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Utility of Linear scale or glass scale in CNC milling machine for mold works

Floyd29

Plastic
Joined
Jan 29, 2017
Hi,

We are considering a vertical milling machine - YCM NSV for mold making.
Its C frame machine with 15K RPM & 45 mm roller guideways on all axis.
Should we go for Linear scale or Glass scale with added cost of 8000 USD?
We make injection & compression moulds for plastic & rubber industry.
Normally, we have found that the accuracy of 15 micron is good for our application.
How much does the accuracy increase with addition of these scales? Is it worth the extra investment?

Our second choice is Okuma Genos M560 which is H frame machine. Again with 15K RPM & roller guideways. However in this machine there is no option of Linear scale (as it comes with Okuma MB series machine which are out of our bugdet..)

YCM NSV with glass scale & Okuma Genos M560 without glass scale, which one would be more accurate in long term?

Thanks a lot.
 
Glass scales will help eliminate any thermal growth in your machine except spindle growth. Any machine with quality scales (heideinhain) should be more accurate than a machine without it.
My biggest concern would be YCM spindle growth (need to research if they have a good cooling system) running it at 15k making molds for hours.
 
Scales are a great addition to help improve accuracy of the axes, but as dstryr points out they are not the entire answer to dealing with accuracy questions. C frame machines can be thermally affected in the Y axis by head growth and Z by spindle growth.

The method(s) for managing heat generated by the spindle system (spindle and motor) and heat introduced into the head (hydraulic oil for tool unclamping, gear shifting if applicable) should be looked into.
 
Hi,

We are considering a vertical milling machine - YCM NSV for mold making.
Its C frame machine with 15K RPM & 45 mm roller guideways on all axis.
Should we go for Linear scale or Glass scale with added cost of 8000 USD?
We make injection & compression moulds for plastic & rubber industry.
Normally, we have found that the accuracy of 15 micron is good for our application.
How much does the accuracy increase with addition of these scales? Is it worth the extra investment?

Our second choice is Okuma Genos M560 which is H frame machine. Again with 15K RPM & roller guideways. However in this machine there is no option of Linear scale (as it comes with Okuma MB series machine which are out of our bugdet..)

YCM NSV with glass scale & Okuma Genos M560 without glass scale, which one would be more accurate in long term?

Thanks a lot.

@Floyd..

Do you have a specific link to the YCM NSV machine you are considering?

Off the top of my head (without further information) I would go M-560V as the basic thermal compensation for the machine is really well mapped out WITHOUT scales. Similarly MAZAK thermal map out their machines too. Obviously as a lot of "old salts" on PM forum have remarked over the years that scales are good for keeping a pretty old and somewhat "clapped out" machine mostly together.

Typically scales can increase part to part accuracy and in a lot of cases for types of machines we are talking here scales will only increase individual part accuracy by a "Smidge"*.

I agree with what everyone has said so far (obviously) ... Spindle/Z/Head growth should never be taken for granted or ever assume as a "Given" that it's not a problem until proven other wise. In think that is one of many good things about the Okuma M-560 V they have a lot of time to make it as good as it can be in terms of numerous compensations and calibrations in a REAL WORD sense... (As compared to completely new models that are relatively unproven).

15 micron part accuracy ??? ... I don't foresee any problem with Genos M-560V (in this context) And frankly the thing will last for f*cking ever... Maybe that's a win win for you ... BUT I'm willing to give the YCM machine a "Sporting chance" :-)

______________________________________________________________________________________________________

* Note the use of the highly technical term "Smidge".
 
Given the two choices, I'd go with the Okuma despite not having scales over the YCM with scales. The YCMs that I've been around have been OK machines, but Okumas are really good machines and the control is great from a programmer and operator standpoint.

I am a big fan of scales and when one starts looking at a builder like Yasda or other really high end machines they are no longer an option, but standard equipment. One can learn something just by taking that into consideration.
 








 
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