UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                 SCHEDULE 13D/A

                    Under the Securities Exchange Act of 1934
                               (Amendment No. 5)*

                             3D Systems Corporation
                             ----------------------
                                (Name of Issuer)

                     Common Stock, par value $.001 per share
                     ---------------------------------------
                         (Title of Class of Securities)

                                    88554D205
                                 --------------
                                 (CUSIP Number)

                                 Kevin S. Moore
                                    President
                             The Clark Estates, Inc.
                        One Rockefeller Plaza, 31st Floor
                            New York, New York 10020
                                 (212) 977-6900
            --------------------------------------------------------
            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)

                                    Copy to:

                            Jeffrey E. LaGueux, Esq.
                      Patterson, Belknap, Webb & Tyler LLP
                           1133 Avenue of the Americas
                          New York, New York 10036-6710
                                 (212) 336-2000

                                  June 8, 2006
             -------------------------------------------------------
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
Schedule because of ss.ss.240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the
following box. |_|

Note: Schedules filed in paper format shall include a signed original and five
copies of the Schedule, including all exhibits. See Rule 13d-7 for other parties
to whom copies are sent.

* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).


                              (Page 1 of 4 pages)


CUSIP No. 88554D205                  13D/A
--------------------------------------------------------------------------------
1     NAME OF REPORTING PERSONS
      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

      The Clark Estates, Inc.
      13-5524538
--------------------------------------------------------------------------------
2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) |_|
                                                                         (b) |X|

--------------------------------------------------------------------------------
3     SEC USE ONLY


--------------------------------------------------------------------------------
4     SOURCE OF FUNDS*

      OO
--------------------------------------------------------------------------------
5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
      PURSUANT TO ITEMS 2(d) OR 2(e)                                         |_|


--------------------------------------------------------------------------------
6     CITIZENSHIP OR PLACE OF ORGANIZATION

      New York
--------------------------------------------------------------------------------
               7     SOLE VOTING POWER

                     2,068,707
               -----------------------------------------------------------------
  NUMBER OF    8     SHARED VOTING POWER
   SHARES
 BENEFICIALLY        0
  OWNED BY     -----------------------------------------------------------------
    EACH       9     SOLE DISPOSITIVE POWER
  REPORTING
   PERSON            2,068,707
    WITH       -----------------------------------------------------------------
               10    SHARED DISPOSITIVE POWER

                     0
--------------------------------------------------------------------------------
11    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

      2,068,707
--------------------------------------------------------------------------------
12    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES* |_|


--------------------------------------------------------------------------------
13    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

      12.6%
--------------------------------------------------------------------------------
14    TYPE OF REPORTING PERSON*

      CO
--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!


                              (Page 2 of 4 pages)


                                 AMENDMENT NO. 5
                                       TO
                                  SCHEDULE 13D

            This Amendment No. 5 is filed in accordance with Rule 13d-2 of the
Securities Exchange Act of 1934, as amended, by the Reporting Person and refers
only to information which has materially changed since the filing of Amendment
No. 4 to Schedule 13D by the Reporting Person on December 10, 2003. The items
identified below, or the particular paragraphs of such items which are
identified below, are amended to add the information as set forth below.
Capitalized terms not otherwise defined herein have the meanings ascribed to
them in the original Schedule 13D or the amendments thereto.

ITEM 5. INTEREST IN SECURITIES OF THE ISSUER

            (c) As of June 8, 2006, the Reporting Person converted 833,333
shares of Series B Convertible Preferred Stock into shares of Common Stock on a
one-for-one basis pursuant to a letter transmittal delivered to the Issuer. The
terms of the Series B Convertible Preferred Stock provided that, upon optional
conversion, accrued but unpaid dividends convert into common stock at the
initial issuance price of $6.00 per share, subject to certain anti-dilution
adjustments, none of which occurred. As of June 8, 2006, accrued and unpaid
dividends on the Series B Convertible Preferred Stock held by the Reporting
Person amounted to 7,406 shares of Common Stock..


                              (Page 3 of 4 pages)


                                    Signature

            After reasonable inquiry and to the best of my knowledge and belief,
I certify that the information set forth in this statement is true, complete and
correct.

Date: June 13, 2006                                    THE CLARK ESTATES, INC.


                                                       By: /s/ Kevin S. Moore
                                                           ---------------------
                                                           Name:  Kevin S. Moore
                                                           Title: President


                              (Page 4 of 4 pages)