I’ve been obsessed with the idea of getting a CNC Milling machine for years now, but haven’t found one small enough to take in my Slotcar Box to the track where I would use it most! And buying some of the other Desk Top mills are just cost probative. I know this is ambitious for my first real post but I’ve been working on the Idea of building my own, since I saw the endgadget Article on a DIY Mill. The other day I was over at an Engineer I work with’s shop, and found some 1”x2” Delrin sticks lying around. I of course snagged them (With Permission) and the last few nights have been sketching out what I think I want to build! Before you get the FLAME THROWERS warmed up I know my spelling and grammar is about 3rd grade, also this illustration is just a sketch not a finished rendered illustration! I’d like to get some input on what you guys think about the design, and some ideas on Low cost stepper controllers. I plan to build 2 versions one all Delrin to learn on, and maybe one Steel / Delrin for in shop use. I’m using the steppers out of old Tandon Floppy Drives, and Harden steel Liner Rods out of old sewing machines. The power head is my Dremel Hand piece off the Shaft drive, powered by a 12v R/C Car motor, I’m hoping to also control with the P.C. I think I can build the whole thing including steppers et. al. Less controller for $20 I intently mad the bed 3” x 5” , with a total working area of 3’x5”
Please let me know you thoughts!
I’m also looking for a low cost CNC stepper controller preferably a parallel port controller so I can use it with an old lap top!
TIA




http://i184.photobucket.com/albums/x128/bigbunny5/millpostillcopy.jpg

What you have there would be better classified as a cnc router.
You'll find plenty of info here (http://www.cnczone.com/forums/forumdisplay.php?s=&daysprune=&f=48).
Good luck

Its hard to find info on mills not driven by testosterone, but they are out there.

I also have a portable 4-axis mill - it uses nema 17 motors, small Aerotech slides with ground ballscrews, and is only about 10 inches square. The Z folds, so when it is folded flat it is about three inches thick total and fits in a padded aluminum camera lens case and weighs about 10 pounds.

Cheaper than building your own stages, look for them used. No one really wants linear stages that only do a few inches travel - you can find aerospace grade stuff on Ebay for cheap. Each stage is self-contained, so it is easy to configure a machine for yourself pretty painlesssly that way.

I like the idea of the sewing machine guide rods. I have seen them before and they would likely work really well. Your steppers might need to be a bit bigger, but small Nema 14 or 17 motors are not very popular and so I have scored brand new sets of them for $5 or less each on Ebay. Usually they don't get bids at all. As for drivers, there are a couple of companies that make nice bipolar microstepping drivers for about $15 - $30 per axis that would work well for this application. They aren't good for bigger machines, but .75 amp/phase is more than enough for what you are doing here. You don't need a full-sized driver. If you get them small enough you can drive the motors from a wall wart or evan a laptop USB port can deliver the current needed, no fans or power supplies needed.

Either that or make a portable machine the normally recommended way here to solve all problems - Start with an X3. Of course, to make it portable you would need to build a horizontal dolly frame with a spot for the X3 on top of it, powered by a Chevy smallblock nested between the frame rails to move it around. Don't forget to add nitrous and an automatic toolchanger.

I also have a portable 4-axis mill - it uses nema 17 motors, small Aerotech slides with ground ballscrews, and is only about 10 inches square. The Z folds, so when it is folded flat it is about three inches thick total and fits in a padded aluminum camera lens case and weighs about 10 pounds.

I'd Love to see it could you post some pics ?

I like the idea of the sewing machine guide rods. I have seen them before and they would likely work really well.

Yea if you stay away from the import machines you can salvage at least 3 1/4" x 16" "Drive Shaft" rods and the singers I found @ Good Will also had 2 1/8" x 13" Rods in it:) cheaper than ordering th am and shipping them plus an easy pick up and lots of other good machined mechanical bits to OHH and AWWW Over :)

I'm still undecided weather to use the Darin to slide on the rods or make Bronze OIlites for the slides?

there are a couple of companies that make nice bipolar microstepping drivers for about $15 - $30 per axis that would work well for this application.

I've bee leaning toards the FET3 (http://www.stepperworld.com/fet3.htm)but at $135 it's a bit pricey for something that may die on my first try at getting it going if you know of a more price effective solution I'm all ears!

BigBunny;

For what you are looking for, Bronze won't actually get to the speed or loads to heat and flow lubricant and so essentially run dry anyway, and the coefficient of friction from static start is much higher than its running coefficient (meaning it has some "stick" during a start or direction change). For your small loading, slide length, and speed, a form of plastic bushing can actually be superior in those cases. Especially those materials that have almost identical resistance from a start and while running. The rails don't have to be as smooth, either, as they will to some degree fill microsurface irregularities of the rails and self-lubricate, and they have the added advantage of running better dry. Good for a portable machine.

