CNC project for beginner operators ( Horizontal twin cylinder)

[Tin Falcon]

I have no idea what speed my spindle is turning. I adjust by the sound. Drilling is about 1/4 of max but the larger the bit, the slower i go. The same applies to cutters. The larger the cutter the slower the spindle speed. Like I said before, you need to find what the mill likes.

well i should have done the calculation I know 1000 is slow for an 1/8 carbide cutter. My spindle is a Pulse width modulator . I do have a laser hand held tach they are cheap.

Tin,
It gets worse when you are nearing the last operation, you have had 13 setups and have over 30 hours invested in the part. A simple "Ah shucks" will not cover the situation.
Gail in NM

This is true and can happen with manual operations as well. to err is human to realty foul things up requires a computer. I am past the point of no return. I either push forward, go backwards, or stand still and have a large expensive paper weight on my desk. so forward I go.
Tin

 

[dreeves]

Are you going to run bushings for the crank in the corian?? If not you might want to thinks about it.

Dave

 

[Tin Falcon]

I typically use a piece of pen tube brass 1/4 ID 7MM OD but I need to get usabnle parts first . I may thorw a 7 mm bit in on my next try.
Tin

 

[kvom]

I consulted G-wizard for a 1/8" 2-flute endmill in acrylic with 1/2" stickout, and for slotting got 4000 rpm (my max), .24 max DOC, and 14ipm. I increased the machine limit to 10k rpm and it liked that too. So use your max rpm. Change all the S1000 codes in the file to whatever your max is, assuming PC control of the spindle.

 

[chrispare]

Ok Steve I gotts a question for you.
I got a few minutes to myself today and decided to try your code for the base.
It runs good untill i get to a particular point in the code..


G1 Y1.469
G2 X-1.375 Y1.8314 I0.3624 J0.0 this is left corner
G1 X1.375 this is top edge
G2 X1.7374 Y1.469 I0.0 J-0.3624 when the machine hits this line x axis stalls every time,unless i slow to a stall
G1 Y0.531

now if i slow it down to like 1in per min it will run through then I can speed back up till it hits it again (that top right corner)
even if I move the x/y to a different position and try that code it stalls.

any ideas??


Chris

 

[RonGinger]

when I try that piece of code I get the error 'radius to end of arc differs from radius to start' and mach hangs.

I think mach should stop completely, in fact it shouldn't even let you start to run, it should see the error as it reads the code.

 

[chrispare]

ok this is the piece of code that is stalling
G1 X-1.6775 Y-1.8187
G2 X-1.8125 Y-1.6187 I0.3025 J0.3497
G1 Y-1.9065
G1 X-1.5247
G2 X-1.6775 Y-1.8187 I0.1497 J0.4375
G0 Z0.025
G0 X-1.6121 Y-1.7431
G1 F10.0 Z-0.1
G2 F60.0 X-1.7374 Y-1.469 I0.2371 J0.2741
G1 Y1.469
G2 X-1.375 Y1.8314 I0.3624 J0.0
G1 X1.375
G2 X1.7374 Y1.469 I0.0 J-0.3624
G1 Y0.531
G1 Y-0.531

it stalls third line from the bottom

 

[kvom]

Sounds as if the CamBam arc mode differs with the controllers. Usually for mach3 it's set to Absolute rather than Incremental.

 

[RonGinger]

That longer block runs without error on my machine.

Mach by default uses incremental IJ mode and thats what this code is doing.

Tell us more about what you mean by stalling. Does the feed rate DRO show a low value? Is the tool still moving? Does it eventually finish OK?

 

[kvom]

I checked my Mach config and IJ mode is indeed incremental; it's distance mode that's absolute.

 

[stevehuckss396]

I checked my Mach config and IJ mode is indeed incremental; it's distance mode that's absolute.

That would be correct as cambam is configured the same. Take a look in the general config in the config menu and check to see if you are setup for these settings. If you change them, exit mach3 and then rerun the program again. Most times its unnessary but some things you just have to do it so now I just do it after making any changes.

 

[stevehuckss396]

when I try that piece of code I get the error 'radius to end of arc differs from radius to start' and mach hangs.

I think mach should stop completely, in fact it shouldn't even let you start to run, it should see the error as it reads the code.

