This question has 18 answers and counting. Is there a limit to number of answers.
If not should there be a limit?
If the answers are not quality, they will get down-voted and eventually deleted. Putting a limit will not increase the quality of answers, just make people rush to get their answers in before the limit is reached.
Edited to add that of those 18, 1 has been deleted, two more have delete votes.
The community keeps on top of things, and is quick to remove the trash.
The SE software does not impose a limit on the number of answers a question can have. Either all the answers contribute something, or some of them should be downvoted and possibly removed. The community is responsible for doing this maintenance. Ours does a pretty good job of that, though occasional reminders aren't a bad idea.
The idea of an arbitrary limit, as others have noted, wouldn't have a significant positive impact.
However, it is possible for questions to be 'locked' to prevent additional answers, comments, edits, etc. If this happens, then while the post is locked, no additional answers can be added, so in effect this would 'limit' the number of answers on a question if it were locked for some reason.
For reference, the below excerpts are from the Help Center.
What is a locked post?
A post which is "locked" cannot be modified in any way. Locking prevents...
...voting on the post (including close/reopen votes for questions)
...answering (for questions)
...flagging (though "in need of moderator intervention" flags are still allowed, except in the case of Historical Significance locks - see below)
Posts can be locked either temporarily or permanently, by Moderators.
However, the reasons for locking a post are fairly limited:
When should a post be locked?
As a general rule, temporary locks should be used whenever modifications to a post are causing serious problems on the site. For example:
Extended bickering in comments (but see: a guide to moderating comments)
A controversial post that is under discussion on meta
Permanent locks should almost never be used, with the exception of those imposed by the system itself.
There's no mention here of locking a post because there are a ton of low-quality answers being added, and the others here have touched on a possible reason for that, which is that the community should be able to review, flag, vote on these answers so that they're deleted.
If there were many, many low-quality answers being added to a post, I'd flag for moderator attention, and if it were causing serious problems for some reason, it's possible they could lock the post. However, I don't realistically see a situation where that would occur in comparison to just letting the community moderate the answers.