[jwillhite]

I really like your design and it looks like you will be coming in under budget. But then again, the right software could blow it sky high. (nuts)

The one I'm drawing up is very similar, down to the vertical placement of the side rails. Could you tell me what the dimensions of your table will be?

Thanks, at this point though with the revised design and looking at everything that still needs to be purchased theres no way I'm going to come in under 1600.

8020 ~650
Steel Plate ~100
Stepper Motors ~150
Power Supply ~ 60
Thrust bearing assembly/connectors ~ 75
Bearings ~ 35
ACME threaded rod ~120
Router + mount ~130
Misc. ~ 100

Total remaining = 1420
Total Estimated Cost = 2101!!!! ouch wow, might have to modify the design depending on how much they say the extrusion will cost.

Won't be spending anything on the software, I enjoy playing around with linux and computer stuff in general so I was thinking of using something like this http://www.linuxcnc.org.

The overall footprint of the machine will be approx. 48"x48", the usefull cutting dimensions should be pretty close to 36"x30"x5". The reason I didn't go longer on the X-axis is the threaded rod only comes in lengths of 36" and 72", I didn't want to buy the 6' length then waste a bunch of it. Using 1/2" drill rod for coupling from the motor to the threaded rod gets a couple extra inches of travel, per Ahrens design here http://www.cncrouterparts.com/parts.html.

Hey if you have your's drawn up I'd be really interested in seeing it, do you have a build log going?

[jwillhite]

Josh,
Your parts went out today -- you should see them Monday or Tuesday. Your design looks quite stout. Nice rendering by the way! I wouldn't worry about the screw on the Y being off center, and I think cutting aluminum will be viable. Just use small bits, take light passes, and keep your feedrate high, since your router will be running much faster than normal metal cutting spindles. Looking forward to seeing it come together!

Best regards,

Ahren
www.cncrouterparts.com

Awesome, thank's Ahren. Man that was a fast turn around, when I get everything I'll post some pictures.

Any suggestions on a router that will cut well at low rpm's? I guess that means finding one that is variable speed and pretty powerfull.

[jwillhite]

Ahren,

jwillhite's latest design sure shows how simple it is to incorporate your bearing trucks into a functional machine. Nice work for both of you.

CarveOne

I agree Ahrens linear motion solution is a perfect fit for this type of machine, just put the peices together and you have working axis. I've been playing around with different design ideas for the last year and for the price this is without a doubt the best option out there. Unless you get really lucky on ebay, or you have access to a machine shop. And in both of those cases it will take a lot more design time anyway.

[ahren]

Josh,
I personally have the Hitachi M12VC, which is a popular one here on the zone. It's adjustable down to 8000 RPM, it's very quiet, and has a solid feeling cast housing. I recommend it highly.

Best regards,

Ahren
www.cncrouterparts.com

[jwillhite]

got the linear motion parts from Ahren in the mail yesterday check it out



just wish I had something to attach them to.

also got the bad news from the 8020 rep.... 780$, + another 130$ for shipping via UPS. This has me seriously considering revising the design... if I just go ahead and purchase as is I'll be up to around 2400$ for a finished machine, wich is about 1K more then budgeted for.

[FandZ]

Ouch, that hurts. I bought a minivan for that once..lol An idea, perhaps not a fun one, maybe you could scour 80/20's ebay auctions and just order the parts you need cut directly from them. With all that is on ebay, you probably could get your machine close to the size you want.

[FandZ]

Looking over the list, trying to trim some fat

Number (E) you have 10 10-inch pieces listed, what are they for?

The econ T- nuts.. You have 140 @ $84. Do you think that many are necessary. They way I understand it they are great because they keep all your connection perfectly centered. My thinking is you just use one per juncture to get your alignment straight and use plane old Harbor freight, bolts, nuts, and washers for the other holes. You follow?

Then you have your brackets. Nothing you can't make on a drill press out of steal and a little elbow grease. Spray paint them afterwards to match.

