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Hi Pipik, Thank you for the advice. the web was suppose to counter any twisting moment acting on the columns. No doubt weight is important to absorb the vibration and having a heavy machine adds to the rigidity. That is why lathe bases are made of CI which is good in absorbing vibrations.
Please share your drawing. That will definitely help.
I can't download or see the attachment.
Hi Pipik, Thank you for the advice. the web was suppose to counter any twisting moment acting on the columns. No doubt weight is important to absorb the vibration and having a heavy machine adds to the rigidity. That is why lathe bases are made of CI which is good in absorbing vibrations.
Please share your drawing. That will definitely help.
I can't download or see the attachment.
Not if you know what to do they are very easy to indicate, either with a round disc for the indicator or a feeler gauge mounted in the tool post of the lathe, this is spring loaded onto the Ballscrew then the indicator can run on thisQuote:
Originally Posted by machinedude
No sleeve needed
This is what I did. Initially i mounted something of this as shown. Later I mounted same thing with more width. To verify the reading, I checked the groove too by sliding the carriage so that dial remains in the groove. The readings are same. former one is easier to do.
nice trick with an aggressive lead screw. but an aluminum sleeve still acts like a set of soft jaws and is extra protection for the screw. so it becomes a matter of preference based on particular needs. the 5 mm pitch screws are not that spacious for indicator work. what ever works i say as long as things are concentric that's the part that matters most.Quote:
Originally Posted by mactec54
I can't see pipik's pictures and I disagree with him about webs.A large and heavy machine will automatically be quite stiff but the design without webs and with comparatively thin side plates will be likely to flex without any external stiffening and as such will be improved by webs.The whole project can be viewed as an exercise in achieving performance without adding bulk or time or cost and the OP doesn't have the best access to supplies or friendly commercial workshops.
Hi Pipik - Please try again with your images. We would like to see your machine. But 1) there is no correlation between weight and stiffness or rigidity. There is no weight component in any deflection calculation that I know of. In most performance devices we have steadily been making them lighter and stiffer over the last 100 years especially in the last 30 years with composites (planes boats bicycles tennis ratchets the list goes on and on cars, ships and mills) We have made them significantly stiffer at same or less weight in the last 20 years...mainly due to better CAD and FE processes available 2) weight does not "absorb" vibration. Its just harder to get something heavy excited, quite a different physical effect. Materials do absorb vibration due to internal friction but again that has nothing to do with weight. The weight is great argument is a poor one.
So lets see those dwgs cheers Peter
Columns and twisting? Suppose that we are not understand each other. Columns can not twist, there is no force like that. Columns most likely bend with X movements. See the sketches, just to understand each other.Quote:
Originally Posted by Tony_Stark
There is one thing I forgot to mention - is it really necessary to have 400mm height of portal? Why? What do you want to machine out that you need that height? This is important question, dont underestimate it ;)
I am building my machines with just a 100mm height, and only moment thats it is not enough is when I have only long drill bit. And other users have the same experience.
And do not forgot that if you want to have, lets say, 150mm height, your Z-axis need to travel 150 + 100mm (length of tool) so you can be able to move the tip of tool over that high material, and also place a tip of tool at bottom of material. Imagine that. .... see? Really 400mm?
Can you open Autodesk Inventor files? It will be much easier for both to send a drawings.
Yes. We are making lighter goods. But there is a huge difference between bicycle and milling machine. See the building process of a professional mill, like Fanuc or Haas. You can find it at youtube. You will be surprised and you can ask yourself why are they casting the beds and portal of mills, why they are not using aluminium instead of heavy iron, and why is there so much mass of iron in that two important parts, why they just not to screw two jackels together.Quote:
Originally Posted by peteeng
There is no corelation to bending with weight. Thats right. But there is a huge corelation with vibration and weight.
In milling machine, you must solve two problems - knife must not to avoid cuts = bending, and whole machine must not vibrate under that repeated cuts = eat that vibrations. If you are cutting plastic, or soft wood, there is almost no problem. But if you want to cut aluminium, thats the different story.
Really good of stiffness example is electricity pylons. They are stiff, you cant say no. But grab some rock and hit some. Can you hear that long sound? This is because pylons are stiff and rigid, but cannot eat vibrations, due to lack of mass. And at right vibrations, you can make the whole pylon literally dance, no matter how big it is.
