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chuckt
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New here. Not sure where to post this question.

Post by chuckt » Fri Sep 06, 2019 12:16 am

I am using QCAD/CAM V3.23 on Ubuntu 18.4LTS and I have a converted mini mill that I am trying to get working. My controller is Masso V3.42. The Z home (Z=0) is "up", X home is with the bed to the left, and the Y home is with the bed closest to me. All measurements are in inches.

My problem is that Z steps in the wrong direction. I have not been able to find a setting for that. I must be missing something simple.

I set the work coordinates to 0 at the top end of the work piece. The safe zone is -1 and the work final depth is 0.2. When I run the job, the depth steps from 0.2 to zero, instead of the other way around. I have tried all of the post processors and I get the same thing, more or less. I have not seen any setting to change that.

{edit}
I added debug spew from the command line.

{edit}
Shouldn't negative cut depth values be allowed? No gcode is produced from any post processor when the cut depth is negative. The spew file attached shows the difference. There is no real error message, but when the cut depth is negative, the spew is much shorter. :D
Attachments
debug.txt
Debug spew from command line
(6.7 KiB) Downloaded 428 times
fip1.dxf
(120.66 KiB) Downloaded 438 times

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Husky
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Re: New here. Not sure where to post this question.

Post by Husky » Fri Sep 06, 2019 6:05 am

Hi,
chuckt wrote:
Fri Sep 06, 2019 12:16 am
My problem is that Z steps in the wrong direction.
Your "Safety Ievels in "CAM Configuration" and "Profile Toolpath" are negative. That should be positive.

Maybe this will help to find the appropriated settings :wink:
https://qcad.org/en/tutorial-qcad-cam
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andrew
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Re: New here. Not sure where to post this question.

Post by andrew » Fri Sep 06, 2019 7:46 am

chuckt wrote:
Fri Sep 06, 2019 12:16 am
Shouldn't negative cut depth values be allowed?
No, the cut depth is an amount (a distance).

CVH
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Re: New here. Not sure where to post this question.

Post by CVH » Fri Sep 06, 2019 8:49 am

chuckt,
imho this is not Qcad/cam related but has to do with your setup.
chuckt wrote:
Fri Sep 06, 2019 12:16 am
The Z home (Z=0) is "up", X home is with the bed to the left, and the Y home is with the bed closest to me.
Nothing wrong with that. these are homing coordinates in machine values.
Usually these have nothing to do with the actual work coordinates.
In most drivers you can set the value you want to use when homed.
My moving bed engraver 'homes' the same as yours: high, left, back (bed to me).
I have a low bridge, 80mm high, about 67mm travel.
I'am homing high as this is obvious the safest way.
Once homed high my mach position is set to 65mm.
The end of my Z down is mach 0.00.
Can't go lower and I have a travel reserve of just about 1mm.
Same for Y: homed with the bed closest to me my machY is set to 750mm.
So zero is in the front.
Once homend my setup has no negative values in machine coordinates.
Much more handier working in an all positive cartesian quadrant.
For humans that is.

Once homed you still have to zero the work coordinates on your piece.
Where you put your zero is at your own discretion.
Mostly this will dictated by on where you put the origin for the Gcode.
On flatbeds it is common to set the Z zero on the top of the material.
Just not cutting.
Minus 0.10 is then the same as cutting 0.10 deep.
On mills this can also be the bottom of your piece.
!Minus 1.00! is in your case the same as cutting an inch deep into your vise or table.
chuckt wrote:
Fri Sep 06, 2019 12:16 am
My problem is that Z steps in the wrong direction. I have not been able to find a setting for that. I must be missing something simple.
Thats your problem, going from Z5 to Z0 or from Z0 to negative should be going down.
(in rare cases an inverse setup might be nececary)
Going down, left or far (the bed) should be moving negative.
Negate your drivers steps/units, steps/turn or swap the two wires of one pair of your stepper.
Or just any two in a three fase system.

