It seems like this will be fun, so I will try to keep track of my doings for those who are interested, and for that matter, those who aren't.

I started this about a month ago, but as this is one of those "free time" projects, it has not progressed as quickly as I would like. (When do they ever? ;) )

I need to take some pictures and start a gallery here, so I will try to do that later. For now, I will just give a brief description of my goal and go from there.

I have been making receiver hitch covers for a couple of years now, relying on a relative to cut them out with his plasma cutter. He has one of those optical things that basically traces a printed pattern and cuts out the part. This is nice, and for low numbers is okay, but seems to require more babysitting that I really want.

So, I started looking at the price of manufactured systems. WOW!!! I guess I wasn't really surprised, but again, WOW!!! For what I am after, I don't need super accuracy. I am using an O/A torch, so I think that will be the limiting factor.

As a side note, my dad used to work for a company which manufactured and re-manufactured mining earth movers. Once he brought home a couple pieces of scrap 1" plate. The parts had been cut with a device similar to what my wife's uncle has, except using an O/A torch. I was very impressed with the quality of the cut. So I know the torch is capable of a clean cut. Which brings me to the real reason I started this project. I wanted to cut a straight line. That was it. That was the whole reason for this madness. Of course, it started as a straight line, then a straight line with a nice clean cut, then a nice straight line, with a clean cut, with the possibility of doing non-straight lines, and so on and so on.

Okay, time for a break. More later...

Dave

There seems to be a problem with the site being overloaded, and I just got a "This Page Cannot be Displayed" error, so I just lost the second "chapter" of my progress so far. :mad: :violin:

So I will start over with that.

I knew there was a reason for keeping my posts short.


Dave

Okay, back to the straight line. I know from years of experience that when it comes to cutting things out with a torch, my hand is not very steady. So, I started by making a cutting guide. Actually, I started by looking at commercially made cutting guides. And then I thought, I can make that, only better. So I made a cutting guide. (I will try to post pictures of that also.) Using this with the straight edge was a vast improvement over freehand, and as long as my speed was right and consistent, beautiful cuts. But, if I had to shift position, my speed would vary and then I would have less beautiful areas of the cut.

But then I got to thinking, if I put this on a rail of some sort and attached a piece of Allthread and turned that with a drill... Or if I replaced the drill with a standard motor which was controlled remotely... And if the remote control was done with a computer... Hey, this has the makings of a CNC project. So I Googled "homemade CNC" and ended up here. Thank God for Google!


Break time again.

More later...

Dave

Now on to the progress so far.

I, after much gnashing of teeth have got one axis moving. Bear in mind that I am not one who puts alot of details on paper before undertaking a project like this. My reasoning is that if I find that something was a bad idea, there is no black and white record that the idea ever existed. :p

So, I have one axis assembled. Really, it is just a test fitment. Welds need to be finished and sandblasting and painting needs to be done, but the fact that things fit together and move is encouraging. I still have issues with the speed at which things move, but I am confident that will be overcome with a higher voltage p/s.

That's it. I did purchase the rails for the short axis today. I have chosen to use 1.625" round stainless tubing for the short rails. I am using skate bearings for all linear motion. My long axis is the gantry which is 60" long. I am using 1.5" square mild steel tubing for that. I'm sure that somebody will tell me that is a bad idea, but I'm stubborn, and I like my own ideas, and this seems like something that should work, at least for awhile. Now that I know I can get stainless tubing for a reasonable price, I may eventually change to that, but for now...

My motors are 100 oz*in motors from the HP3 printer. They will be driven by an as-yet-undetermined driver circuit. I am probably pushing the limits of these motors, but I can always upgrade. My goal is 45IPM. I have no real load except momentum and friction. Friction should be minimal. Momentum I think I can overcome by approaching desired speed and stops gradually. We'll see.

I intend to have a 60"x24" cutting area. With the gantry spanning the wide dimension, I can place the end (or the middle) of a full sheet on the table for processing. For now, everything I intend to cut will be smaller than this. I'm sure that will change eventually. I am designing the short axis to be expandable, so when I do decide that I need a bigger cutting area, I can add to it. One of the reasons for keeping it short is that floor space is limited, and right now I can deal with the smaller work area easier than I can deal with no room in the garage.

