hello
as i am still new to this ,
i gut 6 thk slides 20W (115cm long)
and 2 thk ballscrew for x and y (80cm long)

i also have 7cm x 7cm , 2mm thick steel square shaped sections

from where i live it is so hard to get any other materials. or cast aluminum and finish it with presion at all.

so i decided to build a simple machine from what i have and use it to build another better machines

i have a 200oz steppers for this one.


now i dont know where should i place my ballscrew and how can i make it move the x-axis ?
can i put it on one side or at the center is better ?
must it be at the center line of the thk slide ? or up/down a little bit will be ok ?
is it better to place the thk slide in the x-axis as it shows in the pic or i can put it on the sides and it will be fine as well?

i am open to any suggestion . please give me your advice before i start making big mistakes

thank you

My first impression is to lay the X rails on the side and then extend the gantry straight down to tie back across, under the machine to hook to the ballscrew.

Maybe others will chime in with their opinions.

Scott

but will the thk slides be as good on the sides as in the top ?
i mean in handling loads ?

Shooting from the hip, I would say yes - since you have two bearings on each side. Look up the THK bearing number to determine permissible loading and expected deflection and consider the weight of your gantry, etc. Spread the block out as far as reasonably possible on each side without sacrificing working envelope to maximize stability - standard procedure.

Scott

how about something like this ?

That's pretty clean and simple - can you show how the table would be supported?

Scott

i was thinking of something like this.
and whole machine will be welded to a very normal steel constructed table .

Looks like you are on to something. There are a hundred different ways to do this - yours is one way and probably a pretty good way to do it in my opinion. It's simple, compact and relatively easy to construct.

I would spread those bearings out a bit to help prevent skew and racking. Typically, you space them equal to 1/3 of the spanning distance to eliminate skew. In this case it would consume too much of your X stroke, though. There's a happy medium in there somewhere.

Scott

thank you for your help.
i guess ur talking about spreading the bearing the y axis,
that sure i will do .

will it be better to place one bearing on top of the gantry and another on the side of it , instead of putting them both on the same side ?

Actually, the "rule" applies to any linear bearing arrangement, but I was mainly refering to the X bearing trucks. If the distance between the rails (across the table) is, say, 1 meter then you would be served well to spread the X axis bearings at least 330MM apart from eachother (along the X axis) on the same rail to minimize or possibly eliminate the potential for skew. In stark contrast, I am looking at a commercial router that has a beam of 2 meters and the bearings are only 300MM apart on the X rails, but I have also seen this machine skew pretty easily. I would spread them out (if you can afford to w/o losing too much of your envelope) to the 1/3 rule.

On the Y axis - placing one on the top and one on the front would really help with rigidity but it would also make them much more difficult to align. Placing them on opposite sides would probably work OK but it would be a real pain to construct a structure stout enough to realize the benefit from the slightly unusual arrangement. I would suggest placing them on the front surface as they are shown, but spreading the rails out as far as you can. Same for the trucks on those rails - distance is your best friend for rigid guiding.

Scott

this is turning into a very strange looking machine :)

anyway i hope it works fine.

about the x axis bearing the best space i could do it about 200mm as the distance between them is about 90cm.

what do u think so far ?

thanks

A lot of folks put the gantry cross piece for the ballscrew underneath the square tubing that supports the linear rails instead of running it between the rails. This allows your table to be supported by cross pieces instead of just at the ends.

Another thought is whether you want those rails mounted on top of the square tubing or on the outer sides. Having it on the outer sides gives it a little more protection from the mayhem happening in the middle although it is theoretically a little weaker for the rail. It also makes the top edges very clear in case you need to drag heavy sheets of material over them and don't want to damage the material or your rails.

Now you can imagine the gantry being a hollow box that wraps all the way around your support frame, slides along rails in the middle. It looks a little less strange, you get to use a single uninterrupted piece on either side which is simpler, and the table is better supported.

Just a few thoughts for your consideration. Make sense? :rainfro:

Best,

BW

This is the worst part of doing design - picking a direction!

Bob brings up some good points about the rails and table support but/and I think the design looks pretty decent so far - I don't think it looks all that strange or complicated. You may want to look into a quick design with Bob's suggestions then list the like/dislikes and pros/cons of each design. Either design will work just fine!

Now you are required to keep us informed and post pics of the build progress!

Let us know what direction you choose.

Scott

I agree with Scott that either design will work out fine. It's more up to your personal design aesthetic and what you feel will be easier to build. I will cheerfully add that from what I have seen on these boards Scott has a lot more experience than I do with this sort of thing.

