[DaveN]

oh one other important thing

I work in metric and metric only.

Dave
Cape Town
South Africa

[mikeschn]

oh one other important thing

I work in metric and metric only.

That's perfect... that can take care of the countries that are in metric.

Mike...

[Mcgyver]

imo it would be very difficult to even agree on the objectives let alone a design. Think of how hard it would be to do in a workplace where there are pay cheques and boss to keep things in line. People will not spend their leisure time on something they disagree with. Want to see what can happen? Check out the thread on making a communal pcb mill at the parallax basic stamp site – there, the objective was predefined but what a mess!

As was posted, the idea of building a culture of open source designs is the best idea. Having a variety of designs will help people create what’s right for them and inspire many. Kudos’ to peeps like Phil and Alan and others for contributing to it – that sort of action will have the greatest effect imo. My view is that the culture should encourage people to share their designs and frown on amateurs trying to sell their designs. Me? I don’t have a design to share yet so try to contribute by answering machining Q’s

[80/20surplus]

Tim & I at 80/20 Surplus would love to see some plans using our 80/20 Inc T-slotted aluminum extrusions. We have a sizeable stock of 1515, 1515L, and 1020 T-slot profiles that have some dimensional problems (1 bad T-slot, centerhole dimension errors). Chances are good that the dimensional problems would have no impact on a basic CNC design. We could supply the extrusions in full length or pre-cut. By using the surplus material we can reduce the cost of the T-slot, which is the biggest hurdle for most home hobbyist.

Should we consider a contest with product give-a-way? A % of sales for suggested plans? A discount for material for plans you market on your own site? I'd love hear any ideas you might have that can keep 80/20 Surplus around as an inexpesive source for T-slot extrusions and accessories.

[mikeschn]

Tim & I at 80/20 Surplus would love to see some plans using our 80/20 Inc T-slotted aluminum extrusions.

I hadn't quite figured out where the 80/20 design would fit in. Is it a mid range design because of cost, or an entry level design because of precision?

How much would the extrusions and high cycle, single length, double flanged linear bearings cost for the 15 series?

Figure (2) 36" extrusions for the x rail
(2) 24" extrusions for the y rail
(2) 12" extrusions for the z rail
and (12) double flanged linear bearings

Mike...

[ViperTX]

80/20surplus....details...I'm building a small format (2' x 2') gantry style unit using your Series 10 extrusions...1020 and 2040 along with some jig plate....send me an email and I'll consider drawing up the plans and offering them...

[mikeschn]

80/20surplus....details...I'm building a small format (2' x 2') gantry style unit using your Series 10 extrusions...1020 and 2040 along with some jig plate....send me an email and I'll consider drawing up the plans and offering them...

ViperTX,

It would be great if you could draw up your plans. Shall we start a new thread for your 80/20 design?

Mike...

[frog]

I have a circuit board using 3 16f84 chips with buffers the code came from dak engineering I changed it a little so I could use an external Osc the circuit board is parallel port works with kcam also have my own 3 axis controller program in vb for experimentation only if ya want I will post to my site or this one so you can download the board as for the code you will need to get it from dak also need to be able to change the asm to xt easier to work with I think I have been using it on a homemade mill for circuit boards works great. You will need a pic programmer to use this board my inferface is in VB6 with a special timer it is done in activex ts-timer works ok. just downloaded softwire starting to play with this it also has a timmer thinking about checking its speed. next I think I am going to do an rs232 with a pic16f877 for axis control right now no time going back to work after being out for 7 months with hurt hand.

[phillby]

Sorry I have shifted this to the newer threads

Cheers

[sydney075]

Ok I haven't built a cnc yet and most likely will not be able to for a while due to costs involved. This is of course why I am so interested in this discussion so let me throw my unexperienced 2 cents into the ring here.

Now I have skimmed through the 246 posts but admitedly not had time to read all of them in full yet. I feel that Chuck Knight had a great idea with a proof of concept build. Back on post #18 he talked about a cross slide vise and possibly using it. This is what I feel could be a great possiblity. I myself have a very nice drill press that I have wanted to turn into a small mill which this tool could be the key for me in doing that. What that leads to next is the possibility of a simple 2d cad router that could be built just by assembling parts without building a whole table as a starting project. Before I go futurer check out Habor Freight here and then look at the crudely modfied image that I have attached.

Now the vise is $60 but has a 7"x7" envelope that would have little to no contstruction as a router table would. By mounting two steppers and connecting them to the axises. One could create a 2d cad table with hopefully little cost and labor. Which when run at the right speed could be used to make parts for a larger router as a next project.

So there you have my input, take it for what its worth. I do not propose this as a solution for the low cost cnc but, it could be a new entry level project. In Chuck's words

A good "starter" planset that would encourage people to finish the project with relative ease

This is an idea he has proposed in several forms and I think it is worth pursing.

[chronon1]

That $60 vise looks like the basic X and Y table needed - 2/3 of the machine ..
Z-axis seems all that needs to be built ?

I think you need heavy torque to turn the thing because of all the friction though...
other --- other than the friction, if the accuracy is decent ... why not ?

I suppose you could loosen it up to have less friction, but then the play would increase ... if you only need 1/10" accuracy, I think this could more than do it ...

Guess you need well over 100 oz inch of torque which means big stepper and big drivers, which are not usually found in a DM printer scrap....

[pminmo]

I've bought from this ebay store, maybe one of these tables:

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1

http://cgi.ebay.com/COMPACT-CROSS-SL...QQcmdZViewItem

[triticale]

I've got one of those tables, bought off the well-known truck, and have planned to use it for such operations. Two things need to be improved.