Look around for the stepper drivers used more for electronics equipment than for CNC. You can find microstepping drivers from .3 A/ph to .75 A/ph much cheaper than what you were looking at - they are small, need no heatsinks, and are hard to blow up at that power too, and they are perfectly sized for the kind of machine you are building. If you can't find any surplus new ones are still only $30/axis or less. I will look up some of my old links to try and find some suppliers.

Cheap stepper driver is easy: EasyDriver v3. 0.75A per phase, 30V. Chopper and smart-decay built in. And super simple to boot. Look on the sparkfun site for finished boards, they're only $15. I don't know what controller is compatible however.

*EDIT* Just figured out you can connect them directly to the parallel port! And use EMC2 for controlling them.

--Blerik

Blerik,

Those Easydriver boards are cool! I love the fact they aren't much bigger than a quarter! Looks like they take straight step and dir inputs so anything will drive them pretty readily from a parallel breakout. For $15 bucks they look like a deal.

I'm betting that you could easily hook up the portable mill to a couple of small laptop batteries or similar and run the motors for a decent time frame, and using a laptop or palmtop to control the machine. That would make a very cool little functional setup!

It also looks like Sparkfun has some cool opto interrupters that would make cool optical limit switches, and one emitter/detector that could be used to make a non-contact spindle tachometer. Since my computer case has an LCD display on the front for fan RPM, I think I might wire that up to it instead of the fans sensor wire so I get my spindle DRO right on the front of my mills driver computer. For three bucks its worth a shot and should work. I'll let you know.

Or use a standard PC powersupply. The lower wattage ones are tiny (I got an 120W one here that is about 6"x4"x3"). Search the web for them...

They have a bit of ripple on the 12v lines, but the chopper compensates for that.

--Blerik

Easy now Fellas. I think you are being more detrimental to Big Bunny's thread than you realize. Give advice and move on. If you feel you need to rebut someone's advice, fine. Do it, but the name calling crap is really uncalled for. Take it to a PM so we don't have to see it.
If you think it's a wrong forum, alert the mod's. If they feel it's wrong, they will move it.
It has been useful info that has helped me the most here at the Zone. Childish banter is just no longer of any use to me personally, though it certainly had its place 40 years ago.
Please just do us all a favor and take it to a PM.

Big Bunny, if you are looking to build a small mill or router, you may try to find an old printer or copy machine. They have many very useable parts including motors and geared drives. Just the other day I saw an old Zerox machine and they wanted $20 for it. There is nothing wrong with wanting a small portable mill. It would be a perfect fit for RC parts.

If your not bothered by it, then don't reply stepper.

That looks like a nice little machine. What program did you use to draw that?

And yes the drivers and steppers that were suggested are good enough for this kind of project. You should also look into aluminium profiles. They are good for these kind of projects and they are quite strong and cheap. More then $20 though unless you can find some in a scrapyard.

Hi Guys
Gees "Stepper Monkey" you have been picking a few fights on the forum threads haven't you!
Sounds like you have a grudge against machinists! or did someone burn you?
All your doing is turning the newbies off cncing. Seriously settle a bit.
Sometimes it sounds like they are being force full and telling you this is how it's done and whats best. But they are just giving the benifit of there experience.

Like "don't stuff around using lead screws with delron nuts, use ballscrews with double nuts. Otherwise you will be changing them all the time."

That's true but you build a machine for a price and a purpose.
If you want the accuracy with no maitainence go ballscrews.
If you don't mind changing a delron nut every so offen then go that way.
There was some nice auto adjustable ones on ebay cheap at one stage.

Back to the router/mill. Old carrage rods out of dot matrix printers are good for runners. They have the bronze slides aswell. But As Stepper monkey said they don't have load on them and will run dry. You can run an oil soaked sponge around them like some printers have.

You can get some small steppers from the old big printers.

Cheers
Rod

I think some less than appropriate remarks are being made in this thread. Like the OP, I am also a slot car builder and the work that I do dictates my choice of tools. (Just for the record, the first slot car parts that I made were done on a hand cranked Bridgeport 50 years ago)

1. The largest work envelope that I need is 3" X 6" X 1" - at that size, I am cutting brass and aluminum. I also work in steel 1" X 1" X 1/16"

2. 90% of the work is done with 1/8" or smaller end mills. The largest hole that I drill is 6mm.

3. I currently use a (Grizzly) X2 with 3 axis DRO. I have concluded that the various deficiencies of that machine, including the 4000 RPM max spindle speed (belt drive conversion) do not make it worthwhile to convert to CNC. (Yes, I know that LMS has an add-on hand grinder spindle/motor combo that will go to 20K - but I don't really like the set-up and prefer collets to hold tooling)

4. I am not sure that I know what the distinction between a router and a mill is. (I also do wookworking and have two routers - hand held) I do know that I would not try to work to 5/10s or less in wood) So far as I am concerned, if one is working in metal or plastic to tight tolerances, one is milling.

