Need Help!- about motors and other newbie questions

[Xan]

Hi all,

This is my First post over here so don’t blame me for asking stupid questions.

I’m a electrical engineer who spends most of his free time in building robotics. The main issue I just keep running in to is that I haven’t got access to a decent workshop to make my own parts. I would like to build my own CNC machine which makes it possible to machine parts up to 30 x 30 cm wide. The parts can be made from aluminium or plastic.

It’s my first CNC machine so I don’t want to spend a lot of $$$. And I’m pretty sure it will not look as professional as most of the machines I found on this forum. I was thinking of building a small table version. Like the one’s shown at instuctables, CNC 1, CNC 2 or the on on buildyourcnc.com
The wooden versions will be scaled since I don’t need bigger parts then 30cm.

I’ve got a few questions, I hope somebody is willing to help out.
Let’s say I want to build a scaled down version of the one at buildyourcnc.com. Should these PK268-01A stepper motors be strong enough to move a scaled version around?

There are a lot DIY CNC machines around showing amazing designs in wood. Is there a difference between machining wood, plastic and aluminium except for the IPM?

Maybe a stupid question but can I simply drop in my dremel as router tool or do I need something much powerful?

Thanks in advance!

Xan

[ahren]

Xan,

What you build your machine out of doesn't necessarily determine what you can cut, but it's difficult to get a super rigid machine out of wood, and rigidity (stiffness) is what allows for cutting fast, or in tougher materials.

As for motors, I'd recommend Keling's motors and the Gecko G540 4 axis drive. The Keling motors cost half what those Vexta's cost, and are matched to the G540 for optimal power output. The package is really hard to beat on value.

You can start with a dremel for engraving, but to really remove material, you'll probably want to move up to a variable speed router. I highly recommend the Hitachi M12VC.

Best regards,

Ahren
www.cncrouterparts.com

[Xan]

Hi Ahren,

Thanks for helping me out!

I was suggesting the Vexta’s because I can get them for half the price and they are already in the Netherlands. So no expensive shipping costs. One motor will cost me $46,-

I was thinking of using the stepperdriver kit from hobbycnc. It will cost me $93.80 incl shipping.

3 Vexta motors + stepperdriver will cost me $232,- excl power supply.

The G540 with 3 270 oz-in motors + power supply will cost me $475 excl shipping. I just contacted them for the shipping costs. Hope they aren't to high

The power supply in the G540 package costs $65. The difference between the 2 setups is $175. Do I get much more quality for the $175+shipping extra or should I stick with the cheaper package?

Thanks again!

Xan

[Crevice Reamer]

Hi Xan. Welcome to the Zone!

Maybe some of this will be helpful to you:

http://www.cnczone.com/forums/showthread.php?t=76865.#3

CR.

[Xan]

Hi,

Thanks for the link. I’ve already found that post. It truly got a lot of useful information! That’s where I got my “IPM” from. I might overlooked something because it a real long story…

My major goal is to build a small CNC tool to build small scale robotic parts. Since those parts are always small I don’t want to overdue on power (and money) but I also don’t want to end up with motors that aren’t powerful enough to move things around. The machine won’t be making stuff every day. It’s just to make parts when I need to. So speed isn’t a issue.

I’ve just received the shipping costs for the G540 package. Now it’s $545 for the G540 against $300 for the hobbucnc + vexta setup.

I also found a site in the DIY CNC in the UK. They sell a package (3 axis driver + 3 motors (3Nm)) for $273 excl shipping.

Any feedback would be welcome.

Thanks!

Xan

[Crevice Reamer]

There's a saying: You get what you pay for.

TANSTAAFL!

CR.

[Xan]

Oh yeah, I totally agree on that one!

I’m currently using servos for $40 a piece. They work perfect for the project. Others use servos for $20 a piece. They burn or start shacking. I could also get servos for $125 a piece. But they are really overdone and only use ¼ of the power.

Anyway. if I understand it correctly, you’re saying the Gecko package isn’t overdone at all!

Thanks!

Xan

[ahren]

Xan,

Be careful and make sure you're getting a bipolar driver for whatever motors you get -- most motors these days are either bipolar only or can be driven both bipolar and unipolar. Unipolar is inefficient, and if you get a 4 wire motor, you're out of luck with a unipolar drive (like the hobbycnc).

The Gecko has mid-band resonance compensation, which means you'll avoid headaches as your motors change from low to high speed on your mechanical setup. It's also a bipolar driver.

Shipping costs do make the UK system a consideration -- I may have a solution for you. I'll send you a PM.

Ahren
www.cncrouterparts.com