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View Full Version : CNC Router with THK KR46 actuators Finished! pics & video



wisp
05-27-2005, 04:07 PM
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.
http://home.houston.rr.com/wisp/router/CIMG2676.JPG
Getting started.....
http://home.houston.rr.com/wisp/router/Cimg2010.jpg
http://home.houston.rr.com/wisp/router/Cimg2006.jpg
I finished the controller early on.
http://home.houston.rr.com/wisp/router/Cimg2008.jpg

wisp
05-27-2005, 04:23 PM
The table is a 2" butcher block from MSC. It is very flat, and weighs a TON.
http://home.houston.rr.com/wisp/router/CIMG2471.JPG
The Z column was the most difficult part because I chose to use crossed roller bearings from Bayside (http://www.baysidemotion.com/web/BMGHome.nsf/94fdfea6fb8472928525673900537da3/b1d64fcf238657bd8525673d006a3223?OpenDocument) , 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.
http://home.houston.rr.com/wisp/router/CIMG2675.JPG

Brackets for the router. solid as a rock.
http://home.houston.rr.com/wisp/router/CIMG2464.JPG

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

Click here to see more photos. (http://home.houston.rr.com/wisp/router/)

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

Movie1 (http://home.houston.rr.com/wisp/router/Movie1.wmv) - this is little program with some circle moves, G02/G03 and Z moves
Movie2 (http://home.houston.rr.com/wisp/router/Movie2.WMV) - 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
05-27-2005, 04:43 PM
Which is the price for THK KR46 actuators. I mean at which price have you bought them?

wisp
05-27-2005, 05:18 PM
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
05-27-2005, 05:54 PM
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
05-27-2005, 06:11 PM
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. (group) The table is 32"x72".

pminmo
05-27-2005, 06:11 PM
I see where you used Kirk lead screws, what kind of TPI? Great looking machine.


Phil

mk2lehe
05-27-2005, 07:10 PM
I am so happy! This gives me new hopes to my KR33's. Your machine is a monster!

mrservo
05-27-2005, 07:43 PM
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
05-27-2005, 10:59 PM
Those actuators keep the design lines simple and very clean. Looks VERY professional, well done.

wisp
05-27-2005, 11:39 PM
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
05-27-2005, 11:42 PM
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.

wisp
05-29-2005, 12:50 PM
Depending on moisture a butcher block may expand as much as 3/16” (assuming that your table is maple).

I called Michigan Maple Block, the mafg of the table top, they assured me I should have no trouble with expansion, or warping. yeaee! They say its sealed top/bottom & ends. Here is a quote from their page,

"" A special Wood Welded wear-resistant finish is then applied - DURAKRYL 102. This tough, acrylic coating will repel alcohol, bleach, even paint thinner! Wood Welded Butcher Block is one of the few materials that can take so much hard wear and tear, be resurfaced or repaired without any special tools or particular skill, and come up looking as great as ever. ""

I was thinking of drilling a large hole pattern in the table for workholding, and then pressing threaded metal inserts in the holes from the underside, that way they couldnt be pulled out. Has anyone done this before?

Cold Fusion
05-29-2005, 12:56 PM
I've experimented with inserts in a wood base and I can tell you that it just doesn't work as well as an aluminum base. After many problems with mine expanding and contracting, I finally bit the bullet and bought a 6061 base that I could tap a grid of holes into. It's a world of difference.

ViperTX
05-29-2005, 01:33 PM
Wisp,

For workholding I don't see any problem with that approach unless you're leaving something clamped for long periods of time....ya know through the expansion/contraction cycles of the top.

chuckknigh
05-29-2005, 02:14 PM
I called Michigan Maple Block, the mafg of the table top, they assured me I should have no trouble with expansion, or warping. yeaee! They say its sealed top/bottom & ends. Here is a quote from their page,

Wouldn't drilling all those holes "break the seal" and allow expansion and contraction? The only reason it's stable now is because it's encased in acrylic plastic. Worse yet, it'd just be holes in 1 side, so differntial expansion would probably cause it to cup.

If you put a sealer on the inside of the drilled holes, though, it'd probably keep it stable.

