I'm thinking about trying to build one of these RoGR machines but am learning that the price isn't going to be nearly as cheap as I was initially led to believe.

Some prices I know...
Bearing and rail kit: $400 (sale price from $500) + shipping
Motor and screw kit: $300 + shipping
Aluminum from online metals: $300 + shipping
Router: $100 + shipping <- this of course could be anything you're willing to pay
= $1100 + about $180 in shipping

Some prices that are a little up in the air...

T-Slot Base
I haven't been able to find any 4" x 4" pieces, the closest I could find is these 2" x 4" extrusions from the 80/20 garage sale on eBay...
http://cgi.ebay.com/8020-T-Slot-Aluminum-E...oQQcmdZViewItem
These are $71 each + shipping (~$35), I'd be surprised if an equally long 4" square extrusion would be less than $100
I don't see making the base with much less than 2 of these 96" pieces: $200 + shipping
That's just the perimeter, nothing for the actual bed of the table. Total (conservative) guess for the rest of the table: $100

CNC drivers
I haven't given myself the chore of researching this myself yet, but I've seen people say you could probably build them yourself for $100, I've also seen that building them yourself would be a $300 savings.
It sounds like getting controllers for $200 would be a deal. ^{[edit]There's people selling CNC drivers on eBay for $150 or so, I have no idea if they're any good though.[/edit]}

Wires, cable carriers, bits, other "misc." items...
$100 total would be crazy cheap (aren't these bits like $50 each? ^{[edit]Looks like bits are available for reasonable prices on eBay... Awesome![/edit]}).

Computer stuff
Most of us have a computer or could probably get one for next to nothing
Software: can be free, but it ain't going to be very good.

My total so far is ~$1950... am I forgetting anything?

Dont forget about getting the connectors for the Tslot, gussets and stuff can get very expensive.. i made a projector out of 80/20 aluminum and all my corner connectors, nuts, and gussets cost me more than the aluminum Tslots.

Im also very interested in building one of these machines.. I expected it to be somewhere around $2000-$3000 once i was all said and done.. And being able to build it myself makes me excited.

Im hoping to buy a complete kit though, i'd rather not shop around for parts, but i would if i had to.

Im also looking forward to hearing everyone elses experiences with building and using their RoBLOKS Machine.

you are prob. about on par with the cost, now add 20% and you will know what your final cost will be... it always works out that way, believe me.

Also don't forget software, i know you can go cheap, you know linux EMC2 and some free cam software, but to get into it and make what you want you need the software to do it right. Just ask me how i know. LOL

Joe

HAHA at least 20%! The way I do things it'll be even more.

I'm definitely not forgetting it! It's very much on my mind... I just figured it wouldn't be fair to tack on $1000 when it's not technically required... I still haven't installed Cut3D again, but $300 is looking pretty good right now. There's another package that I'm looking at called MadCAM, it's got an educational version that's $200 (a 90% discount!). It's a Rhino plugin. The cool thing about it is it lets you edit the paths manually, the bad thing is it creates some funky paths that require editing sometimes.

Well, I can add some good news for you. My latest bed design uses a 2" cast concrete slab for the table, instead of needing the T-slot. (I'm always looking for somewhere to use concrete!) Plain steel tubular legs with jack feet can be used to hold the slab. The slab is very very rigid, is never affected by weather changes, and the motor mounts, drains etc are cast into the slab. A piece of sacrifice is still used of course. The cost for the bed is under $25. The cost for the T-Slot was approaching $300!

On the software, we use only freeware at Lumenlab. We are using RoGR to build more RoGRs, so clearly it works fine! I'm compiling tutorials on our exact set-up.

Freeware is good

Concrete is also good. I was starting to look at all that AL for the base, and thinking in terms of steel and my shiny new welder. (Not that it's up to solid 4" chunks of steel, but I figured that I might be able to cheat and use tube. Maybe steel tube, and fill it with concrete?

Or, a trick that car racers use... Expanding foam. Filling the car frame rails with expanding foam gives a signifigant and measurable increase in rigidity in the car's chassis. It could ovbiously do the same to pieces used for a CNC machine. The advantage to the exanding foam is that it's very lightweight, but still rigid. Yes, my Supra's frame rails have been filled.

Anyway, it l;ooks like I'm going to get a fairly decent income tax return this year, and a DIY CnC is on the list of things to get with it... Then again, so is a ceramic ball bearing turbocharger... Decisions decisions...

I'm pretty sure you could build the turbo on RoGR, especially if the spindle had ceramics...

Yeah, but I don't have the equipment to balancce the rotating assembly to 20,000 RPM.

