Summary

Came up with a 3 inch square design that can hold four 50 ml centrifuge tubes or five 15 ml centrifuge tubes or a combination. The test tube rack is really compact but hold these tubes securely.
Print with 10% infill, no support, in PLA or PETG.

Print Settings

Printer Brand:

Anycubic

                                            <p class="detail-setting printer"><strong>Printer: </strong>                     <div><p>Kobra</p></div></p>                                                                                <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>Doesn't Matter</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>Low or Medium resolution</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>10%</p></div></p>

Compact rack for 15 ml and 50 ml centrifuge tubes