5. Putting $ aside, I would not have an X3 in my shop - I don't want to give up that much space and it won't run fast enough to suit the cutter size/materials that I use.

6. There are lower size limits as well. I bought the X2 after discovering that the milling attachment for my Unimat PC was not rigid enough to do what I needed.

Note to the OP: There is (was?) a device made called an Akro-Mill that was, in essence, a holder for a Dremel tool with an XY table attached. I have one. It's OK for cutting with an abrasive disk but not much use for milling.

EM

sounds like taig is designed for this type of work and your need EM. :) it really is one of the best in its class. it is better than x2 IMHO for custom machine, biggest issue with cutting metal accurately is rigidity of machine. smaller machine can be easier to make rigid, but still requires fair amount of structure which will raise cost.

most cheaper gantry router are terrible at milling metal due to lack of rigidity. I have 3 smaller cnc routers. (k2-2514 which I just sold, dynacnc tabletop, and circuitspecialist) only machine that I would consider cutting aluminum is circuit specialist router. (it is only one of 3 with linear rail and very rigid) K2 and dyna will flex(you can see it flex when it is cutting heavy)

Thanks - I have come to the same conclusion - now just a matter of accumulating $ and choosing among the various suppliers. I briefly considered buying a mill and cooking the electronics and packaging myself but, aside from a pretty case*, I saw minimal savings and I'd rather be making parts.

EM

*I have a 1.5 gig XP box hanging around - the empty HDD bays are more than big enough to take the stepper drivers and a linear supply and the pin-out could be to an unused FDD bay in the front panel.

a form of plastic bushing can actually be superior in those cases. Especially those materials that have almost identical resistance from a start and while running.

Good Thought I just got ahold of my Plastics Rep, and he gave me two choices both Delrin, one that is "Pre-Lubricated" and one that is Teflon Filled. so I ordered 2 1""x1"x~4"-6" "Cut-OFFS" of each for about $15 + Shipping :) YEA SALES REP :)

That looks like a nice little machine. What program did you use to draw that?


THANKS MAN, :) I mostly Draw in Auto Cad, that was rendered in AutoCadd's default junk rendering engine, Once I get a final idea of what I'm doing I'll do a real "Photo Realistic" rendering in 3D Studio

sounds like taig is designed for this type of work and your need EM. :) it really is one of the best in its class. it is better than x2 IMHO for custom machine, biggest issue with cutting metal accurately is rigidity of machine.

I have a taig Lathe and Love LOVE LOVE it, in fact lots of the custom tools in our shop used for production are made from TAIG Parts, The guy that owns TAIG is the nicest, and most helpful guy in the world. but based on already carrying my TAIG lathe all over the US for races and such I can imagine carrying the mill, plus the cost is prohibitive. Mostly I'll be machining in Magnesium, brass,Silver, and some plastic, so heavy cutting is not a real requirement

I'm betting that you could easily hook up the portable mill to a couple of small laptop batteries or similar and run the motors for a decent time frame, and using a laptop or palmtop to control the machine. That would make a very cool little functional setup!

I had that in mind, I got a bunch (Like almost 100) New R/C car battery Cells in a trade for some slotcars, another good reason to use the R/C car motors for the spindle. I'm really hoping to use this old Tosiba Libretto P120 Lap/ palm top (http://en.wikipedia.org/wiki/Libretto_(notebook)) I've got laying around from a while back because it's not bigger than a VHS tape :) making the whole thing a lot more portable


It also looks like Sparkfun has some cool opto interrupters that would make cool optical limit switches, and one emitter/detector that could be used to make a non-contact spindle tachometer. Since my computer case has an LCD display on the front for fan RPM, I think I might wire that up to it instead of the fans sensor wire so I get my spindle DRO right on the front of my mills driver computer. For three bucks its worth a shot and should work. I'll let you know.

Yea Great Idea I was looking at the I/R pairs from old Microsoft mice for the limit switches, it'd very kool if I could feed back the spindle speed to the CAM program, and find a controller that will control spindle speed for a 12V 6A Motor :)

I think some less than appropriate remarks are being made in this thread. Like the OP, I am also a slot car builder and the work that I do dictates my choice of tools. (Just for the record, the first slot car parts that I made were done on a hand cranked Bridgeport 50 years ago)

