[lasersafe1]

I've got a Seig X2 and have used it for CNC using a small X-Y stage that I mount on the bed. It has always been my temporary solution before going bigger.

Attached is my first attempt. I'm building it in Autodesk Inventor before making chips so I can test out the motions. I have a clean 12" by 24" throw right now on X-Y, but I can't decide on the Z. I have thomson rails and bearings (SPB10-OPN) for all X-Y and I have two 17" IKO rails with three sleds (LWL12 B) each for the Z. The table surface is an old cast iron router table.

I "think" I can build a fairly stiff metal working machine with these parts, but I could sure use some advice if someone sees a problem lurking.

Machine is mostly used for milling out small aluminum 1/32" faceplates, the type that are used for outdoor electrical box covers. I usually group them in a stack of 10 to speed up my production by doing 10 in a shot. My present Seig mill is actually good enough for this, but I want to start doing some larger 10" by 12" size reverse etching of acrylic panels.

So here is my first question: What is the general consensus on how high of a clearance I should have on the lower gantry rail. Obviously in my present design the spindle can't reach the table, but if I lower it then the rail might interfere when coming forward. With 17" rails, I think I'll always be able to go up for bit changes. Should I just leave the lower rail at about 8" and mount all of my items to be milled on jigs? After all, I never really want to drill or mill the table surface.

[Oldmanandhistoy]

Hi,

I won’t question why you are using the X2 spindle and will assume you will be happy enough with rpm’s as you have been using it already.

As for the Z axis; only you will know what a suitable height is. This will need to be worked out from cutter lengths, material thicknesses + jig height and clamping methods. I would recommend you having a good think about what is likely to be your highest setup and workout how much clearance you will need on the Y axis. It might be a good idea to add some extra for just in case situations. Obviously the lower you can keep it the better so keeping the jig base height to a minimum would make a difference to Z and Y axes rigidity.

John

[zephyr9900]

Those Z rails are pretty long. Would you get more useful travel if you put the sleds on the X carriage and have the rails travel with the Z head? I.e. make a tall plate with the Z rails at the edges and mount the headstock at its bottom end?

Best regards,

Randy

[Oldmanandhistoy]

Those Z rails are pretty long. Would you get more useful travel if you put the sleds on the X carriage and have the rails travel with the Z head? I.e. make a tall plate with the Z rails at the edges and mount the headstock at its bottom end?

Best regards,

Randy

I was presuming the drawing was a draft and not the final design? So did not really look at the picture.

John

[lasersafe1]

Good points.

Seig X2 spindle has the belt drive modification for higher speed. I find it fine for everything I have done so far. I like the R8 collet and the ability to reduce speed while maintaining good torque.

I don't actually plan on doing any milling at the top of the Z stroke. I simply want to ensure that I can always lift high enough to change the R8 collets. I have found this to be of particular concern when using the original Seig mill and the drill press collet adapter with a long drill bit.

I plan on beefing up the Z with metal plate. I just haven't added it to the drawing.

[lasersafe1]

If you mount the Z rails to the traveling head, then your head can't ever go higher than your lowest bearing. Yes, you can travel all the way down, but not up.

[zephyr9900]

If you mount the Z rails to the traveling head, then your head can't ever go higher than your lowest bearing. Yes, you can travel all the way down, but not up.

Sure. But you would place the sleds differently on the X carriage than you have them now.

It seems to me that your Z travel ideally will be equal to the distance between the base and the bottom of the gantry plus your longest tool length. I.e. be able to touch the base with your shortest tool and just be able to retract your longest tool to the bottom of the gantry for clearance. John gave the guidelines for working out the gantry clearance.

On my Techno-Isel gantry I mostly held thin sheet with double-sided tape on a sacrificial aluminum tooling plate that I screwed to the table. I also had taller work that I held in a toolmaker's vise. I was using a Sherline milling head for which I made an adapter plate to fit in the T-slots in the Techno Z axis carriage. Depending on the height of the job, I slid the adapter plate up or down in the T slots. That worked pretty well becasue I didn't have enough Z travel to do it all in one setup. There are a couple of photos at http://www.prototrains.com/gantry/gantry.html

Best regards,

Randy

[lasersafe1]

I see what you mean Randy, but my difference between tool sizes can be substantial. An R8 collet with 1/8 engraving bit vs. the 1/2 drill adapter collet with a 1/2 drill inside can be a difference of 7 inches. In order to quickly pull this latter collet I have to raise the head 12" from the work surface. I realize that I might have to beef things up, but acme thread is cheap and if I can make the Z lift higher to avoid manual adjustments then it is preferred.

Of course I could always put a hole in my table over in the corner to let collets drop through.....

[zephyr9900]

Of course I could always put a hole in my table over in the corner to let collets drop through.....

Looks to me like your table already has a hole... Just don't put your gantry leadscrew exactly in the center...

Best regards,

Randy

[fatal-exception]

Hey, I'm in the same boat as you. I'm about 1/2 through my design, and am kinda unsure about how much head travel I should build in. I've designed it so far that neither the coller holder, nor drill chuck can crash into the table without tools. I don't have the ground rails yet, so I'm still flexible there.

I agree that it's is a personal choice, and one that should be driven by what you plan on using the machine for. If all you ever do is sheet material, you really don't need much travel. I've planned on 7" of travel, which should be plenty for milling and drilling sheet plastics. I'm sure there will be a time in the future that I wished I had more, but that's neither here nor there.

Anyways, that' my 2 cents.

