Homemade balancing

[JeanMicheling]

Hello everyone,

We'll soon need to buy a balancer and a vibration analyser to run spindles up. But before to do that, I was wondering if someone knows an easy home made method to balance a spindle? Also, I'd like to know what would be the best quality/price system. I know I can have both the balancer and the analyser on the same device, is it reliable?

Thanks for your help,

 

[Mendit]

You need to decide what level you need to balance too. ISO 1940 can explain this but it can be difficult to follow. "rule of thumb" If part turns less than 1000rpm G6.3 will work for you, speeds between 1000 and 2500rpm G2.5 will do, faster speed yet G1.0 works OK. You may ask what the heck are the G numbers. Simply put in laymans terms. G6.3=39W/N, G2.5=15W/N, and G1=6W/N (API spec is 4W/N)
Parts are balanced to tolerance based on their speed and weight. Balance tolerance is expressed in force and distance. Oz-In, Gr-mm, Gr-In, what ever units you wish.
a part weighing 100lbs and spining at 4000rpm would be balanced as follows 100x6/4000=0.15 Oz-In or 4.25 Gr-in.
For parts which are symetrical and have 2 supporting planes divide these totals by 2. If your parts assymetrical or overhung use the bearing plane weight at each bearing for your calculations. Note these guys make the best balance machines

http://www.schenck-usa.com/index.asp

 

[corrosionman]

How big are your spindles ?
We built our own balancer to help get started many yrs ago.It worked OK till we found a perfect unit second hand, We still needed to buy the vibration analyser however. tell us more and we can advise. Cheers CM

 

[JeanMicheling]

I'd like to balance my spindles and also my tools. The biggest tool I have to balance weights 550 lbs and will be running at 3600 RPM. I'd like to have at least G1 precision but G0.4 would be great. I had an idea to build my own balancing machine. I found out in the mcmaster some static balancing ways (p.2147)

http://www.mcmaster.com.

I'd like to use them for dynamic balancing. Of course, I'll have to make sure the bearings can withstand the speed and loads. I'd like to know if I put the ways on a 2 inches thick rubber, I'll be able to have the required precision. I also thought using linear bearings with spings.

 

[Tmoose]

Ebay has vibration analysis gear from time to time.

This board does too, but you have to register.

http://maintenanceforums.com/groupee/forums/a/cfrm/f/4311004131

Modern spindle specifications include at least moderately detailed vibration analysis as part of acceptance testing. So, combined vibration analysis and balancing capabilities make a lot of sense.

A couple of acclerometers, a data acquisition board, software and a few more gizmos and you're in business.

 

[JeanMicheling]

I'm interested in designing my own balancing bench test but I just find balancing machines. I need the disks where the shaft is rested. I can machine them myself but I guess I'll have to balance them really precisely before mounting them. I'll but those disks on either bearing or bushing. I think bushing with grease would be better cause they are more precise? Can the bearing run-out could be a potential issue? I'm looking for a guide line to help me started. This is why I thought using the static balancing ways would be a good start but I'm not sure of their reliability on a dynamic application (over 1000 RPM). I found the data acquisition board, the sofware, but I'm struggling with the gizmos.

 

[Mendit]

IRD, once over sold a kit for making a balance machine I think it was called the B50F. They were soft bearing machines and you purchased from IRD the roller supports and axial restraining brackets, the motor drive belts and the pulleys required to make it all happpen, but that was 30 years ago, they also provided you with drawings to fabricate to.
From what I see on your needs, you need to get low tolerances this is required when you are working with high speeds you will need to be able to detect less than 1 gram inch of unbalance at low RPM. No easy task for the DIY.This guy has a Schenck listed on Surplus record etbalance@earthlink.net. Try your luck.

 

[Tmoose]

RE : balance tolerance and arbor shaft and bearings accuracy - page 4 table 1A here

http://www.irdbalancing.com/downloads/TechPaper1BalQualityReqmts.pdf

Depending on the operating speed of your spindles that chart will probably cause beads of sweat and furrows to appear on your brow. Special techniques to ensure repeatable centering will need to be instituted. It is not a trivial problem, and does not have simple solutions.

As a practical matter, if the roller diameter differs from the (perfect) journal diameter by at least 15% or so, the analyzer electronics can separate the 1X unbalance signal from bearing runout.

You may find that bushings have so much drag that a drive belt has a very tough time. End drives and precision balancing probably don't belong in the same sentence.

If you will be testing assembled spindles (and you should) you may need trim balance correction features at each end.
Many threaded holes for set screws makes a balancer smile.

 

[TPL]

Would it be possible to balance these items 'in-situ'?

You would need to install a once-per-rev tacho pulse (white paint mark or reflective tape) amd measure 1X vibration amplitude and phase angle with a relatively simple analyser (single channel is OK).

You can balance at operating speed. This setup should be more than enough to get installed vibration down to just about any level you care to achieve (based on time available) and removes concerns about balancing machine bearings/supports.

The first few might take a little time to get just right so that you perfect your technique, but after a little practice, you should be able to balance quite quickly.

Whatever route you go down - keep it safe - there's a lot of potential for damage (personal and material) when balancing.

 

[JeanMicheling]

I can't balance the spindles in-situ and I don't want to. My responsability is to provide a spindle well balanced and it's up to the mills to make sure the on-site operation is ok. I had a quotation for and IRD machine and I find that really expensive for what I need to do. I'll try to buy a software and maybe build it myself with the user fabricated kit they sell. Do someone know a good software for balancing? I'll maybe try to find a used machine.

 

[Mendit]

Perhaps you should out source some of your work, you can not always do it all yourself. Where are you located. We balance spindles for many wood shops and they are very pleased with our work and quality. tolerances are very low and sensitivity of machines is very important. If your spidle is 10 lbs and has a speed of 15000 your tolerance is only 0.0013 oz in per plane. Not easy for any one to achieve.