mvaughn's CNC machine worklog

[mvaughn]

>>I originally went the the 12V PC power supply because I had on laying around, I'm working on a limited budget, and because I just didn't know any better at the time.

I like your idea of keeping it inexpensive this way. Have you tallied up your total investment so far? Any idea on expected total cost when completed?

Rance

I'll try to tally up the cost when I am finished, however, it will only be an estimate. Part of the reason for trying to be detailed in this build thread is to log the parts I've bought to put into the project.

1. Steppers were free
2. Electronics came to about $50 USD
3. MDF was $40 USD
4. 1, 3/4, 1/2 inch Drill rods were roughly $35 (on sale at the time)
5. UHWM 12x12x1.5 sheet was $26
6. 1/2 10 TPI ACME threaded rod $12
7. Porter Cable 690LR router $99 USD
8. The miscellaneous nut and bolts have turned out to be the most expensive part. There is a ton of hardware in this thing like T-nuts, confirmat screws, nuts, bolts, washers etc... I'll estimate 50-60 dollars in hardware.

I would say that I've invested between $320 and $330 USD in materials.

I'm going to have to buy a speed controller, wire to connect the electronics, and some more nuts & bolts.

I would say that when I'm all done I will have a project cost of about $350

[JavaDog]

I would say that when I'm all done I will have a project cost of about $350

Hot damn, I'm spending that on the Geckos alone!

Can't wait to see what you'll be able to crank out (and accuracy) once you get this up and running. Really excellent work thus far!

[mvaughn]

Thanks JavaDog,

This machine is really just a proof of concept for my wife. If I can show her all the potential that CNC has to offer, then I can build a bigger better machine.

[mvaughn]

I have a question for you guys.


If you look back at my last set of pictures you will see the flange bearings I'm using to mount my lead screws. I will use one bearing per lead screw and use the stepper to hold the opposite end.

The question I have goes like this: Does it matter what end of the lead screw the bearing holds?

My theory so far is that I should mount the flange bearings for each axis near the home position of the machine. That way, on average, there will be less distance between the bearing and the lead nut; which will allow for less flex when "pushing" with the lead screw.

I really need your opinions on this matter...

Thanks,
Mark

[BobLWeiss]

Thanks for the offer cnc2k, I'm going to wait for a while and give my 12 volt setup a chance first.


I've ordered some flange bearings so I can mount my lead screws. Victorbl is using these on his cnc router and I thought I should grab a few of them since they are only $7.95 USD each.

http://www.surpluscenter.com/item.asp?item=1-201-08-4

I also got a new digital camera for Christmas and have no excuse to delay this project any longer.

Since my lead screw flange bearings are on the way, I decided it was time to build my lead nuts. I'm using 1/2 10tpi generic ACME thread from Enco. I cut off a 9 inch piece of it and made an ACME tap with my drill press as a makeshift lathe and a cutoff wheel to cut reliefs in the tap.

For the lead nut I'm using 3/4 inch thick bits of UHMW. I bored a 3/8 inch hole in them and used the acme tap. Each lead nut took about an hour to fully tap and get them running smoothly. I used the drill press to hold the tap perpendicular to the lead nut, and turned the drill press by hand to get it tapped. It took quite a bit of effort to tap the UHMW because it seemed like it didn't cut all the material the first run through. I had to run the tap through several times until it stopped removing material from the nut.

Next, I threw the UHMW lead nuts in the freezer to firm them up and shrink them slightly. I chucked the ACME tap in an electric drill and ran it through the nuts several times.

Now the nuts spin freely and there is no noticible backlash.

How did you get the threaded rod smooth on one end? The rod from Enco is threads from end to end correct?

[BobLWeiss]

By the way, NICE MACHINE!!

I have another question for ya, how did you connect the steppers to the threaded rod? I assume you used a coupler but where did you get it from? The threaded rod is 1/2" right? Steppers 1/4"?

Thanks,
Bob

[mvaughn]

How did you get the threaded rod smooth on one end? The rod from Enco is threads from end to end correct?

This may sound crazy, but it's true.


I chucked the 1/2 acme into my drill press and used a flat file to slowly file the tap down to 1/4 inch. I occasionally used my caliper to check the diameter.

It was a slow process, and made we wish I had a lathe.

[mvaughn]

By the way, NICE MACHINE!!

I have another question for ya, how did you connect the steppers to the threaded rod? I assume you used a coupler but where did you get it from? The threaded rod is 1/2" right? Steppers 1/4"?

Thanks,
Bob

Thank you,

I haven't yet connected my steppers. What you see in the last set of pics is the flange bearing supported by 1/2 inch drill rod. The drill rod is run through some 1/2 inch holes I bored. It's my way of getting the holes in the gantry, lead nut, both ends of the machine, and the flange bearings lined up and centered. After I get the lead nut, steppers, and flange bearings mounted, I'll enlarge the 1/2 inch holes.

I'm planning on turning down the ends of the acme rod the same way I did on my acme tap. Then, I will join the steppers to the acme with a 1/4 inch inner diameter piece of tubing. (hopefully hydraulic line)

[mvaughn]

In case some of you missed my question from above...

I have a question for you guys.


If you look back at my last set of pictures you will see the flange bearings I'm using to mount my lead screws. I will use one bearing per lead screw and use the stepper to hold the opposite end.

The question I have goes like this: Does it matter what end of the lead screw the bearing holds?