I can't think of much to add right now. I will have to take some pictures of what I have so far and post them, but it's late and I'm tired, so they will have to wait.

I welcome feedback, advice, and questions. I will do my best to answer questions, but remember I am still sorta new to this. Don't let your feelings be hurt if you offer advice and I don't take it. Like I mentioned, I generally like my ideas, and because I'm stubborn, I reserve the right to reject your advice until my idea doesn't work.

Later...


Dave

Okay, everybody likes pictures. I will post bigger copies on my website, but here is a taste of what I have done so far. Perhaps I am working backward, but this seemed like the fastest way to see something move.

More pics! Haven't decided what color to paint this. This is a very important decision, as the wrong color will prevent the heat from the torch being directed to the metal properly and will cause the CPU to distort! http://www.cnczone.com/gallery/data/500/icon_lol.gif

Seriously, I am thinking that, as this is a "budget" project, I will probably use what I already have, dark grey metallic or white.

This stainless steel tubing was a bit of a surprise. It isn't exactly what I was looking for at the surplus yard, but, it's shiny! Who could pass that up?

More pics. This time the Z-axis carriage. I don't know if that is the technical name for it, but that's what this one is called. I may lighten using aluminum, or I may not. Weight doesn't seem to be the biggest obstacle I'm facing at this point in time. Speed is. But I am still working on that. (Bigger P/S!!!)

Right now, I am using the 1/2-13 threaded rod as a leadscrew. I think I have enough torque to use 1/2-8 Acme. That will also help with my speed problem, so that is one thing I am going to try. We'll see how that goes.

I currently have the long axis (I'm calling it X) assembled temporarily. I still need to finish the welding. But it moves, so I'm happy. I'll be happier when it moves faster.

I will end up with 4 motors being used, I think. 1 for the long axis, 1 for the Z-axis and 2 for the short axis (one on each end of the gantry). I am hoping that the 2 for the short axis can be ganged together on the same driver circuit so I don't have to build and control another board, but I guess I will wait to hear from the experts on that.

My immediate need for a Z-axis is pretty small. I will be using this primarily for my O/A torch, so I will be able to set the height and leave it, for the most part. Eventually, I'd like to also use this as a router, but we'll see how it moves first.

Well, that's all for now.

More on the way...

Dave

that stainless tubing would be nice if you can find a place to use it.. it should be more rigid, plus the smooth surface will help reduce crud buildup..

I use the HP 100oz motors on my 2nd machine (joes second cnc) i run them with the Hobbycnc 3 axis board at 32v the best i get with them is 40ipm on HDPE and MDF. but I have been cutting with them for several months now.

I use the HP 100oz motors on my 2nd machine (joes second cnc) i run them with the Hobbycnc 3 axis board at 32v the best i get with them is 40ipm on HDPE and MDF. but I have been cutting with them for several months now.

Thanks for the info. If I can get 45IPM, I will be happy. The advantage I have is that there will be no tool force to deal with; only friction and momentum. Hopefully, I can get a little more, but 45 would work.



that stainless tubing would be nice if you can find a place to use it.. it should be more rigid, plus the smooth surface will help reduce crud buildup..

I am already planning on using it for the short rails. The cutting surface should be around 20"-24" so if I cut this in half, it gives me 36" of length, so I'll can have between 12"-16" long bearing blocks. I'm going to try to get these started this weekend. The skate bearings that I bought off of Ebay (40 for $15+$7s/h) were originally supposed to be here tomorrow, but now the UPS site says that the delivery has been rescheduled for Monday, so I'll have to try to put everything else together this weekend and install bearings next week.


I'll post pics when I take them.

Dave

:banana: :banana: :banana: Things are good!!! :banana: :banana: :banana:

Well, I was a little surprised to get the speed I got. Right now I am right at 80IPM! The motors don't have the torque to start out at that speed, so I will have to experiment with the speed and find out how quickly it will change direction, etc.

It was cold in the garage tonight, so I will have to go out there tomorrow after I get some more kerosene and get some video for those interested.

