Posts from — October 2010
Many DXF files use blocks.Â A blocks defines an object, which then be placed in many locations, and each location can be scaled and rotated individually.Â Â For example, the standard Eagle PCB DXF export ULP uses one block for each different style of pad (circular, square, etc), and then scales, rotates, and places these blocks for each individual pad.
But blocks aren’t so great when you’re importing them into Alibre Design (AD).Â I’ll look at a few issues by trying to extrude the Phoenix ZFK3DS 1,5-5,08 (1704415) terminal block outline; for example, I might want to model a cover for the end block (1704554).Â The files are available in a ZIP archive here Alibre and DXF Blocks.zip.
The DXF file provided by Phoenix uses blocks for all the views.Â I removed the views I didn’t want; the resulting file is Phoenix 1704415 Profile – block.DXF, shown below in DoubleCAD XT.Â You can see the blocks on the right.
I can’t extrude that profile; I need to remove the pins and the pegs.Â But I can’t edit the block in the drawing (left side of screen).Â In the Alibre sketch mode, I can only move it, delete it, or copy it.Â Â In the DoubleCAD drawing I can only scale, rotate, move, copy, or delete the block.
But I can edit the block in DoubleCAD by selecting the block in the block tab (shown on the right), and pressing the EC (Edit Content) button.Â The block is now displayed in the drawing area, and I can edit it, then press the check mark (next to EC) when I am done.Â The final result is shown below and in the Phoenix 1704415 Profile – block for Extrude.dxf file.Â Note that when you edit a block, all objects based on that block will update when you finish editing.
Another approach is to change to a no-block approach by editing the block you want, selecting everything, copying it, closing the block editor, pasting the copied part into the main drawing, and finally deleting all the blocks in the block tab (when you delete a block, all the objects based on that block are deleted).Â The result is in the Phoenix 1704415 Profile – No Block.dxf file.
With the no-block file, you can delete the stuff you don’t want in either DoubleCAD or import it into Alibre Design and delete it in AD’s sketch editor.Â The no-block approach isn’t good for a circuit board full of blocks, but it works great for a single profile.
There are some other differences between the block and no-block approaches in Alibre Design.Â Alibre has a non-obvious approach to pasting in sketches: “normal” pasting (Ctrl-V) always pastes the clipboard content in the same position relative to the origin; paste stamping (Ctrl-T) lets you place it where you want (press ESC when you’re done pasting).
The approach is always the same for getting a DXF file into a sketch: import (which opens an Alibre drawing), open sketch mode, select everything, and then paste it (Ctrl-T or Ctrl-V) into the desired sketch.
So far I’ve found that blocks don’t paste correctly; they get pasted with some sort of an offset, whether using paste or the paste stamper.Â Non-block DXF drawings paste correctly.Â Â But it’s easier to move blocks in Alibre sketches: just select them and drag.Â To move a non-block figure, you have to select all of it, cut it (Ctrl-X), paste stamp it (Ctrl-T), move it where you want, and then quit stamping (Esc).
Here’s a picture of the finished profile extruded in Alibre:
I’ve used DoubleCAD XT for all my DXF manipulations because it’s free and it works for me.Â You should be able to do the same things with any other high quality AutoCAD clone.Â DraftSight is another free AutoCAD clone worth checking out; it’s available on Windows, Mac, and (real soon now) Linux.
October 20, 2010 No Comments
I think it’s interesting that there are so few switch mode power supplies (SMPS) designed for powering motors.Â Motor power requirements are different from electronics; voltage regulation isn’t critical.Â Servo motors benefit from a large current peak (overload) capability and sometimes need a shunt.Â Steppers are best with a power supply designed to handle a rapidly changing inductive load.
A typical switch mode power supply, however, is designed for tight voltage regulation, does not have a shunt and handles over current by limiting current to its maximum rating.
Some switching power supplies are better because they have 20% to 50% peak capacity for a brief time.Â I’ve seen this capability in models from Cabur (sold by ASI in the US), Puls, and Delta; I’m sure there are other examples.
I’ve used the Delta CliQ series for servo motor power, and so far they’ve worked well.Â The CliQ can handle 50% over current for 3 seconds, the pricing is quite good (under $150 for 24V at 10A), but they’re only available for 12V and 24V.
The first designed for motors SMPS I discovered was the IMS ISP200/300 series, which are unregulated switching supplies specifically designed for handling the rapidly changing, inductive loads typical of stepper motors or DC motors.Â IMS is now Schneider Electric, and they have discontinued the ISP series.
I don’t really consider the Galil PSR series a SMPS for motors; it looks like an ordinary enclosed switcher with an added shunt resistor.Â The PSR costs $250, and is available in 24V at 12A or 48V at 6A.
I recently discovered a second SMPS for motors, the Cabur XC series (sold in the US by ASI).Â They have a 72-85V output at 3.1A, 6.6A, or 13.3A, have a 20% reserve capacity when <45C, can handle 50% over current for 5 seconds, and have output over-voltage protection (equivalent to a shunt).
It’s interesting to compare the XCSF500G (72V at 6.6A) to the Logosol LS-872.Â Logosol makes my favorite linear power supplies (I own a LS-1148 and use it extensively); they are relatively compact, are switch selectable between 115V and 230V input, have ESTOP inputs, front panel mount fuses, and are available in a variety of output voltages.Â (The only other 120V/240V switch selectable linear motor power supply I’ve been able to find is Copley’sÂ DP models in their PST series, but they cost much more).
|Cabur XCSF500G||Logosol LS-872|
|Input Voltage||90-132VAC or 187-264VAC||100-120VAC or 200-240VAC (switch selectable)|
|Voltage Regulation||<1%||-10%, +15%|
|Current, Max Cont||6.7A||8A (50% duty cycle)|
|Current, Peak||10A for 5 sec||20A for 5 sec|
|Weight||2.6 lbs||9 lbs|
|Dimensions||Not listed; appears to be smaller than the LS-872||8.55″ x 6.7″ x 2.8″|
|Other features||DIN Rail Mount
Output overvoltage protection
Short circuit, overload, and over temp protection
Separate, unregulated 24V 2.5A power supply
|Approx. Price||$550||$425 (no shunt)|
October 2, 2010 No Comments