My theory so far is that I should mount the flange bearings for each axis near the home position of the machine. That way, on average, there will be less distance between the bearing and the lead nut; which will allow for less flex when "pushing" with the lead screw.

I really need your opinions on this matter...

Thanks,
Mark

[yukonho]

I dont think it much matters which end you mount the bearing on. I have mine on the opposite end of the steppers and have no difficulties at all.
colin

[victorbl]

Hey mvaughn, I can provide one perspective on your question. While I'm by no means a seasoned cnc'r like most of the people on the forum, I can say that with my machine it makes absolutly not difference. I have my Y and Z axis with the flange bearing on the home side, and my X axis with the stepper on the home side. Basically, if your machine is aligned properly, your threaded rod should float in the assembly, and all the weight should be supported by your drill rod/linear bearings/etc.

When I aligned my machine, I would place the threaded rod in position w/o the motor or flange bearing...and adjust the drill rod until the acme threaded rod literally floated in the dead center of the flange bearing mount and motor mount. This gave me the best performance in terms of no binding.

[mvaughn]

Thanks Victor, I'll be working on getting my lead screws and bearings mounted up this weekend.

Have a good one!

[mvaughn]

I have a little update on my progress. I spent a few hours this weekend mounting my leadscrews and devising a way to mount my steppers. I came up with a solution but ran out of time.

Currently, I have the x-axis lead screw and stepper mounted. The y-axis is partially done. The good news is that I wired up my x-axis to my driver and can say that I have it it moving under it's own power. The gantry scoots along quite nicely. I believe I had it up to 17 inches per minute before the stepper started missing steps, and that is with my 12 volt PC power supply.

I have some tweaking to do yet. But for all you who question whether a stepper from a HP LaserJet III printer can spin a 1/2-10tpi ACME lead screw, I can attest to it.

I'll post some pics and maybe a movie later. BTW, does anyone know of an easy way to compress an avi down so I can post it here?

[ynneb]

This is a fine thread you have here Mark. I am looking 4ward to the movie.

Do you have windows XP ? It has a movie maker in Start/Programs/Accessories/Entertainment/Windows Movie Maker, While it is limited, it will do what you need. You can then export your movie out as WMV. Most other windows users can see this type of file in their wndows player without having to download some other crappy viewer. Let me know if you get stuck and i will guide you along the way.

EDIT: WMV is the Microsoft equivilant compressive standard to a mpeg video.
For those who do not have a way of vieiwng these files, you can always download Winamp a free media player. It is probably the least invasive on your system of all players. However as I have said b4 most windows installs have a player already installed by default.

[mvaughn]

Thanks Benny,

I'm compressing my edited video as I type this reply. Is should be done in about 10 minutes. I'm not sure how it will turn out, but I'll post a link to it after I find a place to host a 10MB file.

[mvaughn]

Here is the video of the very first movement my router ever made.

As you can tell, the table top is not attached, and the electronics are crudely assorted. I just couldn't resist firing it up as it was, just to see if this project I've been working on the last 8 months could even move.

As it turns out the lighting in the room wasn't very good... and the camera man was a little shakey. It's a little difficult to hold a camera and operate a computer at the same time.

There are two versions of the video... small and large. The small video is about 1.3MB and the Large is almost 9MB

Small Video

Large Video

[santiniuk]

Video looks good to me

Looks really smooth motion. Congratulations !

This is a real incentive for a CNC novice like myself to keep going.

Thanks for taking the time to share your project.

Cheers

[Jay C]

I finally took the plunge and spun the motors up. I was suprised by two things, one, I can't believe that the DIY controller worked on the first try, two, the little HP printer steppers are quite powerful. They have rekindled my motivation to get this thing moving.

Have you already discussed your DIY controller ... I did a cursory look and didn't see it in this thread. also, looks like you are using a PC power supply ... what voltage are the HP motors rated for, and do you plan to use a linear supply? Also, since you moved from 10 tpi to 20tpi, is your speed half of what you may have calculated, or is there enough RPM in the steppers to compensate?

Jay

[ynneb]

Good video Mark.....You will have Hollywood trying to head hunt you now.
Was that maximum speed ? Surely not?
It will be good to see it fully in action and cutting something.

You are a bit like me. just get the thing going even if every thing is not mounted properly. The only difference is you are tidier than me.

[mvaughn]

Have you already discussed your DIY controller ... I did a cursory look and didn't see it in this thread.

I discussed my DIY controller in brief. Basically I bought the schematics and build my driver board from the pikeresque plans at www.buildyouridea.com It was very simple to build and works like a charm. It's not the best driver available, but it fit my needs and my budget.

also, looks like you are using a PC power supply ... what voltage are the HP motors rated for, and do you plan to use a linear supply?

The motors are rated for 5.2 volts, here are the specs that are on the motor labels.

LABELED: Astrosyn
TYPE: 23LM-C701-01
P/N: RH7-1048 04
5.2 V/Phase
1.4 A/Phase
1.8 Degree/Step

I'm not sure I know how to answer your question about using a linear power supply. I don't know what linear, in respect to power supplies means.

Also, since you moved from 10 tpi to 20tpi, is your speed half of what you may have calculated, or is there enough RPM in the steppers to compensate?

Jay

The move fo 20tpi all-thread was short lived. I never used it, only thought about using it. What you see on the machine in the pics and video is 1/2-10tpi ACME rod.

If you have any more questions or need clarification I'd be happy to help.