CNC Milling Machine Computer Cart Stand

Posted by admin on September 11, 2013

UPDATE: This cart has been replaced by Tormach Path Pilot computer and software. The solution is far superior to using Mach3. Path Pilot is as good as production VMC software. The response to input is instantaneous.

I picked up a surplus medical cart from www.kpsurplus.com (it's not listed on their website, you will have to contact them directly about purchasing the medical carts), to use it as the computer stand for the CNC milling machine. The cart is perfect, as it already has a built in computer with plenty of power to run Mach3, the height is adjustable using a motor, it's solid and mobile.

I had to make a few modifications to it. The first was to remove the privacy filter in front of the screen. This involved removing the back cover of the display, which exposed the computer and LCD screen. The computer appears to be a laptop that was attached to the back of an LCD and enclosed. The motherboard has many ports that are available to use, including a parallel port.

Once the back cover of the LCD display is removed, the front cover has to be removed. The front cover is nice, because it completely encloses the LCD, protecting it from spashes, chips, dust, dirt, etc. It's also easy to clean.

The privacy filter can be easily peeled off of the screen. Now the screen is visible from any angle.

Here's the back of the computer.

There are lots of ports available on this computer once the cover is removed. There are even some USB ports open, because most of the USB is connected to a hub under the table top.

 


 

Computer and Display Power Supply

Turn the cart around, and look underneath the back of the table. Behind this panel is the power supply that provides power to both the computer and the screen. The input to the power supply is 12V from the battery (or a 12V power supply). There is also power provided to a USB hub, which has 8 ports. Remove the panel to expose the power supply, USB Hub, and a rats nest of wires.

 


 

Opening the Storage Drawers

The medicine storage drawers on the cart are quite handy for tools that need to be kept close at hand.

The drawers are locked closed by a magnetic latching solenoid. This is controlled from the computer, and requires login credentials to unlock these drawers (presumably used for medicine storage. If you're not interested in the software unlock, there is access for manual override.

Look under the drawers, and you'll see an aluminum plate. There is a small rectangle with 3 tabs attaching it to the rest of the aluminum panel. Snip these tabs, and snap off this aluminum rectangle. Then you'll have to look up into the hole, and find the solenoids with the latch. Pull on the latch, with your finger or a tool, and the soleoid will unlatch, and remain that way. Now the drawers can be opened.

 


Powering it Up

The base of the cart has a power supply, which acts as a battery charger, and some custom circuit boards to run the lift, drawers, and other unkown medical stuff.

The easiest path to get the computer up and running would probably be to install a 12V lead acid battery. Not having one at hand, I opted to connect a 12V power supply directly to the cable running up the post. In the picture below, the large connector to the left with 4 pins, the RED and BLACK wires provide the + and - 12V to the power supply located under the table top.

The BLUE and BROWN wires go to the lift motor that allows you to move the table top up and down.


Lift Motor

If you ditch the electronics boards in the base, then you need a control system to power the motorized lift. The up/down switch on the back right of the table top is a single pole, double throw, which is not enough connections to be able to reverse the motor direction. You would need a double pole, double throw switch, and run extra wires up the coloumn.  We chose to use some relays to switch and reverse the polarity to the motor. David Amis sketched the wiring diagram shown below, and wired it up. It works quite well.

These are the specs of the lift motor used on the stand. It's a high end Linak linear actuator.


Power Draw Bar

Posted by admin on May 29, 2013

Power Draw Bar

Tormach's Power Draw Bar

Tormach offers a power draw bar option for $1200. After already spending a chunk of change on the machine and other accessories, I found it hard to stomach to pay another $1200 for what amounted to be an air cylinder, air valve, and some machined steel plates and hardware.Also, I design machinery with pneumatic automation, and have cylinders, valves, etc lying around just waiting to be used for a project like this.

Tormach uses a 3 stage air cylinder with a bore diameter of 100mm. The part# of their air cylinder is CQ2B100x12-3, and it's made by a company in China called XINYIPC. These cylinders are a copy of the SMC CQ2 series cylinders. Basically they've taken 3, 100mm bore by 12mm stroke air cylinders, and stacked them in series to multiply the force times 3.

