Column support: finishing?

[tooManyHobbies]

I'm going to do this: Hey, Casting Guys!.

Do I need to have the back of the channel surfaced to a certain flatness?

Or can I use it as-is?

I got one from speedymetals, (hc4x7.25), which is A-36 Hot Rolled Steel.

tom

[SCzEngrgGroup]

I'm going to do this: Hey, Casting Guys!.

Do I need to have the back of the channel surfaced to a certain flatness?

Or can I use it as-is?

I got one from speedymetals, (hc4x7.25), which is A-36 Hot Rolled Steel.

tom

Again, I have to wonder if the author of that post actually took the time to *measure* the flex, and determine *where* it was coming from, before jumping to the conclusion that the column mount bracket MUST be a significant contributor. I've only once seen anyone actually take the time to do this (John Pitkin on the Yahoo mini-mill group), and he found the bracket to be a very minor contributor - not even worth messing with. Too many people come up with a "fix", and declare the problem solved, without first taking measurements to prove what/where the problem is, or even to prove that the "fix" really improved things. I've seen an awful lot of "fixes" that actually made things worse! Without measurement, it's all just speculation....

Regards,
Ray L.

[The Blight]

I have done some measurings on the X2 collumn. I put a dti on the head and measured +/-0.2mm flex with just pushing on the head from side to side, and +/-0.1mm back/forth. I then tried locking the head so that the flex from the dovetails would be eliminated. I measured a little less flex, but it was still +/-0.15 left/right and +/-0.06mm front/back. I don't have the spring washer on mine, so the flex can't be located there. I have now made a plate that has mounting holes to the base of the machine. Just have to drill those holes and make a spacer. Will measure flex again when I'm done. I have no idea when that will be though, as I'm working on a new Z axis for the machine.

[SCzEngrgGroup]

I'm going to do this: Hey, Casting Guys!.

Do I need to have the back of the channel surfaced to a certain flatness?

Or can I use it as-is?

I got one from speedymetals, (hc4x7.25), which is A-36 Hot Rolled Steel.

tom

Again, I have to wonder if the author of that post actually took the time to *measure* the flex, and determine *where* it was coming from, before jumping to the conclusion that the column mount bracket MUST be a significant contributor. I've only once seen anyone actually take the time to do this (John Pitkin on the Yahoo mini-mill group), and he found the bracket to be a very minor contributor - not even worth messing with. Too many people come up with a "fix", and declare the problem solved, without first taking measurements to prove what/where the problem is, or even to prove that the "fix" really improved things. I've seen an awful lot of "fixes" that actually made things worse! Without measurement, it's all just speculation....

Regards,
Ray L.

[hoss2006]

skmetal7 reported "befor i had ~15-20 thousandths of deflection and now its around 3 thou.!!!!"
using a column support that ties into the base.
Another X2 CNC Conversion (yay!)
doesn't take much more than common sense to realize that a structure will be
more stable if it is supported on both sides rather than just one.
Hoss

[Dougal]

Again, I have to wonder if the author of that post actually took the time to *measure* the flex, and determine *where* it was coming from, before jumping to the conclusion that the column mount bracket MUST be a significant contributor. I've only once seen anyone actually take the time to do this (John Pitkin on the Yahoo mini-mill group), and he found the bracket to be a very minor contributor - not even worth messing with. Too many people come up with a "fix", and declare the problem solved, without first taking measurements to prove what/where the problem is, or even to prove that the "fix" really improved things. I've seen an awful lot of "fixes" that actually made things worse! Without measurement, it's all just speculation....

Regards,
Ray L.

Ray, you really need to learn some structural engineering basics. You're making a meal of this debate. My build thread shows you were against this channel brace from the start before you even understood it's function. Now it's built and working with major stiffness benefits you're still against it. Don't take this the wrong way but you don't appear to have the insight to accurately critique structural modifications.
I suggest you take some measurements yourself to put your mind at ease.

Toomanyhobbies, you don't need to surface the channel, but if it has any glaring rough spots a file will take care of them.
You do need to tune the length of the lower standoffs while tramming the mill. Both of mine ended up different lengths. I plan to face the back of the base later to get a better contact surface for these standoffs.

I measured ~0.1mm deflection with 50kg downforce on the head with this brace.

[BobWarfield]

Dougal is reporting almost the same result (his in metric is about 3 thou) over on the thread being linked to. He says he is a design engineer too.

The thing is, the mod is so simple, hard not to just want to go do it rather than studying it to death. Maybe that's what you're saying about "common sense", eh Hoss?

Cheers,

BW

PS I see Dougal posted as I was writing this. From the horse's mouth!

[Dougal]

I have a PDF drawing for the back brace, I'll happily give a copy out to anyone who wants one for personal use (i.e. not for commerical gain).
PM me your email address if you're interested.

[tooManyHobbies]

you don't need to surface the channel, but if it has any glaring rough spots a file will take care of them. You do need to tune the length of the lower standoffs while tramming the mill. Both of mine ended up different lengths. I plan to face the back of the base later to get a better contact surface for these standoffs.

Thanks! That's what I was looking for!

tom

ps In the interest of science, I'll measure deflections before & after the mod and post them here.