Donek Drag knife best practices
Posted: Sun Dec 16, 2018 5:52 pm
So I recently got a hold of a Donek D2 drag knife. It's pretty sweet but I still have some things to figure out.
I'm using Fusion 360 to set up the tool paths. F360 does not have native drag knife support so I have to use multiple steps to get the correct corner actions added to the code.
I know there are some users here that use the Donek knives so i thought I would start a new thread on this.
I found this info posted by Donek in the cnc zone forums back in 2012 and there is some good information in here.
The best practice is as follows:
surface or fly cut your table to ensure it is totally flat and true to your machine (most important step)
zero your cutter to the table surface, not the top of your material.
make test cuts in your material, lower or raise your blade until the knife is just barely cutting through the material set this position as your z-zero
Vectric Gadget settings:
be sure you set the z zero to the bottom surface of your material and be sure to enter an accurate value for thickness
never rely on the manufacturers stated value, measure the material with a caliper or micrometer.
In the drag knife gadget:
set cut depth to the material thickness (the same you enter previously)
swivel depth should be between 0.001in and 0.010in depending on the flatness of your material and how consistent it's thickness is.
passes should generally be 1 unless you are cutting particularly hard materials
blade offset varies from machine to machine and is dependent on the model you use (see below)
tolerance angle should be left a 20deg
select a tool with a feed rate in the range of 3 to 5in/sec (180 to 300 in/min, or about 6000mm/min)
Additional advice on cut order and start points
select your paths in the order you want them cut.
it is always wise to cut internal components before external components
adjust the start points of your vectors to be in the middle of a line or large curve
the vectric gadget likes to start cuts at corners, but fails to reorient the blade at the end of the part resulting in an incomplete corner
adjust the start points on all vectors such that they begin and end in the same orientation
this reduces the need to reorient the blade at the beginning of a cut and makes your tool paths begin and end on top of each other.
keep in mind that the vectric gadget will cut all closed paths in a counter clockwise direction
Advise on determining blade offset for your tool and machine.
The best starting point for a D1 or D3 tool is 0.065in
The best starting point for a D2 or D4 tool is 0.160in
depending on backlash and other factors in your machine, these values may not be accurate enough
The best way to fine tune this value is to cut test pieces. I recommend a 1.5in square.
observe the tool in action
if the tool turns too much at a corner, then the offset value is too large
if the tool does not turn far enough at a corner, then the offset value is too small
typically adjustments of 0.005in are recommended.
repeat your test cut.
If you have any pearls to add please share!!!
I'm using Fusion 360 to set up the tool paths. F360 does not have native drag knife support so I have to use multiple steps to get the correct corner actions added to the code.
I know there are some users here that use the Donek knives so i thought I would start a new thread on this.
I found this info posted by Donek in the cnc zone forums back in 2012 and there is some good information in here.
The best practice is as follows:
surface or fly cut your table to ensure it is totally flat and true to your machine (most important step)
zero your cutter to the table surface, not the top of your material.
make test cuts in your material, lower or raise your blade until the knife is just barely cutting through the material set this position as your z-zero
Vectric Gadget settings:
be sure you set the z zero to the bottom surface of your material and be sure to enter an accurate value for thickness
never rely on the manufacturers stated value, measure the material with a caliper or micrometer.
In the drag knife gadget:
set cut depth to the material thickness (the same you enter previously)
swivel depth should be between 0.001in and 0.010in depending on the flatness of your material and how consistent it's thickness is.
passes should generally be 1 unless you are cutting particularly hard materials
blade offset varies from machine to machine and is dependent on the model you use (see below)
tolerance angle should be left a 20deg
select a tool with a feed rate in the range of 3 to 5in/sec (180 to 300 in/min, or about 6000mm/min)
Additional advice on cut order and start points
select your paths in the order you want them cut.
it is always wise to cut internal components before external components
adjust the start points of your vectors to be in the middle of a line or large curve
the vectric gadget likes to start cuts at corners, but fails to reorient the blade at the end of the part resulting in an incomplete corner
adjust the start points on all vectors such that they begin and end in the same orientation
this reduces the need to reorient the blade at the beginning of a cut and makes your tool paths begin and end on top of each other.
keep in mind that the vectric gadget will cut all closed paths in a counter clockwise direction
Advise on determining blade offset for your tool and machine.
The best starting point for a D1 or D3 tool is 0.065in
The best starting point for a D2 or D4 tool is 0.160in
depending on backlash and other factors in your machine, these values may not be accurate enough
The best way to fine tune this value is to cut test pieces. I recommend a 1.5in square.
observe the tool in action
if the tool turns too much at a corner, then the offset value is too large
if the tool does not turn far enough at a corner, then the offset value is too small
typically adjustments of 0.005in are recommended.
repeat your test cut.
If you have any pearls to add please share!!!