MIMF

getting close now! I didn't have nuts for the end brackets and ran out of time to work on it last night.

https://youtu.be/EufNxR4mqxY

Heh - failed to notice before - you've almost re-invented the servobelt drive. Check out this video: http://bell-everman.com/products/linear ... linear-sbl

With a couple small changes, you can eliminate error due to belt stretch. I've got a friend making something very similar.

Good work!

Backlash on a typical hard rack and pinion gear set is around .015".

I think the backlash should be less then that from the belts but we will see. The belts for the x-axis are very much oversized for the loads they should see. The Y-axis might have a bit more. Even if I'm at 0.010" of backlash I'll be pretty happy.

Eric Baack wrote: Even if I'm at 0.010" of backlash I'll be pretty happy.

I doubt that. .010" of backlash is way too high for anything but the coarsest of work.

If you modify your belt drive to be like the one I showed in the link, you should be able to get to about zero backlash and zero stretch. You'll be much happier in the end.

Also, add something to those uprights to make them stiffer. Bolt an I beam or even a simple 1/4" thick angle Al .

I believe I'm being quite conservative on the backlash but we will see!

These belts are pretty stout for what I'm doing. I'll have to run a few test cuts to measure theoretical vs actual.

Did a few jogs last night. Going to have to square up the idler pulleys better. The belt was trying to walk off of the side of 2 of them.

I remade some brackets today on the mill at work. They should work better. The other ones left the idler pulleys out of square. I made an assembly jig too so it goes together square.

New brackets just about did the trick I just had to use a dremel on one of the openings to shift the idler pulley slightly and now the belt tracks straight and true on all of them

Now I need to run a short test program on it and keep an eye on the belt/pulleys... Plus make sure things are square and tension all of the belts the right amount.

A quick video.... I ran a piece of g-code that took about 8 minutes to run before...

took less then 2 minutes!

Youtube - CNC router

Nice! Beware of the DeWalt router. It won't last long in there - I had the exact model and the bearings went out quick. Also, the top bearing is just held in by the plastic housing. I changed to a Porter Cable which fit the same diameter mount but they only last about 6 months too. Next will be a real spindle if I can find a 120V version.

I'd like a spindle someday and I do have 220V in the garage

The 80mm air-cooled spindles are all of $220 for a 2.2KVA. The hitachi 400Hz VFD costs more.

someday.....

No 220V for me.

I'm on a couple of cnc forums and the conventional wisdom is that the laminate trimmers will last far longer if they are dialed back to about 80 percent rpm. Apparently the bearings are too small in that size of router to run at 100 percent rpm for long periods of time. I use that Dewalt, dialed back, and so far it is doing fine. Now that I'm reminded, though, I should probably watch for a sale and get a spare for back up.
Mike

thanks, I'll keep that in mind!

When I was looking for suitable replacement bearings for my bosch 1608 nothing was coming up that could handle the 30,000 rpm in a permanent lube bearing. These are designed to self-destruct. I run my VS colts at about 18,000 and they will go all day at that speed.

Jamie, a step-up transformer would be an easy solution but you'd want 20 amp capacity at 120V to get to 3HP with a little safety factor.
Most VFDs have a huge surge when you plug them in to charge those supply capacitors. Look for a 3KVA transformer on ebay.

David King wrote:When I was looking for suitable replacement bearings for my bosch 1608 nothing was coming up that could handle the 30,000 rpm in a permanent lube bearing. These are designed to self-destruct. I run my VS colts at about 18,000 and they will go all day at that speed.

Jamie, a step-up transformer would be an easy solution but you'd want 20 amp capacity at 120V to get to 3HP with a little safety factor.
Most VFDs have a huge surge when you plug them in to charge those supply capacitors. Look for a 3KVA transformer on ebay.

For a 2.2kW spindle, what size converter should I get?

Jamie, 2.2kw is the equivalent of 3HP (1HP = 746w). Most VFDs aren't designed to run at full power off a single phase source so you'd want to derate them about 30%. That usually means running a 3 PH motor on a 5hp VFD. You do need a VFD that can go up to 400Hz and many of them stop at 120 or 180. I'm pretty sure that the Hitachi is the one most folks end up using because it can run of single phase power at rated capacity.