Reply with QuoteYou can home the machine wherever you want. Home position has nothing to do with the coordinates or coordinate system. It's just where the location of your home switches are.
I'd home it where it's as out of the way as possibly for loading parts.
moving table setup etc
I'm building a cnc for making pcb's the gantry does not move and has the X and Z axis. The Table moves in the Y direction....
I perplexed as to where should I home the machine....
X-left Z-top Y back of machine
X-right Z-top Y front of machine
X-left Z-top Y front of machine
X-right Z-top Y back of machine.......
It appears to me that the Y movement will be totally reversed from what a moving gantry would be, I feel like a deer in the headlights....
Can anybody explain to me where to assign the home, and ho to set up the gcode on this confusing frankenstien cnc I built...
The table is 7" [Y] by 9" [X] and gantry is in the middle so that the full 7 inch Y travel can be used....
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Re: moving table setup etc
You can home the machine wherever you want. Home position has nothing to do with the coordinates or coordinate system. It's just where the location of your home switches are.
I'd home it where it's as out of the way as possibly for loading parts.
Gerry
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Re: moving table setup etc
Ok , but then what must I do to get the gcode to work properly/
Re: moving table setup etc
Hi, just an observation as to the position of the gantry (uprights) ...."in the middle to give full table travel".....the full table travel will be dictated by the stick out of the spindle centre away from the face of the X axis rails.
In most moving table CNC routers the uprights are placed well to the back to allow for the saddle and spindle stick out from the face of the X axis.......usually the bed is twice the length of the table to allow for full travel.......this means the uprights will be placed more to the back.....not in the middle
It's possible,......I'm only guessing that, as I'm into mills not routers...... that with clockwise rotation the table ball screw has a right hand thread when the table is the moving part, and the ball screw thread is left hand when the gantry is the moving part........that's would have to be a construction factor so the tool path in Mach 3 will move in the correct direction for the same program for all machines etc etc.
That is an interesting factor........do mills and moving table routers all have clockwise rotation with right hand ball screws on the Y axis and moving gantry routers all have left hand ball screws?
The same applies to the X axis on mills and routers......with clockwise rotation a right hand ball screw thread on a mill table will move the table from right to left, which is a virtual spindle or tool path moving to the right side move.
A router, with moving gantry or moving table therefore, with clockwise rotation would need a left hand ball screw on the X axis to move the spindle to the right hand side so that the program can do the correct spindle or tool path move irrespective of which machine the program is being run on.
Ian..
Last edited by handlewanker; 03-09-2017 at 11:52 PM.
Re: moving table setup etc
I use the top right corner, as I am facing the spindle, as the home and normal 0,0 position of my moving table machine. From there, all of the moves are -X and -Y. I can also set 0,0 at any position on the table or part. You just need to orient the part and set 0,0 in your CAM program to match the table orientation and where you want to set the part on the table.
The home position could be anywhere, don't confuse the home position with the part 0,0 position, they don't have to be the same. On my machine, I actually rapid the table to the Y - 96'' position to load and unload, but this is just due to the layout of my shop and I can back my truck up to the machine to slide sheets onto the table from the bed.
Re: moving table setup etc
Does it really make a difference? I mean, if the screw rotates in the "wrong" direction, you can just swap the motor phases or, even easier, change polarity for the DIR signal to get the desired moving direction. Also, which way the table or any other part of the machine moves is also depending on where the motors are placed, not just if one is using left or right thread screws. The same screw gives opposite moving direction if the motor is placed on the left or right side, front or back of the machine, or facing up or down. BTW, I had no idea that you can buy left/right threaded ball screws/nuts. Didn't even look for them or thought about it as an issue when I bough mine... but I guess it is a non-issue.Originally Posted by handlewanker
Last edited by A_Camera; 03-10-2017 at 04:50 AM.
https://www.youtube.com/c/AdaptingCamera/videos
https://adapting-camera.blogspot.com
Re: moving table setup etc
I have made a machine similar to yours though mine is a bit bigger, so here is my experience:
Below is a quick drawing of the principle.
The home position is actually totally unimportant in my opinion. Every time you make a PCB you must set up the X and Y zero somewhere where the PCB is, not outside the PCB area, and the Z must be set so that you have Z zero at the top of the PCB, not the table. That is I think the easiest and simplest way of making things. Personally I don't care about home or soft limits. On small machines you can easily change tools regardless where the spindle is, so there is no need to home. The only good reason to have a home is to be able to restart a job without the need of setting up the zeros again after a machine crash into the limits, or some other hard stop, like power failure or contact loss with the PC. For me, those are non-issues, so I don't care about that. My table zero is the left corner, like marked in the drawing. What is important is that the spindle center can reach a bit outside the table because basically that is what limits your work area. You must place the gantry with that in mind, otherwise you will limit the work envelop. In my case, the gantry is about 1/3 from the end, not in the middle, because you must also handle the Z and take care of the hang out, the whole Z plus the spindle holder.
When planning the needed floor space for a given work area, you must also consider the need of vacuum cleaner attachment, the dust shoe. Remember that PCB is fibre glass and PCB making is generating a lot of fine dust which is very hazardous, so it is a good idea to plan for that in advance. This increases the need for total move allowed for the Z.
Another thing regarding Z is that you must consider maximum clearance based on the fixtures and tools you plan to use. For PCB, this may not be a critical factor, but as soon as you want to use a vice or some screws, or work on something other than PCB, the needed height clearance increases very fast. In my opinion, less than 5" Z clearance is not a good idea at all. My first CNC had about 2.7" and I quickly realized that it is seriously limiting my use of the machine. Currently I have 5.3" and that is good enough for now for my needs.
The last point is that in my opinion a cover around the machine is important. It provides personal protection when you break a mill bit which comes at you like a projectile and can cause injury if it hits you. It also provides protection of the environment around the machine, keeping much of the dust and chip particles inside the machine. I have also protection for my table ball screw and horizontal linear guides. This way they can be kept clean even if I don't use the dust shoe.
Good luck with your plans and project.
https://www.youtube.com/c/AdaptingCamera/videos
https://adapting-camera.blogspot.com
Re: moving table setup etc
That depends on how you generate the G code and which software you are using. What I do when I am making PCB is that I set X and Y zero to one corner, most often the left bottom corner, of the PCB. The G-code I use uses the same position as X and Y zero reference. Z zero is set to the top of the PCB and Z movements are negative.
Here is a short blog post with some pictures about a PCB I made and how I am using my CNC for the job:
https://adapting-camera.blogspot.se/...d-diy-cnc.html
Note that X and Y zero for this PCB was the top left corner of the PCB, but that was the way it was fixed to the table and the G code was generated with that in mind.
Here is another post, with a video which shows the actual making of a PCB.
https://adapting-camera.blogspot.se/...stretcher.html
Have a look and see if you find the information informative or want to know more.
https://www.youtube.com/c/AdaptingCamera/videos
https://adapting-camera.blogspot.com
Re: moving table setup etc
Thanks all
I guess I just need to try several gcode files and determine what works for me.
I'm using GRBl 1.1F and finding that sever GUI's fail to display DRO's , ie ugs 1.0.9 , the last nightly build displays ok along with ugs platform.
I think I might prefer OpenCNCpilot , but its not working with v1.1F
Chilipeppr/grbl fails Chilipeppr/jpadie works , I think the CUI is quite cluttered and lacks some Buttons I prefer.
My gantry can be moved, if needed, no big problem, It needs to be trued any way, my table is 2mm corner to corner diff...
Unit is made from well seasoned hardwood, hopfully I can us 1/4 router bit in my 400 watt spindle to true the table
