ABS Plastic Z axis viable?

[navinity]

kickstarter has a project called cnc-building-blocks

http://www.kickstarter.com/projects/...uilding-blocks

From the site:

$500: CNC Building Blocks + Electronics + Nema 23 (~270 oz-in) + Power Supply + Assembled Case.
For our top reward level, you will receive the entire CNC Building Blocks kit to make your own CNC machine ($150 reward level)! You will also get a CNC Controller box fully assembled with electronics board, power supply and 3 plug and play Nema 23 motors.

I Emailed the guy about what it could possibly do and received the response:

We expect 400ipm possible with quick electronics and motors.

The weight is phenominal, several pounds lighter than our previous z-axis.

Woods and plastics should be easy to cut, with soft metals possible
with slow cutting speeds and smaller bits.

-AJ Quick

What kind of opinions can I get out of the pros here? Does sound like it will make a great price / performance machine?

[ger21]

Depends on what you want to do with the machine. It might be OK for something very small, doing light duty work.

Here's a quote from his Kickstarter page:

Most DIY CNC machines use bearings on bolts, or drawer slides or other various hardware store concoctions of parts,

Imo, 8-10 years ago, this was true. But most of the machines you'll find being built here are way beyond what anyone on Kickstarter is doing.
It seems like most of the CNC projects on Kickstarter are from people very new to CNC, who are re-learning everything that the members here have learned years ago.

[flojor10]

The machine looks like a simple cnc machine that was made to be affordable but with a few compromises. First the z axis looks like a copy of the one used on the microcarve machines, just they look cheaper and made of plastic. I also wouldn't have 3/4 unsupported rails that are 18 inches long that support the gantry and expect to go 400in/min without substancial flexing, especially when cutting metals. This looks to be good machine for a begginer who has a smaller budget or can't build their own cnc, but you get what you pay for sometimes.

[Walky]

Those parts sure won't build a pro level machine, but I'm sure they will be very useful for beginners with limited experience, building their first machine on a really tight budget. IMHO, the rewards are not bad at all for the "price tag" of each.

What I really, really don't like is the hollowing of the Z axis parts. Also, the mechanical parts look disturbingly similar to those of the Fireball V90, while the electronics look like a simplified version of the HobbyCNC EZ Driver kit.

[LazyMan]

Others may have success with plastic for structural components in their machine but, the idea alone makes me cringe. Setting rigidity aside, plastic can be very unstable and can easily deform from temperature changes. I machined some vacuum pods out of HDPE and after a few months in my garage they warped beyond belief. I cant imagine the feeling I would have to see my CNC router I invested so much time and money into warp into a useless pile of scrap.

[Walky]

Others may have success with plastic for structural components in their machine but, the idea alone makes me cringe. Setting rigidity aside, plastic can be very unstable and can easily deform from temperature changes. I machined some vacuum pods out of HDPE and after a few months in my garage they warped beyond belief. I cant imagine the feeling I would have to see my CNC router I invested so much time and money into warp into a useless pile of scrap.

Have you tried using polypropylene?, it has worked great for me and seems pretty stable.

[LazyMan]

Have you tried using polypropylene?, it has worked great for me and seems pretty stable.

Never tried it. Not all plastics are the same and I really didn't want to say that it would never work because. I have a mill so I never really had the need to use plastic, but based I my little experience, I personally would avoid it unless I did not have much choice.

[Walky]

Never tried it. Not all plastics are the same and I really didn't want to say that it would never work because. I have a mill so I never really had the need to use plastic, but based I my little experience, I personally would avoid it unless I did not have much choice.

Yeah, I would choose aluminum over plastic anytime too, but since I don't have a mill and machining aluminum with my machine takes 20+ times what it takes to machine PP (plus the risk of damaging my router's bearing) there's not much I can do about it until I get a spindle upgrade

[prcdslnc13]

There was a big controversy over the original project these guys did. The main guy was pretty active in the FireBall V90 Yahoo group until his router kickstarter came out and people called it a blatant knockoff of the v90 with some simple changes.

His ABS Z looks like he copied the v90's Cast Urethane Z axis and made it ABS. That should get interesting.