Building 2nd Machine

[Paulds]

Have a couple of questions for the group

1. What would be the max lenght that I could use 5/8 drill rod for an axis before i would need to worry about flex. Is 30" too much.(see attached photos of bearing assy. on "X" rails will this work.)

2.Has anyone tried to used 1/4" steel angle mounted on piece of 8020 1.5"x3.0" aluminum using roller skate bearings mounted to the gantry. Had to install a smaller bearing in between 2 roller skate brearings to get 1/4" spacing.(See last 2 photos)

Have uploaded pictures of my idea for the "X" axis with the "Z" mounted to it. It is about 30" long for the "X".


Thanks for any input.

Paulds

[CarveOne]

Yes, they have. http://www.cncrouterparts.com has bearing blocks for just this purpose. It uses 1/4" cold roll steel flat stock for the rails. The shorter linear carriage is 4-1/2" long. You can get ABEC7 or standard

CarveOne

[Paulds]

CarveOne Thanks for the reply.

Yes i looked at those and found them to be a little more money than i want to put into it.
I put togather both side of my gantry for less than it cost me for one of the one's that you are talking about. I built my first machine (20"x28" in size) with THK rails but this time i wanted to see how inexspensive i can build the 2nd one but still have good accurate cuts. I want to try this so i can build a bigger machine say a 4'x4'.

[ger21]

My guess is you'll get serious flexing of the 5/8" shafts, even at 24" long.

[Paulds]

Gerry thanks for the input
Do you think that i could support the top rail with some 80/20 1.5x3" aluminum and keep the flex at and acceptable ammount if need be i guess i could support both top& bottom.

Paulds

[Guldberg]

Is that your machine on the pictures? If so, why not just try and put a gauge underneat the rail and apply some force. Im pretty sure the needle will bounce a lot. In my oppinion even 1" would flex at this length. As you suggest, a support is the way to go

[CarveOne]

CarveOne Thanks for the reply.

Yes i looked at those and found them to be a little more money than i want to put into it.
I put togather both side of my gantry for less than it cost me for one of the one's that you are talking about. I built my first machine (20"x28" in size) with THK rails but this time i wanted to see how inexspensive i can build the 2nd one but still have good accurate cuts. I want to try this so i can build a bigger machine say a 4'x4'.

I misread your second question and thought that you were going to place the bearings on one edge of a 1/4" thick angle or plate.

My second build is using Ahren's carriages on the edges of 1/4" thick flat stock rails for a mostly steel 49" x 62" working area machine. For this machine I don't think the linear bearing price was at all excessive. Combined with the cost and amount of cold rolled steel flat stock prices I needed for this size machine - you may be right. But I think it will be completely worth it in the end. I saved some money and expended a lot more effort by buying hot rolled steel flat stock for 40% less money than the cold rolled steel would have cost.

I wouldn't recommend rolling the edges of bearings against the flat sides of a piece of aluminum or steel angle stock. The bearing is harder than the angle stock and will eventually wear a groove into each side of the angle stock. It will work ok as long as you expect this to be a starter system that will be replaced within a year or two or you are willing to replace the angle stock when the wear becomes a problem. Running the bearings flat against the angle stock is much better for a number of reasons and will last much longer. It just means mounting the bearings at 90 degrees to each other as most other builds do it.

CarveOne

[MitzuRazing]

..But i have a new build growing in my mind and was wondering if 1,5metres of 30mm thick unsupported rails would be to long for a decent result?? This was the meaning anyway for the X aksis of the new machine i have buildt so many times in my mind already.. The thougt anyway is to attach this to a ALU boxed section-frame, approx 1,6X0,9m long and wide locally supplied frame. I am not sure what the Y and Z aksis is going to be buildt of yet, but i have a few ideas
-Thanks in advance for all the good advise :-D

[Paulds]

carveone
Thanks for the info, just in pre assy. i have seen what you are talking about in that the bearing is making wear marks on the sides of the rails, do you have any ideas on how to keep this from happening. i have found that setting up the rails for the "Y" is a bit of a problem, both in setup and in just tring to move the gantry without it binding. i was looking at maybe trying to put some sort of delrin pads on the sides to ride against the sides of the angle and remove the 2 side bearings, do you thinks this would work if the angle was really clean. Just was tring to find an easy and cheap way to make a gantry with skate bearings and using the 80/20 aluminum i had. do you think there is a way to use the 1530 aluminum and make something to mount the side bearings at 90 degrees to the side rails. i have a HF mini mill that i could maybe make something out of aluminum. any ideas would be a great help.