What are the consequences if I cut ties with my former PhD supervisor? Background

I did my Master's and PhD with my former PhD advisor in an Australian university. Coming from the experimental biology background, my advisor switched to the field of bioinformatics around the time when I started my Master's.

For my Master's project, I mainly used Graphic User Interface (GUI)-based programs and platforms such as Galaxy. During my Master's I started learning several computer languages without any support from my advisor. After six month into my PhD program, my advisor decided the whole lab would focus on a newly emerged sub-field which relies heavily on command-line-executed programs for data analysis. I have successfully completed a couple of projects and graduated by a series of publications last year and my degree was conferred in Nov 2018. 

My former advisor was not the most knowledgeable person in programming language and statistics.  Likewise, my fellow students in the lab all had the same level of statistical and programming proficiency. As a result, I had to provide support to each single fellow student from data downloading to differential testing and many micro tasks in-between, even after my graduation in Nov last year. I've shared online resources on programming and basic statistics with the lab, however there was little improvement or progress. Six months after my official graduation, I find myself answering emails from fellow students and former advisor on a weekly basis, sometimes ten emails a week; many times I had to rerun their analysis or debug their codes, a good amount of my time went to my former lab. Lately my former advisor even introduced to me via email a new honours (an undergraduate-level research year) student who has just started this year, hoping I could teach the student to generate a specific type of plot for their honours project. Either teaching the student via email or generate the plot by myself will be very time-consuming as the program has a steep learning curve and requires a lot of pre-process of input data, all for a non-essential plot for an undergraduate level thesis. 

Reasons that cutting tiers with my former advisor seems inevitable:

I can't see an end to my current situation as a free labour for my former lab. The more support I offered, the more demanding they become. I've decided to stop replying to the students' emails altogether. However, very likely my former advisor will eventually step in since I am the only person they know who could solve their problems, but I am unwilling to do any more work for them. They have no funding currently so hiring a post-doc or a bioinformatician is out of question. That being said, I don't think the burden is on me. Frankly, having been exploited by them (Should I decline unrelated work assigned by PhD advisor?), I am not particularly grateful to my former advisor and just want to stay away from them.

Questions:

1) Am I obligated to teach other students even I have developed the necessary skills by myself without my advisor's support and that I have graduated almost six months ago?

2) What are the consequences if I choose to cut ties entirely with my former advisor?

I plan to work as a freelance bioinformatician therefore their recommendation letters don't really matter right now. If I want to go back to academia later, I figured the price I have to pay (in labour) will be overly high anyway so I will probably try applying jobs without their recommendation letter.

Any advice would be greatly appreciated.
ad 1) Once you have graduated and you are not employed in the lab anymore nobody can force you to do work.

That being said there are a few options for you that might be interesting (but it depends what you actually want):


If you are interested in a publication record then agree with your
former PhD supervisor that you co-author all papers you gave support
for (even if it was only an email or two).
If you are interested in    the financial aspects then write him a
friendly email saying that you    would be happy to further help if
you are being employed an paid by    him (e.g. on an hourly basis using standard market freelancer rates).


ad 2) He will not be happy (but this is not your problem). If you do not plan any further academic career there shouldn't be any real consequence. If you plan an academic career then (1) see the first point above (2) he might be on certain panels about funding/positions etc (3) he might be reviewer (4) he might have friends in points 2 and 3. But if you do not plan to continue in academia then these points do not matter to you.

In any case I would recommend not to just stop answering but write him a clear email with whatever decision you make (and then stop answering if you want).