Getting frustrated Mega Vibrations

[richards]

(Moved from Test area by admin)

What you're describing seems to be the classical "missing step" problem. A stepper motor that is being ramped too fast or being driven too fast will "miss steps". Usually, missing steps makes a lot of noise.

Here's a quick and easy way to test the motors. Drop both x-axis motors so that their pinion gears do not touch the teeth on the racks, then run the motors at various speeds. You'll be able to run the motors faster than normal with no load, but you'll get an idea how long the ramp has to be to get to maximum speed.

From your post, it looks like you're running the original stepper drivers. Those motors connected to those drivers were not designed for high-speeds. After talking to other 'botters who used those motors and those non-Gecko drivers on their machines, they normally stayed at 2-ips or less.

[roney c]

Ok here goes,
Refurbishing my year 2000 PRT 96
Control board - original
Ver 3.4.27
Computer decent w/USB to serial
PK299 01AA
Whats been done so far:
(lost about 70% of my vision over the past 2 yrs, so this all takes me 4X longer to do then in the old days, so please bear with me)
- touch up rails w/file - Check
- X gantry rolls smooth - Check
- Y car rolls smoothly - Check
- new pinions on - Check
- MEGA VIBRATIONS - Check, Check, Check!
- spent hours messing and reading EVERY relevant post on this fabulous forum.
Here's whats happening;
At any speed above 4ips, (6ips is of course max speed), the X gantry will move out through the ramp and will then make a grinding sound as though the pinions were eating up the racks and the gantry stops moving however the Y car is quiet and for the most part smooth. When I run @ 3ips or slower there is the usual resonance but the entire frame vibrates, I can even feel the vibration through the concrete floor! Please Help, as this Shopbot is going to be seen in operation by hundreds of people as it in a incubator/education facility and although faster cutting would be desirable, it is not primary goal, smooth vibration free cutting at 2ips would suffice.

Thanks to all in advance.
Roney Conca
Botter since 2000

[bleeth]

It sounds like you may be a bit out of square or one rail is out of level with the other. You also may have your turnbuckles too tight. My max jog on my PRT was 4ips with original drivers. The more I tweaked with squaring and levelling the less moans and groans I got. Having disassembled, moved, and rebuilt can easily mean that you have some re-shimming and adjusting to do to ensure the rails are straight on the C-channel as well. The nice thing about a bot is it doesn't take long to put it together but the flip side is getting that state of level, square, and parallel just so can really take a bunch.

[roney c]

Dave, I've been reading everything I can about this issue and see that you were having speed issues as well. Would you care to update us as to what resolutions you have considered / done to your bot, also what year / make is it? Thanks. In response. To your post, tomorrow I'll do my best to relevel. I have this visual issue where Aided or un aided i can only see 2" distance with my left eye (thats how i am able to use my iPhone to read and post on here) and no distance beyond that, whereas with my right eye I can not see anything clearly especially close-up and what I can see is mostly distorted (sigh). Soooo, I do the best I can AND that's designing on a computer using my left eye up against the computer screen, toolpathing and cutting it out on my Bot. I enjoy the hell out of this ability to still be a productive part of society. However when one has to get ones eye within 2" of EVERYTHING that has to be done to reset-up my bot it takes me something like 5X as long as before, but some things are just impossible. So I just try to deal. To Ted, Frank, Dianne, and Brian at Shopbot thanks for such a wonderful machine. And to the SB family, whose threads, posts and general good sameritaism make having a bot even better.

[bleeth]

Roney: I don't consider what I have experienced to be speed issues as much as speed limitations. I have paid attention to all of your posts and empathize, understand, and respect the personal issues you are dealing with as well as your phenomenally admirable attitude in accepting and moving on. The unsaid frustration must be huge.
Unfortunately I am many miles from you and therefore can only offer advice from afar.
I remember well when I was a new Shopbotter and I had an issue that seemed overwhelming to me and after posting about it another botter who used to live in my area came over after his own work day was through and spent hours helping me straighten out my problem and helping me through it. I hope that someone nears you emulates him.
I bought my Bot around 2005 or so a bit before the first Alphas came out. It was originally a PRT with a 5HP Columbo spindle and the motors are geared standards that are the same motors on a new PRS standard today.
I will not say that the upgrade route that I took was the best or the only as I know others who went a different direction and have accomplished excellent things.
Two of the tools that have been a great aid to me over the years in adjusting my machine at setup and/or re-adjustment time have been a tried and true straight edge (or two) of decent length and a digital level. For the straight edge, believe it or not, my favorite tool is an extrusion designed for wallpaper hangers. They are dead straight and sturdy enough to last for years. I used them in my first set up and ever since, but then it is second nature for me to pick one up as I worked as a wallpaper hanger many years ago and have been using one ever since. It helped me tweak my rails straight as well as act as an excellent bridge across my machine to put a level on.
As far as the level is concerned; there is no way that a bubble level can be used to properly level a piece of equipment like this. It can only get you close. I say that from the point of view of someone who used a bubble level for quite some time and after I finally broke down and bought an adequate digital level ended up with a machine that ran faster and quieter then it had before.

Hang in there guy. You are fast becoming another in a long line of heros to me.

