perfect polishing with CNC machine

[JSandSO]

is it possible to achieve a perfect polishing on granite or marble with a CNC-machine or are you guys have to touch up the polishing by hand?

Thanks in advance

byebye

Juergen

[tension]

In my personal opinion there is no way a CNC will make a perfect polish. Any machined polish will leave lines. I've heard glory stories about how "this" tool or "that" tool wont leave the lines but I simply dont believe it. Granted you may have smaller lines that are less noticable but ultimately, they are still there. Nothing beats polishing the stone by hand, its craftsmanship, its an art. Theres nothing bad about the CNC polish, in fact, I did the kitchen and vanities in my own house on our CNC and I have no complaints whatsoever. Theres a definate noticable difference, but you have to be pretty anal about it to pitch a fuss.

If you are that worried about it then simply have someone run a hand polish over the work the CNC has done, or do that from the beginning and save your machine time.

[HuFlungDung]

Amateur telescope makers were frequently warned about 'zoning' caused by machine polishing their telescope mirrors. The trouble with a machine is that the repetition of a stroke is too perfect. Build a machine (or a program) that introduces a degree of randomized stroke length, randomized direction and inexact rotation of the lap, and you might have half a chance at getting a good job off of a machine.

I don't know if that applies to general polishing such as you need, but the underlying principle is likely the same.

[Egar Twins]

techniqiue and tooling....I promise it is possible some machinesa are made for it!

[Making chips]

There are some edges that you can polish with no lines. Flat (Z) profile on some machines (CMS Brembana machines will do this) can be osolated on the cnc to take out the lines. It also depends of course on the stone and the profile as to how the lines stand out. More complex profiles (ex. triple pencil) it is hard to see the lines. I put Santa Cecelia in my kitchen with a triple pencil edge, cut it on the machine, sealed it, and installed it without touching a hand grinder. It is possible. Also if you take care of your tools (keeping them dressed and calibrated) the lines can be left at a minimum.

Hope this helps,

Paul

[T_Kiwi]

simple answer is "no", best thing to do is finish on position 4 diamond and get the boys to finish by hand. osolation for flat edge can be achieved with no lines but lets face it, speed is the key here so again, finish by hand. I was invited to the company Ghines in Italy and was told that achieving no lines cannot be achieved, only minimising them can.

[stonecoldcnc]

Hi T_Kiwi I agree

I have also been to Italy and spoke to another major diamond tool manufacturer and they have said exactly the same as Ghines to you.

We now run only 4x diamonds and then get the boys to finish of the bench tops by hand. I know that some might not agree but over here in WA the standard seems to be much higher then in the US and our clients would just not accept a bad finish.

[T_Kiwi]

Originally Posted by JSandSO is it possible to achieve a perfect polishing on granite or marble with a CNC-machine or are you guys have to touch up the polishing by hand? Thanks in advance byebye Juergen

i dont care what anyone says, you cannot get a perfect polish from a cnc machine everytime. yes you may get one good one but its a lucky dip, as for polishing by hand, its not an art, its the rotatation of the pads that make the difference, the art is to make sure the aris or pencil round is even. oscillation works for a no line finish but try doing that for a pencil round or bullnose or lambs tongue if you disagree then you must be a salesman

[stonecoldcnc]

I still agree with T_Kiwi,

although there is an obvious difference between polishing edge profiles or horizontal flat surfaces like draining boards, were it is possible to achieve a near acceptable polishing, at least on softer light colored granites but not so much on darker and harder granites. I also had good results on engineered stones with polishing draining boards but it took a lot of fiddling with the program settings to get near random movements for all tools and still cover all areas equally.

[judleroy]

I worked in granite for years. I can say that the first few polishes after a good setup can be acceptable if not perfect on the machine. The problem is that if your needing to polish 30-40 pieces a day with each one different the tools just can't keep a good enough finish. There's to many variables with both the profile tools and pollsters to stay consistent. If you need to get the work out you cannot afford the constant time spent readjusting the tools. I've yet to see software that can accurately account for all the variables. In my opinion you only use polishers to finish the flat edges inside of sink profiles. Anything else is a waste of time. There is no substitute for a good hand polish.
Judleroy

[T_Kiwi]

ah well drain boards is a very different story, i have had great success with drain boards, the trick to a perfect polish on any material is making sure you use 2 surface grinders, first on to take the bulk and second one to take 0.1 off and always keep the second one for that purpose only. i can answer questions later but off to work now

[SteinmetzKramer]

Of course it is posible to polish granite perfect.

I use for this a, Master 35Plus with 200mm polishing head but look self
http://youtu.be/uOZT-ek3BLw