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Author Topic: tool force compensation  (Read 4141 times)

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Offline RICH

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Re: tool force compensation
« Reply #10 on: December 04, 2010, 07:43:23 AM »
Quote
Is there a way to compensate the path for the forces on the tool?

Yes and here are some examples:
For  drilling .010 holes  a peck drilling cycle was used and had a dwell time at just below the surface to allow the drill to center itself and then peck in small steps
along with the appropriate feedrate as to not bend or allow the drill to deflect.

Drilliing thru a hardened piece of stock RC 55-60 a 1/2" carbide spade drill was used with a slow but constant feedrate.

Drilling a 1 1/4" hole in steel plate a center drill hole was first used, and then progresssively the drill size was increased.

My point is simple and echo other replies. The work piece must be held appropriately, correct tool for the application, and appropriate feedate rates ( manual or computer controlled),
and practical judgement applied to the task.

You will never drill a sized hole when the material is deflecting and trying to compensate for that is just a waste of time.
Your going to get hurt or possible create an uncontrolled situation because of ignorance on your part.
Sorry, care about your safety  and not your personal feellings. ;)

That said,
You can calculate the forces for metal but to my knowledge there is nothing available for wood. All the calculations are subjective and used along with
engineering judgement.

RICH
Re: tool force compensation
« Reply #11 on: December 04, 2010, 08:15:10 PM »
Hi all,
I use my CNC machine for mostly cutting relatively thin (0.050" to 0.100") aluminum face-plates for electronic equipment. My tool of choice is 0.093". I rarely use the CNC for straight drilling. However now and then I cut thicker 6061 aluminum. Attached is a picture of a bearing block I just cut that will be used to replace the Delrin blocks of the same shape on this machine. One is 0.625" thick and the other is 0.75" thick. I am hoping that these will add a modicum stiffness to the gantry system. I find that the plastic blocks keeps relaxing and needs frequent adjustment. The CNC machine has trouble cutting a piece of material this thick without some drift. The latest blocks were cut reversing the cut direction on each pass (a new experimental technique for me), at a cut depth of 0.008, and I had very good results. The blocks are about 0.005 over sized as a result of tool not holding the desired path. These parts don't need to be any closer than that so I am pleased with them. Had I cut these in only one direction, they would be a good 0.025 over or under depending on the cut direction and exhibit a some taper.  

I am in the process of replacing the wooden parts with aluminum stock, in the mean time I would like to try to compensate for the flexing that the wood permits. I just hope I don't have to replace the steppers to push the extra weight after it is all modified.  

I haven't tried the function routines yet, but I will get around to it some day soon. This is not my day job.
I appreciate all of your input on this matter.

Thanks, Bill