What were your lessons learned?

[WoodSnarfer]

Hi folks, I have a question to those who have gone before me. You might have build a dozen CNC routers, or just finished your first after being inspired by this website.

So my question is this: Could you list the things you would advise those of us still in the planning stage? Like, the things to look out for, or the things you wish you would have done differently.

Your sharing will greatly help those of us reading, thinking, and planning.

Thanks!
-Chris

[JIMMY]

I like that idea.

[anoel]

The biggest things I can think of are....

"Sort of Rigid" is not good enough.
"Sort of accurate" is not good enough.
What seems "fast enough" rarely is.

[sol]

Not to make this into a shrink session but it depends on your personality.
When those who know you hear that you are going to build a machine do they think "Yeah sure, yet another half-fast unfinished project." Or do they think "That guy is always making the neatest stuff."
If you are an "up like a rocket and down like a rock" sort of person when it comes to projects, set the bar very low; build an embarrassingly cheap POC (Proof Of Concept... Piece Of Crud) that allows you to learn while not getting caught up in all the gumption traps that the quest for perfection invites. The next machine can be the good one.
There are over 7000 members here and just over 70 claim to have finished a machine...and it is the same theme on other forums.."I built two while he still plans the perfect one."

Okay, That's said, now for specifics regarding a first DIY machine.

Use gravity as your friend, design so that parts will "fall" to where they are supposed to be.
Remember basic geometry and physics. Design parts so that they are intrinsically stable; triangles are also your friend....and three points define a plane.
Make everything adjustable, getting it right on the first try is unrealistic so allow wiggle room.
Be realistic about your skill set and tool inventory.
High quality parts cannot be made with low quality tools.
Unless you have access to a machine shop, 0.001" accuracy is virtually unobtainable.
You WILL make mistakes (so start small and cheap)
Everything takes longer than expected so have patience, take the time to be careful; don't "Measure with a micrometer, mark with chalk, and cut with an axe"

Can't think of more right now but I address this a bit on my site as well.

Good luck!

[sendkeys]

i got one.

it cost 10 times as much as you wanted and 2 times as much as it should have :P

[ger21]

Originally Posted by sol High quality parts cannot be made with low quality tools.

Not necesarily true.

[sol]

Yeah, I should have said "cannot be made quickly or easily..."
Ancient jewelry and sculpture always amaze me...they made it with just those basic tools?! Patience and perseverance at a level we can no longer imagine.

[senor J.]

I got some advice that I learned the hard way... Trying to construct a z axis with precision bearings and ball screws and ball screw end blocks with minimal tools Ext Ect is 10 times harder and the exact same price as buying a premaid z axis assembly from parkerdaedal or thk on ebay. If you find a linear actuator that has the right stroke length you want but is $50 more than you think you could make it for buying the componets individually, shell out the extra fifty bucks you wont regret it and you'll have a machine up and running so much quicker.

[WoodSnarfer]

Great comments so far!

My personality is such that if/when I decide to do something, it will get done. To be honest, I'd really rather bypass the "build a small cheap one first" phase, and try to do as much homework/design up front for a good "keeper" first attempt. Even if I spend a year designing, to me that part is a lot of fun.

I like the z-axis suggestion...any other comments about ballscrews, slides, rails, motor couplings, drivers, power supplies, etc?

Regarding the budget, I'm trying to be realistic...I figure that to build the machine I have in mind (servos, 30" x 48" x 12" workspace, "very good" accuracy, and "not too slow"), I have to plan on spending around $3,000 USD.

Thanks,
Chris

[yukonho]

Suggestion number 1. Do your homework.
Learn about all the various components, brands, features. Chose your components based on this info and your wallet.
Chose a solid, basic design. Simple and solid rules!
Take your time and build true.

[sol]

Decide what components to build vs buy.
Examples:
A breakout board has maybe $25 in parts in it but a long weekend worth of DIY time ... < $100 will purchase a good prefab that is tested and ready to go.
Motors can be picked up on Ebay but adding encoders, power supply and controllers that work well together can be a challenge. A package, or parts that are sold with good support, can make things MUCH easier, but it costs more of course...in money vs. time.
Same goes for just shopping around, again Ebay has good deals but the time it takes to find them may not be worth the savings. Some folks enjoy the window-shopping, others find it not worth the hassle and risk that goes with used goods.

Oh yeah, your tentative budget sounds realistic except that a good control box with cables will scream past $500 and approach $1000 really quickly. While on that subject; use a big box for your controller system, a computer cabinet is a decent inexpensive alternative. Things take more room than expected and it is a regal pain to work in a tiny enclosure. You know how I know.

Again, I discuss this stuff in a show and tell on my website. Not trying to drive traffic that way, but it already addresses these issues a bit.

And good luck!

[WoodSnarfer]

Wow...didn't realize the controller (and cables) would be that much...good thing to ponder...

If you are allowed to (?) could you post your website address? If not, PM it to me.

Thanks!
-Chris