This might brake your heart but the #1 determining factor for size, is "can it fit in one of my original HOFFMAN slot car boxes" :) having worked for a bunch of manufactures and being John Ford's art guy for Scale Auto Mag. I travel a lot to tracks and it seams I get more done on my stuff at the track than I can in my own shop. in my shop I'm always doing some one else's stuff! plus a large portion of my retirement income comes from building motors and cutting comms , truing tires, ect..., and selling cars at the track :) we still use a Bridgeport to make custom tooling and it sucks hard! I need a mill sized for this kind of work :) esp since I make my own billet GP7 Motor Cans and End bells. I also cut my own Magnets. and finish my own arms, to keep racing affordable :) another big factor is my shop use to be my bedroom, I sleep on the couch in the living room so I have room in my little apt. for the Drafting table / CAD Computer I work at 12 hours a day, and for my slot car bench, I don't get to spend as much time at as I'd like :)


1. The largest work envelope that I need is 3" X 6" X 1" - at that size, I am cutting brass and aluminum. I also work in steel 1" X 1" X 1/16"
Well most of what I need to do will be in Silver, Brass,some aluminum , plastic / phenolic, and Thin Steel I figure I can do every thing in 3"x5"

2. 90% of the work is done with 1/8" or smaller end mills. The largest hole that I drill is 6mm.
EXACTLY :)

4. I am not sure that I know what the distinction between a router and a mill is. (I also do woodworking and have two routers - hand held) I do know that I would not try to work to 5/10s or less in wood) So far as I am concerned, if one is working in metal or plastic to tight tolerances, one is milling.
exactly Routers are for wood workers, nothing wrong with Wood but Racing Cobalt GP7 Open Motors I'm building TOP FUEL tolerances on a Sportsman's budget. I've got Funny cars that will run over 100 REAL MPH and do the 1/24 scale 1/4 mile in .425 seconds, and one wrong mistake can cost you lots of money I don't have !!!

Note to the OP: There is (was?) a device made called an Akro-Mill that was, in essence, a holder for a Dremel tool with an XY table attached. I have one. It's OK for cutting with an abrasive disk but not much use for milling.

EM
HOW much you want for it , I've been looking for one for ever :) I'll give you my sister :) for it. or how about my left Arm ?

no reason couldn t work if you build out of steel also as if you can control any vibration and you build it good and rigid , delrin would be ok for a router but not a mill the strength of the material youd be cutting would be far greater than the machine
i think you should attemp to beef it up more because i would be concerned with vibration if you are wanting to use that kind of a design for a mill ,you may want to make solid angled pieces to fit into all the corners to get more rigidity and lessen the chances of the machine twisting and vibration while taking a cut

Yea Great Idea I was looking at the I/R pairs from old Microsoft mice for the limit switches, it'd very kool if I could feed back the spindle speed to the CAM program, and find a controller that will control spindle speed for a 12V 6A Motor :)


You can find 12v PWM controllers pretty cheaply, even some that will work to control from Mach or similar. You don't even need to feed a tacho input back to get it to work, either. It's just cool to have for reference.
An outrunner brushless motor would actually make a great small and very powerful spindle, that is a great idea there, run with it!

One thing I'm playing with now is a spindle speed control based on a PWM motor controller for an electric scooter. Some of them will handle up to 1/2 HP DC motors or better, and are available in 12v, 24v and 36v. That and they are like 20 bucks now the whole silly electric scooter fad died.
Since they control the speed of the motor through a 5k pot ("throttle" connector) , it is pretty simple to put one on a motor for manual speed control or hook it to an existing PWM-to-voltage breakout adapter for machine speed control from Mach. They also have a "brake" connector that is a disconnect that cuts power to the motor regardless or speed inputs, so a great E-stop it looks like.
Just got a couple in the mail today. Don't know how well they will work, but I see no reason they shouldn't. If so, 40 Amp PWM speed controllers for 20 bucks can't be beat. One is a brushless controller, BTW.

no reason couldn t work if you build out of steel also as if you can control any vibration and you build it good and rigid , delrin would be ok for a router but not a mill the strength of the material youd be cutting would be far greater than the machine
i think you should attemp to beef it up more because i would be concerned with vibration if you are wanting to use that kind of a design for a mill ,you may want to make solid angled pieces to fit into all the corners to get more rigidity and lessen the chances of the machine twisting and vibration while taking a cut

The orange Sections are designed to be interchangeable with 1/2"X1" CRS, Also if you look at the joints The smaller 1/8 holes are for 1/8 harden drill rod locater pins, some thing I haven't shown that I should have was the thought of using a 1/4 Aluminum plate for the base. but my biggest reason for Delrin is the weight of it and the beds sliding on the Delrin surface to help distribute the load off the Axis Liner rods, also the liner Bearing Blocks are designed to slide along the Axis Frames to again distribute the forces, I'm hoping by securing the the frames to a ridged plate it will dampen the vibrations a bit!

Note to the OP: There is (was?) a device made called an Akro-Mill that was, in essence, a holder for a Dremel tool with an XY table attached. I have one. It's OK for cutting with an abrasive disk but not much use for milling.

