Comments to Machinist
"Comments to Machinist" (CTM) are lines or text added to your drawing to indicate
special instructions to the machinist. Use CTM when your job has a simple
requirement outside the scope of the software.
The cost associated with your instructions is determined manually by the eMachineShop staff upon receipt of your order, your approval being requested if the charge exceeds $25. In some cases Comments To Machinist can reduce price - for example if you instruct to omit certain machining. Pricing is not provided prior to placing an order, however you can decline to process an order if the charge exceeds $25.
Example uses of Comments To Machinist:
- 3D shapes that cannot be modeled in the CAD software such as:
- Rounding, chamfering, grooving a portion of an edge
- Drilling holes at angles other than 90 degrees.
- Geometric Dimensioning & Tolerancing
- Special instructions (e.g. "Don't bend 5 of the parts.")
- Minor variations (e.g. "Change diameter to .503 for half run")
- Advanced threading requirements not supported in the interface.
- Countersinks in 2D designs - specify angle and size per the diagram at CAD menu Line | Machine | Chamfer.
- Machining existing parts.
- High quantity of repetitions of a hole or shape in order to avoid long computations.
- For injection molding, to show the desired location of the parting line, gate and ejector pins.
- Capabilities listed here.
- Special finishes including special colors or multiple finishes.
- Hardware or other assembly (e.g. Affix panel A to panel B using mcmaster.com adhesive #123)
- Special bends such as for thick material or large radius
- etc.
Avoid references to stock components such as "Make .005 larger than diam of McMaster bolt # 123456." Instead, review the drawing of the bolt and design your part with appropriate clearance and tolerance.
To add Comments To Machinist:
- Select menu View and select the proper view (Top, Bottom, Left, etc.)
- Draw lines and/or text using the left toolbar. Draw an arrow when a CTM applies to a specific area of the drawing.
- Choose Line | Machine | Comments to Machinist.
- Select a Line Type (Solid, Dashed, Arrow, Font or Dimension)
- Click OK.
Tips
If you draw a line such as a circle, be sure to include text that explains what you want to do with the line. For example, next to a circle you would likely need to specify a Z value such as "Z=1.23" and any settings that would normally go in the Line | Machine dialog. In some cases you may need to clarify a comment by referring to another comment in another view (e.g. "See A in Top view"). To show holes at angles other than the six normal views, model the hole using normal CAD lines and add comment text to clarify the desired angle and position.
Be specific
"Leave some parts not bent" is unspecific. "Don't bend 10 parts" is specific.
Tolerance numerically
"Exactly 1.000" has no tolerance. Use "1.000 +/- .005" or whatever the desired tolerance range is.
Use lines instead of words
Instead of "Second hole must be one inch from edge", draw a line, set the type to Dimension and add tolerance if desired (e.g. +/- .005").
Be concise
Extra words: "As mentioned in my email don't bend 10 parts." Concise: "Don't bend 10 parts."
See
important corrections to the video.
Also see here.
