Duplicator Conversion

[Fiddlemaker5224]

Hey folks,

I have been think of converting this duplicator to Cnc.

Duplicator conversion to cnc?

I think I posted in the wrong place the first time.

Any suggestions would be welcome.

[CarveOne]

How would you want to go about doing this conversion? Salvage usable parts like the linear bearings and rails and build a new design or use the current machine and add the necessary parts to make it move via stepper or servo motors?

As I look at your photos I'm leaning toward the first option since it may be difficult to operate the pivoting router arm by just adding motors and lead screws. I'm not suggesting that the latter option is just not even possible. It may require some creative mechanical thinking though.

CarveOne

[Fiddlemaker5224]

I was thinking and researching the redesign of the gantry. This lead to your post. Since I have all the Linear bearings, it makes sense to use them in the redesign. The bearings currently supporting the pivot will be used on the new Z axis. The Y axis was the problem with the duplicator and allowed a 0.016 deflection. This set up moved with the slightest hand pressure. on the x and y.

I used to work at a company that built recycling equipment, (bailers) and the wire to tie the bails was pushed through the unit on a carriage assembly that held 6 inserter needles. The carriage plate ran on a 1/2" V track. The V rollers (6) had eccentric adjustments to lock the carriage to the V track. In this case I think 4 rollers mounted to a 1/4" alumnum plate will provide a good base to mount the Z axis.

The assembly on the bailer weighed about 2,000lbs and would move easly by hand when the ball screw was disconnected.

As for the steppers I was thinking 240 inoz. I don't need the speed as much as accuracy.

I need to rummage through the spare parts box to see if I have the eccentric hubs for the Vee wheels.

[CarveOne]

Do you have, or have access to, machinery to make the conversion parts yourself or will you need to have it done for you? Having special parts made can have a significant impact your conversion expenses. You will need lead screws and nuts (or other means to drive the gantry and z axis), generally available hardware, and the construction materials you choose to build the new machine with. It's an interesting project, will sometimes be frustrating, and will always be a good experience once it is working to your satisfaction.

If the rails you have are deflecting too much you may need to reconsider using these unsupported rails or find a way to use them in a supported manner. Even with the laminated red oak construction mine will flex if I put any pressure on the end plate that the x axis stepper is mounted to. Just resting my hands on it to steady a digital camera has caused enough deflection to see it in the work piece.

The skate bearing scheme that my Solsylva router uses is cheap and can be used with your rails on the x and y axes. The bearings or v rollers can be mounted in something like a block of aluminum that has three points of contact. Ahren sells these bearing carriages (trucks) for running on the edges of steel flat plates. (Ahren could consider making these to fit a few common sizes of fully supported round rails as well.) The housing can be just a [ shape like channel aluminum or steel.

CarveOne

[Fiddlemaker5224]

I do have access to a lathe and milling equipment. Even though I am not a machinest my dad is a tool and die maker (retired from Ford). He has my lathe in his shop. So most of the parts I will be needing will be done in house. Removing the pivot arm assembly will reduce the weight by 18 lbs. And the router can be smaller also.

I have looked really close at your setup for the Y and the Z. I may go that route on the Y. The X axis in the current set up has 0.000 (I checked that this morning) deflection in the center of travel. If I make the table longer I will have to redo that also. I only need a 20" x 30" cutting area for what I am planning. Maybe the next machine will have a larger cutting area.

[CarveOne]

Making your own parts with your lathe and mill will be a good learning experience in itself.

I am a self taught home shop hobby machinist myself and have spent many long evenings browsing the machinist forums on Yahoo Groups and many other places learning about the subject. My dad was an automobile mechanic before you could buy rebuilt generators, starters, and voltage regulators and browse anything but books. He was the only one in the shop that could rebuild anything mechanical or electrical on a car (well, they were a wee bit simpler back in the 50's too). He would be envious of my machinery if he were still alive. My brother is my complete opposite and thinks pliers and screwdrivers are too technical for him.