I find that sometimes you have to improvise a little. At work, I removed a line supply from a piece of equipment because it was more than a little charred. This is basically an unregulated linear power supply. (We use a separate switcher supply that does all of regulation.) It had been in one of my drawers for about 3 years. In fact, I had almost forgotten about it. Anyway, despite the appearance, it still works. (Well, most of it anyway. It has a crowbar circuit to blow the fuse if anything downstream fails. More often than not, however, the crowbar circuit sacrifices itself to save the fuse, and when it does, it takes a good portion of the board with it.) I had scrapped the part, but saved it, because you just never know when you might need a burned, charred, scrapped power supply, right? It puts out about 25 VDC when unloaed. Loaded, it puts out between 18 VDC and 22 VDC, depending on the load. The power supply that I have been doing all of my stepper testing with was a 13.5 VDC supply. With one supply isolated from ground, and the two put in series, I have enough voltage to move the motor at a pretty good clip.

So I started the motor moving and sped it up to the max speed of my controller and let it go for 15 seconds. It moved a little over 19 inches, but that included the time to ramp up. I may alter my test circuit a little to see just how fast it will go, but then again, I may not. I doubt that I have enough torque at that speed to be useful, so it would really be just to know.

So tonight was good. Now I'm tired, so I'm going to take a shower and call it a day.

Dave

I like what seems to be your design premise, use what's laying around, make it strong, functional, maybe pretty it up later ...
I think I will look a little closer at your design, it may not be real accurate or fast, but then again, for oxy or plasma cutting 1/32" is more than sufficient for the larger pieces that are normally cut in fab /repair shops around here, and I kinda like the 'rough' look...
functionality is more important in my opinion, and it looks like your design doen't require any specialized machine tools to fabricate, or having to sub any components out..
it would be nice to have this type in my garage, just no room right now..
just finished cleaning up an old Gisholt lathe, maybe 25% done on an old South Bend cleanup /update, maybe 80% done on a firewood processor that takes up 1/4 of the garage [only 2 car garage],

all in all, I love the look of your critter...:)

enjoy..

Vladdy,

There isn't room in my garage either! :cheers:

Actually, space (lack of) is the main reason it is only going to be about 5' x 3' overall. Despite many warnings not to put castors on a device like this, I am going to. That way, if I need to cut part of a big piece, I can always turn it so that the workpiece sticks out the garage door. Or, I could always wheel it outside and use it there.

Regarding the use of whatever I can find for materials, I didn't really choose that road. My wallet did. It was either build on the cheap, or dream of gold. I'd rather play! :banana: I will eventually clean everything up and paint it, probably. That is one thing that I really hate about fabrication work. Cut, weld, piece together, take it all apart, paint, put it all back together again. (Of course, the 30" apron brake, the throatless shear, the mini-press brake and the hydraulic press all started life with the intent to eventually disassemble and paint, too.)

There are certainly things that I already think I would have done differently if doing it again. While the use of square tubing for the rails works, it is not the easiest thing to align. I think that I would have been better off using round tubing there with a piece across the top to provide rigidity. The use of skate bearings is working great though. From the way everything feels right now, I think that I can get better than 1/32" accuracy. I will have much better resolution. Of course resolution doesn't matter in the presence of slop. But the only play I can feel anywhere so far is in the leadscrew. Of course, I do not have an anti-backlash nut, and the leadscrew is just hanging on the end of the stepper for now, so improvement will be made there. I don't know yet whether I will bother with an anti-backlash nut or not. I will have to wait and see how much backlash there is to see if it is worth the effort.

I also intend to switch out the 1/2-13 with some acme 1/2-8 or 1/2-10. It seems that I have the torque to do that, and if what everybody says about acme being so much more efficient than Allthread, I should even gain a little. Of course the reason I used the Allthread imitation was that at 7pm on Saturday evening, I wasn't going to be able to get any acme threaded rod, and I wanted to see something move!

If you have any questions about the construction of this, let me know. I don't know if I will ever put together any formal plans, though I applaud those who do. I just do so much design in my head. I think I mentioned before that that means there is no evidence of design changes unless they are made after construction. ;)

I am getting ready to upload some really bad resolution video to my website. The video is really pretty boring, too. But for me, well, IT MOVES!!!!

