CNC Router with THK KR46 actuators Finished! pics & video

[wisp]

Well, its been a long road, but ive finally completed my 1st cnc router. I used precision grade actuators from THK. They have ground ballscrews rated at .0001 backlash. Thought everyone might like to see some pics.

Travel is about 22"x41"x6"

First I drew everything up in CAD.

Getting started.....


I finished the controller early on.

[wisp]

The table is a 2" butcher block from MSC. It is very flat, and weighs a TON.

The Z column was the most difficult part because I chose to use crossed roller bearings from Bayside , they are rated for over 2100lbs load in any direction. Crossed roller bearings are much more rigid than recirculating ball type linear bearings. The down side is limited travel, but for a Z axis, 6" was enough.


Brackets for the router. solid as a rock.


If post too many pics this post will load too slow I fear, so,

Click here to see more photos.

And here are a couple movies of it in motion, you will need windows media player10 to watch them.

Movie1 - this is little program with some circle moves, G02/G03 and Z moves
Movie2 - this clip is me jogging the router through the max X-Y travel

I done a bit of test cutting, and stalled the router with a 1/2" mill at 60 IPM, DOH!

Also, I recently purchased a large CNC knee mill, so this router will be going up for sale possibly on eBay, pretty soon...... If your interested its located in houston TX, you can come by and see it. It's VERY rigid, the thing has no deflection.

[zoltan]

Which is the price for THK KR46 actuators. I mean at which price have you bought them?

[wisp]

I bought a bunch of them from at automation place that went bust. I can sell you as many of the KR46's as you need for $475 each. retail was $3600+ because they are the precision grade. I also have some new crossed roller sets left.

[Chris D]

Please don't take this the wrong way buy you made a nasty error in your design. That butcher block top looks pretty, but you have to keep in mind that it will expand and contract with changes in humidity. If your rails are solidly mounted to the bench top, one of two things will happen...

If the top was dry when you attached the rails to it, the top will either bend your rails as it expands, or elongate the screw holes that you attached the rails to the top with.

If the top was wet when you attached the rails to it, the top will either split or elongate the screw holes.

Either way, that top is going to cause problems.

You will be much better off putting a piece of MDF on the workbench top and attaching the rails to the MDF. Fasten only one edge of the MDF to the workbench top so that the two can move freely of each other.

As for how much the top will expand and contract, it's tough to say as I don't know where you are and what the humidity swings are in your area. Here in the midwest, I have seen tops of that size (about 18" front to back) move 3/8".

Again, please don't take this the wrong way. I just want to prepare you for potential problems that will pop up.

The rest of the machine looks FANTASTIC!

Chris

[wisp]

Thanks for the tip, I had no idea one of those table could expand like that. Putting MDF between the rail and the table would be a snap, plus it would give extra table clearance for taller work peices. The table has never been wet, so I will keep it that way.

The actuators have 2 rows of about 12 holes each for screwing them down. Currently i only have four screws holding each actuator to the table, beacause they are so solid already.

The rails have been mounted since December, i will keep a close eye on the table, it doesnt seem to expanded/contracted any.

BTW, the whole thing, table included, weighs about 200lbs, you deffinatly need help when moving it. The table is 32"x72".

[pminmo]

I see where you used Kirk lead screws, what kind of TPI? Great looking machine.


Phil

[mk2lehe]

I am so happy! This gives me new hopes to my KR33's. Your machine is a monster!

[mrservo]

Nice looking machine. Thanks for putting up the pics and movies. Like I emailed earlier, I'm putting together almost the same type of setup, with double KR46's
for the X axis, etc. I was very interested to see anothers KR setup. There
are so few on this forum.

I second the notion to watch the wood table top. That thing looks great, but can
only be so flat, and the dimesions will change day to day. A granite surface
plate would be perfect, if it were only the size of a minimill. Maybe attach
it to a thick ground plate if you plan to machine metal. I was planning on
attaching mine to large profile alluminum extrusions and ground plate.

Keep up the nice work. Let us know what length KR's you have access to.
All the best...

[2muchstuff]

Those actuators keep the design lines simple and very clean. Looks VERY professional, well done.

[wisp]

Originally Posted by pminmo I see where you used Kirk lead screws, what kind of TPI? Great looking machine. Phil

Only the Z axis uses a Kirk anti-backlash lead screw. The screw I used is Kerks NTB series leadscrew/nut rated at 100lbs dynamic load. The lead is .05 per inch, 20 pitch screw. It is very smooth, i highly reccomend Kirks lead screws, they are very smooth, have 0 backlash, and are self lubricating. As the nut wears, a coiled spring takes out any backlash, and, they are almost as efficient as a ballscrew. check out www.kerkmotion.com if you can only get rolled ballscrews, try a kerk leadscrew instead, less backlash, cheaper.

[gdc]

Depending on moisture a butcher block may expand as much as 3/16” (assuming that your table is maple). The wider the block the greater the expansion. But it will only expand and contract in width, not length. And expansion will be greatest in the summer months. I presume you're in the south since you mention Houston. I'm in Gautier, MS, so we both know miserable summer humidity and I know you'll get max expansion in the summer.

Of course, if your machine is in a stable environment and humidity is controlled, you could seal the board and you probably wouldn't have that much expansion, if any. But I wouldn't take the chance. I do a lot of woodworking, I personally wouldn't recommend it.

And very nice machine! If you feel like giving it away (ha!) please email me.