A few years back I acquired a Dahlgren system 400 engraver system with a non-functional electronics box. It turns out that the power supply and the stepper drivers are functional, and at this point I have been able to drive them from Mach3 via an $11 parallel port breakout board. So far so good, at least for X&Y.
I have taken the thing mostly apart and have cleaned everything really well, and am now reassembling. The biggest issue remaining is what to do about the Z axis.
This machine was a 2.5 axis machine. The Z axis was simply up or down and used an air solenoid to do this. I need a full Z axis. I am planning to mount a Porter Cable trim router (at least initially). I hope to do things like engraving of panels and signs, pc board fabrication, and light machining of plastics and aluminum.
But here is a problem. There is less than 1 1/2" clearance between the table and the Z mounting bracket. This imposes a design limit on my Z axis mechanism.
Table installed.
How rigid will this 1 1/2" linear bearing be? It is a very high quality Thompson rail and bearing, but it is not very wide, hence inherently limited on resisting twisting force.
The mounting columns are 6" x 1" solid aluminum. I am considering machining riser blocks to raise the entire gantry up an inch or 2 or 3. If I'm designing a new Z axis, I want to have at least a few inches of travel.
The gantry columns are attached from the bottom with 4 1/4-20 allen head cap screws. I'll just need to buy longer ones. I have a very nice Rockwell mill with DRO and I will be able to machine accurate riser blocks with no problem. It is just a question of how tall to make the risers.
Also, how much Z travel is reasonable to design into a machine like this? If I make 2" risers, that will give me 3 1/2" clearance between the table and the Z bracket. and that will be the max Z travel. Should I take it up another inch?
About the Z axis- I have a number of parts but my current plan is to use 8mm ground rods (from ink jet printers), cheapo recirculating ball linear bearings I got on ebay, stainless lead screw and delrin zero backlash nut from Nicosia, Cypress, bought on ebay. For a Z stepper, I have a few that I got from laser printers, and I also have some old Slo-Syn steppers. I'm trying to keep the mass of the Z axis mechanism to a minimum.
I also have a 16mm ball screw and ball nut that I could use, but that will involve more work- notably I'd need to machine the ends. The cheaper non-ball screw and delrin nut will require no machining. It will ride in 8mm bearings and I have an 8mm flex coupler to connect it to a stepper.
It seems to me that you can't make use of very much Z travel anyway unless you have a bit protruding quite a ways from the router. The Z axis mechanism and the router body would get in the way- so maybe having more than a couple inches of Z travel is pointless. Thoughts?
4 comments:
CNC machines usually applies to machining tools right, but how does it really work? I kind of don't get the whole point about this machine.
- CalWire.com
Great Post! thanks for sharing your experience here. Cnc machines provide high end security and improve the way of working.
Cnc precision machining
This will be a light duty cnc router, capable of working in wood, plastic or aluminum. I'll be able to do things like create nameplates, printed circuit boards, artwork, and all sorts of things. Largely, it will be for me to gain experience with CNC machines. I have a Bridgeport size CNC machine that I'll be building up soon.
CNC machine is helpful in to make the mechanical work easy and also perform the work in quick time so it is also helpful in to do the work is quick time.
Himes Machinery
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