You have a great kit going. Now you just need to shave off some pork.

Really someone needs to try and contact 80/20 with a design like yours and negotiate a group buy. Say 10 for 450 or so.

[ahren]

Josh,
Glad the parts made it to you -- I hope you find something to connect them to soon! I echo FandZ's comments. T-nuts are way over-rated. They don't really center things, and are honestly not even that strong of a connection. 5/16-18 carriage bolts are the connection method of choice if you ask me -- you turn them upside down so the head rides in the track, and the square shoulder happens to fit perfectly in the slot of the 8020, serving as an anti-rotation feature. You can really crank down on a nut on top for a super solid connection. And the best part? Carriage bolts cost about $0.04 a piece from McMaster Carr, and a hex nut costs about $0.02.

Another note -- most of the brackets are available from 8020 surplus for about half of retail. Since they don't cost much to ship, you might be able to save a lot of dough here as well. And if you have access to a drill press, don't discount the budget method of drilling access holes and tapping the ends of the extrusion. This is actually quite strong as well, and can save a lot of joining plates.

I'm sure you'll find a good compromise between your $175 initial estimate and the $750 behemoth you've got right now. Excited to see the rest of your build!

Ahren
www.cncrouterparts.com

[jwillhite]

Fandz, good catch on the Tag (E) I sent the rep an excel file with the part numbers length and quantity just double checked mine he must have made a mistake entering the numbers because it should be 4 of the 10" 1530's not 10, well that cuts the price by ~47$ right there. Wow I need to be careful, glad I haven't ordered yet.

That would be awesome to do a group purchase from 8020 if enough people were interested.. They probably wouldn't give much of a discount though as they would still have to break it up and ship it all over the world.
__________________________________________________ _______

Everyone talks about the 8020 surplus store but when I look on there the buy it now prices are exactly the same as whats shown on the quote? http://cgi.ebay.com/8020-Inc-T-Slot-Aluminum-Extrusion-15-S-1530-x-36_W0QQitemZ320290082274QQihZ011QQcategoryZ29402QQ tcZphotoQQcmdZViewItemQQ_trksidZp1713.m153.l1262
36" 1530 extrusion from 8020 surplus is 33.50, on the quote its 33.48? I've never really used ebay, I feel like I must be missing something here.. I know you can bid on items but most of the stuff listed on the surplus store is buy it now only it seems? Anyone care to educate me?

I spoke with the rep about using carriage bolts instead of the T-nuts they offer he seemed to think that that was a bad idea as "they aren't designed for that application", haha and of course he would think that at 10x the price. I guess I'll just go with the carriage bolts for everything, that will save ~ 70$.

Ahren, Yeah your right just like everything else the key will be finding a happy balance between the ideal set up (780$) and the amount I want to spend (175$).

Would definately save time and money if I got something like this http://www.harborfreight.com/cpi/cta...emnumber=44505
I do wood working with hand tools... saws, gouges, planes..etc.. I have a hand drill which I was planning to use for the 1/4" steel that would probably not be much fun though. If I got that drill press I'd be able to forgo some of the joining plates in favor of just through bolting the extrusion like your suggesting.. hmm might do that.

Thanks for all the suggestions

[FandZ]

You should probably get an X-Y axis clamp for the drill press too. That way you could stack your flat braces and drill them all at once. Then again you could do the same thing with a well placed c clamp.

http://cgi.ebay.com/4-CROSS-SLIDE-DR...3A1|240%3A1318

On the issue of group buy. If a machine was designed to take say 12 equal pieces of 80/20. And each of those pieces were a third of their full sized rods, meaning they would only have to make two cuts per length, I'm sure they could set it up their machines to cut them quickly. That would be 120 equal pieces on an order of 10 machines. I have no doubt they could accomplish that rather quickly. They probably have the ability to cut groups of 6 or more beams at a time. As far as shipping goes, 10 boxes, typing in addresses and hitting print.

