Yes, you certainly can. You can purchase them at the pressing cost price.
You can "Self purchase" your vinyl records anytime during the funding period. If you already know how many copies you are going to sell at your gigs, it would be best to purchase soon after the project launch. If your project is reaching its end date and still needs a few more pre-orders, you can self purchase the vinyl to make the project succeed.
-How to use "Self Purchase"
After logging in, click on "Management" inside the "For Artist" menu on the upper right hand corner of the screen. From there, you should be able to see all of your projects, and by clicking on one of them you can see the detailed menu with the "Self Purchase" option.