It must be a setup thing. I used the code to make 10 pieces.

 

[stevehuckss396]

This week will be the flywheel!

I started out by cutting 3 pieces, 3 inches square. They only need to be rough sawn. There is no advantage
to trying to make 3 perfect squares.

Sand the pieces up with some sort of paper or scotchbrite pad to remove the glossy surface. Create a surface
that will allow the glue to stick. I used the superglue gel. I completely covered the surface of one square on both
sides and sandwiched it between the other two pieces. Then I put it in the vise for 30 minutes and let it set.

After the glue set, two parallel sides of the stack were machined to make it easier to hold in a vise. The height
of the stack needs to be reduced to the width of the flywheel. Measure the gap between the standards and
minus another .010 - .015. That should be a good width. Cut the stack to thickness.

With the stack being 3 pieces I removed half of what was needed to be removed from each side of the stack.
That centers the center piece in the stack and assures me that the spokes will be one solid piece with no
parting or glue line in them. I'm not sure it would make a difference as long as a good job was done with the
glue but I still avoided a possible visible line.

Find the center of the stack and setup for cutting. The vise was installed quickly and I didn't bother to indicate
the fixed jaw. The eyeball method should be more than adequate and the vise will be removed again for the next
step. It is used for less than 15 minutes.

Load up the FlywheelSideOne code and get ready to cut. After the holes are drilled and you load your 1/8
endmill make sure it's a 1/8 shank and you have at least .750 of bit out of the mill. The first side cuts the
spokes completely thru so the bit goes .700 deep into the stack.

When you go to cut side 2 the wheel will get cut out from the stack. The big square of material will fall away
and I have no idea what will happen when it does. It could pinch the cutter and break it or who knows so what
I did was cut some slots in the band saw. Now I can predict the pieces will fall away without causing any damage.

To complete side 2 the piece needs to be rotated 180 degrees and perfectly aligned to X,Y center. I do that
by cutting a fixture. This is great if you are making more than one.

Load a piece of Corian that is ugly or a piece you think you will never use. The Gcode will do a few things.
First it cuts a .01 deep pocket to make sure the surface the flywheel will contact is perfectly flat. Then the
Corian is cut out so the part can be fixtured, as is, right out of the vise. A boss is cut so the stack will be
perfectly aligned on center. I made the hub and this boss .004 different to allow for slightly under sized
cutters and backlash.

Load the FlywheelFixture code and cut the fixture. Then move the table to a clear spot and tap the hole 1/4-20.

Load up the stack and bolt it down. The top surface of the stack will be Z0. X,Y should be set from making
the fixture and NEVER be changed in any way until the flywheel is completed.

Load up the FlywheelSide2 code and finish cutting out the flywheel. As expected the 4 corners fell off without
trouble.

Drill and tap for the set screw. Ignore the drawing and tuck that hole back from the edge as far as you can.
Corian loves to crack at edges. Drill slow and clear the tip of the bit (peck) often. Same when tapping. Slow
as you go and back out often.

Put the flywheel on the crankshaft and chuck it up. Turn the OD down to finished diameter and your done.

View attachment FlywheelFixture.tap

View attachment FlywheelSide1.tap

View attachment FlywheelSide2.tap

View attachment Flywheel.pdf

 

[stevehuckss396]

I have decided to run the air to the cylinders using some fittings and a small piece of 3/16 tubing. The 3 fittings can be made from anything you have handy. 1/4 inch hex bar would make it easest.

I will post the new PDF drawing here and have replaced the old one in the earlier post.

View attachment Standards.pdf

 

[stevehuckss396]

This week is the piston and air fittings. You will need to make a pair of pistons and three air fittings. I made
my pistons from some acrylic pen blanks I had sitting here. Very simple turning here to get them to the
correct shape.

Whats nice about the pen blanks is they are square. That made it easy for me to hold the blank to mill the
tail of the piston. The hole was drilled and the piece was rotated 180 degrees and the other side was milled.
Then I took it back to the lathe and parted it off.

I'm still waiting for a length of 1/4 inch brass so the air fittings will not be covered but they are a simple turning
so I'm sure it won't be missed.


