First time builder log with questions

[deemon328]

Hello all,

I'm a first time builder and have decided to build a Model D Imperial sized at 32" x 48". I'm sticking pretty close to the plans and have chosen 1/2"-10/2 start lead screws with the dumpstercnc anti-backlash nuts. I'm going to build the machine framework first, then get the electronics next month or so. I plan on either using a trim router like the Bosch Colt or a larger router like the Milwaukee 5616. My goal is precise wood cutting for patterns and wooden gears and signs. I expect to use mostly 1/8" pattern cutting bits and ball nose carving bits with a bit of 60 degree sign making thrown in as the major operations for this machine.

I'm in the process of making the runners and wanted to share my progress and ask a couple questions.

My X and Z runners and caps are fabricated. I sized them to 2.5"W x 5"L. I bought 2 new router bits for this job, a 3/8" and a 7/8" diameter ball nose bits from Magnate.net. I'm exceptionally pleased with the quality of these bits over cheaper alternatives from Rockler. I'm new to using Magnate bits since I picked up a Legacy Ornamental Mill, and I have to say that they are top quality bits, an even match for Whiteside bits, IMO.



OOPS, I messed up the x and y axes in the questions. Please see post #3 for corrected questions

My questions are regarding the length and width of the runners on each axis. I've stuck to the guidelines of making the length of the runner twice the width, but is 5" long too short for the X-axis? Does the X-axis runner need to be the same size as the X- spacer gantry or the gantry side itself? I'm trying to maximize my X-axis travel, so any advice would be greatly appreciated.

I have the same question for the Y-axis. Does the runner need to be wider than 2.5"? It appears to be about double the width of the X and Z axes based on the Model_d_assembly.easm file, but I'd like to know how critical this decision is and what the advantage of a wider Y axis is.

My initial thoughts were that a well built runner would be rigid even if it was smaller. Is this bad thinking on my part?

Thanks for any advice you can give! I'll leave you with some images of my fabricated parts for the runners and caps.

[rockcliff]

I might be confused on the Axis, here's the model D with the standard Axis Labels, on this example of a 36" x 24" table the Y Axis Runner is 12" long

[deemon328]

OOPS! I see now the axes in the drawing. My carvewright has the X-axis as the long axis, so that is the source of my confusion. Now that we're on the same page, I'll rephrase everything

My questions are regarding the length and width of the runners on each axis. I've stuck to the guidelines of making the length of the runner twice the width, but is 5" long too short for the Y-axis? Does the Y-axis runner need to be the same size as the Y- spacer gantry or the gantry side itself? I'm trying to maximize my Y-axis travel, so any advice would be greatly appreciated.

I have the same question for the X-axis. Does the runner need to be wider than 2.5"? It appears to be about double the width of the Y and Z axes based on the Model_d_assembly.easm file, but I'd like to know how critical this decision is and what the advantage of a wider X-axis is.

Here is the progress so far on my Z-axis runner and cap assembly. I'm holding off on finishing the others until we discuss these questions above.

Thanks!

[rockcliff]

Hi
Not really oops, you can assign x or y anywhere, it's just so we both understand, what we are talking about.

2 times the width rule is really an absolute minimum,

Becuase the two Y axis's carry all the load, ( gantry, X and Z slides, plus the router) I would personally go longer in length, 10 to 12 inches, long x 2.5 to 3" wide, the longer you can go, makes it slightly more stable,


The X axis is a little different, you want it as wide as possible, you get kind of a pry bar effect, where the Z has some mechanical leverage, so in reality the wider and longer you make the X , it gets more stable

You could follow the sizes of the 24 x 36 machine,(drawing D8) but just stretched longer and wider to meet your larger machine payload,

Not to say smaller will not work, if they are made why not give it a try, the small cost to make longer ones later is so small, I've seen some comercial routers with even smaller.

Nick

Originally Posted by deemon328

OOPS! I see now the axes in the drawing. My carvewright has the X-axis as the long axis, so that is the source of my confusion. Now that we're on the same page, I'll rephrase everything

My questions are regarding the length and width of the runners on each axis. I've stuck to the guidelines of making the length of the runner twice the width, but is 5" long too short for the Y-axis? Does the Y-axis runner need to be the same size as the Y- spacer gantry or the gantry side itself? I'm trying to maximize my Y-axis travel, so any advice would be greatly appreciated.

I have the same question for the X-axis. Does the runner need to be wider than 2.5"? It appears to be about double the width of the Y and Z axes based on the Model_d_assembly.easm file, but I'd like to know how critical this decision is and what the advantage of a wider X-axis is.

Here is the progress so far on my Z-axis runner and cap assembly. I'm holding off on finishing the others until we discuss these questions above.

Thanks!

[deemon328]

Thanks Nick for the explanation. I'll definitely re-cut the Y-axis to 10"; I think I have enough aluminum for that. I'm going to keep it at 2.5" wide so that I can keep my table saw setups the same for the Y and Z.