EM

Can you PM me a pic of it PLEASE? look I'll give you my sister and the girl in the front office in trade for it man, plus i'll even throw in 2 free Hair Cuts ! Name your price, if it's what I'm thinking it is, I've been hunting for one for years

Can you PM me a pic of it PLEASE? look I'll give you my sister and the girl in the front office in trade for it man, plus i'll even throw in 2 free Hair Cuts ! Name your price, if it's what I'm thinking it is, I've been hunting for one for years

Hey Bunny -- I can't speak for Pretorien, but I *think* he's talking about this, the Acra Mill Plus by Vanda-Lay Industries:

Acra Mill Plus (http://vanda-layindustries.com/html/acra_mill_plus.html)


I recently saw an aftermarket drill press for a Dremel by Vanda-Lay, I visited their website, and the Acra Mill stuck in my mind.

Dan

I agree with the concerns about cutting metal on a little portable machine to some degree, but rigidity for your size unit is not as frightening as it might appear. Remember that rigidity and deflection numbers go up by cubes of distance, so for a little unit like yours the small distances involved, as well as the vertical bridge mill design keeping the members supported at both ends will go a long way toward rigidity. (Having a gantry does not automatically mean it is a router, no matter what some might think! Plenty of bridge mills out there.)
A bit oversimplified of an example here, but in general a 3" free span could require roughly 60 times less material than an identically constructed 12" span for the same rigidity. Not that I'm suggesting going THAT minimalistic, but remember that even using a small fraction of the material used in a bigger mill will still give great rigidity. Keeping the distances as short as you are and eliminating any cantilever are really good starts to some serious rigidity. Even if the mill only weighs 20 pounds or less, with a three inch span it could easily be a lot more rigid than a several hundred pound unit with a foot or more of cutting area.

Hey Bunny -- I can't speak for Pretorien, but I *think* he's talking about this, the Acra Mill Plus by Vanda-Lay Industries:

Acra Mill Plus (http://vanda-layindustries.com/html/acra_mill_plus.html)


I recently saw an aftermarket drill press for a Dremel by Vanda-Lay, I visited their website, and the Acra Mill stuck in my mind.

Dan

That's the unit I have - without the drill press attachment - sorry, I would have posted a photo but my digital camera battery went south and I'm awaiting a replacement.

Pretorien

That's the unit I have - without the drill press attachment - sorry, I would have posted a photo but my digital camera battery went south and I'm awaiting a replacement.

Pretorien

That is BAR-NONE the koolest Dremel Toy I have ever seen! I got to have one! it looks like it would make the best on the road / at the track Drilling machine. I'm thinking of putting all my 1/32 stuff on the ePay and buying one.

I agree with the concerns about cutting metal on a little portable machine to some degree,

Well the only metals I Will be machining will be pretty Free Machining, light stuff like Brass, Magnesium, light thin Aluminum, Silver, and Plastics. Nothing too Heavy like Steel or Stainless.


but rigidity for your size unit is not as frightening as it might appear.

That's my hope, and one of the main reasons for keeping it as small as piratical.

(Having a gantry does not automatically mean it is a router, no matter what some might think! Plenty of bridge mills out there.)

Thank You, been having that argument with an Engineer I work with!

distances as short as you are and eliminating any cantilever are really good starts to some serious rigidity.

My original Plan had the Table at 90 degrees but made the Y axis almost 10.5" long and the X Axis only 3.5" but by turning the table 90, it gave me a good compromise and equalized the axises


Even if the mill only weighs 20 pounds or less, with a three inch span it could easily be a lot more rigid than a several hundred pound unit with a foot or more of cutting area.

I took a rough weight of the rough cut materials and Figured out it may weigh as little 1.5 lbs SO I'm starting to wounder if I need to add a box on the bottom to fill with lead to keep it from dancing off the table. or permanently mount it to my Caring box with a lead lining, to see if I can't keep it stable with out screwing the base down to the table top


http://i184.photobucket.com/albums/x128/bigbunny5/millmodel.jpg

I took a rough weight of the rough cut materials and Figured out it may weigh as little 1.5 lbs SO I'm starting to wounder if I need to add a box on the bottom to fill with lead to keep it from dancing off the table. or permanently mount it to my Caring box with a lead lining, to see if I can't keep it stable with out screwing the base down to the table top

I would say that 1.5 pounds is probably underestimating the finished weight, but even so you should probably look into beefing that up quite a bit. Just adding weight where it is non-structural isn't going to do much other than hold it down while it goes all bendy-straw on you. Any flexure will add to the chatter and vibration and so adding structure is still better to smooth it out and keep it in place than vibration-damping weights.
Remember that three Nema 17's and your spindle and motor have to be added in there. The steel fasteners and rods are going to add a pound or so by themselves. How thick of aluminum are you making the frame and bridge out of? Considering the size I wonder if steel might not even be a bad idea, the weight difference is probably incremental at this scale. Either way it could work well if you figure out the right material thicknesses for proper stiffness.

