OT - but look at the specs on this one.

http://www.physikinstrumente.com/en/products/prdetail.php?sortnr=700800

Also it the velocity range 0.001/min - 0.00025/min or really 0.001/m  
-  0.0025/min?

Dave

On May 23, 2008, at 5:13 AM, [EMAIL PROTECTED] wrote:

> all grinders have linear incoder and all feed back comes to  
> computer not
> from revolution of ball screw but from actual move of the table. in  
> that
> case the accuracy of ball screw can not make table move faster or  
> slover.
> grinder usually program with 0.001-0.003 per minute when grind  
> ceramics.
>
>> Aram,
>>> From your numbers it could take over a month to traverse the  
>>> entire table
>> and perhaps four days to grind a single end mill. Does this sound
>> excessive
>> to you?
>>
>> On anther thread, you say accuracy is not as important as speed.   
>> Do you
>> mean smoothness of travel is more important than accuracy?  Why?
>>
>> Glenn
>>
>> -----Original Message-----
>> From: [EMAIL PROTECTED]
>> [mailto:[EMAIL PROTECTED] On Behalf Of
>> [EMAIL PROTECTED]
>> Sent: Thursday, May 22, 2008 9:36 PM
>> To: Enhanced Machine Controller (EMC)
>> Subject: Re: [Emc-users] Harmonic gear and EMC2. ????
>>
>> Machine make up to 1 inch in diameter and 6 inch long end mill.  
>> max travel
>> is 12-13 inch
>>
>>
>>> Aram,
>>> What is the total travel distance of the grinding table?
>>> Glenn
>>>
>>> -----Original Message-----
>>> From: [EMAIL PROTECTED]
>>> [mailto:[EMAIL PROTECTED] On Behalf Of
>>> [EMAIL PROTECTED]
>>> Sent: Thursday, May 22, 2008 6:59 PM
>>> To: Enhanced Machine Controller (EMC)
>>> Cc: [email protected]
>>> Subject: [Emc-users] Harmonic gear and EMC2. ????
>>>
>>> I am building CNC tool grinder.
>>> The feed for tool grinder should be from 0.00025 to 0.001 of the  
>>> inch
>>> per minute.
>>> The servo motor must perform at this feed perfect to make a good
>>> grinding job.
>>> I will use direct drive and my ball screw has 5  pitch per inch.
>>> So talking in degrees, 5 times 360 = 1800 degrees of revolution of
>>> motor to get 1 inch for linear motion.
>>>
>>> To get 1 inch need turn 1800degrees/minute of motor.
>>> To get 0.00025 need  0.45 degrees/minute of motor.
>>> Is this too slow?
>>> I think so.
>>> The one solution is to take high end controller and large AC servo
>>> motor and that is expensive.
>>>
>>> Jon Elson said about harmonic drive. I found here
>>> www.harmonicdrive.net That gear can reduce up to 1 to 160. If I will
>>> put two side by side, it gives to me 25600 to 1 reduction.
>>> So 0.45degrees/minute times 25600 equal 11520degrees/minute, or 32
>>> revolution per minute.
>>> 32 revolution per minute is good range to any AC servomotor and with
>>> 8192 pulse per revolution drive and EMC2 will have enough pulses  
>>> to be
>>> accurate.
>>>
>>> All harmonic drives have 0 backlash. One piece for NEMA34 cost $1500
>>> and per axis it is $3500 with special plates etc.
>>>
>>> 5 axis is $17, 500 is to gears a lone to make good CNC tool grinder.
>>> I think it is very good idea!
>>> Instead of making electronics part and programming more  
>>> complicated (
>>> and not all can understand that part - I can not for sure) it is  
>>> much
>>> better use mechanical gear reducer and use less expensive and more
>>> robust drives and software.
>>>
>>> I am correct?
>>> Aram
>>>
>>>
>>>
>>>
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>>
>>
>>
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