I've learned that being contrary to what is usually common is the hard way.
Eventually you will follow the pack.

Kind regards,
CVH

CVH
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Re: New here. Not sure where to post this question.

Post by CVH » Fri Sep 06, 2019 8:55 am

PS: also negate homing direction or speed if you don't swap wires

chuckt
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Re: New here. Not sure where to post this question.

Post by chuckt » Fri Sep 06, 2019 1:27 pm

As you have seen, I am very new at this. I don't have a machinist background at all. I can do a credible job on some things, but I have zero training.
CVH wrote:
Fri Sep 06, 2019 8:49 am
Thats your problem, going from Z5 to Z0 or from Z0 to negative should be going down.
(in rare cases an inverse setup might be nececary)
Going down, left or far (the bed) should be moving negative.
Negate your drivers steps/units, steps/turn or swap the two wires of one pair of your stepper.
Or just any two in a three fase system.
I am going to see about making the zero position near the table and home whatever it is at the top. I am sure I can use the controller to reverse the direction. So, what would be a normal configuration? Would zero be the top of the vise? The bed? With a tool? Without? The controller will not drive it past machine zero, but it seems unsafe to set it at the maximum travel. (i.e. touch off the bed)
CVH wrote:
Fri Sep 06, 2019 8:49 am
I've learned that being contrary to what is usually common is the hard way.
Eventually you will follow the pack.
One of the problems I am fighting is my lack of experience with all of this. I recognize the need to set up the machine "properly" but I don't really have a clear idea of what that means. :) When you don't know very much, it's hard to know what you don't know. You know? Any advise is appreciated. :)

All the best,
-=chuckt=-
All the best!
Chuck Tilbury
http:/whistlemaker.com

CVH
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Re: New here. Not sure where to post this question.

Post by CVH » Fri Sep 06, 2019 2:07 pm

As specific help is a bit off-topic.
You may send me a private message with your F1 setup screen grab.
Add a photo off your setup with X+ Y+ Z+ directions and home sensor positions.

Regards,

chuckt
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Re: New here. Not sure where to post this question.

Post by chuckt » Fri Sep 06, 2019 3:52 pm

CVH wrote:
Fri Sep 06, 2019 2:07 pm
Add a photo off your setup with X+ Y+ Z+ directions and home sensor positions.
Will do....

I have changed the Z homing such that the home position is 9.5" and the zero is at the bed. After several air runs, I think that fixes my immediate problems. I can run the job, then home, then run the job again to make sure that I am not missing steps or something.

The next thing is to come up with a post processor. I am using the "G-Code (offset) (in)" and that seems to produce usable results. I would like for it to go back to zero when the job finishes so I can take the part out of the vise (more easily). I don't have a tool changer so specifying the tool in the gcode is a little redundant. Masso does not support G41/G42. I am learning a lot.

All the best,
-=chuckt=-
All the best!
Chuck Tilbury
http:/whistlemaker.com

CVH
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Re: New here. Not sure where to post this question.

Post by CVH » Fri Sep 06, 2019 4:28 pm

I would like for it to go back to zero when the job finishes.

I'am not using Qcam so I can't help with that.
Introduce a G0 Z-'high' at the end of the Gcode.

What I have is a Park Spot.
Set at 5mm from the home sensor.
I can park high and I can park global.
At job end I'll park high. one click.
Before switching of the machine I allways park it global. one click.
That saves a lot of time in the homing sequence at startup.

Regards
CVH

chuckt
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Re: New here. Not sure where to post this question.

Post by chuckt » Fri Sep 06, 2019 4:46 pm

CVH wrote:
Fri Sep 06, 2019 4:28 pm
What I have is a Park Spot.
Great idea! I can do that without writing any code. Thanks!
All the best!
Chuck Tilbury
http:/whistlemaker.com

CVH
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Re: New here. Not sure where to post this question.

