dougsnash published a new build:

Read more about this build...

 

Design work is continuing for my Roto-Ox CNC machine. I have the OX CNC X/Z plates modified to use 20x80 V-Slot rail and have done the preliminary design work on the gantry plates which will support the ends of the machine. While the end plates appear to be serviceable in the sketchup drawing, I am not sure about the room I have left between the face of the Z-Axis and the centerline of the A-Axis (Y-Axis adjustment). Until I can mock-up the prototype with an actual router and mount I won't be sure how much space will be required for the Y-Axis. Also, I do not like the long single slot I have left for fine tuning the Y-Axis spacing and will likely break it up into two or four shorter slots once I figure out exactly where the bolt holes need to be.

 

Most of the parts are on order. I hope to be able to start building the prototype between Christmas and New Years

 

Hi Carl, nice to know I'm not the only one thinking of making spindles. Now that I have the basic design laid out in Sketchup I am starting to think about adding a short stroke Y-Axis to the Roto-OX. By adding a derivative of the Z-Axis to each of the end plates I would end up with far more flexibility in what the machine would be capable of making. I might try making up a set of plates as I have them designed now and see how they work before trying to get any fancier.

Doug M

 

My build is progressing. I had a few minor tuning challenges with my OX CNC which made the cutting of the sample plates a bit time consuming but now have a set of plates made to build up the prototype RotoOx. I have the X-Axis installed and the beam for the A-Axis but hit a small snag when I went to install the 20x40 stiffening rails. While the 20x80 rails are exactly 1500mm long, the three 20x40 rails vary in length by between 5-8mm oversized. Fortunately, the rail that is 8mm too long has a tap broken off in the end of it and hopefully I'll be able to extract it during the trimming process.

My plans were to use 6.0mm hardboard for prototyping purposes so I was not wasting expensive 1/4" aluminum plate figuring things out. I figured the hardboard would work for layout but would not be up to supporting a running machine. Although I am not yet done assembling the machine, I am surprised how stiff it is becoming even being build out of inexpensive compressed sawdust. I doubt the hardboard will stand up to much abuse but at least I should be able to make the machine run a bit before upgrading to aluminum plates.

I'll snap some pictures once I get the 20x40 rails installed you can see how it is coming together.

 

Most of the mechanical assembly of the Roto-OX is complete with the exception of the Z-Axis due to some parts on backorder. I am pleasantly surprised at how stiff the machine is lengthwise even with the hardboard ends. The stepper motor for the X-Axis has some play in it so will not likely stand up to much use as is but should be solid enough to at least make a few test cuts. I will update as the build progresses.

 

Yes, the wood is just for prototyping. I am hoping that the wood will stand up long enough to cut a piece or two to prove the concept of the Roto-OX but I am not expecting any more from it than that. I have the aluminum to make the plates already but my OX CNC is not working reliably enough yet to cut it. I did some tuning on the OX yesterday so maybe it will be up to cutting aluminum when I'm ready for the final plates. I want to be absolutely sure the OX can handle the 1/4" aluminum before cutting into a $100.00 plus piece of metal.

 

Robert, I'm in the southwestern corner of Northwestern Ontario.

The X and Z plates that I have cut are modified versions of the new eight wheel plated listed for the original OX. The main modification I have made to the X and Z plates was to stretch the plates twenty additional millimeters to accommodate 20x80 V-Rail for the X-Axis instead of the original 20x60 used on the OX. The prototyping I have done suggests 21mm might have been a better plan as the fit over the double 20x80 rails is a bit tight. The end plates are 295mm wide by 247mm tall but these dimensions will likely change a bit as the design matures. I have already started to mentally design a Y-Axis assembly to add to the end plates to offer true 4 axis spindle machining. The Y-Axis will use two short stroke ACME threaded assemblies to move the centre of the A-Axis fore and aft under the router bit. Since the radial capacity of the spindle assembly is only 49mm, I will only need a Y-Axis stroke of 100mm to be able to route a flat onto any portion of the work piece.

Unfortunately, I am almost as far as I can go with this project until some more parts come back into stock at the Openbuilds Store. Mark says the stock will be replenished sometime this coming week so hopefully I'll be making chips with the Roto-Ox soon.

Doug M

 

It's Alive!!! Well sort of, at least.

I did a quick and dirty installation of my new TinyG controller board yesterday and have the X-Axis working well (Mainly because I was able to re-use the tuning numbers for my OX CNC). The A-Axis will move but I have had to map it to the Y-Axis because TGFX doesn't have a jog control for the A-Axis. Still, I am able to make the X carriage move side to side and have the A-Axis spin a block of wood I have clamped in the chuck so I call that progress. There is not much information on the TinyG wiki about tuning a rotary axis so I am going to have to do some experimenting to get the A-Axis functioning as it should.

