Waterjet and
Abrasivejet pictures (Page 8):
This page of
pictures is
dedicated to the idea of tilting
the
nozzle.
There are multiple uses for tilting the nozzle
such as:
- Increasing precision by removing taper
- Creating beveled edges for artistic purposes of for die relief
- Creating sharp edges to use for knives / cutters
- Probably lots of other reasons.
There are two
main ways in which tilting is achieved: manual tilting, and tilting under program
control.
Manual
Tilting:
One of the
easiest ways to create angled cuts is by simply mounting the
nozzle at the desired angle. The advantage of this is that it is
cheap and easy to do. No special programming is required. A
disadvantage is that significant more splash will occur, and there is
no control over varying the tilt for different features of the
part without having to stop the tool path and re-adjusting the tool.
Note: If you
modify your machine to do this kind of work,
be sure to consider the splash. I recommend that you aim the
nozzle such that the splash shoots towards the back of the machine, and
away from the user. Also, cut yourself a nozzle guard from
perhaps a piece of pipe, that is at an angle, so that the bottom of the
pipe is flush with the surface to cut. And, as always, wear eye
protection! Also, remember that the jet is a lot more powerful
than it looks. When you tilt it sideways, it shoots sideways, and
ricochets sideways. Take extra precautions with this in
mind. Don't cut yourself to pieces, and don't cut your machine to
pieces either.
Below are some
pictures of some blades cut with a
fixed tilt waterjet:
Above:
Blades with tapered cuts in stainless steel, and the one
with the blue background is in M2 high speed steel. A typical
part like this would take perhaps 2-5 minutes to cut depending on the
complexity of the shape. With precision waterjet machines, little
or no additional grinding is needed.
Above: Close-up
of the edge of the blade.
Above: Special
mounting for the nozzle to allow it to tilt. A nut
is loosened, and the nozzle is manually tilted to the desired angle,
then the nut is re-tightened. Depending on how the plumbing for
the high pressure tubing is handled, it may need some adjusting as
well. The big red plug in the side of this assembly is simply a
plastic plug to prevent dirt from falling into the nozzle assembly,
since the plumbing is not hooked up in this picture. If you look
carefully, you can count at least 6 parts of this assembly that were
made on an abrasivejet.
Tilting
under program control:
A more complex
method for tilting is with a multi-axis machine.
Below are some various pictures of one such machine that I have been
involved to some degree with writing software for. In this
particular case, the main purpose of the multi-axis cutting head is for
taper removal to make perfectly straight edges in the part for
high-precision work. Multi-axis heads like this can also be used
to purposely introduce small angles into the part as well (but things
get a bit more complex when this is desired.):
Above: A
programmable 5-axis tilting head.
Below: A high
precision part machined with it, showing nearly zero
taper:
Above: (Right)
Waterjet part with virtually no taper. On the left
is a picture of the same part set vertically next to a 123 block on a
surface plate,
demonstrating it's lack of taper.
Above: another
pair of parts cut with a tilting head: 0.5" (12mm) brass
bicycle and 0.5" (12mm) stainless steel test part.
Computer
controlled tilting cutting heads can offer a significant
improvement in cutting precision over non-tilting. The big
advantage, is that you can make a virtually taper-free part, without
having to slow the cutting down.
It's also
possible to cut almost taper free parts without
tilting. However, it takes a much more careful setup, and it also
takes slowing the machine way down. The end results are not quite
as good as when cut with tilting, and the part is way more expensive to
make, but if you rarely care about taper, then maybe a no-tilt strategy
is fine.
Above: This
pictures shows a lot of things:
- In the foreground, there is a mechanical drill mounted to the
same motion system as the nozzle. This is used primarily to
pre-drill start holes for cutting (which is almost never required, but
is useful when cutting materials that don't pierce well, such as some
laminates that otherwise might blister. Note that although this picture
shows teflon being cut, the drill was not used in this case, as teflon
cuts nicely without it.)
- Tilting cutting head in the background for taper removal.
In this setup with both accessories attached, the drill drills, and the
cutting head then moves over to do the cutting.
- Some Teflon plastic material, and some parts cut from it.
Notice that all of the parts are linked together with short bridges so
it's one single part that is cut, and then the small pieces are cut off
with wire cutters or similar later.
- Waterjet brick supporting the material. This is useful to
use when the splash-back from the slats might mar the material (in
this case, to prevent the teflon from getting scratched up). It
is also useful for supporting the material when cutting tiny parts that
might otherwise fall through the slats. In this particular
machine setup, the waterjet brick is mounted on on half of the machine,
while traditional slats are mounted on the other side.
- Aluminum "square" that the teflon is pushed against. By
cutting a square like this from a sheet of aluminum bolted to the
table, it is possible to precisely locate parts for secondary
machining. Because the machine was used to cut the square, it is
assured that the square is indeed "square" to the machine, and the
corner of the square's position is known exactly, so that it can be
used as a reference point.
- Notice the Quick-Grip clamp and weight used to fixture the
materials. This is pretty typical.
Above: Another
picture of a tilting cutting head, and a handy splash
guard is in front to protect from the occasional spitting.
Some notes about
programmable tilting heads:
- They are great for making precision parts, because the taper is
compensated for.
- For safety reasons they may be restricted to the total amount of
tilt, or special precautions must be taken care of. (With a fixed
tilt nozzle, it is possible to add nozzle guards and tilt it away from
the operator. With programmable tilt, it tilts in all directions.)
- You do not have to use a tilting cutting head to make precision
parts. You can make nearly taper-free parts without tilting by
simply slowing the cutting down. However, it is necessary to slow
the cutting down a LOT to get rid of taper in many parts, so the
tilting head allows you to make the same part without having to slow
down so much.
- If you are trying to minimize taper, and you don't have a
tilting head, then here are some suggestions
- Use a small nozzle such as a 0.010" jewel and 0.020" mixing
tube
- Use the best abrasive that you can, and the largest grit size
that will fit the nozzle without plugging.
- Use the lowest amount of nozzle stand-off that you can get
away with. The lower you can get to the material, the less taper
you will have. (Consider pre-punching the starting holes with a
pass at a higher stand-off, then lower the nozzle to do the rest of the
cutting. Some controllers may have automatic mode(s) for doing
this.)
- Cut slowly. Generally speaking, the slower you go the
less taper you will get. However, if you go too slowly, you may
experience "reverse taper" in some cases.
- Tilting heads are relatively easy to use. In the case of
the one
pictured above that I am familiar with, using it to remove taper is
simply a matter of checking a check-box for "use tilt':
A cutting
model determines how much to tilt at every point along the tool path,
and does so. There are a few other user interface items for doing
things like squaring the head, providing additional taper to the part,
etc., but in general it's fairly simple to use.
- They won't completely eliminate taper for all parts. In
very thick parts, where "barrel" taper can occur, the tilting will only
get rid of some of the taper, but not the barrel. Note: Barrel
shaped taper is taper that looks like this: ( ) instead of
this \ / or this / \
- When cutting over "waterjet brick" (the plastic stuff in one of
the pictures above), recognize that tilting the head will cause the
brick to wear out faster than usual because you are shooting it in the
sides.
<>They are really fun to watch, especially when cutting thin
materials that cut quickly and have lots of taper. They have a
great "wow that's cool" effect. Click here to watch a video.
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Olsen Software, LLC