I would suggest using the parts you have now to reconstruct your violin carving machine with cnc (if you want to continue making violins) and plan ahead for a larger more general use type of machine. You can acquire the new parts while having the use of the violin machine to make parts for the larger machine. What you learn with this conversion will help you know what you want the second machine to do, look like, and how large it needs to be.

CarveOne

[Fiddlemaker5224]

Originally Posted by CarveOne I would suggest using the parts you have now to reconstruct your violin carving machine with cnc (if you want to continue making violins) and plan ahead for a larger more general use type of machine. You can acquire the new parts while having the use of the violin machine to make parts for the larger machine. What you learn with this conversion will help you know what you want the second machine to do, look like, and how large it needs to be. CarveOne

This is the same thing I was thinking.

Was going through the spare parts today. Found 6' of 3/8" 4 start acme with 2 plastic nuts in brand new condition. 5' of 3/4" acme single start (used). I may not use 3/4" acme at all. I would like to keep all 3 axis with the same thread.

Question?

If I use a 1/2" 4 start acme on the x axis and the 3/8" 4 start on the Y and Z, will the speed be the same for the X and Y?

I do plan on using anti-backlash nuts on all three.

[CarveOne]

I think the answer to your question is no. 1/2" acme rods have fewer threads per inch than 3/8" rods. However, EMC2, Mach 3, and other controller software have parameters that can be set to compensate for the different thread pitches and multi starts so that all axes act the same.


CarveOne

[Fiddlemaker5224]

Thanks CarveOne,

I see I need to do some more reserch.

[CarveOne]

We all tend to do a lot of research while building these things... A year from now you'll probably know more than I do. I think my pea brain is reaching saturation level.

Assuming that you don't know where to start (which may be a wrong assumption), the first software you need is the machine controller program that runs the stepper motors. That would be EMC2 (runs on a Ubuntu Linux PC and both are free downloads) or Mach3 (runs on WinXP or Vista PC and is $159) or TurboCNC (runs on a Windows PC and is free or pay a $60 registration fee if you like it) I'm using EMC2 since I have two Ubuntu PCs anyway and a WinXP main computer.

With one of the above you can find gcode files in these forums to use for your first test cuts. Nothing else is required. Gcode files created in Windows programs will run on EMC2 by renaming the file extension. You can edit the gcode (text files) to modify, comment out, or remove gcodes that don't apply to the default EMC2 gcode list or don't apply to your machine setup. (Things like flood coolant, spindle speed, 4th, 5th, and 6th axis movements, etc.)

If you want to create your own 2D or 2.5D gcode files you'll need a CAD drawing program and a dxf to gcode converter. (Mach3 has a gcode export feature built in)

If you want to create a solid model of a violin top you will need a solid model CAD program. Those can be rather expensive. You may be able to find a solid model file on the internet that you may like and just use it as it is.

CarveOne

[CarveOne]

Btw, you can mix the acme rod pitches as you need to but I suppose most people don't since there is usually enough pieces left over to make the z axis lead screw. The settings you need to use for each lead screw pitch are not difficult to figure out. You just enter the threads per inch and 1:1 gear ratio if you connect the lead screw directly to the stepper motor shaft with a coupler or use a belt drive with same size pulleys. Software settings make the hardware move the correct distance.

CarveOne

[Fiddlemaker5224]

Thanks

I currently have AutoCad 2008 and Punch ViaCad v.6, I will be going with Mach 3, That is the program that was reccommended I learn by my friend. I have been repairing violins for Her family for 5 years, She and her husband offered me a position if I got the cert in the AutoCad.
I think he also wants to learn violin building. To me its easy, but not to everyone. I havent decided on the G-code converter.

I was reading more about chooseing the motors and screws last night. Lots of info.

I started the lay out of the machine yesterday just to get the basic cutting area dimentions. The 1" open rails and linear bearings I will stay with for the X axis. I'm searching for the best price for bearings, the first Qoute was 340.00 that included the track. I am leaning more to the Vee Track roller system due to the reliabilty has been proven to me with the balers.
I also located some 1/4" Aluminum plate I will use to make the gantry uprights lamanited to 3/4 oak.

Well at least I am making some progress.