View attachment PistonFitting.pdf

 

[stevehuckss396]

I'm going to post the last piece early in the event that someone has the week off and might want to
try to make one over the holidays.


I changed up the design so the entire cylinder can be made CNC except the cylinder hole. It will still need
to be drilled and reamed. I also wanted a more modern look to go along with the more modern looking base
and standards. Glue up 3 pieces 1-1/4 X 2-1/2 long in the vise and let them set for 30 minutes. This code
will handle a 2-3/4 X 1-1/2 stack. I also tried to cut the entire stack away in the roughing stage so cutting
slots like the flywheel to control the scrap wont be nessessary. When ready, mill the stack to a thickness
of 1.188 inches.

Load the CylinderBottom program. Center of the stack is X0,Y0 and top surface is Z0. The program will center
drill and drill 2 holes. The hole closest to center should be tapped #8-32 before moving on. Use a bottom tap
and get as much thread as you can in there.

After threading the 1/8 inch endmill is loaded and the bottom of the part is cut to completion. Make sure your
endmill measures .125. I have purchased cheaper endmills that were as small as .122. Not a big deal when
milling in manual mode but when in a CNC machine you can see where a circle will be .006 to big.

Now check the diameter of the 1/2 inch long shaft sticking out of the bottom of the cylinder. If it will not fit
into the hole in the standard, there are a few things you can do. You can get into cutter compinsation using
Mach3 but this is supposed to get the newer folks cutting. Mine were to big to sand or file so I went to the
next size drill and redrilled my standards.


The shaft is then cut to a length that equals the thickness of the standard. If you miss, make it a bit shorter
rather than longer. Dont want the shaft sticking out the other end.

This part is made using a fixture like the flywheel. I forgot to get a shot of the fixture but it a simple corian
fixture with a hole in it. When making the fixture I had to use the same drill bit that I used to redrill the
standards. Things like under sized cutters and backlast can have an effect on how the part will fixture so
be aware. The part is set into the fixture and secured with a single screw from the bottom.

The ball end mill is the only tool needed to cut the top. Load the CylinderTop program and touch off the top
of stock to zero Z. Like the flywheel, do not change or zero X and Y axis. I made the code for this side less
agressive because the part will be held in the fixture by only one screw. It will take longer to cut but
increase the odds of nothing bad happening while cutting.

After all the cylinders you are making are cut, use the fixture to hold the cylinders to drill and ream the 1/2
inch hole for the piston.

That's all you need to build the engine. When you assemble the engine be sure not to over tighten the screws
that hold the cylinders onto the standard. Use a real light oil to lube everything. The only 3/16 ID tubing I
could find was 5/16 OD but it doesn't look to bad. Make sure the engine turns freely and put a little air to it!

Hopefully this exercise has taken the mystery out of setting up to cut a piece and was of doing simple setups
to speed up making multiple pieces. If you have a CNC mill but have not run it in automatic, download the
code, get a few pieces of corian, go out in the shop and break some bits! Once you get going the errors become
few and far between and it keeps getting easier.


Here is a video running slow on less than 1 pound of air.

[ame]http://www.youtube.com/watch?v=f2uGxEHwLsI[/ame]


This thing flies on just 4 pounds of air.

[ame]http://www.youtube.com/watch?v=99_zorw5Zjg[/ame]




Cheers!!

Steve!




View attachment CylinderBottom.tap

View attachment CylinderFixture.tap

View attachment Cylinder.pdf

View attachment DoubleCylinder2impTop.tap

 

[Tin Falcon]

cool stuff steve . I need to get moving on this.
Tin

 

[stevehuckss396]

cool stuff steve . I need to get moving on this.
Tin

Now that the proto is done, I have 5 more going. Going to test some new code for the cylinders. I'm trying to smooth out the top. If it works well I will replace the old one.

 

[stevehuckss396]

I have replaced the cylinder Top code with this one. Not much different but will give a much improved finish at the very top. I had to do just minor hand work to get a great looking part.



View attachment DoubleCylinder2impTop.tap

 

[stevehuckss396]

I have two ready to ship to the person they were intended for. The brown one runs better than the prototype. It lopes along and the needle on the pressure guage never comes off of zero.

I put 20Lbs of air on the prototype to see if it would explode. It held together just fine. I could not blow it up.