I would say that 1.5 pounds is probably underestimating the finished weight, but even so you should probably look into beefing that up quite a bit.
Stepper :)
well keep in mind my brother I'm using 500 series Teflon reinforced Delrin not Aluminum

Remember that three Nema 17's and your spindle and motor have to be added in there.
I'm not too sure what size steppers these are, but I'm planning on using the ones out of OLD IBM Full hight 5 1/4 Disk Drives. The Spindle is a Hand piece off an old Dremel Shaft Drive and the Spindle motor is a 12V cobalt R/C Motor about 85 Grams in Race Trim :)

The steel fasteners and rods are going to add a pound or so by themselves.
Ya got me there I figure about 36 1/4-20 Screws and 18 1/8x? screws. I also got a hold of some 1/2" UHMW rod, I'm thinking I can turn, and use instead of Steel rod. due to the short rod length and adding the boxing plate for the liner barrings to slide on, deflection should should not be a problem.

How thick of aluminum are you making the frame and bridge out of? Considering the size I wonder if steel might not even be a bad idea, the weight difference is probably incremental at this scale. Either way it could work well if you figure out the right material thicknesses for proper stiffness.

Well like I say I am going to use Delrin and if you look at the original drawing, the orange is 1/2"x1" BAR STOCK
the sea-foam is 1/8 delrin sheet
The Dark Blue is out of 1/2" Sheet Stock

I'm also thinking of adding a sheet of 1/8 in the upper area of the to box it in to stiffen it up like in this updated rendering, I also am showing the 1/2" Delrin or Phenolic Baseplate

http://i184.photobucket.com/albums/x128/bigbunny5/millupdate1.jpg

I appreciate all your input It's making think hard about design Choices! That is one thing I miss, being Semi-Retired is not having others to challenge my designs, so I can talk out all the problems before wasting Good money on Mistakes I should have seen on paper.

That sheet on the back acting as a stressed skin will definitely vastly improve lateral strength. Warping and particularly fore-aft tilt are not improved by it, but if necessary, simple angled braces can always easily be added to solve both if either proves a problem.
I like this. I wonder how well the Delrin will attenuate vibration? Possibly quite well.

Stepper :)

I also got a hold of some 1/2" UHMW rod, I'm thinking I can turn, and use instead of Steel rod. due to the short rod length and adding the boxing plate for the liner barrings to slide on, deflection should should not be a problem.


Well like I say I am going to use Delrin and if you look at the original drawing, the orange is 1/2"x1" BAR STOCK
the sea-foam is 1/8 delrin sheet
The Dark Blue is out of 1/2" Sheet Stock

.

An alternate approach to the rod might be to use 1/2" OD, 1/4" ID Delrin tube and run a 1/4" steel rod down the center, thread it a both ends and tie the system together with nuts.

Delrin is about 50-60% the weight of aluminum depending on composition but I wonder if its compression strength will provide sufficiently strong screw holding to maintain the rigidity of the joints.

EM

An alternate approach to the rod might be to use 1/2" OD, 1/4" ID Delrin tube and run a 1/4" steel rod down the center, thread it a both ends and tie the system together with nuts.

I LOVE that idea:) So you're thinking, like make the make the liner Rods stressed members to put compression on the Delron tube like Pre-stressed concrete? That would work, with one small problem. I'd have to spend money for the delrin tube :) or I could bore the UHMW :)and use it :) I like the idea of 2 low friction surfaces :)


Delrin is about 50-60% the weight of aluminum depending on composition but I wonder if its compression strength will provide sufficiently strong screw holding to maintain the rigidity of the joints.


I just tapped a 1/2-20 hole though 1/2" and put 45 lbs of torque on it OK but the Loc-tight did nothing to help hold it

I LOVE that idea:) So you're thinking, like make the make the liner Rods stressed members to put compression on the Delron tube like Pre-stressed concrete? That would work, with one small problem. I'd have to spend money for the delrin tube :) or I could bore the UHMW :)and use it :) I like the idea of 2 low friction surfaces :)

Standard dimension 1/2 X 1/4 Delrin tube (+/- 0.002") from McMaster is $9.55/60" piece - and Mcmaster is a great source but always near the top in price.

I just tapped a 1/2-20 hole though 1/2" and put 45 lbs of torque on it OK but the Loc-tight did nothing to help hold it

I was thinking not so much of the axial load capacity i.e. torquing a bolt, but the lateral compression when you get a twisting moment directed at one side of the bolt.

EM

I was thinking not so much of the axial load capacity i.e. torquing a bolt, but the lateral compression when you get a twisting moment directed at one side of the bolt.

