Frequently Asked Questions

Click questions for long answers.

How much do the tables cost to build?
$370 to $1300+

How long will it take to build?
A day to a week.

What tools are required?
Home shop tools.

What are the tables made of?
Hardware store parts and standard components from online suppliers.

What are the metric sizes of the materials?
List given, substitutions possible.

Can the machines cut metal?
Steel, no. Aluminum, yes; best with precision Acme leadscrews.

How accurate are they. What is the resolution?
With low cost leadscrews: Accuracy 0.003" Resolution 0.0007" and better.
 

How much do the tables cost to build?


For the tables only, no electronics.
13x13 Fixed Gantry ~$120.
10x9 Fixed Gantry ~$150
18x24 V Bearing ~$600
25x25 Dual Leadscrew ~$300
24x48 Rack/Leadscrew ~$600 and up

These prices are with hardware store threaded rod leadscrews. Acme leadscrews with anti-backlash leadnuts will add ~$40 and up for each leadscrew.

The 18x24 is designed to use Acme leadscrews with racks and pinions. This is reflected in its higher price.

The prices do not include the router-spindle, the stepper and drive packages, or the software.

The steppers, drives and power supply packages range from $250 to over $600 depending on the features and power.

The range in price for a Dremel type roto-tool to a router is $20 to $150+

Software can be free shareware and up.

The computer can be an ancient 486 and up.

 

How long will it take to build?


The 10x9 and 13x13 fixed gantry tables can be built in a day.
The 18x24 and 25x25 require at least a weekend.

The 24x48 will require around a week full time.
These estimates of course depend on the skillsand tools brought to the project.

 

What tools are required?


The 13x13 table was designed to be simple and not require many tools.

Hacksaw
Wood saw
Drill
Drill bits: 1/16 to 1/2 inch
Screwdrivers: Phillips and Slot
Wrenches: 1/4 to 7/16 inch or Adjustable Wrench
Scissors or Shears
File
Measuring Tape or Rule
Center Punch, Scribe, or Pencil
Combination Square

Helpful but not required:
Nut Drivers
Power Screwdriver
Power Chop or Miter Saw

The 10x9 and 25x25 were also designed to use a minimum of tools. Their requirements are the same as the 13x13 plus paddle or Forstner bits.
Here is a PDF of the other tools for the 25x25.
 
The 18x24 tool details are on the 18x24 Tools Page. This machine is made of aluminum and wood. A power miter saw with carbide teeth for cutting the aluminum is very helpful.
 
The wooden version of the 24x48 requires the same tools as the 25x25 and 18x24. A table saw is helpful for cutting the sheet stock.
For the aluminum version a carbide toothed power miter saw and drill press are very helpful.
A basic set of taps is also required. (#6 to 5/16")

 

What are the tables made of?


The machines were all designed around stock sizes of USA materials that are available from homecenters and online. This includes framing lumber, steel pipe, threaded rod, nuts and bolts.

Here are the plans' materials lists.

13x13 Materials.pdf

10x9 Materials.pdf

18x24 Materials.pdf

25x25 Materials.pdf

24x48 Materials.pdf

The named dimensions of wood and pipe are not the actual dimensions. For example a 2x4 is actually 1½ inches by 3½ inches.

What are the metric sizes of the materials?


These metric dimensions are from actual stock. They are not the nominal (named) dimension.

   Named  Actual
Wood2 x 4 lumber38 x 89 mm
Wood1 x 4 lumber19 x 89 mm
Wood1 x 6 lumber19 x 140 mm
Wood2 x 6 lumber38 x 140 mm
Wood¾" Plywood19 mm
Pipe½" Steel Pipe21.6 mm OD
Pipe¾" Steel Pipe26.2 mm OD
Al. Angle ¾" x 1/8" 19 mm x 3.3 mm
Al. Angle 1" x 1/8" 25.4 mm x 3.3 mm


 

Can the machines cut metal?


Only soft metals, and it must be done slowly.
Machines built of wood and thin aluminum lack the mass and rigidity to cut metal aggressively.

The 10x9, 18x24, 25x25, and 24x48 machines have been used to mill and drill aluminum, but the depth of each pass has to be kept shallow. Small (¼ inch diameter or smaller) bits or end-mills are necessary to keep the cutting forces low.

There are aluminum work examples on the 10x9 details page.
There is information about milling aluminum on the Bits page.

A retrofitted bench or knee mill would be a better choice when the primary jobs will be heavier metal work. Expect to spend thousands of dollars,not hundreds.

 

How accurate are they? What is the resolution?


