Accuracy problems with CD

[bruce]

I have two problems that have been driving me crazy in CD:

1: I drew a part in CD that I wanted cut, and I also needed a mirror image of this part, so I flipped the original using the Transform function. However, when I converted the file to DXF, then SB, the Bot cut the orignial image perfectly but made a 1/2" error in the flipped image (the part incorporates a slot which became 1/2" wider in the flipped part). It has done this consistently on several test cuts. Any ideas on what's going wrong?

2: On every file that I've converted and tried to cut, the Bot starts the cut by plunging the Z axis at the exact center point of the CD file (It plunges to the depth that I've set in the file, then lifts to the safe moving height, then starts the cut at the proper place, leaving a hole exactly where I don't want one!) Any ideas on how to stop this?

As a related question, I haven't figured out yet how to get the Bot to just plunge: everything I do requires a path to be drawn, so how do you direct the Bot to move to a specific point and plunge (in CD that is)

Thanks for any suggestions,

Bruce

[artisan]

Bruce....Which version are you using? To create an exact mirror of another piece, use the Duplicate command "Control, D"....then hit the mirror icon on the upper toolbar in most versions. Check size and position in the upper left hand corner of the toolbar.

When you create a duplicate in Corel, it offsets the new piece so you can see it, instead of dropping it directly onto the original. If you have not "Grouped" or "Combined" your original part, you may be offsetting only a piece of your original.

As for setting the beginning point in Corel, the default is in the center of the table. There are multiple discussions on here that you can "search" and determine the best method for yourself. Fear not.....I use Corel ( 3 thru 12) and it is VERY accurate and useful, once you get used to it. I no longer use it for toolpathing however....just designing....D

[fleinbach]

Bruce

After converting to DXF what program did you use to make the SB tool path?

Have you looked at the SB file to see if a line is being added that you don't want causing the plunge?

[bruce]

Thanks for the suggestions. I have irregular internet access, so I can't respond or check as often as I'd like.

I'm using version 12. I'll try making sure that I've "combined" the drawing and then try it out on the Bot. Unfortunately, I live a long way from where I've stored the machine, so it'll take me a few days til I can get out there again. Frank, I'm going directly from dxf to Shopbot (converting the file directly in shopbot: I'm not using an intermediate program to create tool paths) Do you think this might be causing the problem? I have looked at the file, and it begins with the plunge. Funny thing is I haven't tried simply deleting the line. I guess I'm wondering why I'm getting the line in the first place: is it pretty normal to have to clean up or edit files when converting from CD?

Thanks again for the suggestions,

Bruce

[fleinbach]

Bruce

You say you are "going directly from dxf to Shopbot (converting the file directly in shopbot:" Shopbot software only runs the Shopbot itself; it does not create a tool path. Do you mean Part Wizard provided with the Shopbot?

I have not used Corel draw since version 5.0 so I'm not sure if it has anything to do with the problem. But all software is capable of creating a glitch from time to time. Particularly Cad programs. Most problems can be detected by magnifying the problem area as large as possible. Then you can usually see the cause.
As for stray lines in the cut file, I have only ever experienced this twice. I am fairly good at working with cad software and could not find any problems with the dxf file. For me the easiest fix was to remove the stray line from the cut file using the Shopbot file editor.

[mikejohn]

Frank
If you draw the .dxf as the toolpath, then convert it in the Shopbot software to a .sbp file, will this not cut as you want it to?
You want a 3" dia circle, for instance. You draw it 3.25" in diameter to take account of a 1/4" bit. Will this not produce a 3" diameter disc?
.......Mike

[fleinbach]

Mike,

No, the Shopbot software runs the Shopbot it does not make a cut file. Of course there is a routine in the software for simple cuts, ie, circle, rectangle, etc.

To make a cut file for more complex work you need a cam program. Shopbot comes with one called Part Wizard.

[mikejohn]

Frank
Now I'm confused.
In the Shopbot software ShopBot control Console/File/file Conversions, I introduce a .dxf file, and it creates a .sbp file that 'cuts' in simmulation.
I expect to use a CAM program, but isnt the cutting program a .sbp file?
Mike.....

[artisan]

Frank.....there is a DXF converter utility with the Shopbot software that will create a toolpath. You can create a DXF file in Corel (be sure you "convert to curves" first) and then create a cut file without the need for Partswizard at all. I used this exclusively when I first began....

Mike....the .SBP file is your cut file. You can create toolpaths in Partswizard and other CAM products such as Visualmill, Artcam and Millwizard.....and then convert them via a postprocessor to an .SBP file for cutting. Hope this helps....D

[mikejohn]

Thanks Darrell
I was worried I was seeing things!
It seems clear to me you really have to get to grips with the various software.
Luckily, I start with a pretty good understanding of AutoCad, but know nothing about G-code.
Thanks
.....Mike

[fleinbach]

Guys,
I apologize for giving you wrong info. I checked and see there is a way to cut using Shopbot control software. I was so used to using other software for making tool paths I never looked at the conversion feature.

[bruce]

Thanks for the info anyway, Frank. You had me slightly worried for a second, but I wonder if using something like Part Wizard might solve the problem, particularly the "random" plunges I'm getting at the start of the file.

Has anyone else found that using real toolpath software is more predictable than relying on the SBP conversion utility?

Darell, I'll try your "convert to curves" suggestion in case that's the problem. Thanks.

In my first post, I asked as an aside whether or not it was possible to tell the Bot to plunge in a CD drawing: what I mean is, let's say I wanted a 1/4" hole, and I'm using a 1/4" bit, how do I tell the Bot to just drill in and out with no lateral movement? How do I simply place a point in a CD file? Is this a dumb question?


Bruce

[fleinbach]

Bruce,

I think I can answer your question this time from actually having used cut path software including Part Wizard.

I can't answer the one about tool path software verses using a tool path program like Part Wizard, but in Part Wizard as well as Insignia if you want to drill a 1/4" hole there are actually three methods. Circular Vector: Just draw a circle any size. The software will plunge in the center. So you will get a hole the size of the bit you are using. This is the method I use and prefer. The second method All Vector: In this selection holes will be drilled at the centre of a vector irrespective of its shape. The hole will be in the centre of the bounding box that surrounds the shape. The third method is all vector Nodes: Holes will be drilled at each node on a selected vector.

There is one other way to drill holes and that is in the tools menu of the shopbot software. It’s called drill press and will let you drill just one hole anywhere or multiple holes in equal spaced lines.

[bruce]

Thanks, Frank. I hadn't discoverd the drill press yet. That'll do until I get myself a copy of Part Wizard (I bought my machine second hand and didn't get Part Wizard with it).

Bruce

[bruce]

I just thought I'd post an answer to my own question re: plunging. Like most questions, the answer is so simple, I feel stupid not having figured it out sooner, but that's all part of the learning curve!

In CD it is possible and very easy to "draw" a plunge instruction: you just draw a circle and give it a diameter which is less than CD can resolve(.0001"). CD treats it as a point. ShopBot will convert any such points to an MZ instruction with no x or y movement.

As for the random plunges that I was getting at the start of my cutting files: I'm still getting them, and they really are random. I'll cut the same file a dozen times, and sometimes I'll get an uncalled-for plunge at the start of the file, sometimes I won't. I've checked the code (the SB text file) and there is never an unintentional "MZ" at the start of the file, so I don't know where the Bot is getting the instruction to plunge. It's bizarre. I've learned to simply start the bit at some point on the cutting surface where it's OK to have a hole.

Have a great Christmas, everyone.

Bruce