# CNC milling



## Mk (Jan 7, 2013)

*Hi all 

Does anyone know if a CNC milling machine that runs on plt format can cut dept? If I have to draw the model (my loco's wheel) on TurboCad Deluxe V19 how do I know what part of the wheel will it cut away, because in plt format it you cant create a 3D model you can just draw it.

Any help will be appriciated.

*


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## Dwight Ennis (Jan 2, 2008)

I'm afraid I don't understand your question. If you have, for example, a spoked driver, the part that will be cut away is the part between the spokes - doesn't matter if it's 2D or 3D. 

Are you trying to lay out the tool path?


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## Gary Armitstead (Jan 2, 2008)

I was a CNC machinist and MasterCam programmer/Die Sinker by trade for 40+ tears before retirement in 2001. I'm not familiar with TurboCad because it is considered a program more for the home machinist and not high-end industrial work. BUT the principle is similar for ALL cad programs. Like Dwight said you don't need to have a 3D drawing to cut a part in 3D. You can even "draw" the toolpath to force your cutter to go where you want it to cut.Middle and high-end software will have the capability to control the offset of the cutter or have it follow a centerline of the cutter. Step-downs and depths can all be plugged in to the software. You can cut a part with wireframe ONLY or cut to Solids or surfaces. Lots going on here. Please explain plt format. I'm familiar with the extension *.prt used in solid modeling. Need some clarity here.


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## Mk (Jan 7, 2013)

Thank you Dwight and Gary for the reply. I have to draw the locomotive wheel with spokes so that a sign shop can cut the a wooden driver for me to make moulds for casting the wheels from alu and then make a steel bush and tire so that the alu don't wear out. "PLT -Hewlett-Packard Graphics Language"


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## Dwight Ennis (Jan 2, 2008)

Based upon what you're telling me, my guess is: 

Depending upon what your sign shop needs, a drawing of just the driver with a front view and a side view may be enough, with perhaps a sectional view of half the driver and another sectional view of one of the spokes. 

That assumes they can generate their own tool paths from a simple "orthographic projection" drawing (a 2D drawing having at least a front and, usually, a right side view - may also contain a top view, bottom view, left side view, and a whole host of sectional and auxillary views depending upon the complexity of the part being described). If they can't, and require a 3D model for their post-processing software (a program that generates tool paths and g-code from a drawing), then either they will have to make a 3D drawing from your 2D orthographic drawing, or you'll have to find someone to do the 3D drawing for you.


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## SteveC (Jan 2, 2008)

Posted By Gary Armitstead on 27 Mar 2013 07:38 AM 
{snip...}[/i] Please explain plt format. I'm familiar with the extension *.prt used in solid modeling. Need some clarity here.








*Gary:*
A file with a .plt file extension is a file created using HPGL (Hewlett-Packard Graphics Language; sometimes hyphenated as HP-GL).

Wikipedia - HPGL[/b]

*Marinus:*
Just a FYI type of thing, the following is a link to an on-line HPGL/PLT to G-Code converter. Note the company does not make milling machines but CNC hot-wire cutters, so I don't know if this conversion would work for what I think would need to be a CNC milling machine with a least three axis control (i.e. X, Y, & Z).

DoCaDo - CNC Hot-wire Cutter - HPGL/PLT-to-G-Code[/b]


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## Greg Elmassian (Jan 3, 2008)

You mean HPGL like "PU", "PD", "PA 100,500", "PR 200,3" ??? 

That language? 

Greg


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## Gary Armitstead (Jan 2, 2008)

Posted By SteveC on 27 Mar 2013 04:05 PM 
Posted By Gary Armitstead on 27 Mar 2013 07:38 AM 
{snip...}[/i] Please explain plt format. I'm familiar with the extension *.prt used in solid modeling. Need some clarity here.








*Gary:*
A file with a .plt file extension is a file created using HPGL (Hewlett-Packard Graphics Language; sometimes hyphenated as HP-GL).