[myxpykalix]

RONEY,
I HAVEN'T HAD MUCH ISSUES WITH MY BOT BUT YOU MIGHT THINK ABOUT GOING OVER AND CHECKING ALL THE POINTS OF CONTACT.
THE WHEELS AND RAILS
THE RACK AND PINIONS

RUN A FILE THAT YOU KNOW YOU HAVE THE ISSUES WITH.

THEN TAKE THE STEPPERS LOOSE SO THEY DON'T TOUCH ANYTHING.

TRY TO ROLL YOUR CARRIAGE UP AND DOWN YOUR TRACK TO SEE IF YOU HAVE ANY ISSUES RELATIVE TO THE RAILS AND WHEELS

THEN TRY TO RUN THAT FILE WITH THE STEPPERS UNOBSTRUCTED AND WATCH AND LISTEN TO SEE IF YOU HEAR OR SEE THE SAME ISSUES.

IF THE GEARS IN ONE STEPPER ARE BAD I COULD SEE HOW THAT MIGHT MAKE YOUR CARRIAGE BIND UP. CHECK THE PINIONS WHILE LOOSE AND THE CONDITION OF THE RACK TEETH.

IF THEY HAVE NO PROBLEM THEN I WOULD TIGHTEN THEM BACK UP AND TRY IT AGAIN

IF THE PROBLEM PERSISTS THEN AND IT IS NOT THE GEARS IN THE STEPPERS THEN THE ISSUE MIGHT BE THE RELATION OF THE GEARS AND RACK. MAKE SURE THE TENSION ON THE TURNBUCKLES IS NOT TOO TIGHT.

ISSUES RELATIVE TO LOOSING STEPS I HAVE NO EXPERIENCE WITH.

I HOPE YOU GET YOUR PROBLEM SOLVED UNFORTUNATELY I AM IN VIRGINIA AND CAN'T PHYSICALLY HELP POSSIBLY ONE OF YOU NEW YORK BOTTERS COULD LEND A HAND?

[Brady Watson]

Roney,
If you are experiencing jerkiness on both X and Y, then it sounds to me that your computer is not able to put out reliable pulses fast enough at those speeds - AND/OR - Your motors are out of torque at that speed and they are stalling. Keep in mind that even though the control software allows you to set your move speed to 6 IPS, that it is impossible for a 3G PRT to go any faster than 4.5 to 5 IPS in all actuality. Take a stop watch & time it going a long distance and you will see.

Your tool was originally run on DOS, which would max out the tool around 3.5 IPS - which is really about all a 3G PRT is good for because torque falls off very quickly. SB3 offers much better ramping which smooths the tool out a bit and also lets you go a little faster...but speeds should be limited to 3 IPS for reliability.

The speed of your computer is important too. If you have a 1GHz or better, with no nonsense software on it, you should be fine.

Going forward, if you want to really get that tool where you want it to be for speed, resolution and overall reliability, I would encourage you too look into a 4G control box. You will instantly pick up 2.5x finer step resolution and about 2x faster speeds with higher reliability. The 'diesel' motor resonance that vibrates the whole tool will be a thing of the past, except at very specific speeds (because of mid-band resonance inherent of ALL stepper motors) - but overall it will be a MASSIVE improvement over what you have.

-B

[roney c]

Hey guys thanks for all the support.
-Dave, those are very kind words indeed but I'm afraid I'm not hero material, just love being able to get back out into the working world after aprox 2+ yrs of not being able to. The shopbot is my last remaining TOOL that I can operate safely and accurately. Ex. Tried to drill a 3/8" hole (one of 4 needed to attach the new SB supplied PC router bracket) and even with all the preparatory careful marking using digital calipers et al, the hole STILL ended up 1/8" off in both directions haha (really chuckling here) whata ya gonna do? But not my Bot, she cuts, drills, shapes, and just DOES everything right. Can a human love a machine? But, I digress. As far as straight levelers go I hunk I've still have in storage back in PA 3 alum 2X3 ( I ) beams, hmmm. Im going to do a search for a decent digi level now.
-Brady thanks for getting involved. Between you and Gary, Dave and Jack, I feel like I'm being coached by the SHopbot Allstars! That being said in all humility, I want to do the leveling and then if you don't mind discuss further the part you said about upgrading.
- Jack, I do believe my pinion is too tightly tensioned am. Gonna loosen them a bit and test.

[cnc_works]

Roney, I have had similar experience. My rails are worn and really should be replaced. When I rapid anything over 200ipm it stalls or loses steps, etc. If I keep my rapids under 200ipm...no problems.

Good luck in troubleshooting. I know when you are alone (physically anyway - the forum is great company) all the possible variables can drive you crazy. Sounds like you have the patience to deal with it, though.

[roney c]

OK! Came into the workspace this morning and did a few 30" runs on the X direction and threw my hands up in discust. Then I followed the advice given about loosening the spring tensioners and dropping down the motors so that the pinions were no longer engaged and ran the same 30" trial.....and as Gomer Pyle used to exclaim, SURPISE SURPRISE SURPRISE!!! the motors weren't skipping or otherwise acting weird. SO, again I did what was recommended and engaged the pinion gear and retensioned the spring BUT not too tight, greased the racks and as Gomer used to say Voila! Bot has been air moving quietly @ 5ips with mid-band harmonics coming in bet 3.5ips & 2.5ips. Still have to reinstall the part on the Z axis that I removed in order to put the new PC holder on....many thanks to you know who you are...more later