600 IPM is just madness!

I wonder what some typical speeds would be for various other tools (table saw, jig saw, drilling into different materials, planer/joiner, etc.)

And how will you find out?

I did a quick search on Google, but I didn't find anything in the first 2 minutes so I gave up...

I would guess 200 100 IPM might be about how fast you would cut lumber using a circular saw. Maybe 30 IPM to drill into wood by hand. 600 is just darn fast!

By my challenge I mean: Every machine is different. With this obsession; it pays to find the limits quickly. Thereafter, you know your machine and can feed it properly.

I got a vid of the flattening needed to make the final micRo prototype: Driven by hand, the bed must be flattened.

About driving the servos with direct rectified half wave A/C.

One thing you might want to look at is the instantaneous current across the filter caps. Normal power supplies have a transformer and therefor a natural Re value (series resistance) this resistance is a current limiter at time 0. You will want to use lower voltage caps just to get them fit under the cap of the motor so their instantaneous current value may be lower than the ones you now are using. A fix for this problem is to use a long thin wire to drive the motors. The power switch will arc a little without a small amount of resistance.

The resulting rectified voltage from a half wave rectifier or a full wave rectifier is the same, at about 172 volts so your caps will need to be at least 180 volts DC rated. 180 volts DC = fairly large cap.

RMS 120 volt line voltage is taken from the zero line to the peak of ONE wave of the A/C waveform (the other wave is at zero when the 120v wave is at peak). If you take a reading from both the negative and the positive going waveforms or peak to peak this is 220 Vac RMS or about 311 volts peak to peak. The household 220 volt line is just what you get when you have two 120v lines 180 deg out of phase with each other. You zero line is now at -120 Vac RMS.

You don't get 82 volts ever with any kind of direct rectifying of 120 Vac. You can double the voltage with a voltage doubling rectifying circuit and get about 311 volts DC but thats not what you want. The lowest filtered voltage from 120Vac you will get is about 172 volts DC.

If your motor controller can handle a 172 volt supply voltage then everything is fine. This has been a problem forever with high power audio amps and many other devices. They often need 100V or even 130 V DC but you don't get that without a transformer or zener diode type of voltage regulator. Many transistors have a max junction voltage of around 90v to 120v so they can't be used with a 172 volt DC line.

Would it be possible to talk volts in a new topic?

There's a lot involved...spindle power, type of tool, machine rigidity, material, surface finish, tolerance, level of drunkeness....

Not to sound cryptic, but there's no real 'standard' to reference. This and other cryptomes are 'solved' for you with RoBLOKS, since the machines are 'standards'.

I could tell you values based on what I use now, but they wouldn't mean much since the machine I use is only a 'crutch' to RoGR.

600IPM is useful though...printing and plotting come to mind. You'd really need ball-screws though!

The direct rectifying power supply idea of RoBlocks is a unique concept for the machine. All the other large gantry routers have a huge power supply to power their machines and RoBlocks would be the first to remove the transformer.

I think the servo drive system is also the last major unsolved problem of RoBlocks.

Direct rectification presents some special problems but you need to start with the correct values in order to solve them. (This statement will not make me vary popular .) Half wave rectifying will give you around 172 volts DC not 60 volts DC. I think the servos can take the voltage but the driver transistors on the controller board won't. I do have the part # for a 61A transistor with a 500 Vdss rating they are about $22 each and you should need 4 per motor so the cost for the whole system will be higher than you would want. I could look for some lower power FETs but the Vdss will have to be at least 200 to last.

There is a lot involved in a power supply and controller system a separate thread might be in order.

600IPM is crazy fast the guy I use to cut cabinet parts uses 200IPM on his machine and that thing is a two ton hunk of steaming funk. 600 IPM would cause all knda hell on tooling pieces of carbide shrapnel flying in the shop.. wingged out angular momentum gyroscopic forces

When talking about plain, non-smoothed rectification, the DC always measures as the RMS of AC (115v full-wave, 57.5v 1/2-wave). When smoothing caps are added, DCV out will rise to near AC peak, which is 1.4x RMS. I'm not concerned though: Let's do the numbers: 115v(mean) x 1.4 = 161 VACp. 161 x .80 = 129VDCp (bridge is only 80% efficient) 129 x .90 = 116VDC (~10% is lost to smoothing cap and bleeder R). Right where I wanted to be.

PS; several 200v h-bridge packages exist with many cool features! Almost plug n' play.


Gyroscopic forces!

Without getting into a discussion over properly wired American household power...... un-smoothed output from the bridge rectifier is 106vdc when plugged into the wall. Didn't bother to measure AC ripple or anything like that, but..... It's 106vdc. power at the shop is actually 120vac (as opposed to the more common 110-115vac), so subtract accordingly.
Which still makes it a bit hot for almost all drivers and off-the-shelf H-bridge chips (the Doug Phelps board uses IRF540s which are rated to 100vdc, which makes me wonder)..... Fortunately there are other solutions, and while not cheap, power transistors can be found in the 200v 15a range for not too much $$$...


