Need help designing an hybrid
June 19, 2015 09:24AM
So, i have this project:
A machine capable of printing; drilling; cutting; laser cutting; PCB etching and/or drilling; SLS... for wood, plastic, metal, glass...
I believe it's possible. It wouldn't be an "all-in-one" machine, but a "modular" one. For example, for changing from printing to laser cutting, i would unplug the bed and hotend, and replace them by the laser versions.
So the only fixed parts would be the main frame and electronics, the bed/axis/motors + drivers/heads would be pluggable.
For the design i'm thinking something like that would be nice: blue Chick CNC Machine Kit
I belmieve the bed must be static, it would help the "pluggable" design, and from i read it also allows better quality.
The build area should be about 200x200x200mm (more would be nice, less is not an option).
The precision is the important point here, i'd like be able to get a precision of 0.01mm on every axis.
Speed is not really an issue, i'm really about the precision, if it can be fast too, great, but it's not a must have.

The idea is to start simple, and make the machine improve itself. So right now i'm on the first "stage" machine design.
This one should be able to do plastic FDM and a bit of cutting/drilling using a dremel, in order to build the next generation using self-made mettalic parts instead of wood/plastic (lighter/stronger).

Now for the questions:

Stepper motors:
what size? what specs?
I'm thinking NEMA 23, since even the smaller ones would be a good start and can be easily replaced by stronger ones later if needed. I guess a step angle of at least 1.8°, the smaller the better. What i'm struggling with is the holding torque: how can i calculate how much i need?

Axis trains:
Belt, chain, rack and pinion, something else?
Rack and pinion might be a bit difficult to build, maybe i should keep that idea for a next generation.

Firmware/CAM software:
Is there any already existing capable of handling FDM and "CNC dremel"? If not i guess i'll have to write some.

Same as above.

For the "pluggable" design, it is not really an option at this stage (except swithing the FDM head for the dremel), but something to keep in mind, so that i don't have to re-think the whole thing on the next generations.

Thanks for reading. Any advice are welcomed.
Re: Need help designing an hybrid
June 25, 2015 02:50AM
Hi Domovoy,

Note that this has been discussed before, I think in the General forum.

My personal opinion is that the constraints for each type of machine are so much different, that any attempt at building a hybrid machine will result in something with mediocre performance in one function and very bad performance in all the others.

3D printers are basically designed for speed and extra resolution in the Z-axis, with a print volume of 200 x 200 x 200 = 8L.

For a laser-cutting machine, you also want speed, but you want large X and Y dimensions and you basically don't need the Z-axis. You may also need to evacuate toxic fumes and provide an enclosure to avoid laser reflections which are dangerous to the eyes.

For a CNC PCB drilling/milling machine you need a slow but strong (and heavy) mechanism and you need to pay attention at how it withstands vibrations and abrasive dust.

As you can see these requirements either contradict or are orthogonal to each other.

My advice is to simply build one machine optimized for each function, having as many machines as required. They will perform better and in the end, may cost less than a hybrid that will cause you many headaches.

Edited 1 time(s). Last edit at 06/25/2015 02:52AM by AndrewBCN.
Re: Need help designing an hybrid
June 27, 2015 05:43AM
Hi Andrew, and thanks for your input.

I thought about the "opposite" requirements of each machine before; and that's why i was planning on a "pluggable" design.
If the main frame and electronics are just a strong, stable base on which you can then plug different beds/axis/trains/tools, wouldn't that be enough to be able to setup several machines, without the performance/precision problems implied by a static,all in one design?

In the end it's almost the same as having several machines, but the advantage is that it only takes the space of one, and a big box for storing the elements not currently in use. Some of these elements might even be used in several configurations (FDM and laser cutting could be setup with the same set of X/Y axis for example).

So i understand that many machines is definitely a better solution, but since i don't plan on getting a "industrial grade" quality, wouldn't a hybrid/pluggable design be enough for home/DIY tools?
Re: Need help designing an hybrid
July 07, 2015 09:41AM
Look at this.

Mostly Printed CNC / Multitool

Pretty much has what your asking.
Re: Need help designing an hybrid
September 09, 2015 06:53PM
i would not build such a flimsy frame!

First of all:

Use aluminum Extrusion - no less than 40x40mm or 1,5inches Profiles.

Nema 23 Moors sound good!
Try to select motors, which require less Amps to dive, so you can use standart eprap electronics (Radds 1.5 for example)
then use 24Volts and you should get decent power output even with 1.5A motors.

I woul personally either use a big belt which is really tightly fastened and tensioned - HTD 5m or similar,
or go all the way and use 1204 or even 1605 ballscrews!

Ballscrews in combination with nema 23 motors and a moving Y-Table will easily get you in the range of movement speeds up to 200mm/s
with basically no backlash and the ability to easily hold up to milling tasks.

Many machines for illing with bigger and heavier portals are build around 1605 ballscrews - which are widely available via china.

So thrre steps ot successful 3d printing/milling hybrid:

1. rigid frame out of aluminum extrusion the bigger the better
2. Low-amp, medium to high volatge nema 23 motors with radds 1.5
3. Ballscrews on all axis and a very good build with lots of precision

Sorry, only registered users may post in this forum.

Click here to login