With this economy, especially after this Christmas with all the retail chains closing, it'll be hard for any company to turn down a $3000-5000.00 order.

[EvanZ]

HEY jwillhite I JUST baught one of those drill presses, well I just took it back, but that's cause I decided I didn't need it. I was in a rush but decided not to hurry. When I took it back it was on sale at my local HF it's called the Holiday sale or something, anyway it was $54.99. Might wanna jump on that. It was a good press for it's size for sure, will had NO problems with extrude and steel plates.

Hope that helps.
Evan

P.S. DON'T try and to it with a hand drill, you will never get it true and straight. For $55 go get that press!

[jwillhite]

You should probably get an X-Y axis clamp for the drill press too. That way you could stack your flat braces and drill them all at once. Then again you could do the same thing with a well placed c clamp.

http://cgi.ebay.com/4-CROSS-SLIDE-DR...3A1|240%3A1318

That looks like a really good deal, I have an abundance of clamps on hand so I'll probably just go the cheap route and punch it then clamp it.

On the issue of group buy. If a machine was designed to take say 12 equal pieces of 80/20. And each of those pieces were a third of their full sized rods, meaning they would only have to make two cuts per length, I'm sure they could set it up their machines to cut them quickly. That would be 120 equal pieces on an order of 10 machines. I have no doubt they could accomplish that rather quickly. They probably have the ability to cut groups of 6 or more beams at a time. As far as shipping goes, 10 boxes, typing in addresses and hitting print.

You might be right about them giving a discount on a large order.. not sure you'd get any two people on here to agree on an exact machine geometry. I'd be happy to post my cad files if anyone thinks they could use them for there own machine.

[jwillhite]

HEY jwillhite I JUST baught one of those drill presses, well I just took it back, but that's cause I decided I didn't need it. I was in a rush but decided not to hurry. When I took it back it was on sale at my local HF it's called the Holiday sale or something, anyway it was $54.99. Might wanna jump on that. It was a good press for it's size for sure, will had NO problems with extrude and steel plates.

Hope that helps.
Evan

P.S. DON'T try and to it with a hand drill, you will never get it true and straight. For $55 go get that press!

Hey good deal, glad to hear its not a piece of junk. haha yeah your right about not drilling that steel by hand I think thats just asking for trouble. I'm moving this weekend and I'll be about 5 blocks from a Harbor Freight store, hopefully they have the same deal going on. If so I'm buying it for sure.

[jwillhite]

Ok so I've gone through and revised the design again. This configuration knocks 199$ off the previous 780$ 8020 order. While increasing the stiffness.



Per the suggestions bellow I'm going to tap the ends of the extrusion and through drill the intersecting t-stock. It seems to me that this will provide a better connection then the joining plates anyway. I've replaced the 3030 and 1530 that runs across the top of the ganter with a single piece of 3060(3"x6"). With this configuration I'll have to modify the motor mount on the Y-Axis to make up for the extra 1/4" I get placing the bearing block's on top of the steel plate. Another plus with this setup is that I can get away with ordering 2x36" ACME lead screws instead of 3.

Here is the updated total cost to complete.

8020 - 580.92

Bearings - 19.95
Shaft couplers - 24.45
Thrust Washers - 5.22
Thrust Bearings - 18.12
1/2" Drill Rod - 8.58
Love Joy Connectors - 26.70

ACME Lead Screws - 55.78

Plate Steel - 136.14

Router - 120
Stepper Motors - 147
Power Supply - 60

Fasteners - 25

Total=1227.86$ + 50$ Misc.
Total Project Cost = 1958.86$(not including shipping)

Just need to buy this stuff and put it together. Hope to order everything this week and have a working machine withing 2 weeks.. I'm optimistic.

[FandZ]

I'd be happy to post my cad files if anyone thinks they could use them for there own machine.

Glad you were able to shave off a hundred or two there. Looks great, if not better than the last design.