First of all, the ways are just plain rough. The improvement process can be started with a file, before you even think about stoning scraping and lapping.

The lead screws are very sloppy. One axis, I'd call it the Y, uses a floating nut which rocks back and forth a visible fraction of an inch. This can be coped with when using the table as a fixturing aid, but a CNC conversion will need a systemic leadscrew replacement.

[pminmo]

I've got one of those tables

Which one, where did you purchase it?

[mckmck]

It might be a good idea to look at what has been done. I think quite a few such machines have been built. Some of the builders have web sites showing their machines and their solutions to design problems. Some such references have already appeared in this thread.

A list of web sites showing such machines, details of their design, and discussing
the problems, and lessons learned would be exelent reference material for anyone involved.

Could anyone who knows of sites with usefull information or good ideas list them?

Craig

[chuckknigh]

Actually...I've worked on my 2 vises, and managed to improve them significantly. I intend to hook them up as follows, as mine are a 4x6" envelope. Mount 1 horizontally, and 1 vertically. Arrange them so that X is a 6" axis...Y is the other vise's 6" axis, and the 4" axis is the Z. Should work quite easily, and produce the same effect as a fixed gantry router.

Here is how I'm improving my vises.

Step 1: Remove the lead screws completely and disassemble the vise. Now, use VALVE GRINDING COMPOUND from Auto Zone or similar, and polish the ways. This works quite easily... Near the end of the process insert the gibs and polish them as well.

Step 2: Secure the Y axis nut. The easiest way to do this is to drill a hole in the top of it, and thread it for a 1/4" bolt. A cheap tap from Harbor Freight is more than good enough for this purpose...the idea is to "secure" the nut to the axis. Use a fender washer to "fill in the hole" in the casting. Works quite well...no visible play. I've not measured runout, yet, since I haven't completed work on it...but it's extremely low, and wouldn't be an issue in a simple machine.

Step 3: Replace the leadscrews. Bearing in mind that the purpose of this is a low cost machine, we can dispense with the need for ballscrews, etc. Cheap 1/4" threaded rod is sufficient...and over the short distances we are discussing (at most 7x7") thread wander is of no significance. Why not ACME? It's not available locally, taps are hard to find and comparatively expensive, and the difference in efficiency and precision for a small project will be negligible.

Since we replaced the screws...the nuts will need to be replaced, too. My local hardware store sells a 1/2" nylon spacer...a nylon tube of 1/2" outside diameter and 3/16" internal diameter. Shave down the end a little (taper it like you would a homemade tap) and thread it into the existing ACME nut. This insert is both replacable, and presents extremely low backlash. A split design could also be implemented, if desired. The existing ACME nut aligns the insert in the perfect position...just thread it in and be done.

Step 3: (Alternate) A 5/16" threaded rod coupler is just slightly larger than the ACME threads. Threading the outside of the coupler, and the inside of the existing ACME nuts with a traditional tap and die should produce a good mechanical connection, while providing a metal nut... Something to think about if you intend to work hard metals. I've not tried this, because I don't have a tap and die of sufficient size to do this.

Step 4: (What I'm at now) Take a rollerblade wheel and slice/split it in half like you would a bagel. You now have 2 high quality thrust bearing mounts. Insert a bearing in each one, and attach to either end of each axis. Tighten a washer and nut on both ends, and tension the threaded rod slightly. This should provide a very smooth motion...especially if the threaded rod is wrapped in wire to make the rod fit snugly, as per JCK's suggestions.

From this point forward, you have a reasonably precise machine tool...one with relatively low friction because of the nylon nuts, the pitch of the screws, and the newly smoothed ways. Now, hook it up as CNC. Hook up your printer motors and have at it.

-- Chuck Knight

P.S. The vise shown is available for $20 at Cummins Tools, on a regular basis. Harbor Freight will price match, if one of the Cummins sales is in the area...maybe for the web site, too.

[triticale]

To answer Phil, Cummins is the truck I bought mine off - they do a tour of the country selling out of cheap auditorium space.

Chuck detailed the processes I hinted at in my post. The one other thing I would suggest is making a stiffer, flatter end plate.

[chuckknigh]

I actually read, on someone's blog, that the included lead screws are pretty good. The problem lies in the rough mountings.

What they did is take out the leadscrews, turn them down on their lathe to fit proper ball bearings, and then remount them. Said the results were so good that their friends were jealous.

Of course, that's just hearsay...but in fairness, the included leadscrews aren't bad. They're slightly bent, and run rough...but that really could be just the "friction fit" at the one end.

The problem is, that I just can't figure out an easy way to deal with them, without using machine tools like a lathe...and not everyone has easy access to those kinds of tools. Much better, for a starter unit, to use stuff you can easily get at the local hardware store. 1/4" threaded rod is pretty darned common.

BTW, I chose 1/4" rod because it's 20tpi -- each rotation, if used manually, is .05 inches. 5/16" x 18tpi results in .0555 repeating inches per rotation.

See? There's a method to my madness! While this wouldn't matter tremendously with a CNC conversion...it leaves it easily usable if they decide to stop at just the upgrade step, and use it as a decent manual table.

-- Chuck Knight

[chronon1]

http://www.cumminstools.com/browse.cfm/4,92.htm

is this the one your talking about ? so if i take a printout of that to HF i should get the same thing on that 4" that they want twice for ( http://www.harborfreight.com/cpi/cta...itemnumber=538 ) and theirs weights 2.5# less ( which i think in the case of vices is probably a bad thing).

[triticale]

Yes, that's the x-y rig under discussion. HF item looks just about identical, including the close-together bolt down slots and the cheap stamped end plate I suggest replacing. Weights listed are for shipping; the actual weight of my Cummins is 19 lbs.