I considered a few different options of making a power draw bar that would work with the TTS tooling system.

 

At first I considered using an impact style draw bar, like is commonly used with bridgeport style milling machines that use an R8 taper. This is a proven, effective, cheap method to change R8 tooling. I spoke to someone who had done this for their Tormach, and later switched over to Tormach's power draw bar solution, and said that theirs was by far better. The main problem he had was stripping the draw bar bolt, and he was spending too much time keeping the thing working. This could probably be resolved by improving the lead in for engagement, and only activating the impact wrench once properly engaged. The problem I was trying to figure out (without having the mill available to test the idea) is how to loosen the collet just enough to allow the TTS toolholder to slip in and out, without the impact driver completely unscrewing the collet from the draw bar. There needs to be something that limits the rotation. I may experiment with this later to see if I can find a solution.
The second idea was to use an air cylinder that I already have that has a smaller diameter than what Tormach uses (100mm), but a longer throw, and use a lever to increase the applied force. Although not that difficult to build, it is still more complex then what Tormach has achieved using 3 stacked cylinders. Not yet having the mill at hand to take measurements, it was difficult to design something that I knew would fit.
While waiting for the mill, I did a little research on CQ2B100 air cylinders. SMC, the original manufacture sells a 15mm stroke for about $230. Take that times 3, and add the time machining open the backs in order for the rod end to push the piston of the next cylinder, machining grooves for o-rings to seal between them, and you may as well pay up the $1200 for Tormach's solution. From China, the cylinders can be purchased individually for about $25 each. I spoke with a vendor, and they said that they could make a 3 stage version for $125. Although I was interested in trying to make my own from individual cylinders, I thought that having them make it may be better since they have more experience. Of course shipping cost more at $130, but it's worth a try.

This is your basic SMC QC2 Air cylinder clone.

Looking at this cross section, it appears to me that it would not be difficult to machine a hole in the back of the cylinder, machine a groove for a seal, and sandwhich the air cylinders together.


3 Stage Cylinder Arrives!

And it's just what the engineer ordered! This is a nice looking, hefty cylinder for the price. Matches my specs, now we need to make the rest of the parts.


Machined Spindle Pully Nut

A new spindle pully nut had to be made that has a flange that the cylinder mount could grab onto when the cylinder is compressing. This elliminates any force applied to the spindle bearings.

Since these were steel parts, which I did not have a lot of expereince machining, Helton did all the machining of these parts, and I assisted and learned.

 


 

Replacing the Spindle Pulley Nut

 


Eccentric mounting pin

An eccentric mounting pin is used for fine tuning the position of the cylinder and cylinder mount such that it does not touch the spindle nut, and is concentric with the spindle.


So, How Does the DIY Power Draw Bar Work?

It works great, probably just like the one that Tormach sells. I wouldn't want to be without it, it's a huge time saver. However, the retention force is not good for end mills over 3/8 in, and this is a problem that has been discussed on many forums. At the recommended tension (2.5 turns of the draw bar after hand tight), it took about 95psi to release the tool. The pull out was horrible with a 1/2inch tool. I would have to go back to the original draw bar, and hand tighten in order to use a 1/2inch end mill without any pull out.

I did a few things that greatly reduced (but not totally elliminated) the pullout.

How did I reduce the pull out.

  1.  I have the release pressure set pretty high, in the 120psi range. This means tightening the drawbar more than 2.5 turns
  2. Ditched the Tormach TTS Collet, bought a Hardinge 3/4 R8 Collet, and ground the face down to allow clearance for the TTS Collets. This was a huge improvement in retention.
  3. Added an additional bellville washer pair, so now there's a stack of 4 pairs. This increased the travel, allowing the collets to release easier under the high force.
  4. Always make sure that the TTS shanks are clean, dry and free of lubricant. Keep the collet inner faces clean.

Based on this experience, I don't believe that a Air Piston/Bellville washer power draw bar is the best design for the TTS style tool holders. The Bellville washers allow the tool holder to be pulled out, even when providing the theoretically necessary retention force. Tightening a rigid draw bar to the correct torque provides much better retention. This leads me to believe that a torque type power draw bar would be better. I may consider replacing this draw bar in the future with a impact style power draw bar. The downside is that the hex at the top end of the draw bar tends to wear out.


