Nasty resonance / rattling - possible assembly error?

[MitchL]

Great info, thanks!

I haven't peeked in the control box yet - my comments were basically the hobbyist in me looking at a machine to tinker with :-).

But: this isn't my machine, it's owned by a school district, and eventually my sons will graduate, meaning I'll be moving on. So, over the years if we add upgrades, they should be official ones that ShopBot will support.

I should be able to spend a little while with the machine this evening to see if it's square and true, everything's tight, etc. Will report findings.

/Mitch.

[MogulTx]

Mitch,

If you can follow Dave's suggestions, you may well be done. If not a call to Shopbot is definitely in order... and as he says- the support is for LIFE and it is pretty darn great, too.

I would not upgrade a PRS to a PRS Alpha unless you are in a production shop environment and found yourself using up all your available hours in actual cutting time. There is little opportunity to recoup the $ unless you are able to speed the machine up significantly.

For what you are probably going to be doing, this is the right machine. If anybody ever gets antsy for increased performance, a spindle ( vs the router) is probably a much better investment.

Good luck.

Monty

[Brady Watson]

That sounds like mid-band resonance, which happens to a degree on all stepper based systems, even Alphas. Try changing your move speed to something a little faster, say MS,2,1 and see how that sounds. Certain speeds will sound like that - not much you can do about it.

Without seeing your control box, I cannot see what motor drivers you have. If you have the Gecko G203 drivers, you can adjust some of the resonance out on the driver itself.

The important factor should be how the tool cuts & what the cut quality is. My original SB sounded like that, all day, every day. It made me lots of money and then I upgraded to an Alpha.

-B

[MitchL]

That sounds like mid-band resonance, which happens to a degree on all stepper based systems, even Alphas. Try changing your move speed to something a little faster, say MS,2,1 and see how that sounds. Certain speeds will sound like that - not much you can do about it.

I agree, I think this is the way it is for me. I've been in touch with ShopBot support (great service!). They had me check a few things (connectors, wires). Everything looks good.

I played with feed rates. Speeds <40IPM sound great. Speeds >90IPM sound OK, except during the curves, where the steppers need to pass through the 60IPM barrier. It just happens that around 60ipm is the good place for feed rates with a 2-flute cutter in aluminum at 10K RPM. I'll try some more experiments, like 90IPM/13K RPM.

Our controller has the Oriental Motor C006Q-044 step drivers inside, and the Oriental Motor A7238-9412KTG steppers and gearboxes on the carriages. I believe our ShopBot is pretty "plain vanilla".

Without seeing your control box, I cannot see what motor drivers you have. If you have the Gecko G203 drivers, you can adjust some of the resonance out on the driver itself.

Yep, I use 203Vs on all my home CNC builds -- my go-to standard.

The important factor should be how the tool cuts & what the cut quality is. My original SB sounded like that, all day, every day. It made me lots of money and then I upgraded to an Alpha.

You can feel the vibration in the head when it's rattling (even on air cuts with no spindle power). Since I'm cutting aluminum, and taking very light passes, it really shows in the bottom and side walls of the cut. When the resonance gets really bad, it sounds like chatter, then I start to get nervous.

Thanks all!

/Mitch.

[bleeth]

A relatively low cost upgrade would be the 4-G (Shopbot Gecko), if SB is still offering it. Their current upgrade control box, which has a lot of very good reasons to do so, uses RBK drivers and is pretty expensive. Otherwise you may be able to find someone with a 4-G available to sell you. I believe the retail price was around 1400 or so.
Go down to my earlier post on getting it all square and level, tight bolts everywhere, and make sure your pinions are in good shape. I never tried aluminum on my PRT when it had the pre-gecko control box but Brady did and will likely have a better comparison.
I have seen other PRT's that were noisier running in air than mine was originally and I am convinced it had to do with how anally cumpulsive I was about physical alignment.

[Brady Watson]

Mitch,
I am not familiar with the stepper drivers that you list. Any chance you can take a pic or two of the control box, with some shots of the drivers? I'm a little tired from driving for 9hrs today...but to the best of my current (brain drained!) knowledge, there are only 2 types of oriental drivers that were offered from the factory: The AlphaStep drivers, beginning with an "ASD-" prefix, and the more recent Standard line of tools that have non-Gecko drives, that use the "RBK" series.

So - I am a bit curious to see what you have there & can make suggestions after I see it. If these are separate from the main board, then they should be step & dir drives, which means you can most likely upgrade to either a Gecko or RBK driver with a hotter power supply to gain some smoothness, resolution and power. The one caveat is that all drives need to have the same 'common' polarity, and depending on the board you have, you can change it with a jumper.

Thanks!
-B

[MitchL]

I happen to have photos of the drivers and the steppers:

They're definitely step/dir drives, the board that attaches to the front of the drivers has signals labelled as such.

I thought I had a vanilla picture of the inside of the control box, but I don't (the main board's part number is 090704). The USB interface says "Shopbot Tools Contorller V206").

Here are the photos that are still lurking in my phone:

/Mitch.

[bleeth]

The appearance of that driver is identical to the way the RBK's look. It could be an earlier model number, a precurser to it, or a "special" number assigned to ones for Shopbot. I don't think you have any reason to change them out. Check the settings on the two dials and make sure they all match. Also let us, or SB know what those settings are to verify they are correct.
The further along we go, the more I think your frame/gantry/car alignment is out of whack or loose, and your pinions may be worn, and your motors may not be tight enough against the pinions.

I'm still betting that if you dial all of that in your resonance will go way down.

[Brady Watson]

OK - Yes, those are RBKs.

See page A265; Function Switches [2]: http://www.orientalmotor.com/product...usa_st_rbk.pdf

It may take a little trial an error messing with the dip switches, but concentrate on one axis at a time to test for smoothing (say the Y axis). Don't fool with the dials & MAKE NO CHANGES WHEN THE POWER IS ON!!!

Start with SW2-1 and make no other changes. See if that smooths things out a little for you.

Yeah...A bit of a pain since you have to pull the main board off, but should be worth it. Take care when putting the board back on the drivers. It is really easy to bend or break pins. You are doing all this at your own risk. Be deliberate.

Post back and let me know how you made out.

Thanks!
-B

[Mayo]

At the risk of sounding obvious, before doing all the mechanical stuff,
have you verified that the unit values, speeds and ramp settings are correct?