Wikipedia - HPGL[/b]

*Marinus:*
Just a FYI type of thing, the following is a link to an on-line HPGL/PLT to G-Code converter. Note the company does not make milling machines but CNC hot-wire cutters, so I don't know if this conversion would work for what I think would need to be a CNC milling machine with a least three axis control (i.e. X, Y, & Z).

DoCaDo - CNC Hot-wire Cutter - HPGL/PLT-to-G-Code[/b]

Thanks Steve. Learn something new everyday!









I know about HPGL only because of HP printers hooked up with graphics plotters and HPGL LPT2


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## denray (Jan 5, 2008)

MK I only know of using DFX or DWG format for going to the milling machine or router or plasma, I draw in a CAD much less sophisticated than Turbo Cad. Many CAM controllers will have the ability to do the CAM (computer aided machining) set up to do all the line configuration to cutout an area that is larger than the diameter of the cutter bit. We rout hours per day on a cnc router that has all the drawings just done in CAD turned into dxf and imported into the CAM program that feeds the controller. Our CAM automatically converts to g code from dxf, one step that we don't have to do. Most CAM programs I have looked at just does it by going through one more step , converting dxf to g code. My controller follows the line in the center of the cutter. All you have to do is draw up your wheel as you want it to look like. Front view and a cutaway view showing your desired cut depths.If you want to use a 1/8" diameter bit, draw up your lines for the router or mill to follow, remember it follows the center of the line. Don't be intimidated it is really fairly easy, if you need a sample drawing I can do you one as an sample. Dennis


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## Greg Elmassian (Jan 3, 2008)

Now you know the guy who invented the HP-GL language for plotters too... it turns out it is a funny story. 

Greg


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## armorsmith (Jun 1, 2008)

Mik, I used a version of Turbo Cad years ago and it had an export to .DXF. Gary can correct me if I am off base, but I believe that all modern CNC machines will directly read DXF files. HPGL is an output intended for plotters, not machine tools. 

Bob C.


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## Gary Armitstead (Jan 2, 2008)

I was always under the impression that *.DXF is a type of file that is intermediate between one cad systems file extension and another cad system. An example that I can remember from years ago: At Glendale College, my professor and I were building some Baldwin Electrics in 1.5 inch scale (ride-on stuff). I drew the sheet metal bodies in MasterCam V4. It's file extension was *.GE4. There was a "translator" in the software to take these geometry files from GE4 to DXF. We then took these files to a local sheet metal shop so they could use those DXF files and translate into whatever cad system they were using. We had no idea which system they were using AND it didn't matter! The shop just put our DXF files into their system and programmed the "commands" to be used on a CNC sheet metal "cutting" and "bending" machine. We had 7 identical sets of body parts for the cabs including ends , sides and roofs. The roof curvature was rolled by a CNC roller and came out just perfect including the "stretch factor" caused by the rolling procedure.


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## Dwight Ennis (Jan 2, 2008)

I was always under the impression that *.DXF is a type of file that is intermediate between one cad systems file extension and another cad system.That's correct. DXF stands for "Drawing eXchange Format." Most post processing programs I've seen will also read DXF files and will generate g-code from them. In fact, the ones I've seen and played around with (freebies/el-cheapos designed for the home user, not professional packages) _*require*_ DXF and do not read AutoCAD's .dwg files directly.


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## toddalin (Jan 4, 2008)

I've been using G-Simple (it's free and fairly easy... once you figure it out) and IIRC, it can even import .DXF files and convert them to G-code. I take the output and edit it in Notepad and add a .TAP extension and it runs under Mach3.

I don't know about CAD programs, but G-simple does things to speed up the milling process and reduce the strain on the machinery.

For example say you want to cut a block into a "bowl." You could program the unit to cut a ring into the block, then move to the next inner ring by lifting the quill, or just moving it 90 degrees through the medium, and cut that ring, etc. But that is not efficient and hard on the equipment.

Using G-simple the program would cut the first ring as above. Then instead of lifting the quill and moving it, or just moving it 90 degrees, it will "spiral" in/out to the next ring in a smooth arc. This is automatic to the program when telling it to cut a recessed area and requires no thought on the part of the programmer.


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