EM

I was also thinking the same thing, hence the suggestion for angle bracing or similar. I would be concerned about the Z bridges ability to resist pivoting movement at its attachment points as designed now, as the two fasteners only look to be spaced a few millimeters apart. Even in metal that might prove a problem, in Delrin I would be very concerned.
I really like the idea of steel in tension, where the material is it's strongest. That is cool. Truss rods properly incorporated would add quite a bit of strength and likely some rigidity and damping as well. Virtually no weight or cost penalties either. Good thinking.

... I would be concerned about the Z bridges ability to resist pivoting movement at its attachment points as designed now, as the two fasteners only look to be spaced a few millimeters apart. Even in metal that might prove a problem, in Delrin I would be very concerned.
Stepper I been given enough concern to raise questions in my own mind about the pivoting problem. I got to thinking that adding some 1/2" sheet bracing on the sides like in this revision below, I'm also thinking it might be a good Chip control Guard as well, with the addition of a hinged lexan plate across the top (Not Shown)
http://i184.photobucket.com/albums/x128/bigbunny5/MillPostRev3copy.jpg
I also wanted to Offer to send, to any of you guys that participated in in the design process, a set of 2d prints for ll your good suggestions!

You know, I have been thinking about this. I was wondering why I haven't seen more designs like the one I built. There are several plasma machines that also use the same style gantry. That is with two horizontal rails on the gantry instead of vertical rails. If you look here at my little router design, this is what I am referring to.
http://www.cnczone.com/forums/showthread.php?t=8632&page=1&pp=40
I am also building my plasma cutter this way.
http://www.cnczone.com/forums/showthread.php?t=34626
It gives a nice balance to the gantry. No real stress on the plasma, but I mill aluminum blocks with my router as well as aluminum sheets and lexan. I could mill steel if I mounted a good spindle on it. I still call it a router basically because that is what is mounted on it. With a spindle, I guess it could be called a mill.

The point I am trying to make is with a little design change on the gantry, I think you can really stiffen up the whole thing.
Boxing it in would help with this. As it is, the design is cantilevered, which is fine when using stiff enough materials, but plastics would see more benefit through a boxed and balanced gantry and Z axis.

the first gantry style mill i made was made from 12mm nylon sheet
12mm silver steel for axis guides, plastic plumbing clips gripping 16 mm plastic
conduit carrying delrin bushes, 10 mm threaded rod /delrin nuts as lead screws
spindle was a dremel clone and cheap 23 steppers (£8 each)
this was built just to prove the theory but it worrked so well that i used it to
do the most of the ali parts for its sucsessor

I just reread my post. It sounds like I was claiming that type design. Apologies for that. ;) It's just the style I used. I have seen it before on other machines. In principle it's like the tried and true railroad track design. Two parallel rails with the mass centered between. Most people use this configuration for the X. Few use it on the gantry.
The vertical rail setup on most works okay when they are built beefy enough. The cutter is still at an unbalanced cut hanging off to one side. In this case, the weight of the gantry and Z does very little positive.
With the train track setup, then the weight of the gantry and the Z are working for you to help keep down any chatter. Not much weight in a very light machine, but none the less, balanced weight over the cutter.
Granted, you do have to fully design the Z or leave enough room for one between the rails. I thought at first it would interfere with my access to the router as well. Not so. On tool change it raises up to Z home. Then I just release the two cam clams and the router pops out for changing the bits. The PC has a collar and positively goes back into the exact location in the mount every time. Quick and easy.

I think it would be very easy to design a nice little plastic bridge mill using the boxed in RR method.
I have seen nylon rack and pinion gears too. Those small ones have to be pretty accurate. At least as good as threaded rod with a lot less lost due to friction.

Lee
Good Ideas, But with all the concern of chater on the X and Z Axisis, I've done another redesign on the Vertical members of the Gantry, so I can Screw the bottom of the member up from the botom of the baseplate. thier is even room to add a truss rod though the vertical memers

I have seen nylon rack and pinion gears too. Those small ones have to be pretty accurate. At least as good as threaded rod with a lot less lost due to friction.

I wish I could find a Cheep 48 or 64 pitch rack I could use!

http://i184.photobucket.com/albums/x128/bigbunny5/MillPostRev4copy.jpg

Very nice work. The design seems to be evolving quite nicely without losing any of the original desired traits. I just might take you up on that offer of plans when you get it finalized. Looks like fun!

Don't get me wrong. This design does work. It's simply that you have to over build it to do right. The design may very well suit your needs. However, if you would like to push the envelope some while still keeping cost low, a box type machine will serve you best IMO.
I'm sure you may find differing opinions as this thread progresses, but you could never get the structural integrity of a box design from one where the spindle is offset.
I say never, but that really isn't so. It depends on how much material and money you apply to the project. For low cost materials, you will really need to rely on a good structural design to achieve good results.
If you have ever seen an overhead crane working in a building, the concept is similar.
Don't do what bigger machines do. Design this on the small and sturdy.
BTW, Mcmaster Carr has the nylon racks at about $3 per foot.