UC100 USB Motion Controller for Tormach

Posted by admin on May 29, 2013

UC100 Motion Controller

The UC100 Motion Controller is difficult to install with Tormach's PCNC version of Mach3. I was able to install the drivers, but the PCNC Mach3 would not recognize or use the UC100.

The problem lies in the configuration file. PCNC Mach3 makes you install the Parallel Port driver and it sets this as default control device. You have to go into the configuration file, and set the UC100 as the default control device.

  • Open the PCNC3 folder, usually at the location c:/PCNC3
  • Find and open the xml file called PCNC1100M3-3.xml (name might be different for the 770 series) in a text editor
  • Find the the line: <Control>
  • Delete the code between <Control> and </Control>
  • Paste the following code between <Control> and </Control> (you may have to change the version of your controller, based on the version of the driver you are using):
    <Device>UC100-CNC-motion-controller-V2.125</Device> <Default>1</Default>
  • Save the .xml file
  • Start PCNC Mach3, and you should see a dialog box that pops up asking you which driver to chose. Choose the UC100.

Laser Engraving Aluminum

Posted by admin on December 25, 2011

 

Engraved the Boston Dynamics (of Big Dog Robot fame) logo on the back of the phone of my friend who works there.  The engraving looked stunning, and it turned out bright white.  

Settings:
Speed: 150mm/s
Power: 30%

Boston Dynamics Logo on the back of HTC Phone
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Laser Cutting and Engraving on Wood

Posted by admin on December 25, 2011

Jelly fish flames wood box.  Cigar box which was sanded, engraved, and then coated with wax/orange oil.  I only learned later that the discoloration around the engravings can easily be removed with a wet rag.  The box was made in 3 separate steps.  Engraved the top, rotate 90 degrees, engrave the right side, rotate 180 degrees, and engrave the left side.  Unfortunatly, pictures don't do it justice. It looks amazing in person.

Settings: 
Speed: 500mm/s
Power: 50% (considering that 60% appears to be max power, ~20ma, while cutting) 

 
Other side of the box.

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LED Light for CNC Mini Mill

Posted by admin on December 21, 2011

This light was built from surplus parts I had.  A 3W Luxeon Star LED from a headlamp that I upgraded, a cheap flashlight, a heatsink with a threaded plate, and a flexible arm.

The plastic lens was scratched with a brass brush to create a diffuse light.  This reduces glare, and is not blinding if you happen to look directly into the light.

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Laser Cutter is Complete!

Posted by admin on December 7, 2011

Finished the laser cutter project!  There are still a few things to add, like the exhaust blower, and air assist.  Thanks to David and Greg for help on this project.

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Z-axis Drive Pulley 3D Printed

Posted by admin on December 1, 2011

I had a stepper motor and matching belt pulled from a surplus printer that fit the Z-axis bracket, but did not have the matching pulley.  The belt is a 1.5mm pitch, which has tiny teeth.  1.5mm pitch pulleys are also not readily available, so I modeled one in Solidworks and printed it out on my 3D printer.  I was unsure of how the teeth would resolve due to their tiny size, and the resolution of the printer.  The printed part turned out to be functional.  The teeth are rounded quite a bit, but the belt still engaged properly.

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Air Assist and Auto Focus Nozzle

Posted by admin on November 29, 2011

The stock air assist nozzle left a little to be desired.  Being made from a chunk of aluminum, it was heavy, and the barb fitting was straight instead of 90 degrees (which made the air assist tubing stick out too far).

The DSP laser controller has an input for the autofocus sensor.  I thought it would be handy to have the autofocus sensor integrated into the nozzle.  The nozzle shown below is the result of these design requirements.  It has a spring loaded tip.  When the table is raised, and the part touches the tip, the electrical contacts inside the tip are lost, and the DSP autofocus input is triggered.  The table then lowers a specified distance away from the tip to achieve proper focal distance.

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Design Patent Application Info

Posted by admin on November 23, 2011

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