Adding 3D printer ability to my CNC / advice needed please

**FatFreddie** · 07-01-2015

Originally Posted by dudz

If this gear will extrude Nylon or Delrin ( Acetal ) plastics, then I can think of a few good uses straight away.

Taulman do various nylon formulations - I've used Bridge which prints on glass with a dilute PVA coating ok. I'm quite impressed with the strength of this material.

You can also get an acrylic (t-glase) from them - have a look on http://taulman3d.com/

PLA is still a useful material even though it's not the toughest available - I've made a laptop stand from it and various bits for the kitchen - custom hooks for ikea cooking implement racks, plate racks for a cupboard, kitchen roll dispenser etc. Oh, and parts for the next 3d printer :-)

**Trispectiv** · 08-01-2015

Originally Posted by dudz

I use my CNC for small motorcycle parts. The 3D printer add on, is just because I would like to learn it, and to let my children learn something new.
I have always thought of 3D printers as Useless , apart from making parts for other 3D printers. But the wife though it was a good idea, so I thought I'd have a go. So far all I have seen is toys and 3D printer parts made. I am sure I will come up with something one day .

It pretty much depends on your view on plastic objects. Plastic will never match metal in terms of toughness. On top of that, printed parts are printed in layers and small sections where the contact area between two successive layers is small, are prone to delamination. Also, you will have to live with the vertical ridges representing each layer. Overall, you should be able to use printed objects for very many application, or at least give it a try before machining the real part.

**Boyan Silyavski** · 08-01-2015

Originally Posted by Trispectiv

It pretty much depends on your view on plastic objects. Plastic will never match metal in terms of toughness. On top of that, printed parts are printed in layers and small sections where the contact area between two successive layers is small, are prone to delamination. Also, you will have to live with the vertical ridges representing each layer. Overall, you should be able to use printed objects for very many application, or at least give it a try before machining the real part.

I cant agree with you . With a good extruder and hot end, like in this case, there is no delamination and the parts are super tough. Even where overhang meets with other part of the model.

Thats the good thing of the CNC retrofit, combining additive and removal in one machine. You can build the part and later machine its surface. That's a big big saving. 20 kg block of plastic versus 1kg of material, for example. Which is cheaper?

And i have held some parts from a good print and honestly i was impressed by their strength. And i am not that easily impressed. I like breaking stuff and i couldn't

At the end all is art. Its not automatic. But once you have it, all stuff that goes out from a machine is strong and beautiful.

**Trispectiv** · 08-01-2015

The problem is that delamination is not tested with your hand. Among others things, I am designing and assembling 3D printers and there are numerous cases when the part had to be redesigned and made beefier in order to sustain the mechanical stress. In some cases the thinner part showed unacceptable wear during testing; in other cases it happened after the machine worked for a while and the stress broke through the part. As a side note, in particular elastic filaments such as NinjaFlex and nylon are very hard to delaminate as the object is also elastic, but that's a different story.
However, I am not the debating type, if you consider that 2 layers that have a too small contact area cannot be delaminated, that's ok.

**Boyan Silyavski** · 08-01-2015

It seems you may know then better than me. My impressions were as you said, just trying the material with my hands. I have never done extensive tests. One thing is clear though, that of course the part should be beefy, compared to normal one. I have more experience with stereo lithographed parts and most of all PolyJet-ed.

As i said its an art. At least when you have all good set up, you can start to reliably test and play until you have it figured. Having unreliable setup will further complicate or even make perfection impossible.

**Trispectiv** · 08-01-2015

Yes, that is also true, printed object are amazingly tough. First impression usually is that you can tear it apart with your hands, but a well printed part won't go down easily. However, in very many assemblies plastic parts will join against metal parts. If you don't factor the forces pushing against that plastic part and you size it as a metal part for example, you stand a good chance to get it delaminated. A good strategy is to design and print the part so that the force pushing against it goes the other way around, squeezing the layers together, instead of working against them. It obviously is not always possible, sometimes because of the shape of the part, sometimes because there are multiple vectors pushing against that part and you can only satisfy one or a couple of them.

Anyway, on topic, before adding 3D printer capabilities to a CNC, one should also check that the machine can sustain decent travel speeds, main reason being oozing during non-printing very slow moves.

**dudz** · 08-01-2015

MY X and Y cnc Axis will travel at over 2000mm/min. My Z = 1800mm/min without stalling. Hope this is enough
Anyhow, If this is a success I plan to build a separate / much lighter machine for the 3D printer hardware I have. I am using my existing CNC now, to keep costs down.

**Trispectiv** · 09-01-2015

Being belt driven, 3D printers usually move faster. But than again, don't worry yet, it pretty much goes down to what size your printed object has. A very large object will mean longer distances during travel moves, while smaller objects require short distance moves. Also, nowadays slicers can use various toolpath strategies such that using already printed areas from the current layer (when possible) for traveling moves, hence minimizing the ooze - the already printed area from the current layer being at the same height as the nozzle and acting as a plug.