I'd love to take a look at your cad files if you wouldn't mind posting them or emailing them to me.


You are right though, it would be a hard thing to get 10 people to commit to a single design. But if it is a proven design and the price is right who knows.

[rlrhett]

I would be worried about the gantry racking back and forth as a bit pushes into the material. Is there something that would prevent that?

[jwillhite]

I would be worried about the gantry racking back and forth as a bit pushes into the material. Is there something that would prevent that?

Err yeah I worry about that as well, I think the renders of the machine are a little misleading its not very large. The vertical part of the gantry is only unsuportted for ~ 10".

Here you can see what I came up with when I ran the 8020 deflection calculator:



It takes about a 2000lb load to cause a deflection of .001", even for a centered point load. Thats just for a single side, the top beam the 3"x6" beam will take a load of 500lb before distorting .001", that doesn't count the increased moment of inertia provided by the 1/4" steel. I'm not a mechanical engineer but I would guess that before the gantry starts racking I'll break the bits. A big part of it I'm sure will be adjusting the linear carriages on the 1/4" steel... I guess I'll find out.

Any ideas on how to reduce the chances of that happening without adding a second stepper and all that goes along with it?

[rlrhett]

Just to be clear, I mean racking in this direction not the kind of racking people get from a center drive screw.

I don't think the issue is going to be deflection in the 80/20 itself. The problem is that there is nothing that is holding the gantry perfectly upright except one of ahren's bearings. Will that be enough to resist the torsional momentum of the gantry when it accelerates or stops (not to mention the upward pressure on the spindle)? Maybe it is. I have seen this design before. I'm just asking the question. Is there anyone else who what built this configuration before? Do you experience problems with racking or the bit bouncing?

[TOTALLYRC]

Just to be clear, I mean racking in this direction not the kind of racking people get from a center drive screw.

I don't think the issue is going to be deflection in the 80/20 itself. The problem is that there is nothing that is holding the gantry perfectly upright except one of ahren's bearings. Will that be enough to resist the torsional momentum of the gantry when it accelerates or stops (not to mention the upward pressure on the spindle)? Maybe it is. I have seen this design before. I'm just asking the question. Is there anyone else who what built this configuration before? Do you experience problems with racking or the bit bouncing?

Perhaps a better way to say it, is to say that the z axis will tip in relation to the x and it will affect the tram of the Z.

The farther apart that the bearings are along the x axis the more stable the whole assembly will be, at a loss of X axis travel. I would willingly give up a few inches of X axis travel, if needed, to make sure that the machine is as stable as needed. I am sure that ahren will coment on the design as they are his bearings.

Mike

[jwillhite]

Just to be clear, I mean racking in this direction not the kind of racking people get from a center drive screw.

I don't think the issue is going to be deflection in the 80/20 itself. The problem is that there is nothing that is holding the gantry perfectly upright except one of ahren's bearings. Will that be enough to resist the torsional momentum of the gantry when it accelerates or stops (not to mention the upward pressure on the spindle)? Maybe it is. I have seen this design before. I'm just asking the question. Is there anyone else who what built this configuration before? Do you experience problems with racking or the bit bouncing?

Ahh now I see what your saying and I'm happy to say I'm not too concerned about it. If you look at the original design I was considering, on page 1 of this thread you can see I had a 2.5" piece of plate steel running horizontally under the X-Axis 8020 extrusions.

I changed the design to have 5.5" pieces of plate steel running vertically along the X-Axis because I was worried about the torsional forces your talking about. Basically the way I look at it the momentum of the gantry at top is a force acting on a lever arm, if the length of the lever arm is reduced then the amount of torque produced by the movement of the gantry is reduced proportionally. I think if Snowgrain's machine http://www.cnczone.com/forums/showthread.php?t=53316 and Glacialwandering's machine http://cnczone.com/forums/showthread.php?t=62271 work fine with there configurations I definately shouldn't have problems... I hope