-- Chuck Knight

P.S. Your machine is absolutely beautiful.

zoltan
05-29-2005, 03:40 PM
I have a question for who can help - how do you syncronize those two axis in the case X? What kind of wiring diagram or do you use a different type of stepper driver, or you just connect in parrallel the two steppers?

zoltan
05-29-2005, 03:43 PM
Wisp,

Do you think that if I buy three actuators of 475$ you can ship them in Romania to me? Can you give a pm to discuss this subject?

gdc
05-29-2005, 04:51 PM
I called Michigan Maple Block, the mafg of the table top, they assured me I should have no trouble with expansion, or warping. yeaee! They say its sealed top/bottom & ends. Here is a quote from their page,

"" A special Wood Welded wear-resistant finish is then applied - DURAKRYL 102. This tough, acrylic coating will repel alcohol, bleach, even paint thinner! Wood Welded Butcher Block is one of the few materials that can take so much hard wear and tear, be resurfaced or repaired without any special tools or particular skill, and come up looking as great as ever. ""

I was thinking of drilling a large hole pattern in the table for workholding, and then pressing threaded metal inserts in the holes from the underside, that way they couldnt be pulled out. Has anyone done this before?

I don't really think they can guarantee there isn't going to be any expansion. I've been doing woodworking for 30 years. Wood will always expand. It may not expand much, but it's going to regardless of how much you seal the wood, especially when you're using solids.

But if you do decide to risk it, make sure to seal any holes you make. If the wood fibers have access to moisture, you'll eventually have expansion, albeit minimal.

You mentioned using screw inserts. They do work well. They're tricky to get started and more so in a hardwood. Good luck to you.

pminmo
05-29-2005, 05:44 PM
I too have been woodworking for over 30 years. You have several things going for you: Hard Maple is a very dense wood, the laminations of multiple slices gives a ton of strength, and makes it less apt to warp and dimensional variation. ALso the fact that it is sealed. If you put it in an enviornment that is fairly tmeperature stable and humidy stable you will help yourself. But I seriously doubt it will stay as stable as your bearings. If you want to maintain the accuracy that you have invested in your parts, slap some steel bar on the the top of the wood.

Phil

wisp
05-31-2005, 11:12 AM
I have a question for who can help - how do you syncronize those two axis in the case X? What kind of wiring diagram or do you use a different type of stepper driver, or you just connect in parrallel the two steppers?

I am using API 3535 stepper drives (http://www.applied-motion.com/products/stepper/drives/3535.php). The two drives running the Y axis motors are both wired to the same pins on the breackout board. I had originally planned to use one motor with a timing belt running to the other actuator, but I wanted to try running two motors in sync first, as I already had the motors. So far I have had no problems with the motors loosing sync. They are rated 540oz, wich is overkill for this setup, so I have the amps turned down to 1/2 the motor rating as it makes the motors run smoother.

wisp
05-31-2005, 11:28 AM
Wisp,

Do you think that if I buy three actuators of 475$ you can ship them in Romania to me? Can you give a pm to discuss this subject?

For those interested, I have put some photos of the KR46 actuators I have available up HERE (http://home.houston.rr.com/wisp/KR46%20photos/)

And here is a link to a PDF file with full specs. (http://home.houston.rr.com/wisp/KR46%20photos/KR46.pdf)

I also have some Nema34 motor mounts made by THK, for KR46 actuators, they are $16 each there is also a picture of one.

And if anyone is interested, I can make X-Y gantry kits to allow you to bolt three KR46 actuators together the way I did for $60.

Also, what do you guys think would be a reasonable price for brackets to hold porter cable/makita, etc.. routers like the ones in the photos? Or brackets for RotoZip also. They would be precision machined from solid aluminum. I know these brackets can be tough to make if you dont have access to the proper equipment.

Thanks for the complements and advise on the router table also.

wisp
07-08-2005, 11:10 PM
Hey all, just an update on the maple table flatness/warping concern. I ran an indicator over the whole table again, I did this also when the router new> and it is reading .02" max out of flat, the same as the first check. It has been in the garage for over 8 months now, in Houston heat/ humidity, and has shown no detectable sign of expansion or warping, so far.

Unless some crazy wood warping action happens in the next 4 months, which will mark one year since the router was assembled, I would say any concern over using a laminated wood table are unfounded. It has been a VERY stable, flat and rigid surface for me in the last 8 months.

I will check it again in a couple months, if it starts to show any warping, I will post it.