Spindle runout correction in CAM

[DMC]

If any of you have mill that costs less than $100k....you may want to invest in a high-quality tool to measure spindle runout.

You are using a 2mm tool for roughing for example, but I seriously doubt you have concentric rotation of tool.

You need to add the runout value to the tool diameter in the CAM

So, you may be entering a false value for tool to compensate for poor spindle.

You may end up with virtual tool diameter of, lets say 2.09mm to achive better results.

You don't know, unless you measure! Your reseller should be well versed in this and aware of problems/issues with incorrect set-up of CAM.

Poor tool life, poor fit, and broken margins are an indication of this problem, or you can just stick your hand into mill and feel the tool shank.

Does it feel like it's not even spinning? Or serious vibrations? You really should know...at all times.

Just my $.02

Scott

 

[DMC]

Measuring spindle runout

http://www.ebay.com/itm/MITUTOYO-ID...342?pt=LH_DefaultDomain_0&hash=item3a6a712dbe

You need to be able to Jog CNC mill's Z-axis into good position to measure.

Maybe make custom G-code file to make this happen?

 

[DMC]

Did your CNC mill come with specific tools to clean the collet? (chuck as you may call it?)

You need to maintain that. Prevent corrosion from humidity in compressed air lines and to clean out Zirconia/wax particles.

A small amount of Grease or something would do the trick. Very small amount for the corrosion, but this also makes dust sticky, so it's a trade-off.

Your tools will have all sorts of dust on them. As the mill changes tools, this crap gets packed up in the collet, or tool holder.

Spindle runout will be more and more. The collet needs to be maintained all the time. Once a week maybe examine this part, and even pull it out on your bench and inspect it. I do this with my Lava mills all the time.

 

[tap]

Scott
These are very wise recommendations that I bet not everyone follows--we call them PM's where I work (preventative maintenance) and we usually shut down 4 hours per week to perform them. Usually an OEM will supply a list to follow for such items as grease points, air pressure settings, etc. They should be followed to the letter for warranties and peak performance--especially when I see how much coin you guys are dropping for these mills--wish I could play with toys like that but that's not in the bankroll for now. I enjoy reading most of your posts and you sound like you know how to handle success--wishing continued good luck to you! Keep yer collets clean and yer runout low!
Tim

 

[DMC]

Yeah, but for some of the cheaper mills on the market these day, I doubt the PM is as extensive as it should be.

The training, service, etc just can't be amazing for that price.

 

[DMC]

The KaVo and many other high-end mills have a Laser tool setting device that will measure not only the tool lenght, but also the diameter of tool as it spins. This value is applied by the CNC controler and overrides the CAM instructions and makes on-the-fly correction to G-code.

This is another benefit of fancy CNC controler.

The cheapest mill that I can think of that would have this as option is the Haas OM2-a. Otherwise you need to do this manually on occasion if you want maximum accuracy of finished part.

Scott

 

[Vazone]

Yes, we make it each week! We have special jäger kit for cleaning and lubrication. Manufacturer also recommend us to use ultrasonic for cleaning chuck

 

[DMC]

Nice. That's the ticket!

I like the Ultra-Sonic idea. I will do that also.

Maybe use WD-40 and NOT water?

 

[Vazone]

you use wd40 for lubricating ?

 

[DMC]

No, it is not really a good lubricator.

It is good at displacing water.. (hence the name.....Water-Displacement....40th trial)

It is good solvent and cleaner and prevents rust.

There is no need to grease up the collet.

You do not have access to the spindle's bearings, unless you remove from mill and take it apart.

Many people are so cornfused about the need to grease the spindle/collet area.

You cannot grease the bearings while spindle is in the mill. The Collet only moves a millimeter or so up and down for tool changes only.

You really do not need to grease that area all that much. Only a wee-bit, or not at all. Usually there is an o-ring to prevent dust from entering the internal of spindle and that seal does not really need much lube at all IMO. It is rubbing on a super smooth surface, and is NOT spinning against another surface or creating friction during milling.

A simple exploded view of the drawbar mechinism of most spindles would help better than words, or take apart a spindle and see for yourself?