Dachsunds love to burrow as well as many of the smaller breeds. My project cost less than 20 dollars and allows you to use it on just the floor or with an existing pet bed.
Using a 1x6 piece of wood, drill a 1/4inch hole about 1.5 inches in from the corners. Your wood should be the same width of their pet bed if you're using an existing one. Because the pet bed is soft, the vertical part of the threaded rod frame will recess itself into the bed and serve to keep it in place.
I wanted the opening of our bed to be recessed from the front of their bed so I bent mine in an offset. If you're not concerned with that then your project is more simple because you just have to bend an arch. Having said, bend the 1/4: threaded rod as shown in the photos and cut off the remainder after you've settled on the width and length of the arch you're making. I had the part that goes through the wood about 2" long giving me enough room to have a nut on the top and bottom of the wood to hold it in place. The height of the arch I formed was about 12" above what the upper level of the pet bed is.
I used an existing inexpensive blanket and folded it over on the edge and punched a hole through the combined layers the entire length of the edge. Be Careful!
Now the fun part-----beginning with one end of the threaded rod, thread the blanket onto the rod. Because of the threads, you'll find the material wants to "catch" a little so you just have to be patient and thread a few at a time and scoot and scrunch as you go.
Screw a 1/4" nut onto both ends of the threaded rod up to your first bend (if your arch is offset like mine). If not, just go ahead and thread the nut about 1.5" up from the end. Place both ends in the hole drilled in the wood then put another 1/4" nut on the bottom. Tighten the top nut down to the wood to hold the rod in place.