I think I'll re-cut the X-axis to 6" wide and keep the length the same as it is now (5") so that I can use my already cut aluminum. That would make only one part to remake if that turns out to be a disaster.

[deemon328]

Well, today went pretty much as planned. I was able to make 10" Y-axis runner assemblies, and I stuck to a 5"x5" X-axis to re-use previously cut material.

While I spent a great deal of time making sure all of my stock was cut correctly, I think I"ll have a little bit of adjustment to make on the runners because the MDF blew out a little bit in a couple of spots where the screws hold the aluminum angle. Better pilot holes might have helped here.

On the original Z-axis runner, I added the brass screws as an exercise in drilling and tapping. As it turns out, having these brass screws near the end of the runner helps to keep the MDF from splitting when the aluminum gets screwed on.

Also note that I went with a full length runner cap. I don't know if it will help with rigidity or not, but it wasn't any more work than having a shortened cap like on the Z-axis.

[deemon328]

Sometimes, no matter how carefully you measure, little errors will conspire against you. When making the end cap and motor mount for my z-axis today, those errors caused a problem that required a thoughtful (for me) solution.

Even precise measurement can't help you when you plant your forstner bit 1/64" off center. I know I should have used an awl to mark my hole location, but sometimes the ego of being a woodworker gets in the way of a good process. Here's a shot of good measuring amounting to a hill of beans before drilling:



I proceeded to drill for my motor mount and lead screw holes. When I dry assembled the perfectly square parts to the base and rails, I noticed that my holes did not line up with the anti-backlash nut. I needed a way to align these holes.

I placed bearings in the end cap and motor mount.



Then I ran the lead screw through the runner. This was the trick I needed to properly align everything.



Note how this alignment made the motor mount not fit squarely to the base.



Now that everything was aligned, I clamped and screwed the ends together to maintain my alignment.





At this point, I was ready for priming and painting.



I had to shim my runner by .006 on two of the bearings that were tapped slightly off. I still wasn't happy with the fit, as there was a little wiggle that I could detect on one end. I decided that the entire runner could use a few thousands shimming. Instead of using my brass shim stock, I decided to let the paint do the shimming for me. A few coats of paint made the rails fit tighter which tightened up the runner to where I can not detect any play.





I'm overall happy with the result so far, although I rushed my finish and it's not as nice as I would like.

I made a couple modifications and allowed one error to creep through that makes me pretty mad. My first modification was to increase the width of the rail by 1/4" so that it would totally enclose the runner bearings. This is also my source of error, because I intended this extra width to account for mounting my motor (a Keling KL23H284-35-4B). In my planning stages, I did account for the screw holes of the motor which were 47mm(1.85in.), but I did not account for the overall width of the motor base which was 60mm(2.36in.). I have only 1.125 in. from the center of my motor mount hole to the edge, and the motor is 1.18in from the center, so I'm going to have a slight bit of overhang from the motor. My error is that in my head I was thinking that I accounted for the overall width, but I only actually accounted for the screw mounting hole width.

The second modification was the addition of an end cap to the Z-axis which is not in the plan. I placed a bearing in this end cap to help keep the lead screw aligned. This addition seems like it will make things more accurate, but I really don't know. I'm thinking that I can remove this end cap and create a new one that has an integrated motor mount as one of my first CNC projects once I get my machine operational.

[deemon328]

So, as it turns out, the end cap is not as perfectly centered as I had hoped. I put the lead screw in and as I move the runner down to the end cap, it gets harder to move, but not so much that I can't turn it by hand. There's a slight mis-alignment, but it's only noticeable when the anti-backlash nut gets within a couple of inches to touching of the end cap.

My question is how much do I need to worry about this? I'll be making my long Y-axis rails tomorrow, so any comments would be great. I doubt that I can correct it and make a piece any more precisely than I already have.

[rockcliff]

Hi
As for the end caps, what I like to do for better alignment, is cut the caps slightly larger, I then slide the runner block with screw all the way close to the cap, basicly let the screw determine the correct position of the hole, then glue or screw the oversized cap in place, I then take a flush-trim router bit and trim around the cap making it flush to the rail

The shoter Z slide you just finished is a little more difficult to align, as there is no give , you should find the longer rails are more forgiving

It's sometimes best at this point to try and drive a slide with a motor attached, to see if the motor can overcome any friction, but my guess is that if you can turn the screw by hand the motor should be able to aswell.

It's almost impossible to be perfect when hand fabricating anything, I always say, I never need a serial number on any of my work, if it were ever stolen, I could identify it a mile away

Originally Posted by deemon328

So, as it turns out, the end cap is not as perfectly centered as I had hoped. I put the lead screw in and as I move the runner down to the end cap, it gets harder to move, but not so much that I can't turn it by hand. There's a slight mis-alignment, but it's only noticeable when the anti-backlash nut gets within a couple of inches to touching of the end cap.

My question is how much do I need to worry about this? I'll be making my long Y-axis rails tomorrow, so any comments would be great. I doubt that I can correct it and make a piece any more precisely than I already have.