[zephyr9900]

An R8 collet with 1/8 engraving bit vs. the 1/2 drill adapter collet with a 1/2 drill inside can be a difference of 7 inches.

Unless you have really deep holes to drill, CNC-length drills are great. I bought a whole set (number, letter, fractional) when I had a Sherline mill and still use them with my Tormach. They are short and stiff.

For that matter (not knowing your budget nor what you already have invested in tooling) have you seen the Tormach Tooling System? It uses a flat-faced R8 collet to hold toolholders in which you can preset mills, drills, etc. The vertical clearance required to change tools is much less than changing R8 collets, and the ability to use preset, repeatable tools in multi-tool programs is sweet.

Best regards,

Randy

[Rodm1954]

Well that makes three of us at the same stage. I am working through the design problems. My biggest concern is having the weight of the X2 head sitting out so far from support. I see both designs have done what I did and remove the dovetail casting to reduce the weight. I have the pulley kit fitted and all the gears stripped out but it still weighs in at 9kg less the switch box and motor controller. These items I plan to mount on the Y axis and just extend the motor cable.

For changing the R8 collets I am going to either drill a hole in the table or pivot the head so it can be turned to 90 degrees (maybe less) to clear the collets.

I was planning on Z axis travel of between 4 to 5 inches.

My choice to use the X2 head is to reduce noise so that I can work later into the night. The routers and die grinders are not making me popular with the neighbors.

I am pleased to see a couple of others that think the X2 head is a good way to go.

Are you planning on using flood coolant?

[Oldmanandhistoy]

For changing the R8 collets I am going to either drill a hole in the table or pivot the head so it can be turned to 90 degrees (maybe less) to clear the collets.

I very much like that idea and very nearly suggested it but wondered how easy it was going to be to implement.

Another possibility if you want to go that kind of route would be to hinge the spindle vertically so it could be turned 90 degrees and would hang over the side of the table for tool changes; did that make sense?

John

[Rodm1954]

Hi John

Thanks for the suggestion.

I had thought of hinging the X2 head but then thought of all the problems in making a hinge with zero play. Decided to go one of the other ways as they are much easier to fabricate. I lean towards the hole in the table as it is the simplest solution.

I am going to use ER25 collets so most of the time I will not need to use the change hole or pivot.

[Oldmanandhistoy]

Hi John

Thanks for the suggestion.

I had thought of hinging the X2 head but then thought of all the problems in making a hinge with zero play. Decided to go one of the other ways as they are much easier to fabricate. I lean towards the hole in the table as it is the simplest solution.

I am going to use ER25 collets so most of the time I will not need to use the change hole or pivot.

I agree that either hinging or rotating the spindle is going to add unnecessary complexity also doing either will increase the distance from the line of the cutter to the Y axis which in turn will add more unwanted lever action to the Z. With this in mind has anyone considered turning the spindle around 180 degrees or fixing the Z rails to the front of the spindle instead of the back. In my mind (a dark and jumbled place lol) it would bring the line of the cutter very much closer to the Y axis thus greatly reducing lever action and increasing rigidity? Take a look at fatal_exceptions drawing to see how much difference it would make.

John

[Rodm1954]

Hi John,

Yes I did think of that but the majority of weight in that assembly is in the motor. By reversing the weight is now further away from the Y axis so it might be self defeating. I do see your point though and any movement will be less closer to the Y axis than further out.

I like your input as you certainly are a lateral thinker as I have found on your other posts.

[Oldmanandhistoy]

Hi John,

Yes I did think of that but the majority of weight in that assembly is in the motor. By reversing the weight is now further away from the Y axis so it might be self defeating. I do see your point though and any movement will be less closer to the Y axis than further out.

I like your input as you certainly are a lateral thinker as I have found on your other posts.

I’m just trying to thrash out a few possibilities. What about fixing the rails to the side then?

John

[Rodm1954]

Fitting it side on is a much better option. There is a motor pivot to get around but nothing too difficult. The motor side will have to be mounted closest to the Y axis to retain the spindle locking pin but this can be easily moved if needs be.The Y axis will also have to be extended a bit to allow for the extra width but again nothing too difficult seeing we are all in the design phase. I'll play with the head on the weekend and report back here on what I think.
:cheers:

[Oldmanandhistoy]

It will also mean that the Z rails can be further apart so will make the Y axis extension to accommodate this worth while imho. Just finding a bit here and a bit there can make all the difference to how the final design will perform.

John

[LeeWay]

Just a couple suggestions or thoughts you might want to consider. I know that most guys built the gantry in the fashion you have drawn. Many remark that they get a little play or slack because the axis bends or gives a little. Most apparent with larger axis builds, but something you might want to design around.
If you design a bridge type gantry, I think it would be far more rigid. I only designed my router to cut plastics, but it happily mills aluminum as well simple because there is no play in the Y or Z. I did design a bridge type gantry. Many others here have as well, so there are some nice machines to look at in designing yours. Mine uses roller skate bearings. They work great. I had intended to install some linear bearings and rails, but I just don't need them yet. Probably do it when I wear out the first set of bearings. They show no sign of wear yet after running about one day a week for a couple years.
Here is an image of mine.



You can also make a notch in your table for the tool change. Doesn't have to be in the center. My tool change location is plus 3.5 on Z and 10 on X and Y. I only use router bits and end mills so far, but could use drills. I am able to pull my router out with two cam clamps, so you won't have that option with a mill head. You won't be able to access the spindle quite as easily with a bridge type, but it sure does make a strong axis.