[truman]

well I feel I am at a stage where I will make steady progress so I thought I would start sharing some pictures. Maby get some advice along the way.

[Switcher]

What board is that in the enclosure (to run the motors)?

[truman]

it is an arcsin board from www.buildyouridea.com Dave is a really nice guy. He has been taking a break for a while but he just told me he was going to do another pcb run and sell a kit for the board. There are a couple of features that caught my attention 1. it has a buit on interface for a joystick 2. it is capable of running a second stepper on the x axis. I did build the 3977 drives from Phils site but I wanted something that could take a little more voltage. here is a pic of what I was going to use I think I will use them for a small desktop mill one day.

[truman]

ok here is some more progress on the gantry I have to wait until monday or tuesday for my T nuts to mount the bearings so I think I will test fit the gantry then. this is only a temporary gantry so I can use the router to cut my alluminum hopefully this one will be sturdy enough to cut alluminum. I am learning very quickly that a mill would save you alot of time and headache or even a friend with a mill would be nice LOL!

[truman]

OK here is some more progress unfortunately I still don't think this will be rigid enough to cut aluminum any suggestions to stiffen it up any help would be much appreciated.

[HayTay]

OK here is some more progress unfortunately I still don't think this will be rigid enough to cut aluminum any suggestions to stiffen it up any help would be much appreciated.

You could use aluminum or steel angle to stiffen up all of the corners on the gantry. The outside corners for sure, and maybe the inside ones, too.

It looks like you should remake the sides of your gantry to make them longer on the underside of your table frame. You could then add front and back plates made from wood or metal to stiffen the assembly up even more. A torsion box assembly would probably make it even stiffer than just the front and back support pieces.

See Joe's CNC Model 2006 gantry for inspiration:
http://www.cnczone.com/forums/showpo...0&postcount=42

If you're going to remake the gantry, now's the time. I hope the suggestions give you the help you were looking for.

[truman]

This is only a sacrificial gantry but the idea of angle might be what I was looking for. actually the gantry I made is based on Joes second machine I have been following Joes stuff for a while now he is the one who cut my router mounts for me. what I was hoping to do is cut my aluminum gantry with this one.

thank you

Rob

[truman]

OK I have stiffened the gantry up with 1" square tubing but I have found out that it is the bottom plate that is the weakest link. If I hold both gantry sides and move them in opposite directions I get what I think is called gantry rack. Anyone have ideas how to improve this? any help would be greatly appreciated.

thank you
Rob

[randyf1965]

Without rebuilding everything... I would get a large piece of angle (red part)and fasten it on the gantry sides and bottom on each end of the gantry.

Or you could try the flat metal 90 degree corners (Yellow part)and put the on the front and back ends of the gantry and attach to the gantry bottom front and back edge.

Both probably wouldn't be a bad idea either

[HayTay]

OK I have stiffened the gantry up with 1" square tubing but I have found out that it is the bottom plate that is the weakest link. If I hold both gantry sides and move them in opposite directions I get what I think is called gantry rack. Anyone have ideas how to improve this? any help would be greatly appreciated.

thank you
Rob

Again...

You could use aluminum or steel angle to stiffen up all of the corners on the gantry. The outside corners for sure, and maybe the inside ones, too.

It looks like you should remake the sides of your gantry to make them longer on the underside of your table frame. You could then add front and back plates made from wood or metal to stiffen the assembly up even more. A torsion box assembly would probably make it even stiffer than just the front and back support pieces.

See Joe's CNC Model 2006 gantry for inspiration:
http://www.cnczone.com/forums/showpo...0&postcount=42

If you're going to remake the gantry, now's the time. I hope the suggestions give you the help you were looking for.