I have made one mill, making it light, stiff, like that pylons. I realise my mistake at the moment I accidentaly hit the construction. Almost 20s long sound. You can say it can not generate any problems, but, when I finished this mill, and whole machine is vibrate under some cuts, making these cut ...ugly is not the right word, the problem is alive. Not mentioning that you are spending bits much much more. See that bad construction -
If you look at the chuck you will see that it has some aluminum flat bar under each jaw this is how it is normally done to protect the screw it makes not difference what the screw pitch is I have done hundreds of them like this 2 mm to 50mm pitchQuote:
Originally Posted by machinedude
i did not see the aluminum flats until you mentioned it. but i will say if you do it this way something thicker in the chuck would be better like you have in photo. i think it would be more prone to distribute the camping force of the chuck. and use a thick feeler gauge since they are surface ground and a thicker one won't deflect. but i don't see any issues with how you do things. probably would not hurt to take the time to set the tail stock on center to the chuck too if you plan on centering the screw and using the tail stock for support with a center. but that just depends on the stick out of the end from the chuck and how big the screw is to begin with. i don't do end machining that often so it sounds like you have done your share of them so i will keep this method in mind if i have a need in the future. 30 years of machining and i learned something new :) wish i did the same kind of work all the time but that's not the case for me in a job shop setting.Quote:
Originally Posted by mactec54
Unfortunately I am not able to see the attachments. It just show "Attached thumbnails". Are you not uploading picture format with extensions like .jpeg or .png? As I am not able to see the pictures, I am not clear on many of the things you said. Not able to visualize here. Also what is portal?Quote:
Originally Posted by Pipik
The Z height was initially 400mm when I started this post. I am new to this and it was just a amateur wish or draft concept. The current configuration is having 150mm total Z travel (60mm tool mounted in router).
Damn!! I also missed that aluminum angle under the dog chuck. For a 4 jaw its a easy way. For three its difficult to mount three flat plates likes this.
Hi Pipek - cast iron is the tradition solution to a Mills main parts. But many of the best mills are now made using mineral castings. These are much lighter then CI yet 20x damper. Look up Hemle mills. I think that any machine maker would now seriously look at mineral casting vs cast iron for all the technical pluses it has. Peter
https://www.schneeberger.com/en/prod...neral-casting/
https://www.youtube.com/watch?v=WRvPQnUAe0s
https://www.hermle.de/en/machining_centres/models
cast iron is over 7000kg/m3 and mineral cast epoxy is about 3000kg/m3
also look up granitan
re: milling machines and bicycles. I suggest you talk to someone in the Tour De France. They understand damp frames very well. After a 300km day in the saddle a live frame is truly a pain in the butt. Then there's stiffness, they want a frame that does not flex so they can go up hills fast. Cyclist have understood rigidity and dampness since they have been invented. They want exactly the same thing as the mill, max stiffness and max damping.
i think the sleeve is easier to deal with setting up but it takes extra time to make one. if your screws are all the same diameter then that might be the way to go? both methods should work well. my original statement was directed at the fact you can just slap the screw in a chuck and indicate it without some form of assistance for locating it so things are concentric. Mactec54 has a good method that i am sure works well. i just wanted to point out the screw itself is worth protecting since it is a bearing surface. i missed the flat bar in the picture as well but it's an important part of the set up.Quote:
Originally Posted by Tony_Stark
Not like the mills, bicycles are not cutting another bicycles. At the normal circumstaces, of course :)Quote:
Originally Posted by peteeng
Out of fun - what I am talking about is that bicycle doesnt need to solve problem to hold position at 0,01mm precisely and deal with constant vibration at steady freq.
I know about granitan and epoxy. This is really major invention, moving this sector a bit after a ... 100years? We make one, just to try, and result was excelent. It has almost no minus against casting iron. Only one - you almost can not mill it, so you must insert iron parts, which is not major problem. But the pros of this technology is large. And there is one superb - because of not unified structure (sand + epoxy etc., what means a different density of material), its excelent with eating vibrations. And because lower density, you can easily make it more massive.
And this is what I am talking about. There is no need for weight. But mass is important. I know, there is a straight corelations between this two, but what is important is to distribute mass at the right place.
Dont know why you cant see the pictures, they are really *.jpg, but I see them normaly at all PCs around.
I will prepare some pictures of sketches and upload them somewhere else ;) This forum have limitations over everything.. :(
Pipik, I can't see any of your attachments either.
You have to upload them onto this site.
I see them normally on this forum, at the same page you are reading this post. Its weird...Quote:
Originally Posted by davida1234
This is really weird. Can you upload it in your Google Drive folder and share that folder link.Quote:
Originally Posted by Pipik
See this is how it looks to us.