Dave

Oh, yeah. Regarding the use of specialized tools...

It would be nice to have a lathe and a mill to make this, but I don't have any of that.

I am using the O/A torch that ultimately will be attached, an angle grinder, a $39 Harbor Freight drill press, handheld drills, and my bench grinder. I am at an advantage when it comes to the electronics part, though. I work for a test equipment manufacturer, so I have access to all kinds of test equipment, like oscilloscopes, power supplies, freq counters, etc. Also, parts are pretty cheap. ;)

It's funny in a way. I, like so many others, build many of the tools we need to complete other projects. Some do it because its cheaper. Some do it because the tool they need is not commercially available. Some do it for the fun of it. Most do it for a combination of those. Sometimes, though, to make one tool, you need another tool, so you make it. I read a post somewhere on another forum complaining about people who feel they need to build everything themselves. I laughed. I think some people cannot afford the time it takes to fabricate the tools they need, especially for a business. But for some of us, it's a hobby, which means we do it because its fun! :cheers:

Dave

Hey, that was post #100!! :cheers: :cheers: :cheers:

Dave

I uploaded some video clips to my website. The image quality is poor, but that's what I get for using my digital camera instead of the camcorder.

http://workshop.d-hanson.com/

Just click on the links. You may have to download to your local hard drive to play the videos.

Enjoy.

Dave

I know what you mean about paint, it seems here that if it's not getting some paint at least before it's complete, it's not going to get any..:)

On the one rack I have some 12 foot lenghts of 3/4 acme [the cheaper stuff], and all I intended to use for the nuts were what was called 'coupler' nuts, about 4 inches long..if they are fairly tight at least they will last for a while before getting wear slop, and if they're a bit too loose they can be slightly deformed to tighten them up, once anyways..

If I can get the firewood processor [mostly] finished before the new year, it will give me some space to start another project..

enjoy..

Just came back in from the cold garage. I think it's supposed to get down into the upper teens tonight. Thank God for kerosene!

Anyway, I made an interesting (at least for me) observation about the operation of the motor. At full speed (>60IPM), there is a substantial amount of linear force on the carriage. In fact, I was a little surprised by the amount that exists. However, every once in awhile the motor starts missing steps and then won't start moving again until you slow the pulse rate down.

I don't have the non-motor end of the leadscrew secured yet, so it sometimes flops around a bit. I don't know for sure if the flopping corresponds to the motor stalling. What I am wondering about is, could this be a resonance problem? I am doing full steps. I don't need the resolution that microstepping gives me, and I am afraid if I microstep, I will lose too much torque.

Ideas?

Dave

I don't think you will lose as much as you think, especially if you only go to a half step mode, there should be some threads on here about microstep torque, I remember seeing them sometime back..

temp in the teens isn't too bad, I used to run fairly regularly down to Marion, KS. delivering dozer blades and rockpickers way back..miles and miles of miles and miles...:)
It's -24C here today, not even thinking about garage projects today..

enjoy..

I don't think you will lose as much as you think, especially if you only go to a half step mode, there should be some threads on here about microstep torque, I remember seeing them sometime back..

temp in the teens isn't too bad, I used to run fairly regularly down to Marion, KS. delivering dozer blades and rockpickers way back..miles and miles of miles and miles...:)
It's -24C here today, not even thinking about garage projects today..

enjoy..

Vladdy,

-24C!!!! :eek:

Okay. Let's see. That is -11F! I guess we are fortunate to have only a few days a year below 0F. Brrr.....

I need to see what happens when I put bearings at both ends of the leadscrew. Then I can use a rubber hose or maybe a better coupler at the motor. I'll see if that helps. I have to believe it will help some.

As I mentioned, I was impressed with force I was getting at the speed I was at. One thing that I will have to work on, and maybe software will help, is the change in direction. Right now, I have to slow down quite a bit to change direction without missing steps. Ultimately, that may prove to be a bit of a problem. If I was using this as a router, it would be no big deal, but since I will have a torch attached, the slower speed will affect the quality of the cut. More research is in store, I think.

