I guess I should start this thread by going through my thought process for selecting the type of CNC router I wanted to build. I have a very limited work area in my basement so that was going to be a limiting factor right out of the gate. This is going to be a woodworking tool and later a laser etching & engraver. I love lasers.
The other major factor was budget. CNC routing can get very expensive, very fast! My target budget for this project was 2000 USD.
I have an existing sturdy worktable where I plan to locate the router. Next, what am I going to do with it; basically, small woodworking projects and laser engraving. Therefor I chose to build a machine with 750 x 750 mm footprint which will give me about 22.44” x 20.66” of travel.
The next consideration is what materials will this router be constructed from. Most DIY CNC routers are built using either MDF, aluminum extrusion, or steel. MDF can be easy to work with and cheap to buy and many first time builders use this material. Slotted aluminum extrusion, commonly from a company called 80/20, is used on many DIY CNC router design plans available on the internet. It offers many design options due to the large amount on mounting brackets and configurations the slotted design allows. Aluminum extrusion would also be the most expensive of the three methods I listed. Steel is also used to construct many DIY routers. Square tubing, angle, and flat stock are common and can usually be locally sourced. In most cases steel machines are welded together so a welder and the ability to weld are necessary. Steel is generally going to be less expensive per foot than aluminum extrusion. Unfortunately I don’t have access to a welder and power hacksaw so I am forced to go with the aluminum extrusions even though the cost is higher.
The OX kits available from Bulkman 3D
all use aluminum extrusions and this is the mechanical system we will utilize for the construction of our CNC router.
The OX kit utilizes V-groove bearings. The chamfered slot along the aluminum extrusion is designed to fit standard V-Groove Bearings that are part of a carriage assembly built with a simple Dual Bearing Plate. Bearing pressure is easily adjustable using a wrench and Eccentric Bushing. This seems to me to be a good compromise as opposed to the much more expensive linear rail systems.
One of the keys in making my decision to go with the OX kit was the type of linear drive that it utilizes. The most common on DIY CNC routers are ribbed belts, ACME screws, and ball screws. It seems to me that the main consideration when choosing which system to use is not about how “good” each system is, but what materials you are intending to cut, and what tolerances you will require.
Belts are the cheapest of all solutions, and look increasingly cheaper on longer runs where you would otherwise have to deviate away from standard 8mm leadscrews. All in all, belts are the simplest and cheapest to implement. Belts have the additional advantage that when the motors are powered down, you can move the gantry around by hand. The OX kit utilizes belts for the X and Y axes and a lead screw for the Z-axis since this machine will primarily be a woodworking tool as well as a laser engraver.
All of the OX kits include an option for stepper motors. I chose to include the stepper motor option when I purchased my mechanical kit of parts. The motors are NEMA 23 rated at 345 oz-in torque (2.45 Nm).
I estimated my cost for the complete machine and electronics around $2000. Here is the breakdown:
Mechanical kit including NEMA 23, 345 oz-in (2.45 Nm) stepper motors: $535.00
Router spindle assembly including VFD, mounting bracket, and W.C.: $265.00
Motor drivers: $100.00
Controllers & Misc. Electronics: $400.00
Miscellaneous tooling: $200.00
Total Project: $2000.00
I suspect that I will end up going over budget given the cost of tooling and software, but that is down the road. I will try to post to this thread on a weekly basis as we go through the selection process for the stepper drivers, controller and spindle, as well as getting into the wiring of this machine tool.