20,000? That's nothing. I make air tool accessories that hit 25k, and they hardly ever blow up. Lesse, if I were to cut a turbine, I'd leave small sacrificial "nodes" radially around the turbine that could be filed for precise balancing.

Can stuff like that be balanced statically or must a dynamic balance be done? Or is the dynamic balance "run her up and see if she self-destructs"?

Also, where does one get the info required to determine material properties that would subsequently tell one whether a particular material would sustain the stressors inflicted by a given rpm -> g force?

Lord....

Q #1: Definitely both: qualitative and quantitative. That said nearly everything can go that fast, but for how long? (Bamboo instrument reeds come to mind, many of which are still going after 20+ years use). The mass forces for a turbo are axial, radial and centrifugal. It is rather simple to measure each of these dimensions, though it doesn't mean success is assured to have a perfectly "balanced" device since "resonance" is always lurking. BTW: Hard bearings can "bear" the imbalances for much longer, so as speed increases, so does bearing hardness. That said, it isn't like "esoteric technology" or anything. Go to Harbor Freight; pick up a $15 "die grinder" and grind away happily at 25,000 RPM for the next few years, so long as you oil it (hint hint hint).

Q #2: First by trying. If you survive that, you may want to learn why. I suggest an obsessive-compulsive desire to learn, followed by obsessive-compulsive beer consumption.

Good, because the other way around usually ends up with me on the couch, my wife really pissed and the housepets looking at me funny for a few days...

Din't I ask you to never use my proper name here?

Well, to me at least, a die grinder is hardly an apt comparison to a turbo. But I won't argue the point.

Were I to cease asking silly questions I'd never post again.

Never thought about resonance. That must be a real bitch.

A die grinder is a high speed air turbine, how does it not compare?

Wow....thats a first...

You're gonna get fat eating all that p-corn.

Get fat? You haven't seen any recent photos of me I guess. LOL!

Okay, okay then!!! You want fatTER you got fatTER!!!!!

Sorry Hirudin.

What's the "fatTER" mean? fat ass tumor on Totally Erect RoGR?

The T stands for Throbbing...

Heh, this thread is past being derailed.

Lemme guess. You just happened to be in OCBDP when you posted that reply?

Derailed? Farging double head-on train wreck is more like it!!!

Edit: No, it was the fading aftereffects of that industrial vibrator!!!

I am so close to locking this thread up....

Get it back on topic...














Did that sound tough ....like a "real" MOD ?

It doesn't matter how much it's gonna cost since I can't afford it right now.




MOD?



I just love that I found the "spoiler" and "Acronym" posting options recently.

Click to view attachment
I've had that pic for a year, I've always wanted to use it...

Know sumpin'? I'm no animal rights activist but clubbing baby seals kinda turns me off.

Well, actually it makes me wanna go home and get some fresh venison to settle my tummy.

I'm hoping you have some photos taken in the next few milliseconds as well???

JJ's gonna be JACKED!!!!!!!!!!!!!!!!!!!!

Yep, it's FRIDAY!!!!

That acronym tag is cool Durachko, I'll have to start using that...

So diving in on this one a little late, I know that one of the most important parts of high-tolerance machining is vibration dampening, which is yet another advantage of using concrete over steel or aluminum. Some industrial mills and lathes ship from the factory hollow, and you can fill them with sand on site, the mass helps dampen, but concrete is really one of the best things you can use to stop chatter, the only common material which is better is "gray iron", one of the cast iron types.

Any DIY sand-casters out there?

I built a refractory furnace and got my green sand boxes together about 5 years ago, then moved and couldn't take it with me!

Haha. I KNEW someone one here would. Strangest hobbies ever, this site!

You must mean coooooolest...

Might wanna rethink the turbo thing, your not talking 20,000rpm your looking at speeds between 60,000and 150,000.......a bit tougher to balance. And if you try balancing it I think we want a live video feed to watch the carnage! oh there will be blood................

Turbocharger run much tighter bearing tolerances. They are terribly tight and 'float' on a film of oil. Also 40k rpm isn't unheard of.

That's an answer.

you don't need to balance at high speed, the only time you need to do that is when you have multiple shaft running inside one another and you need the control resonance-cause deflection

I balance a 14 inch compressor and rotor assembly that has an operating speed of 38Krpm
to balance it I use an hoffman dynamic balancer and I'm balancing at a speed of 1200 rpm +/- 0.5 rpm
specification call for a maximum unbalance of 300 milligram*inch on one plane and 150 milligram inch on the other

btw, if any of you guys have worked with a hoffman or a shenck, why the **** are you not DIY making one, those machines are all software based, there is only 2 vibration (ultrasonic transducers) sensors the rest is WAY simpler to make than a ROGR