Robert, I have adjusted the eccentrics to their minimum tension but still found the spacing around the X-Axis beams a bit tight. I can work with the tension as I have it for prototyping but would like to have some adjustment in the final version. The currently installed X/Z plates are v0.2 which included an additional 0.5mm of clearance and they are better than the v0.1 plates which fit but were way too tight. That is why I am leaning to use 1.0mm as the additional measurement from my original design to allow for some wheel tension adjustment. I think I am going to take some detailed measurements of what I physically have and modify my plates accordingly. There is no sense repeatedly tweaking the design based on guesses when I have a built assembly to measure.

I am using 20X60 for the Z-Axis. In the picture above, if you look behind the machine you can see a piece of black 20x60 which will be used for the Z rail. I had forgotten to order 45mm bolts for the Z-Axis when I ordered the parts for this build so I cannot mount the Z-Axis wheels till my next parts order arrives. Also , the Openbuilds store is out of ACME threaded rod so I can't install the Z rail even if I did have the wheels. Supposedly more ACME rod will be arriving soon so hopefully I'll be able to finish the build up and give the machine a try.

Thanks for following my progress.

Doug M

 

Thanks Carl. I am a bit worried about rigidity on the horizontal 20x80 rail which has the head stock and tail stock mounted to it. The end of the rail is well supported by the endplates but I am worried the rail will flex a bit if the tailstock is mounted in the middle. I have a couple of ideas which will stiffen the horizontal 20x80 rail if vibration becomes an issue but I won't know how bad the shake will be until I get the rest of the parts assembled. I don't want to get too carried away designing solutions to a problem which may or may not be that big of a deal.

 

A progress update.

A small order of parts arrived on Friday which has allowed me to make a bit more progress on my Roto-OX. I have installed the wheels and cut the piece of 20X60 rail for the Z-Axis. I cannot finish the Z-Axis completely because I don't have the necessary ACME threaded rod yet (on order). I also have begun piecing together the motor assemblies for the Y-Axis modification I have planned. I can see that there will be some minor modifications necessary to the end plates to make the Y-Axis assembly work but I kind of expected that from the beginning.

A question for anyone following this build. Have any of you got any advice on how to connect an eight lead stepper motor to a four lead stepper driver? I understand both the four and six lead installations but the recycled NEMA 17 motor I am trying to use for my Z-Axis has eight wires. Essentially, two sets of leads are going to have to be connected in parallel but I have no idea how to tell which lead sets need to be paired.

Work on the project is likely going to stall for a couple of weeks due to my work schedule but I will keep plugging away at the design.

Doug M

 

Thanks dddman. I've read something similar someplace but don't remember exactly where so the link was useful to me. The issue I have is the motor has eight coils and four wire pairs so the connection of opposite coils is taken care of internally. I need to figure out an easy way to detect which wire is connected to which coil so I can wire every second coil together in parallel for connection to the driver output. I took the motor apart the other day to see if I could identify which wire went to which coil but due to how the wires connect to the coils, I cannot specifically see which color wire goes where.

At the end of it, I am not beyond spending the $15.00 or so for a new NEMA 17 motor. I figured I would re-purpose this salvaged motor if possible but I'm not going to waste too much effort trying to re-invent the stepper motor to save $15.00.

Thanks for your feedback.

Doug M

 

For those of us who are interested in designing our own wheel plates, I have taken a few measurements of the V-Slot rails and standard wheels. I do not know if it makes any difference but I have noted the colour of the rail I measured in brackets.

20X80 = 80.0mm (silver)
20X60 = 59.8mm (black)
20X40 = 40.0mm (silver)
20X20 = 19.9mm (silver)

The diameter of a standard black wheel (not the newer clear heavy duty one) is 23.9mm
The distance between the top of the wheel and the edge of a v-slot rail is 21.7mm (as close as I could measure).
By calculating the difference between the two above measurements, I get a wheel axle center point of 9.75mm from the surface of the V-Slot rail.

Keep in mind that my shop was about 0 degrees F when I took these measurements so temperature may have had an effect on the accuracy of my measuring.

 

All I did was take the measurements, only took a couple of minutes. I'm Canadian so 0 F is almost warm in January.

 

A progress update:

I have spent much of the last two months traveling for work so I haven't had much of a chance to work on the Roto-OX. The ACME threaded rods that I had on order came in and I have completed assembling the Z-Axis. I decided to spend the $10.00 or so and buy a new Z-Axis motor and have it mounted as well. Unfortunately, I haven't had a chance to run any testing on the system yet. I will let everyone know when I get a chance to wrench on the Roto-OX again.

 

Anybody have a suggestion where I can get a router mount that will fit a 89mm diameter router? The router mount is kind of the last thing I need to sort out before I can start testing my creation.