I traded acceleration for speed in the settings and the overall cut time reduced significantly. As far as the OP's question is concerned, I think that that is going to raise some interesting design trade-offs with regards to things like pitch of leadscrew/ballscrew.

[cropwell]

Acceleration for 3D printing seems to be the keyword, which is one of the reasons 3D XYZ mechanisms are light and nimble. You don't need the power to push a cutter through a material, you are just squirting out plastic, icing sugar, chocolate or whatever. I just think that a hybrid machine would be the ugly son of widely different parents.
Cheers,
Rob

[xtrcom]

its looking like its going to be just a decent DIY CNC which il try and adapt for some 3d printing. I'l see how i get on :)