Ted's Machine Starting at Sq #1

[Treischl]

I have been lurking and reading a ton of the stuff on this forum for that last month or so. The advice and comments are really good and have certainly helped me get started on my router project. The first post in this thread (namely this one) will give you some background on myself and me early experiences after I decided I wanted a CNC router sitting in my shop.

I have a mixed background, started out as a tool and machine designer. 30 years ago I designed compound table laser cutters, large industrial ones for 4 X 8 sheets of steel rule die board (expensive plywood). After that I moved into CAD/CAM sales. Then, of all things, I started writing CAM software for industrial lasers. Eventually I worked in that capacity for Mitsubishi Laser. While all that was going on, I picked up the woodworking habit. 2 complete kitchens, lots of furniture and my specialty small jewelry boxes. I do both power carving and hand carving, usually blending the two.

So, long story short, I have quite a bit of experience, I have the tools, but I am not an electronics guy at all. So there is my weak spot.

When I made the decision, I originally wanted to build my own. I like doing that, because then if something is wrong, I know what to do to fix it, or at least how it was built. I do not like complicated things that are not made to be fixed or adjusted.

But, I thought about the time it would take (which I have lots of, by the way, since I am semi retired). And sure enough I sucked into buying one of those worthless HDPE machines. It was a nightmare. But I learned a lot during that time. The builder did not send me a MACH file for setup, so I went through that and figured it out, very enlightening! And I must say, one fantastic program! I returned the machine two weeks ago, got my money back minus some shipping costs and began designing my machine.

I investigated various drive mechanisms, ball screw, lead screw, rack and pinion and belt drive. My favorite is the belt drive, but I am not building that, instead I am starting with a lead screw. I looked at designs. When it comes to designing machines there is exactly one place where the rubber meets the road, and that is the machine ways. If these are not sturdy the machine will never be totally succesful. Of course, designs that use things like THK or HIWIN are top of the line. Next would be round shafting supported over it's entire length (similar to the Joe CNC). V track rails come next in my book. And finally, unless you are building a VERY small machine, with maybe 8 inches of travel, are unsupported round shafts. Unsupported shafts are not the way to go. Even the double ones, simply put they flex, they sag. My machine will use V Track. This may be the one area I will have the most problem with, but I am going to give it a go. The Z axis will use round shafting, but the shaft will be supported on both ends and in the middle. More on this later.

The machine travel will be 38 in X, 26 in Y and 4 in Z. The Z axis will clear the bed by 4 inches as built. However, the deisgn allows riser blocks to be added to increase Z clearance but not Z travel. Oh, the design is moving gantry.

The basic frame members of the machine are being built out of MDF. I chose it for its stability and ability to absorb vibrations. Also, it is not all that expensive. Later on, I will be posting pics and some of the design drawings for the machine.

On to the electronics. Wow, is that mine field if ever there was one! Sheesh. After floundering around, reading everything I could find, turning my already aging gray matter to mush, I finally gave up and yelled for HELP! Ger and a couple of other guys came to my rescue and pointed me in the right direction. Like I said, I am really ignorant on this electronic stuff and do not want to get overly educated in it, just not my cup of coffee.

I have ordered the CADNC package with the xylotec board in it. Yup, I know, the gecko is better, etc, etc. And I agree, but money is a slight object here. I ordered the package with 500 in/steppers ( I am using 4 axis, 2 slaved on X). It includes an external relay to control the spindle, pendant, dual parallel ports and the extra parallel port for my computer. I spoke with Tom, great guy, helped me out quite a bit. I opted for the 500 in oz motors because I may reuse them in a large machine later on, they are not needed for this machine. What I like about the system he sells is that it is all wrapped up in some nice, neat packages. I am not into 'put a shunt resistor or a cap with 3.5 giga joules' stuff, I just want to plug it all in. I guess I like my electroncis like my truck. Open door, get in, turn key, put in gear, GO.

Leadscrews are coming from Precision Tech in Florida. Lemme tell ya, really nice people. They are 1/2-10 double start for that magical .200 per rev. They do the end machining at a very reasonable cost. I also bought their bearing blocks. I am a firm believer in "Thou Shalt NOT Use Motor Bearings for Support". (Like the guys with the HDPE machines do)

Anti Backlash lead nuts are coming from Dumster CNC along with his couplers. I know a thing or three about anti backlash, his look darn good. It is a design that dates back 30 years in my experience. We used a special spring washer called a 'wave' to accomplish what he does. Of course, ours required a LOT more force for the machine size.

All the aluminum for motor brackets, etc is coming from On Line Metals. I have used them before for other projects. Very happy with them.

V-Track wheels are coming from IMService. It was the best price I could find.

Ok, this was pretty windy, I know, but I wanted to get a base established so everyone knows where I am coming from, and hopefully where I am heading. As soon as I figure out how to put pics up here, I will start with some of the design stuff (remember, I was a Tool and Machine designer, so I dispensed with the niceties like drawing dotted lines, etc.) This drawing was for me. I do not do solid modeling. A comment on that, when building machines, the biggest mistake I see is not making allowance for adjustments, shims, etc. These CAD programs lead you into a kind of euphoria, where everything will be machined exactly as drawn. That don't even happen in a precision tool and die shop, nevermind most of our workshops. So, I tend to design things with the shim already added, for instance, I will put a 1/4 pad between members to allow for differences. That way, I can sand one down slightly and it still looks like I planned it. This is much better than sticking shim stock in all over the place.

Ok, so off I go. This morning, I need some 1/2 - 13 threaded rod, nuts, washers and some Kreg pocket hole screws. I will try to post later today as this is my first day of building!

