New O/A Cutting Table

[whateg01]

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

[whateg01]

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.

So I will start over with that.

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


Dave

[whateg01]

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

[whateg01]

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.

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

[whateg01]

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.

[whateg01]

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!

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?

[whateg01]

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!!!)

[whateg01]

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

[vladdy]

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..

[joecnc2006]

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.

[whateg01]

Originally Posted by joe2000che 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.

Originally Posted by vladdy 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

[whateg01]

Things are good!!!

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