Thanks for the input.

Dave

I guess I need to get my computer up and running so that I can tell what speed I am actually running at. The other option is to continue using my test circuit and put together a frequency counter to connect to the step line to see how fast I am spinning the motor. Then with a divider circuit, I can convert to IPM.

Eventually, I will need to dig out my old laptop that I am going to use, so I may as well do that now. I still need to load all of the software on it. I am planning on using as much freeware as I can, though I did purchase TurboCAD. So far most of the g-code I have I hand-wrote. I haven't figured out how to get the dxf-to-g-code converter I am using to do a tool path for a profile. If I wanted to rout the shapes I have done, it would not be a problem, but it doesn't want to do a profile. I will have to go back and see what program it was. Probably no support for it if it was free. Don't remember. Well, here I go on another quest...

Dave

I took a look at the videos...lots of whip on the end...
fancy approach is bearings, turning down the end to fit, etc..
simple [read cheap] approach is to bolt on a piece of ie: brass bushing just so it takes ..most.. of the slop and whip out..and will probably run easier

on my old mdf critter i used small hyd / air line hose between the motor and lead screw, in my case 1/4 x 20.. and those single use clamps to get final clamping..

A nice proper coupling would work better, hose has a bit of inherent backlash, increases a bit under higher loads..

for o/a or plasma cutter wouldn't matter, router it would be affected by side loads..

Vladdy,

Thanks again. Your feedback is greatly appreciated.

Everybody talks about turning the ends of leadscrews down. That would be feasible if I had a lathe. But I don't. I think I can get a 1/2" pillow block bearing that I can mount to the end piece. I don't know how much play they have, but I am sure I can tolerate a little bit. Like you said, on a cutting table such as this, a little backlash is acceptable, and with no tool force to be considered, should be fairly easy to control. I did cut a bigger hole in the endpiece so that I can bolt another piece in with the bearing attached. I did this to allow some adjustability. I find that for most of the stuff I do, it is easier to allow for adjustment than to try to eliminate the error up front. Remember, I don't have a full machine shop to work from; just an angle grinder, bench grinder, O/A torch, drills, drill press, and welder.

Dave

a pillow block bearing would work ok, or
just a piece of pipe a little larger than your threaded rod, weld a bracket to it, and bolt it down so that it takes out most of the whip.. a little smear of grease inside and it last quite a while.

what are you running for profiling software?

later

I.M.G. - Image to G-Code

It's shareware. I think the trial period has ended, and so far, since I can't seem to get it to do what I am after, I haven't registered it.

The software is actually intended for a router, or 3D stuff. I guess I need to look for something that does 2D.

Dave

Okay, I've had ACEconverter for a few weeks now. I finally installed it. It works for creating the g-code.

I haven't decided on software to drive the machine. I have read some good things about Kcam. But I don't have a computer it will run on to try it out. I guess maybe more research is in order.

Any suggestions? Remember, cheap is good. Free is just the ultimate in cheap. And FYI, I do not consider $1000 cheap.

Dave

Spent a little time in the garage. My daughter had a Christmas program tonight so it was about 10:30 before I got out there. I stated a few days ago that it was pretty cold in the garage. Last night it got down to -2F. Vladdy, that would be (OMG!) -19C where you are at. Not quite -24, but still pretty darned cold, if you ask me! Fortunately, tonight it is only getting down to about +6F. Said it before, I'll say it again - thank God for kerosene!

Anyway, I drilled a hole in some UHMW that I had laying around to keep the end of the lead screw from flopping around. That solved the random stalling thing. Vladdy, thanks for the advice there.

Now I can run at 80IPM from one end to the other minus time to ramp up, except when the middle starts whipping. I was really hoping that a 1/2" leadscrew would be enough to keep it from whipping in the middle, but it isn't. So, I will evaluate it at the intended operating speed and see how bad it is. I may end up making this machine a little smaller than originally intended. I am afraid to go to a bigger leadscrew, as that will only make the need to ramp up and down worse due to higher inertia. Right now, based on where the leadscrew started to whip around, I am thinking I may shorten the gantry to 3 to 3.5 ft. The leadscrew doesn't whip around in that distance.