[Treischl]

Here are some of my design drawings:







So far, I have started building the base of the machine. The side pieces are connected by three pieces of sch 40 pvc. This is done by using boss pads on the inside and passing a 1/2 -13 threaded rod through the pipe. This worked out nicely. The rails are made from MDF, I lightened it up a bit by pocketing out the insides in several places. I calculate each piece now weighs about 20 pounds.

Pardon my crummy jpg files, it is the first time I have set up to show pics on a forum.

You can see the strategy I am going to use for the ways. Steel angle iron with V-groove wheels. The top wheels will be fixed (there are two on the top of each side rail). The lower single wheels is going to be semi adjustable so I don't have to drive myself crazier with real tight machining.

[Treischl]

[Treischl]

This is a view of the base construction, very simple as you can see.

This is a close up of the pvc, how exciting!

The counterbore for the threaded rod

Tomorrow I am going to build the table for this machine to sit on. Not very interesting, but it needs to be done. As you can see, there is no way I can build this machine on my bench. My bench is big, 39 inches deep X 80 long. Nothing fancy about the stand, that is for sure.

[crocky]

Hi,

Looks like a masterpiece is being built, I have been lurking here for a while too and I am about to get started as well.

Keep up the good work

Regards,
Bob

[ger21]

Looks like where the gantry beam attaches to the sides is a possible weak point. And it's hard to tell by the drawing, but the plate the router is mounted to my flex a bit.

[Treischl]

Hi Gerry,

Those drawings don't quite tell the whole story. Once I have the assembly lined up, I will be putting side plates on that Z-Axis slide. Unfortunately, my lack of skills creating pictures don't show the method used on the slide. Most slides have two blocks that the guide rodes are mounted to and two blocks for the bearing mounts. I have set up mine so that the rod plate actually uses three supports. One on each end and one in the middle. This way I do not end up with 10+ inches of unsupported rod.

Think of it this way, with most slides, when the router is fully down, one set of bearings, the lower ones are right next to the support block. That is excellent. But the upper set is in the middle of the rods, and of course this creates a very weak spot. In fact, the lower set acts as a fulcrum point.

However! I am not the end all be all in machine design! As the build develops, I may alter some things depending on what I see. Your point is well taken. As we all know, the goal is to not have any movement at the tool tip. The first place it can move is the one you pointed out. Then they start adding up as we go thru all the axis. So each one has to be the best it can be.

I am going to build the legs (table if you will) that this thing will sit on today. I would have started at 8 this morning, but Mother Nature dumped nasty wicked mean snow, sleet and rain on us over night, so I have been clearing things out.

More to come later today!

[Treischl]

Here is the base frame for the machine, with machine base on top. It is not as crude as it looks, ok, almost. The stretchers are let into the legs, All screwed and glued. Ridgid, no wobble, no shakes.



While I was at it, I went ahead and got the upper surface of the x-axis base planar. I used the old time winding stick method to do it. Works good, quite accurate. If you have not seen the method, it is simply two fairly thin sticks, about 1/8 thick by an inch wide and however long you need. One of them has a face blackened. You stand one on each end of the machine, then sight across them. The top edges should line up.

I also checked the straightness and parallelism of the side members. Straightness on one was very good, the other, slight bow inwards of about 1/32. In other words, the inner pvc tube is a bit short. I can either shim it out, or do a recut. I am going to do neither. I will adjust the v-track rails accordingly, cause they will probably need it even if the side members are perfect.

The machine will get attached to the frame with aluminum angle brackets.

Tomorrow I will start making the tracks up. I have not got my steel angle in yet, but there are some other things I can do to get ready for it. Probably make the gantry side pieces while I am waiting too.

[Treischl]

Some progress has been made. I made up the pieces that the angle iron will mount to for the x and y axis tracks. Also all the small support blocks for the tracks on the x-axis. Y-axis won't need them. They are all installed and I made a gage to check that they are parallel. Took care of the bow problem I mentioned earlier by adding OMG shims. How straight is it? As good as I can check with a 48 inch scale. Not worried at this point cause some adjustment may be necessary after adding the steel angles.

I also made the main gantry pieces, side pieces and beam. Also turned up four eccentrics for the v-groove wheels for adjustment later on.

The thing is actually starting to look like it will be a machine. Amazing.

Enjoy the pics below:

All the major pieces. The y axis beam will drop down about 5 inches when it is installed.


A shot of the angle iron support pieces. Maple.


Looking in from the end of x-axis.


My v-rollers came in today. They are from IMService. They look good, nice and smooth. 12 bucks a piece for a total of $144.


End shot



The plan tomorrow is to start building the Z-axis mechanism.

Oh, a tip! I see a lot of talk about problems gluing up MDF edge grain. It is a problem, but a glue that works better (I never said it was GREAT) is Mold and Trim glue. It is much thicker and sets up real fast. It is made for doing miters. I don't depend on it completely though, lots of screws too.

[wcarrothers1]

I'm not a big fan of the triangulated V grove setup vs using 4. Course I used 4.. So Of course I'm partial to 4 rather then 3..hehe

b.

[Greolt]

I am enjoying looking at your pics and following your progress Treischl

Have to second what wcarrothers1 said about the X axis rollers.

You will be adding another roller eventually so might as well do it now.

The only other comment is can you tighten up the Z axis design a bit.

Reduce the amount it hangs out from the Y carriage. Closer it is the more rigid things will be.

Anyhow good effort so far. Keep the pics coming.

[zoltan]

Hi,

Could you, please, elaborate little bit about how you connected the side memebers with those PVC tubes?

Thank you.

Zoltan