Robin

Am I getting the sense here that us Europeans actually have an advantage of brute force when it comes to electricity?

Only if your voltage is delivered with the same amps. Our "common" household circuit is 15A @115V.

Hi Robin, The voltage should be 96V with only the rectifier. I remember measuring 106 after the SCR chopper (which certainly has a smoothing cap) and rect, did you measure the rectifier-only V later? If so, our rectifier is beating the odds (.8 eff), or the standard formulae are failing us.

Quite a few options here...I've been pining for a 4227:

http://www.mskennedy.com/client_images/cat...iles/4227rc.pdf

Brain,
Been following this thread with much interest...
I havent seen anyone mention IGBT's yet so hopefully this won't send you out on a wild goose chase but I seem to recall that they were the favored option for power switching - they are typically used in VFD's (variable frequency drives/variable speed drives) and other industrial type motor controllers.

Also the 80% figure for the bridge rect sounds like a full load approximation, off load these should only drop 1-1.2v (forward voltage across 2 diodes). I think

Cheers

OK, I see were you're going with this. My apologies Brain. Yes the peek voltage is going to be MUCH higher than you need, but the RMS (or average voltage) is around the amount you listed. So yes, we were both right, however you were talking apples, and we were talking oranges.



Cant wait to see it finished tho!

David

Hi MJ, IGBTs are considered depending on the quotes I get on the packaged h bridges.

Let's see, I learned that full wave rectification has a max of 80% efficiency. The first google hit returns;

... The maximum efficiency of a Full Wave Rectifier is 81.2%.


Apology not needed, but accepted with thanks.

Voltage:

I realized later that I was wrong to use .81% as the voltage drop. Our measurement of the voltage for full wave was 106v, which is .87% of pre-rect RMS. Since efficiency is a measure of heat dissipation, the 81% number should be applied to I, not V, but it only adds a few volts to my former equation and isn't significant to the outcome of the amp.

Robin stands vindicated!

Oh yea! I got a quote on the h-bridges, $90 each! OW.

screeeeeeeeeeeccccccchhhhhhhhhhhhhhhhhhhhhhhhHHHhhehhhhHHHHHchHH

Robin, how much were those 'FETS again?

KOS should be pleased to know the Z assembly is being prepared:

Click to view attachment

KOS is pleased!


Okay okay...


Pleased KOS is!

More properly:

Pleased KOS be. Assembly Z together nicely comes.

Does Yoda salivate (drool)?

Brain,
I see you have alot of these UHMWPE blocks threaded for your (pardon the ignorance) pulling nuts. How are you tapping these? Are you using an ACME threading tap? What is your success with this?


MyYz400

Yes using an Acme thread-form. The tap works fine, but UHMW is gripey stuff!

No pics to show, but got some more done on RoGR. The motor mounts were causing issues, as part of my design criteria was ease of assembly for the end-user, with just a few critical parts from LL. Practically everything I tried required the end-user to have a real lathe, or to do difficult drilling of >1" holes through steel pipe. It's just too painful to expect someone to do this in their garage, yet RoGR must be completed in such an environment as this is my vision.

For two weeks I've stewed over this; problems like these cause me pain, discomfort, oily discharge and void where prohibited by law.

I can be an uncompromising person at times and therefore I may reject handy solutions for their lack of "elegance". I had to accept that this is one of those times and move on.

With this resolution, the design picked up again, and freed from the tripping constant became something I actually like...

Indeed it is. Either 10A or 16A @ 240V, depending on the wiring (wire cross section). Of course, the serious DIYer also has 3-phased 380V, 16 A in the workshop.

... sooooo, please consider a power supply solution for us, too, preferably of a non-selfelectrocuting sort.

Our wiring also has two live wires and a separate neutral (ground).

Is it really "common" for one to be able to get a 3-phase service entrance there? Around here if you live off the beaten path it's a bit of a big deal to bring in 3-phase. That's more of an industrial/small business thing.

Here in Oz it’s not a big issue to get extra phases ran to your house, it will cost though. Our garden variety GPO is 240VAC 10A. It’s officially supposed to be 230V but the power companies run it at close to 240 to stay within the tolerances. You can have 15A GPOs and I’ve even seen them at 20A. The earth pin is larger on these types to prevent anyone plugging in a high current device into a 10A GPO. After 20A the device needs to be hardwired in. We use allot of split system air conditioners here, my last house had a 60A surge and 30-40A running current on the air-con alone.

DJ

Well, I had all three phases coming straight into my fusebox (connected in 1976, no less), so it was only a matter of paying an electrician an obscene amount of money to string the wires from the box to my (inhouse) garage and mount a socket on the wall.

If only two phases had been present in the box, I'd have had to get connected to the nearest junction box. That would have been expensive. But more and more people choose to have it installed now - you just never know if a big hunk of a welding machine or something turns up cheap.