Very nice work. The design seems to be evolving quite nicely without losing any of the original desired traits. I just might take you up on that offer of plans when you get it finalized. Looks like fun!
Thanks Stepper, but if you ask anyone involved in one of my projects, Due to my Laziness no Design is finalized until 6 months after production begins or I get too lazy to remake Fixtures :). Just shoot me a PM with an email any time and let me know if you can open a DWG, and I'll send you the current version of the shop plans :) I do though plan to keep a good photographic Record of the actual build. Being that I have moved in to an apartment, I no longer have a real shop to work in, and I'm waiting till I can get a SMALL Jewelers drill press or something like it to build the actual version until then I'm just experimenting around with building small portions at a time to try the design ideas.

However, if you would like to push the envelope some while still keeping cost low, a box type machine will serve you best IMO.
.

Lee, Can you like me to these box type machines your talking about

BTW, Mcmaster Carr has the nylon racks at about $3 per foot.
Thanx Found them :)

http://i184.photobucket.com/albums/x128/bigbunny5/NEWMillPostRev2.jpg
Last night I was talking to a Friend on line and playing around with the parts I have in hand, and as much as I tried to simulate the total build in 3d virtual space, there were things that had to be worked out in the META world with parts and calipers in hand
and on a tangent thought :
am I the only one that is so use to using calipers that Tape Measures and rulers have become foreign objects? I have become totally Fraction Challenged due to the use of calipers. and I have a set of digital Starret's but still prefer my Dial Calipers. I literaly carry a set everywhere I go. like when I have to go to a clients to talk about drawings or pretty much anywhere You'll almost always fins at least a 4" pr. in my Laptop bag :)
But anyway back to the origin of this post Last night I decided to start all over with a blank sheet of paper and recalculate everything with parts in hand to fix lots of little things:)

Just had a thought, if you rotated your spindle and motor 90 degrees to the Z table (along Z), you would have less offset weight and maybe a little less deflection. I know you're using a small motor, but every bit could help.

Just had a thought, if you rotated your spindle and motor 90 degrees to the Z table (along Z), you would have less offset weight and maybe a little less deflection. I know you're using a small motor, but every bit could help.

That's a Great Idea :) :) :) I'm gonna work on that. Now now the bad news for any Jeweler, I'm thinking of Cutting up my Fordom Hand Piece instead of the Dremel one :) Seriously I Kin of think the Fordom will run a little more concentric! I wish I could figure a way to use WW Colets, I have a bunch of them I collected with ePAY Watchmaker Lathe Bargain's.

No need to apologize, I made a Foredom #40 handpiece I had laying around into a little wax lathe. Modify away!

I have an extra Dremel flex shaft now. I burnt out my dremel cutting on some thk linear rails. I actually had used it a bunch. I bought the Rotozip with flex shaft to replace the Dremel. It comes with a bunch of different sized collets and I believe they would fit the Dremel shaft. I think Dremel makes the flex shafts for rotozip anyway.

The box suggestion I was making before was a pretty simple thing really. Due to the size of this machine, it may be difficult to mount something to the table that way though.
Take your drawing with the bridge solidly mounted like it is. The add another bridge to the other side. That would make it like a box and the cutter would then be balanced and not want to flex back and forth when you are cutting.
You would only need one screw and the two top rods if they were ridgid enough. Add two bottom rods or bearings for even more support.

The little Compucarve or CarveWright machine is built similarly I think.
http://www.carvewright.com
Though it has the standard rail setup for the bridge like yours, the bridge is actually built like a box for structural rigidity.

No need to apologize, I made a Foredom #40 hand piece I had laying around into a little wax lathe. Modify away!
OMG i had one of those clamp on Wax lathes I got on a whim and never did anything with it until I needed a tire lathe for slot car tires, worked so well I sold to aq guy for twice what I got it for on clearance, and used it for 2 race seasons :) but I used a Cheepie Harbor Freight Chinese Shaft drive foredom clone :) The hand piece I got in the parts box I got at a Garage sale for $10 no motor :)

Where has this gone??????? what does the final design look like???? I wanna KNOW!!!!!!!! I wanna know how it works damnitttt!!!! *Bangs fist on table*

HAHAHAHAHHAHAA

Are you still working on this or has this thread gone dead? The last design that i saw was starting to look brilliant! please keep up the good work!

Are you still working on this or has this thread gone dead? The last design that i saw was starting to look brilliant! please keep up the good work!

Here is something that looks close to what you are designing might give you some new ideas. I am not sure how to make this a link you can click on this is my first post.

http://www.engadget.com/2006/06/29/how-to-build-your-own-cnc-machine-part-1