CNC Router Templates

Nema 23 Step Motor Template

Since there are at least three step motors on the CNC router, a template will save time and provide a higher degree of drilling accuracy. Here is how I made mine.

1. 1/16" aluminum sheet cut to 3" by 3". 3/32" or 1/8" will work
2. Draw a line between two adjacent corners
3. Using the other corners draw a short line crossing the first. Using center punch, dimple this center point.
4. Set an adjustable divider to 1 5/16" using machinist ruler.
5. Scribe a 2 5/8" diameter circle using center point.
6. Using long crossed line, dimple places where the line crosses circle.
7. Use these points and a little geometry to determine a line 90 degrees to first.
8. Dimple points where this line crosses circle.
9. Drill the four points on the circle with 3/16" bit. Use center drill to start hole.
10. Drill center with1/4" bit.
11. Check on step motor for accuracy. Motor shaft is 1/4".
12. Enlarge center hole to 5/8" with step drill.

Tools:

• Carbide scribe: HF #97336, 
• Divider: Alvin Basic
• Awl or hand center punch, small hammer
• Hand Punch (optional): Amazon, Roper Whitney, Grizzly H7862
• Drill Press with center drill, 3/16" drill bit and Step Drill

Notes:

1) If you are involved in sheet metal work, particularly electronics, you will find this small hand punch is very useful, especially with the optional bench base.  I purchased a RW No.XX with a base several years ago. There now seems to be many Chinese knock-offs, and except for the Grizzly, none have bases. Many individual punch and dies can be purchased for the RW; however, they don't fit the knock-offs..

2) A compass can be used for the divider, but steel points must be used on both legs.

3) To make it easier to see the scribe lines, the metal can first be coated with layout fluid, such as, Dykem Blue DX-110. This product comes in a bottle with a brush and can be found at machine supplies like McMaster Carr.

4) Another useful tool is a tap guide which can be used to find the hole center on a drill press and hold a tap vertical during thread tapping.

Building a CNC Router: Part 2

Discussion of Linear Bearings

There are several CNC router designs on the web constructed of MDF. Many of them use two 3/4” precision rods per axis with two bearing points per rod. Since the precision of construction with MDF is no better than .03” and probably worse, getting the bearings adjusted for friction free motion has to be a problem. Solving this problem should simplify the construction of the CNC router with MDF.

Starting with the Y axis, let's call the upper rod the primary rod and assume it is fixed in place. The lower rod, which is the guide rod, is located 2.5” below the primary. These two rods, ideally, should be within a vertical plane defined by the Y and Z axises and be parallel. Now, if we place two linear bearings 3 inches apart on the primary rod and attach them to a 4” by 4” by 3/4” piece of MDF, the bearings should move freely. Two points define a line. To define the plane of motion, we need one more point, so lets place a single bearing on the guide rod and attach it to the MDF. As long as the guide rod is exactly parallel to the primary rod, the MDF plate should move freely along the two rods. Of cause, because of the .03” accuracy the rods are not likely to be parallel or in the same plane. The variation in the Z direction, that is the separation between the rod is what will cause binding. The variation in the X direction will just cause the plate to swing back and forth as it moves left and right. To remove the binding, either the guide rod or the bearing on that rod must be allowed to float. It seems the easiest solution is to allow the bearing to move vertically 0.1 inches. This design should allow free motion of the Y axis plate, but does not correct any variation in the X direction. This problem could be corrected with an X axis adjustment blocks at the ends of the guide rod. The design shown here could be used for the X and Z axises also.

Bearing Features:

• Guide-ways: Two precision steel rods per axis, one defining the axis.
• Linear plastic or metal pillow block bearings
• X axis, Gantry, will use 4 linear bearings
• Y and Z axis will use 3 bearings each..

CNCRouterBuild Index

Design and Construction of CNC Router

Part 1: Introduction
Part 2: Analysis of Linear Bearings for the CNC Router

•     A discussion of existing designs and a new solution.

Part 3: Design and Building the Base
Part 4: Design and Building Gantry Base (not yet)
Part 5: Design and Building Gantry (not yet)



Other Related Projects

Electronics:

• CUMC: CNC USB Motion Controller, our version of "planet_cnc.com" device
• Step Motor Driver: SLA7062M , both opto-isolated and non--isolated versions
• Step Motor Driver: SLA7078MPR,                  "
• Step Motor Driver: TB6560, (not yet),         "
• Step Motor Driver: L297.298, (not yet),       "
• 
  

Building a CNC Router Table

Drill Press Accessories and Secrets

• You and your drill press: Is it usable or junk? or What should I buy?
• What is runout?
• Fixing up an old 10" Craftman drill press: Measure runout, change chuck, etc.
• Making a drill press table.

Jigs and Other Useful Tools

• Table Saw Sled

CNC Router Templates

• NEMA 23 step motor template

Building a CNC Router: Part 1

A Woodworking Project

My background is Physics and Engineering. For years I have wanted to build a CNC mill, originally to drill printed circuit boards, but now my interests have shifted to woodworking. I have spent hours examining the many designs for CNC Routers on the Web and finally started my own design which I believe will be relatively simple to construct and align.

In this blog I will post my design as it progresses. The design will include both the construction of the router machine and the electronics. At the beginning of the construction section, a complete bill of materials, BOM, will be provided and will include sources for the parts.

Design Features:

• MDF construction
• Gantry Design
• Steel bearing shafts with linear bearings
• Lead screw: ½-10 single or double start Acme threaded rod
• Nut: Antibacklash
• Dremel or trimmer router

Construction:

The purpose of this project is to design a CNC router for woodworking that can be constructed with woodworking tools and easily obtainable mechanical parts. The design will take account of the accuracy of woodworking and make assembly and adjustment simple. Further, the design will use wood furniture assembly hardware.

Several of the MDF pieces are duplicates and the shape and alignment of holes critical. Methods to do this will be shown and will require special jigs. The base front and back, as well as, the gantry sides and the Z-axis top and bottom plates are mirror images. To assure that the holes in these mirror parts are perfectly align, they will be drilled simultaneously after being pinned with 1/8" dowels. This method assures that, though distances between holes have an accuracy of 1/32", the mirror alignment is exact.

For construction you will need the following tools.

Essential Tools:

• Drill press with a table and fence
• Router
• Forstner and router bits
• Home made jigs

Additional Tools

• Table saw with plywood blade, 80 teeth
• Cut off sled for use with table saw
• Cut off (miter) saw
• Router Table

Substitutes for additional tools, but will make construction slower

• Hand power saw with plywood blade and jigs

Since the construct material is MDF and this project is basically a woodworking project, precision of construction is no better than 1/32 (.03”) of an inch. A further complication is the hydroscopic nature of MDF which is not as bad absorbing water as particle board but is no better than pine. This can be alleviated by sealing the finished MDF. As a result of this accuracy of construction, aligning the bearings and maintaining that alignment is a problem unless flexibility is built into the design.

Construction projects for a drill press table with fence, cut-off sled and router table are also included in this blog. If you have the funds, the drill press and router tables can be purchased, but construction is not difficult and saves money. In addition, these projects are good training for building the CNC router.

Note: As to the electronics, prototype pcb's for both the Toshiba TB6560 and the L298/L297 and a PIC based tester are completed and being tested.