Problems with importing DXF into OBcam

Total noob here, so please bear with me.
I recently built a workbee 1050 with black box for use with a hypertherm 45xp plasma cutter for cutting small parts for my hobby shop.
Both the workbee and plasma cutter seem to work perfectly from an accuracy and control standpoint when I import drawings from the openbuilds sample library.
I was planning to use Fusion 360 to generate drawings for the parts I need, and for the time being, at least, export those drawings into the ob cam to generate the Gcode to send to OB control, because I know those last two steps work perfectly.
I have run into a problem importing the DXF file from Fusion 360. When the document shows up in the OB cam, it is always inverted, and in the negative x and y coordinates compared to where it was in Fusion. When I go to move it to the positive quadrant in cam, it gets highly distorted,rendering it permanently unusable. Following through any relative strings in the CAM forum, I have found that the solution to this recurring problem seems to be:
A) ensure you export as a DXF r14 file .
B) explode your splines into poly lines
C) export your DXF from fusion 360 into something like Librecad then export it to OB cam in the correct DXF format.

However for solutions A I don’t have a clue how to achieve this in Fusion 360. For Solution B , I don’t even know what a spline or polyline is, let alone know how to convert one to another. As a side note, I have also noticed that I have no ability to view the 3D capability in ob cam using windows pc, but I have observed 3D view when viewing using iPad. Any help on this would be greatly appreciated, before I resort to trying yet another software.( solution c)0

 

I agree that Fusion 360 seems way overkill for the simple drawings I need to produce, so I’ll probably go that route with 2d software. Just a bit frustrating to have learned how to navigate, create sketches, bodies and projections, and then be stymied by not being able to create the right version of DXF to fit OB cam .

 

I’d really like to hear from someone that produces DXF’s for plasma in Fusion360 and then successfully imports those DXF’s into OB cam without problems.
This doesn’t seem like it should be a unique workflow, given that all this software is free and well known!

 

Again, total noob here, I did follow the steps and successfully loaded the ob post processor into fusion, but I really got bogged down when I discovered I would have to edit the post processor in order to accommodate the floating head and touch off sequence in my plasma cutter. I don’t know how to do that, so I thought I’d just go the easy way and use the OB cam which creates the Gcode and runs my plasma cutter perfectly( if its got a good DXF to start with).

 

Ok, great. But please be aware... You asking me how I’d like the Fusion post to work is like me asking my dog how he wants his dinner bone prepared.

Here goes:
The build is just a Workbee 1050 ( the smallest one) with black box which was purchased just a couple of months ago so I’m assuming the firmware is right up to date. I have limit switches installed on xo yo and z120. I also have another limit switch installed on the z axis for probing to the top of the work. For tool initialization I select “ turn plasma on and off (M3/M5).
I use a home built plasma torch floating head carrier that is spring loaded such that when the g38.2 probe z zero is performed, the axis slowly dives down until the tip of the torch contacts the work surface and starts to compress the spring moving the carrier up on the z cbeam. When it has compressed the spring and moved up exactly 5mm, the probe z limit switch is activated. My understanding is that at this point the z zero is marked because that is what happens for someone using the z probe.
In my case, because the true work surface is 5mm above this newly marked zero, I pad all my height inputs to OB cam (Cut height, pierce height and safe height) by the 5mm switch offset. I don’t know if this is the best way to do it, but seems to work great for me. Off course, I need to repeat this process at every new pierce cycle. I also need a way to input a G4 pierce delay of 0.5 s ( but should be configurable by material thickness ,just like the heights) at the beginning of every cut as well.
Having messed about a little in in Fusion cam, I got really confused in setting up the correct heights. I think for plasma cutting, this should be much simpler than the general case, but my floating head arrangement seriously kerfubbles this in my ordinary head.

thanks again for your help in this!

 

Sorry if sounded a bit flippant. The OBcam processes a DXF perfectly for my use. The only thing i have to do to account for the z probe switch offset is fudge all three heights by adding the 5mm. I use Peter's touch off sequence, etc exactly as written.

The existing Fusion 360 post for Blackbox will produce a GCODE for me, but the heights are all screwed up. I dont really understand what the three different configurable heights in fusion cam are supposed to be representing, and when I throw my z axis probe offset in there, it really makes it worse.

what i need the gcode to do is move to the beginning of the first cut, probe z to sense the position of the work top, mark that as z zero ,move to a peirce height (which is 250% the cut height above the work top) , then start M3 the plasma, then pause for 0.5 seconds ( to peirce) , then move to nomal cut height, then follow the cut line. At the end of each cut, it should m5 the plasma arc, move to a safe height , rapid to the next cut location, and then repeat the process for the next cut.

