DDSCV1.1 3 and 4 axis offline motion controller

[magicniner]

Unfortunately DIY cnc machine will be always one step behind due to the lack of absolute encoders or scales that at all time tell the machine the exact position, even if power switched off.

That statement is true but is not relevant.

Having your bed as machine Z zero and using a work offset is no more complex than having your bed as work zero and setting the bottom of your stock as your Z zero in CAM, it doesn't require any fancy encoders or switches, it does require a little planning, but no more so than using a bottom of stock zero in CAM.

Having your bed as machine Z zero and using a work offset does have the considerable advantage that if machining or engraving a series of features in a surface you can do this on a variety of thicknesses of stock without having to refer to CAM to see what stock thickness you had set and then calculating a compensating offset ;-)

- Nick

[John S]

Dangerous to use the bed as work zero.

What happens if your machine decides to go to Z 0 without switching the tool offset off ?

Bang cutter all the way though the work.

If the top of the work is Z0.0 then all cutting moves are negative, any positive Z moves are safe.

[Boyan Silyavski]

We are talking different machines here. Who uses tool offsets on non repeatable tool holder, like ER20 on a Chinese spindle????? Me not.

You are talking about mills and i am talking about routers.

In reality i use the work offset that suits me better for each separate job and have the good custom to mark that in my file name. like xxxxx 0vacfixt or xxxx0bed or 0top. I would have told that from the beginning but was just making a point here.

its obvious that i don't work in machine coordinates and use different coordinate systems G54 to G59. What i was saying above is that there is no point making fixtures and each fixture to have a predefined work offset, cause the machine anyway will not find properly the 0 just from homing without manually finding the zero.

or am i not explaining what i want to say?

Let's say it in another way. I use nothing complicated but every separate job i find the zero again and again not only in Z but X and Y also. All else is time wasting time on a DIY machine that every time runs totally different job

[Ger21]

To rely on working offsets on a machine equipped with cheap chinese limit switches is ridiculous.

I use DIY hall effect switches, which are supposedly accurate to .01mm or better. There's a thread on CNC Zone where the designer showed his testing for accuracy. Cost about $15 to make.

I've resumed jobs many times after homing, with no issues at all.

[magicniner]

Who uses tool offsets on non repeatable tool holder, like ER20 on a Chinese spindle?

It's not Rocket Science! All you need to do is bond collars onto your tools to set their insertion depth into the collet and your tool height will be repeatable in a correctly torqued ER collet chuck ;-)

- Nick

[John S]

We are talking different machines here. Who uses tool offsets on non repeatable tool holder, like ER20 on a Chinese spindle????? Me not.

I do all the while and also teach it other wise if the tool is set to zero it drags it across the top of the work between moves.

It's very simple to follow a set of standard directions when cutting to protect the work, cutter and operator.

CNC isn't new, what is new is everyone thinking their way is better when it isn't.

[Boyan Silyavski]

I can not waste my time to argue with you guys, plus may be you are professional machinists and teachers and i learned about CNC a couple of years ago. Some of it from you. if you say its right for you, ok. If you say all the world does it that way, i agree and would not argue. My mistake then.


But i couldn't care less for all that. I am having a strong opinion what is good for me, what saves me time and how jobs should be run in my home workshop. I have extremely flexible and open mind plus a good memory. I use whatever technique for the moment that best suits me. As i said i mostly use material top as Z0 but sometimes not. So if i hit go to Zero and tool digs in material, bad for me, but it does not happen, because when i program Z0 to be worktable, i program save Z movement higher than material+bit and usually XY0 is material corner not center, so that have never happened. Anyway, machines are not to sleep at, and one should be very awake when working. When i am tired or not in a good shape, i don't use machines


I have tried to use collars as the Kyocera engraving tools come with collars. They are not precise neither repeatable to my liking. So from that time on i dont care for collars. Its faster not to use that way of thinking,.

Another good reason not to use tool offsets and premeasure tools. I have a small case of tools which in total are around 1500euro worth. They basically just cover my pretty basic needs. i don't have 10 000 to spare on tooling. Many times i use the same tool for various jobs, materials plus even for various type of toolpaths on same job. Which means every time i recalculate toolpaths as needed. Which means every different time i insert the tool into the collet just enough for the job. I dont see the reason to have the same stickout just the tool to be repeatable, to make the work offset and so on.

And yes Dean, i use work offsets and i know what they are. I think you should have guessed when i am saying something is not working i am talking about after power loss. I will demonstrate the switch imprecision with video. Hysteresis. That's what i am talking about. But good for you that your switches are working right. What i have discovered is that all depends how you read the switch, from the moment that gets off or from the moment that gets on again. There is difference between both cases. So i found that when i read in forums and people said there:"use simple on /off switches" and i thought " well that's too simple, sensors must be better" i was wrong. Simple switches work better.


So let me again explain the simplest way to Z0 and use the probe with the DDCS controller:

1.put any flat bottom tool in collet and tighten by hand, not by wrench
2.lower Z axis until the bit touches the work table, then move z down 1-2mm so tool moves inside collet up. Stop.
3.hit preprogrammed button to 0XYZ or just use controller and zero Z
4.lift Z axis
5.put probe on table and hit A for probing operation / + is connected to probe -to spindle or machine/, probe has insulator at the bottom
6.probe is touched and probe thickness is rcorded
7.now you can use the probe whenever you like, top or bottom or whatever, cause thickness is recorded

-hit Zero all button again and all of the above is lost. So don't do that or just have it in mind


That's all. So simple. i take back my words and edited the post where i explained the 2 touch probes scenario, as i just found that i was mistaken and in certain cases this will lead to error. I deleted it so nobody makes the mistake . So just use the above said or the below variation, which i find better, but you need a Z setting gauge.

variation of the above using Zero axis setter with known length and DTI:

2. lower until bit touches zero axis setter and all is zero there.
3. if Z axis setter tool is 50mm high/the typical one/ , hit Z0 and enter 50mm, hit enter. Now machine knows its worktable zero


SB shared that video with me in a message, so thanks! I decided to share here. Don't ask me how is done, i know nothing more but will write or call the guys to see if they share.They are Russians or Ukrainians: