Working With Woods
How come my circles are not perfectly round?
Then you are machining circles on a CNC and your circles are not coming out perfectly round, it is commonly caused because there is some backlash developing on the machine. Backlash is a tiny amount of play that appears over time and is noticed when a drive changes direction.
When running in a positive direction, the gears/lead screw are engaged with the lead screw nut on the gantry, but when the stepper motor reverses direction there is a tiny space between the lead screw and the lead screw nut that has to be made up before there is positive engagement in that direction. After many, many hours of use or if your machine is not properly maintained and lubricated, then this backlash can develop.
If this is happening to you, please download this document: Stepcraft UCCNC Backlash Compensation.
This will show you how to setup backlash compensation in UCCNC so that you can “dial” out any backlash and go back to having perfect circles again.
STEPCRAFT CNC machines have two parameters in the specifications for their machines: Clamping Surface and Travel Distance
Clamping Surface is maximum size of work material that you can place onto the machines bed. Travel Distance is the maximum amount that the gantry and cutting bit will move.
As an example, the STEPCRAFT-2/300 has a clamping surface of 14.96″ x 8.74″ (380x222mm) but the travel distance is equal to 11.81″ x 8.27″ (300x210mm). This means that you can place a slightly larger workpiece onto the bed than you can actually cut.
The number that is most important when choosing which size STEPCRAFT machine to buy is the Travel Distance.
The following chart reflects these sizes as well as the overall dimension of the machines. Clamping Distance is the middle set of dimensions and Travel Distance is the Lower Set of Dimensions.
What is the maximum height of the work material that I can place on the work bed?
The total travel distance for the Z axis is 5.5″. However, you need to keep in mind that some of that height will be used up by the systemheld tool that you place on the machine. For example, the HF500 spindle and collet stick below the tool holder by about 1.2″ This would reduce the total material height to 4.3″ From that you need to account for the length of the tool as well.
Is the chuck reversible on the 4th Axis unit?
Yes you can remove the three tabs from the chuck and put them in the opposite way to allow for a larger opening for larger stock, up to 2 inches in diameter.
To remove them, simply turn the inner ring behind the chuck counterclockwise and the threads will push the chuck tabs out. Then you can flip them around and while putting pressure on them turn the inner ring clockwise and they will be threaded back in.
Many CNC machines will offer a dust boot or adapter that surrounds the spindle with a brush or rubber gasket material that rubs along the workpiece. A vacuum is connected to this adapter and dust is extracted right at the end mill. STEPCRAFT, for example, offers an exhaust adapter with a removable brush.
To get the most out of your dust collection system you need to make sure that the brush is contacting the work surface. If not then only a percentage of the dust will be drawn into the dust collection system. Depending on the system you might need to use shorter bits to achieve this.
To extract the dust you can use a simple shop vac or an integrated dust collection system.
No, you do not need to use different spindles. The main factor will be how fast the feed rate will be that you run and how much material you remove per pass.
If you with to run a light duty spindle like a Dremel 4000, you can run wood, plastics and metals just as well as if you were using a Kress 800W spindle. The only difference is that you will not be able to remove as much material and your feed rate will be slower the harder the material is.
Keep in mind that dedicated CNC spindles will have better quality bearings which will offer less runout and therefore a longer life span and higher accuracy. Using the Dremel example, this device is not meant for hours and hours of prolonged use, nor is it made to have lots of pressure side loading the main shaft. You will find that if you are not careful on the feed rate and pass depth that you will quickly wear out the bearings.
A router like the Dewalt DW611 will also cut all types of material, but as with the Dremel, the bearings are not as good as with a dedicated spindle so you can expect more runout with a router. The STEPCRAFT HF500 is a purpose built spindle that was designed to work with all types of materials and has an excellent bearing system that provides very little runout and a much higher accuracy.
The bottom line is that you can pretty much cut whatever you like with just about any spindle. You just need to be cautious on feed rates and pass depth.
Can I use MDF as a spoil board when cutting aluminum?
Often times when cutting aluminum you will need a spoil board under the aluminum, especially when you are cutting all the way through the material. MDF is a very common material to use as a spoil board for the following reasons:
- There is no grain so it cuts the same in any direction
- It is usually pretty flat
- It cuts easily so when your bit goes through your work piece, there is no additional strain on it when it makes contact with the MDF
- It is easy to find and relatively inexpensive.
Some things to be careful of when machining aluminum with an MDF spoil board:
- Make sure the MDF is secured well to the machine bed
- Make sure the Aluminum is clamped tight to the MDF/machine bed – if it is not you will get vibration, chatter, poor cut finish, and can possibly break your cutting bit.
- You can not use any lubricant when you use an MDF spoil board! It will swell and expand if it gets wet. So using spray or mist coolant or oils like Tap Magic is not recommended.
An alternative spoil board that we use is acrylic. Acrylic is hard, flat, easier to machine than aluminum so it will not strain your machine and if you want/need to use lubricant, then you can without worrying about it damaging the spoil board.
Can I engrave a photograph into a piece of wood?
Yes, you can use Vectric’s PhotoVCarve program, which allows you to create an engraving tool path for photos.
Additionally, you can use the new Laser Engraving Head DL445 which can laser engrave your photos into a variety of materials.