 

I just decided to try out qcad for generating my part drawings and creating DXF files. I was happy to see that qcad gives you a great variety of DXF file types to save in, including dxf R14 format.
I was really disappointed however, when I loaded that dxfr14 file into OB cam and I STILL get the same issues as the DXF from Fusion....just like above, the part shows up inverted, in the negative x and negative y quadrant, and when I try to move it into the correct location it becomes permanently distorted.

 

Ran it again, and this time it came into the correct position, and it was moveable, but all the arcs are partially missing.
I tried to explode arcs to polylines?..., but it wasn't really easy to find that in qcam, and I'm not sure it worked, or if it did any good.

 

Thanks Peter!.. I was trying to use "modify" rather than "draw" to get those arcs converted to polylines, and I guess it only worked in a few places.
I have to be honest....I like using the Fusion 360 CAD better than QCAD as it just feels more structured, and so I would still like to use the Fusion CAM like you suggested earlier. I have been able to use the Fusion360/openbuilds post processor to get the CAM to make GCODE that will work on black box, but of course there is no provisions for the floating head and touch off. Do you know if there is a good tutorial somewhere about how to edit post processors to accomodate special requirements like that? Or is there a way to use the macro in OBcontrol so that i can easily add it every time to every plasma job I do?

 

Hi David
Thanks so much for this.
Unfortunately i had to leave my machine for a few weeks so I wont be able to test this until end of February.
I was however, able, to get the GCODE to load properly in OB control and the simulation looks great.!

 

I finally got back to my workbee this week and had a chance to test the new Fusion 360 post processor for plasma cutting.
It loaded easily into OB control and looked fine in simulation there.
First few times I ran it, it failed at the very first move, and I eventually traced the problem back to the G53 command that moves the head to a safe height before doing the first touch off. It seems like my workbee wasn't able to get the head to the clearance height without triggering the probe limit switch when it was in the G53(machine coordinates). I think this is because the way I'm set up, my machine z zero position is actually about 40mm below the piece of metal I am cutting. I dont know of a way of resetting the zero and span on the machine coordinate system,. I think this would be the right way to correct this problem, but since i didnt know how, i just edited the Gcode file to eliminate the G53 code so that the the safe position goes to z15 in G54 mode (work coordinates) and the gcode runs perfectly! Many thanks to David the Swarfer for getting this new version done!!

 

Hi David,
I do have a z homing switch set up near the extreme postive z position. I also have a pseudo z zero switch mounted in the floating head assembly but it really can only be used to determine the top of the work'
I guess I have always assumed that the machine zero was calculated by using the z homing position switch as the top of the range (120 mm ) as specified in the OB GRBL setup default for the z travel on a workbee 1050. Perhaps I should modify this value to be 60mm to more closely approximate my machine with the 2" plasma support base in place.

 

i think Im missing something here... My (pseudo) z zero switch IS wired to the the probe input...that is how I'm doing the touch off with the floating head. My problem here is I dont know where my G53 machine coordinates offets are, and I dont know how to reset them or display them on OB control. David the Swarfer said that that I could reset my Machine Coordinate home position (X0,Y0,Zmax) by manually jogging the machine to the machine Home and then resetting the black box. ( I assume with the little black button on top) That makes sense, but how does OB Control now set the upper limits of the Machine coordinates X,Y and the ZERO location for Z? I've *** u me'd that it does this by referencing the default distance ranges that are input to GRBL settings in OBcontrol......DO i have to physically measure these, and then go in to GRBL settings and edit them? ( doesn't seem like that would be very accurate).

If this is the case, it seems like I missed this setting of Machine coordinates step when I first set up my workbee.

 

I still dont understand why the post processor produces the line "G53 G0 Z15"
When I home my machine it goes to the highest z position and the lowest x and y positions...this is the bottom left corner of my table but with the z in highest position. in this position all three switches are contacted.
GRBL marks this as x = -280 y=-700 and z =0. This means that machine xyz zero is actually in the extreme top right position of the table with z fully raised. This also means that every possible and achievable position is negative using the machine coordinate system. Therefore when the G53 G0 Z15 command is given, the machine tries to get the z position 15mm above the top of its travel, and it goes into alarm state as it hits the soft and hard alarm before getting there.
i think the G53 z15 command is just to ensure the head doesnt bang into something when its current location is not known, but i think it should be a G53 z-15 command instead no?