I also have been thinking about the other axis and the bearings for it. I did receive the skate bearings I bought off of Ebay. That was an experience. I have purchased and sold several things on Ebay and never had a bit of trouble. But this time I requested that the items be shipped to my work address - addressed to me c/o work. BUT NO, I get notification that the item has been shipped to my personal business at my daytime work address! So, I emailed the seller and expressed my concern about that. He blamed it on UPS and their computer system! So, my package arrives at work, but takes an extra day to get to me, because it was not addressed to anybody that the receiving department recognized. I am lucky in that I work for a relatively small company and I deal with the shipping/receiving department quite often, so I was able to ask them if a package arrived for D. Hanson Enterprises, and they said that they had seen something like that, and to check with the stockroom. Fortunately, they still had it there. So, I took the box to my desk, noticing that there were thing rattling around inside. The box was undamaged, so I decided to wait until I got home and could take photos immediately upon opening and as things were unpacked. Upon opening the package, I found 1 plastic case of bearings open and the bearing not in it. One case had 4 of the 8 bearings in it. Two others still had all 8 bearings in them and the last had all of the bearings in it with a rubber band around it. I emailed the seller and explained what I had found and sent him photos. He said that he could not be held responsible for what UPS did to it and if I felt there was damage I needed to file a claim with them. Well, none of the bearings appear damaged. It just got my attention and I felt as though I should at least inform the seller. When he showed no concern, and again blamed UPS for everything, I left neutral feedback with comments why. So, he left me negative feedback and asked me to retract my comments and he would retract the negative feedback. I guess I didn't look deep enough into his feedback or I would have seen that this is apparently his MO. So, that bites. My only negative feedback for something the seller did. Oh, well. It won't stop me from using Ebay, but it sure makes me mad! Okay, done venting.

Anyway, I wanted to see how I was going to adjust the fit of my linear bearings on my 1.625" polished stainless steel tubing. I have read the posts about drilling a hole in the head of a 5/16" bolt and then welding a threaded rod into that hole. I have also seen the eccentric bushings for other bearings. So I thought to myself, as I often do, "I can do that!" So I did. Sort of. I found a 2" long 5/16" bolt and cut the head plus about 3/8" more. Then I clamped it in the vise on my drill press and drilled a 3/16" hole through the middle for a #12 (I think) screw to fit through. Then I'll get a #12 (or whatever the correct size is) stainless screw and thread that into the bearing bracket. The remaining bolt head will allow me to rotate the bushing to make contact with the SS tubing rail. I guess the correct term is way. Sorry about that. I'll post some pictures when I get some taken.

That's all for tonight.

Dave

Just finished cutting down the width of the gantry to 36". This will leave me about 28" of workspace. I have also decided that in order to make it easier on the motors, I will remove some weight. However, lightening the gantry also creates less accuracy, so I have also decided that this will be a dedicated cutting table, with a router now postponed until I get this done. That does simplify things quite a bit, though, so it should make things easier, and thus it should get done a little quicker.

More tomorrow, hopefully.

Dave

Got some photos taken of the eccentric bushing for the skate bearings. This will allow me to tighten the bearings on one rail.

Something that occured to me that should make life simpler is that I will be using dual leadscrews. Therefore, I only need the gantry located laterally at one end. I have reduced the height of the gantry so there should be little to no flex in the end. Both ends will need to be located vertically, but the dual leadscrews will prevent any racking which is what the additional bearing surfaces would have prevented. Hmmm...

Dave

It may be a few days now before I get back to this project. My dad just bought a new welder and the stand that came with it is less than perfect. So, I am going to try to build him a new one for Christmas. Of course, it can't just be a simple stand. That wouldn't fit my style, so it may take a few days to complete. Hopefully, I'll be able to work on the cutting table again after the holidays.

Dave

Hi Dave.
¿ How this these project end? ¿ Did you finished it?
I like the double square tube with the bearings, the way you handled.
Regards
Hugo Carradini

How this these project end?
We may never know Hugo.