Accuracy (tolerance) and resolution are often confused.
Accuracy relates to the play in the actual machine.
Resolution relates to the software and the smallest distance the table can be commanded to move. High resolution without good accuracy is useless. (Measure with a micrometer, cut with an ax.)

With hardware store threaded rod for leadscrews, backlash will be between 3/1000" and 10/1000".
This range is the thickness of one to three sheets of paper.
The photos on the Work Examples page show what this accuracy can and can't accomplish.

Acme rods with anti-backlash leadnuts will improve performance significantly. The Delrin leadnuts are flexible, but can give accuracy better than 0.003 inch.

Resolution is in the software, computer, motors and gearing.

On machines with hardware store threaded rod for leadscrews and 200 steps per revolution steppers, the worst resolution on an old DOS computer is: 200 steps/rotation with ½ step micro-stepping and 18 threads/inch = 1/(200 x 2 x 18 ) or 0.0001389 inch per step.

This number can be made better (even smaller) with a faster computer and 1/8 or smaller micro-stepping.
This may give smoother stepper operation but otherwise there is little benefit since the accuracy of the leadscrews is the limiting factor. Also smaller micro stepping can adversely affect stepper performance.

 

Do the plans cover any of the electronics or software?


The plans go as far as stepper installation, but do not cover the set up of the drives and software.

The prototype tables use products from HobbyCNC, Xylotex and Geckodrive because these companies work with the Do It Yourself market and offer support and documentation. There are other suppliers who offer similar products and support, and their drives and steppers can also be used.

The plans do include directions for determining the Steps per Unit value required by the software.

There is more information on the Drive & Stepper and Power Supply pages.

There are a number of software choices though most prefer Mach3. This product also offers excellent documentation, support, and tutorials.

 

What software do I need?


The software required for 2 or 2.5 D work shown on the examples page can be downloaded for free or low cost.

In a nutshell, three distinct types of programs are needed. Some software combines the functions and others just do one aspect. The three functions are:
  • CAD . . . To draw object.
  • CAM . . . G-code generator.
  • Machine Controller . . . Reads g-code, commands drives to move steppers.
To create the drawing on the computer a CAD program is needed.
A9CAD is a 2D program that is free. Older versions of Corel Draw will also work. This program is used rather than Paint Shop Pro, for example, because it can export DXF files.

Once the file has been drawn in DXF, it needs to be converted into g-code, which is what the CNC machine's controlling program (e.g. Mach3) understands.

A free g-code generator is ACE Converter. It only does 2.5D which means the Z axis is either up or down, like a plotter pen.

Since ACE only converts DXF files it is important for the CAD program to be able to export in DXF.

Once the CAD drawing has been converted to g-code, the g-code is given to the computer that controls the actual CNC machine.

TurboCNC and Mach3 are popular controller programs. These tell the drives how to move the steppers.

3D work requires more expensive programs for the CAD and CAM components, and for the most part begin in the over $500 realm.

Mach and TurboCNC can control multiple axis machines, so they do not have to be upgraded to do 3D work.

 

What is the difference between Mach and TurboCNC?


TurboCNC is a shareware application with an unlimited free trial. It has a registration fee and the source code is available to registered users, so customizing is possible.
It is DOS based and can be used on a very old 486 computer. The down side is the user interface is not as easy as point and click.

Another disadvantage with TurboCNC is it does not have a constant contour/velocity function.
CAM software often codes curves so they are a series of short line segments. Without constant velocity the machine ramps up and decelerates for each short line. This causes jerky motion that can telegraph through to the work, which can cause the edges to be scalloped.

Mach is Windows based software and requires Windows XP or newer.
It uses a mouse interface, has a dynamic display of the work as it is being cut, and has constant contour. It is a much more feature rich product in ways too numerous to list here. It offers a free trial version as well, but the trial version is limited.

Note that our shop is still using Mach2 because it works with the older computer's integrated graphics. Mach3 does not work well with this slower graphics card.

 

What kind of computer is required?


TurboCNC controller software can use an ancient 486, and Mach requires Windows XP or newer.

An old entry level Compaq 3000+ AMD Sempron with 256 MB SDRAM is still used in this shop with Mach2 and it works fine. This is mentioned because there was once concern about computers having the processing capacity for CNC work. Now a basic computer is fast enough.

The computer used for the CAD and CAM work can be a different unit from the one used to control the machine. Often a better computer is kept in the office for design work, and a hand-me-down computer is used in the shop to run the machine.

The g-code files can be transferred by USB thumb drives when the shop computer is not networked.

 

Do you sell a parts kit or an assembled table?


No. I have prototyped parts packages, but the time drives the price beyond an acceptable level.

Do you give refunds?


Of course! You must be satisfied. I'll proudly put these plans and the machines against any comparably priced product out there.