Post by CVH » Fri Sep 06, 2019 5:49 pm

chuckt wrote:
Fri Sep 06, 2019 3:52 pm
I can run the job, then home, then run the job again to make sure that I am not missing steps or something.
For a dry run and configuring your accelerations, yes.
For production this is not the way to go.

If you have a high accuracy home sensor with a high repeatability, yes.
If you can fit another piece with extreme repeatability, yes.
But no, it is easier and better to re-zero on the next piece.
In my case I am speaking of a repeatability of better then 0.002mm.
The last engraving point I used had a cutting flat of less then 0.08mm.

Steploss may occurs at collisions and by too high accelerations.
Your car can't make a short U-turn at 90miles/hr neither can your setup.
The actual FEED is usually less of an issue. It's the time to speed up or speed down.
Remark that with µstepping a small step-loss is coming from the sensor repeatability.
When you loose real physical stepper steps (µsteps/turn/200) then your accelerations are to high.
Remember mother earth induce an acceleration of 1G downwards.
Going up is harder then going down.

I wasn't correct.
I park, home and park again.
So I can see if I've lost real steps at the end of the day.
Only to tune the acceleration if any.
In the meanwhile it did not matter because I re-zero.

Lets close this off-topic branch.
There are lots of CNC forums out there.
Regards,
CVH

chuckt
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Re: New here. Not sure where to post this question.

Post by chuckt » Fri Sep 06, 2019 6:05 pm

Thanks, man. I appreciate it.
All the best!
Chuck Tilbury
http:/whistlemaker.com

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Husky
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Re: New here. Not sure where to post this question.

Post by Husky » Fri Sep 06, 2019 6:25 pm

@chuckt
chuckt wrote:
Fri Sep 06, 2019 3:52 pm
I have changed the Z homing such that the home position is 9.5" and the zero is at the bed. After several air runs, I think that fixes my immediate problems. I can run the job, then home, then run the job again to make sure that I am not missing steps or something.
With an "air run" you will only recognize if you loose a lot of steps - you can't see if you only loose a few steps what could result in an ellipse shape instead of a circle shape etc. Use for testing styrofoam as a workpiece what takes out a lot of the guesswork. It is cheap and gentle to your milling cutter ...
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If a thread is considered as "solved" please change the title of the first post to "[solved] Title..."

chuckt
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Joined: Thu Sep 05, 2019 11:41 pm
Location: Poteau, Oklahoma

Re: New here. Not sure where to post this question.

Post by chuckt » Fri Sep 06, 2019 6:38 pm

I have been doing a lot of testing. An "air run" is just the start. My machine is just a mini-mill, so it's not very stiff or accurate to begin with. I am good if I can get 0.001" repeatability. I am mainly cutting holes in thin aluminum tube, so I have been doing repeat runs on some PVC scrap I have. Changing the Z axis really fixed the gross issues. I am still trying to see what the mill will and will not do. I had to dial the feeds down a lot and make the depth of each pass a lot less to get a clean cut. It sure beats making those rectangular holes on a manual mill. :) I think I am getting close to getting things nailed down.
All the best!
Chuck Tilbury
http:/whistlemaker.com

CVH
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Re: New here. Not sure where to post this question.

Post by CVH » Mon Sep 09, 2019 9:50 am

Still off-topic
Husky wrote:
Fri Sep 06, 2019 6:25 pm
Use for testing styrofoam as a workpiece what takes out a lot of the guesswork. It is cheap and gentle to your milling cutter ...
Is indeed a good way to start but keep your SPEED down or you will be melting instead of milling.

If a circle turns out to be an oval, a square, a rectangle, then your axes are not calibrated uniformly.
If a squared object turns out to be a parallelogram then your setup is not squared out correctly.
If you loose steps by the continous changes in accelerations in a circle you will not get a proper closed form.

And if you really put the dots on the i, there is no such thing as a circle in CNC.
Only if your driver is able to parse an infinite amount of new speeds per second a circle will be round.
In real life it will be nearly a circle.

Regards,
CVH

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