New Machine Build- Yet Another Build Log

[davecaswell]

I'm about to set about building one of Fine Line Automation's FLA-100 kits. I'm going to start by posting some photos of the components right out of the box. Hopefully, this will get the bugs worked out of the posting process before I get going with the build.

Today's pics are of the threaded rod, lead-nuts, bearings, and the mount for the Hitachi Router. The router mount is actually from K2, not FLA.

[DonFrambach]

Looking forward to seeing your progress. Is that a single start lead screw?

[davecaswell]

Originally Posted by DonFrambach Looking forward to seeing your progress. Is that a single start lead screw?

Yep, single start. My brother, who has built a couple of CNCs tells me that for the sort of thing I'm wanting to do, I wont miss the speed that the 5 start screws would give. And the step size on the steppers will be totally out of the accuracy picture.

Clearing out a work space to build in is taking more more time than I hoped, so I haven't really started building yet. Definately between Xmas and New Years.

In the mean time, here are a couple of pictures of an experimental bearing assembly that I did before I discovered the bearing blocks that the FLA kit uses. It's made of 3/4 inch square extrusion and really cheap skate bearings. It seemed to work pretty well. I gave up on that plan because I discovered the CNCRouterParts and 8020 stuff. Plus I worried that using aluminum rails, slack would creap into the system.

[ger21]

Yep, single start. My brother, who has built a couple of CNCs tells me that for the sort of thing I'm wanting to do, I wont miss the speed that the 5 start screws would give. And the step size on the steppers will be totally out of the accuracy picture.

I think you'll end up being disappointed with the performance of the single start screw. 1/2-8 2 start is a very good middle ground choice, that gives very good precision, and 2-3 times faster speeds than 1/2-10 single start.

It's what I use, and it's capable of 200+ipm, vs 75-100ipm that you'll typically get with single start.

[davecaswell]

I should give credit to:
Scratch: [Complete] 2' x 3' Custom CNC Router from 80/20 Aluminum Extrusion - Overclock.net - Overclocking.net''
for being an excellent step-by-step guide to putting the kit together. So far I've followed his suggestions with the exception that instead of putting the bolts in the slot and trying to put the rail on them all at once, I've slid the steel rail over the slot in the aluminum, adding one bolt at a time. Seems to be pretty easy.

Today's pictures are of the 5 start lead screw that I decided not to use. And the frame as it was just before adding the rail.

[davecaswell]

Today I set about putting together the drive components for the bottom axis. Ran into a problem, seems the single start screws I'm using are just a bit larger in diameter than the 5 start screws. The 5 start screws fit easily through the bearing on the opposite end from the thrust bearings and motor. The single start screws jammed into the bearings, completely preventing things from lining up correctly. So, I sanded off a bit of the threaded rods so things would fit together.

[davecaswell]

As it sits as of now. I can tell I need to get some cross bracing of some sort on the legs. It's pretty wobbly along the long axis.

[davecaswell]

The metal parts and electronics are assembled. I've even mounted a sharpie and written my name a few times. The top one I overwrote over the previous one as a quick check of repeatability.

The machine makes loud rattly noises at the middle of the ranges starting at surprisingly slow speeds, especially on the Y axis. It may have something to do with the single start screws. Anyone know what sort of speeds are possible with the 5 start screws?

[ger21]

How long are your screws. I can spin my 42" long 1/2-8 2 start at 760 rpm, which is limited by the motor/drive I'm using. That would be 380ipm with 5 start.

However, my 62" screws can only spin around 600rpm before whip get's too bad. That would be 300ipm with 5 start.

But your motor/drive combo may limit you to slower speeds than that.

[Chris D]

Originally Posted by davecaswell The metal parts and electronics are assembled. I've even mounted a sharpie and written my name a few times. The top one I overwrote over the previous one as a quick check of repeatability. The machine makes loud rattly noises at the middle of the ranges starting at surprisingly slow speeds, especially on the Y axis. It may have something to do with the single start screws. Anyone know what sort of speeds are possible with the 5 start screws?

The vibration (rattly) sound could be the natural resonance of the stepper motors. My machine is belt driven and uses micro stepping drives (10 mico steps) and I get a vibration at around 20 IPM. Any velocity above or below that is fine so it appears to be the natural resonance between the motors and the mechanics. In other words you are hitting a point of harmonic vibration. As for fixing that problem, I have not tried yet to work it out, sorry.

Chris

[davecaswell]

First part from the mill. A bracket to hold a microswitch to sense when the X axis is home.

Still having problems with vibrations when I let the speed get up towards 40 ipm. How fast do folks using the 5 start screws get? And what is the limiting factor for speed in that case?

-davec

[DonFrambach]

My router is much smaller than yours (14" x 14") so I don't have as much of a leadscrew whip problem. I have been able to achieve 75"/min with single start 1/2 x 10 lead screws and delrin nuts on my small machine. I was only able to do this after lubricating the screws. Prior to lubrication, I experienced horrible noises at speeds as slow as 15"/min. Not sure if this is relevent to you but if you haven't lubricated your screws yet then I suggest you give it a try.