It will be fun to watch your project unfold whatever course you decide to take. I'm in the process of laying out a table of my own along the lines I have suggested. My gantry will be made of aluminum plate bolted together, while the lower frame will be 1/4" wall rectangular tubing. My thought in using the aluminum plate was that I could achieve something lighter, more rigid, and more square/accurate with that medium. Having invested in ballscrews and linear rails, I worry about building an accurate enough framework that I can take advantage of their precision.

I read what you have said about availability of materials in your area, so I think your approach is a good one. I just wanted to share some thoughts. FWIW, you may want to take a look at this link:

http://www.thewarfields.com/MTLatheCNCBlog.htm

It's my blog where I gather up all of the interesting material I have found on the web for my projects as well as ruminate on design issues. Also, a lot of good links here:

http://www.thewarfields.com/MTLinksIndividuals.htm


Enjoy!

BW

Bob -

You have some very neat stuff on your site! A must browse for those that have not seen it. Very interesting!

One thing I noticed on your list of links - the Zone is not listed. Shame on you. (chair)

Sorry for the slight hijack - back to the topic....

You may also want to check this site out. I was impressed with this write up and many of his chosen methods:
http://oneoceankayaks.com/madvac/madvac_index.htm

Scott

the 3 links are GREAT , thank you very much for both of you and for the great advice

well here is my final desgin (I hope)

i have reinforced the y axis sides, placed the ball scew in the middle.
for the x-axis i check with thk technical and my bearing are not very good on side loads. so i decided to use the it as in but i have placed them at the edge of the sides to make room for another section to be welded on the y axis iner sides and go all the way down to the x-axis ball scew
i think this will make the y-axis even more stronger, and will enhance the overall look of the machine , the sections are 7mm x 5 mm 2mm think (they are the blue sections on the picture)
no bolts will be used , all will be welded togther

i will be using a 200oz motor for a start (maybe directly or geard down ?)
i am not looking for speed at this stage as i already have servoes to install on later stage.

so what do you think so far ?

I like it!

Will you finish the design or is this as far as it goes? I suggest a little more detail on the table before you start making smoke. Will your table be vacuum or T-slots?

Scott

you mean the cad desgin ? if so then yes i will, if you mean the actuall machine then actually i didnt think of HOW to finish it yet , any suggestions ?
also about the table details , what do you have in mind ?
i will use vaccum .

Bob -

One thing I noticed on your list of links - the Zone is not listed. Shame on you. (chair)

Scott

Oh Scott, you've hurt me!

There are actually a total of 5 links pages, accessed via an index at the top of each one of them. I only forwarded a link to the page that links to individual's (i.e. hobbyist's) web sites. However, at the top of that page are the links to the 4 other links pages. You will find that CNCZone enjoys a very prominent position at the top of the "Home Machinist Groups and Organizations" page. For the record, there is also a page of suppliers (i.e. people selling), tool brands (useful for keeping up with what's a deal on eBay or looking for some new widget that needs the right brand to be well made), and lastly a page of links and "reference" type information. For example, the dimensions for an R8 collet system.

It's funny you mention the Madvac. When I sent my original note, I was desperately trying to find the site. Despite all those many links, I had forgotten to record that one. Doh! (chair)

That omission has now been corrected! :cheers:

Enjoy!

BW

....i didnt think of HOW to finish it yet , any suggestions ?
also about the table details , what do you have in mind ?
i will use vaccum .

Finishing - I was referring to the cad design - for the table.

Table - I really can't suggest either vacuum or other. Put some thought into the actual table design before you start cutting steel - the table structure and such could easily require more space than you might anticipate and it would be a shame to run yourself out of much needed vertical room. Just a suggestion.

Personally, I would look into what you are cutting and what you might get into cutting and build whatever table will accomodate your needs. I prefer versatility so I would design maybe a T-slotted table sub-structure and make a vacuum table that is removable from the T-slot table. You may not need this option, though..... I don't know.

What kind of stuff do you plan to cut - plastic, wood, aluminum, etc? Just curious...

:wave:

Scott

steel offcourse :)
just kidding
actually i want to expermint with multiple material,
mainly aluminum, i have an 18k spindle so i think it will be more than enough, and maybe attach a plazma cutter later on.

about the table i am thinking of something that i can move around anytime in case i want to move the machine fast.

i am thinking on making the best machine i can handle to do,. then use it to make other better machines and parts, then try to sell these type of machines in my area