help my machine has to much flex

[stk2008]

hi all as some of u know ive built my machine but i was having problems getting it to be consistent.

well ive checked a few more things and my Y axis has way to much flex in it im gutted it now means i have to go back to the drawing board and re do the Y axis.

ive come up with a solution but it will cost me £250ish for that i get

http://www.worldofcnc.com/products.asp?recnumber=18 x4

http://www.worldofcnc.com/products.asp?recnumber=85 x2 at 800mm.

im wondering is there a cheaper place than Marchent Dice? i did buy all my stuff from them a few years back but now im skint

heres pics of my machine for ref

My home made cnc in progress

so on the Y axis as it gets to the middle it droops 0.005" but with every thing on it router,Z axis assembly it droops well over 0.050".

i can make it bend well over the 0.050" still so if im doing a cut it will bend like mad.

im gutted any advice would be great cheers all again for you help.

[posix]

I'd just buy 4 (or perhaps even just 3) of those bearings (26 quid if you're using 16mm ones), cut your existing blocks if possible and rework your y axis to resemble your x-axis i.e. put the rails along top and bottom of those y-axis extrusions you got there and support them with those bolts. you'll just need to extend your z-axis mounting plate somewhat to accomodate the new geometry. got it?

[stk2008]

hi thanks for the reply.

ive been giving it a bit more thought and decided to buy 4 25mm bearings use me old blocks and machine them open like i did on me other ones then drill into the rails and support them with studs as the flex is not up and down on the Y axis its forward and backs so if i grab the top and push down it dont move because the load is being taken by two rails.

but if i grab the top and bottom and push back and forward it then moves loads studs will fix this so woot.

cheers for reply and i will keep you all posted on this as to if it works.

[posix]

the supports will stop it from flexing in both up and down as well as back and forth. you also forgot the diagonal flexing as well (like when you're plunging into material at an angle for example). support is good. the quickest fix would definitely be just to put some bolts between your horizontal extrusions and rods, cut the blocks open and put those new bearings. get nice fat bolts. you can even drill the rods and screw the "supports" into the rods, that'd be even better.

[stk2008]

hi posix yes i will on this axis drill into the rails and screw the bolts onto them as it will be needed to cope with alot of forces where the X axis has gravity and the weight of the machine pushing down on it so i only needed the bolts to stop it from dropping.

will be taking it apart tomorrow and getting it all ready for monday at work woot.

p.s its still very disapointing when this kinda thing happend i realy thought thats it all built lets play but nope hehe.

thanks

Dan

[posix]

to be honest I fail to see the reason why you went unsupported on y and z when your x is supported. never been a fan of anything unsupported, ever since my first pipe router "enlightened" me.

[stk2008]

posix u speak the truth.

well when i designed and built this machine even the X axis was unsupported i failed to relise how bloody much even 25mm rails bend over 1000mm so i gave them support but i did look at the Y axis then and thought well lets see later wish i had just done it then.

but like you said i will never build another machine without unsupported rails never.

tbh tho the Z axis is very solid i realy dont need to have that supported but then its a very short distance.

so yes you are correct supported rails nothing else is worth it now i see my mistake and will never do it again.

lesson to all you new comers (still me) please just use supported rails it will save you loads of time.