[truman]

I know you allready said that haytay and stupid me assumed that the bottom plate wouldn't be the problem I guess I should listen to people who have built machines anyhow the idea for the flat corner brackets was also very good I think i will use both angle and the corner brackets should I double the thickness of the bottom plate as well?

thank you
Rob

[Madclicker]

I don't think you can do much to help the torsional strength of slab MDF by adding pieces of metal. That's why people build torsion boxes. Your problem is the lack of torsional strength. Laminating the slabs of MDF will help a lot, as will doubling the the thickness of the slabs.

[truman]

now that I added the square tubing you can stand on this thing but the only thing that I did not fix is the gantry rack the side to side play was eliminated. I did however think of making a torsion box for the bottom plate just don't know how i would attach it don't want to start from scratch just need to cut a few aluminum pieces with it then its job is done.

[spalm]

Truman,

I found out that no matter how much strength I had in my gantry, it still racked. I pretty much solved it to my satisfaction with dual leadscrews. Using a taught cable and pulleys has also been mentioned a few times, but I have not seen it in use.

Steve

[HayTay]

Okay, how about this...

Keep what you have and remove the square tubing from the gantry uprights. Cut another set of the gantry sides making them longer so that they hang down 3" or more below the current gantry bottom. Make a another gantry bottom to attach at the bottom of the new sides and cut a front and back piece to square everything up and solidify the structure to minimize the "racking". take your news sides, bottom and front and back pieces and slip them onto your current gantry assembly. Glue, screw, & bolt as necessary to attach the new pieces to the current assembly.

This will give you the added stiffness of doubling the thickness of the gantry sides and extra support on the gantry bottom to keep the sides from pivoting/racking as much. Check out the JGRO CNC Router plans for an example of the gantry bottom modification and Joe's 1st (and 2nd?) CNC Router for examples.

You can even place the square tubing back on once the extra gantry pieces are in place to reduce the flexing of the sides.

That's a quick, cost effective solution that should give you the result your looking for. Sound OK?

[truman]

what about going one step further and making the bottom piece an actuall tortion box and for attaching it to the new uprights run threaded rod all the way through?

[HayTay]

Sounds good to me, I was just trying to keep it simple because you...

just need to cut a few aluminum pieces with it then its job is done.

[truman]

I tend to over think things I think I will just square it off as you said I will cut the new uprights and front and back pieces tomorrow I now see where the light bulb wasn't going off in my head but thanks to your persistence it finally turned on I totally omitted the bottom being like it was on Joe's machine thinking the different bearings would make the difference I guess I like learning the hard way hope I didn't frustrate you to much.

[HayTay]

I tend to over think things I think I will just square it off as you said I will cut the new uprights and front and back pieces tomorrow I now see where the light bulb wasn't going off in my head but thanks to your persistence it finally turned on I totally omitted the bottom being like it was on Joe's machine thinking the different bearings would make the difference I guess I like learning the hard way hope I didn't frustrate you to much.

truman,

Keep plugging away and it'll all work itself out. We all sort things out in our heads in different ways and at different speeds. And sometimes we need to be told, or shown, something a couple of times before it sinks in. That's what all of the CNCZoners are here for: help and support.

If you were going to keep the gantry permanently other suggestions and designs, such as the torsion box with rods and an extra set of guide rails, would have been forthcoming. You're still going to get some flex/racking due to the design and MDF contruction material, but, between the proposed reinforcements and some experimentation with cutting speeds, feeds & DOC, you should be able to get what you need cut.

Have fun, and don't forget the pictures!

[JavaDog]

Keep what you have and remove the square tubing from the gantry uprights. Cut another set of the gantry sides making them longer so that they hang down 3" or more below the current gantry bottom. Make a another gantry bottom to attach at the bottom of the new sides and cut a front and back piece to square everything up and solidify the structure to minimize the "racking". take your news sides, bottom and front and back pieces and slip them onto your current gantry assembly. Glue, screw, & bolt as necessary to attach the new pieces to the current assembly.

That's what I did with mine and it is seriously rigid (well, except for the unsupported rails).