I have three phase but at the moment I changed the Air -A/C to a 220 single phase so I have no 3 phase components running right now.

The third phase is used almost always to start large inductive A/C motors. There is 3 phase welders but thats mainly because that is what is all over the shop. My A/C was three phase and it had no start cap, that is what the third wire is for, it is set out of phase to get the motor turning.

For a 220V setup in the USA both wire are hot and most of the time no ground is used! The current is the result of the two waveforms being 180 deg out of phase.

To get 110V you just use a real ground and one leg of a 220V wire.

If you have 220V I would think if you wanted 110V you would just have to find a true ground wire to get 110V. A meter connected to ground will show the voltage.

There is a chance they just used a single 220V line which would bugger up the idea of just using one leg.

A riddle:

What arrives in a coffin,

weighs more than a car,

is stiffer than stone,

and travels very far?

umm.. a shipment full of bearing kits?!

How'd you guess?

Yes they are here, but I'm not ready to ship them! The wooden cases were supposed to have screws but came with nails, so I have to "bolster" them. The one going all the way to Denmark will certainly need special attention. I've had the servos for weeks now, but I didn't ship them since we were waiting for the bearings. There was one person who didn't want to wait...sorry! You're on "the board" with the rest, and it took me until yesterday to find out who you were! Blah, help wanted!!!

Click to view attachment

Oh yea, the 30mm ways finally came too, man look at those fatties! They make 25mm look downright dinky. These are in your bk if you ordered from this batch...but after moving 1500lbs around for a few kits, I'm not sure I can support this (at all)...and at the price I'm charging is a bit suicidal!

Click to view attachment

I'm not sure which batch I'm in. How do I ensure that I get the 30mm ways?

I'm curious, how are you testing them for straightness?

-Brian

You're in the first wave (I think), but I haven't ordered any lower spec so you are granted 30mm.

For the straightness: We use the Hasselhoff test to insure 100% straightness. This test is the most accurate in the industry and I assure you, we have the straightest shafts in the business.

Um, I'll take your word on that!

-Brian

I wonder what they used before this new standard came in?

are the bearing kit shafts cut to size? or will we have to do that ourselves?

I worked in a shop many years ago that had bad results with the Hasselhoff test, perhaps we were just using it incorrectly but I suspect our crew lacked the background to appreciate this alternate approach (which was little talked about at the time). We ended up with a high failure rate on shafts that subsequently tested OK using more conventional procedures. In the end, we did find which shafts were compatible with the Hasselhoff approach (it was impossible to correctly identify these by visual inspection, but oddly a high percentage were of German origin)

Unfortunately, incompatible shafts that were repeatedly subjected to Hasselhoff testing often required extensive re-alignment and hardening. Initially we attempted to handle this aspect in-house but the only employee qualified to do this work quit when faced with her additional work load. To boost efficiency and morale we sought out an outside specialist in this area and got lucky when we located a true professional. We eventually satisfied everyone on the shop floor with this new setup, but overlooked the drain it was having on productivity.

When the boss found out about all of this he nearly fired everyone but ended up just sacking the contractor.

Of course, this was many years ago and I guess it's a different world out there now.

Yes, it was discovered that without proper sheilding, Hoffian radiation would cause even the hardest shafts to sag, some shafts even shriveled and shrank! OSHA now recommends proper sheilding of shaft workers prior to exposure.

Just wanted to point out something that's obvious in person but isn't obvious with the above picture of the 30mm way on top of the 25mm way................
25mm diameter ways= about 491mm2 cross section.
30mm diameter ways= about 707mm2 cross section.
A cross-sectional (and general) size increase of about 1.44 times.
This translates into more rigidity and higher tolerances.
At first I thought the ways had been cut to the wrong length... But really it was a matter of proportions playing tricks on me.

Eh? You mean they looked longer 'cause they were fatter?

Question: was this shipment covering the first batch (which as I understand was sold out some time ago), with the next batch due to arrive Aug 30th ? Eg .... if I order one now , when would it ship ?

eh, I think ill order it now regardless and let it sort itself out

That's what she said.

bloody fantastic. I will definitely be in for a kit when completed....
How much longer till this is finalised for commercial release?

btw, greetings from Sydney!!

Hi Phife,

The ways are cut to the RoGR final spec, so if you build this exact machine you won't be cutting any shafts (a good thing since cutting hardened tool steel requires some equipment..).

For those so inclined; The ways can be cut to your dimensions if you have another design in mind.


Every time I make an estimate, I'm wrong. I know we don't have any extras from order #1, actually far from it...I've been agonizing over taking one of the kits for the 'house', NEED 30MM...BRAINS BRAINS! Ahem, whoa! In truth these things move slower than Absolute Zero. I think this is reflected in the price though...enjoy trying to buy a 5' length of 30mm ground-chromed shaft which easily would cost more than the entire RoGR BK.


Howdy, by commercial you mean the whole kit (everything for RoGR) or the bearing kit, which is on sale now?

This is awesome cheese!