Page 698 - Mastik®

Direct assembly in thermoplastics Construction recommendations
®
using Delta PT screws

®
The Delta PT has all the well-known r *ODSFBTFE TUBCJMJUZ BHBJOTU WJCSBUJPO
®
properties of the PT screw. In addition thanks to the smaller thread pitch
®
the Delta PT screw offers all the follow- r *ODSFBTFE DZDMF TUSFTT TUBCJMJUZ
ing advantages: r 4NBMMFS ‹ UPMFSBODFT
r 5ISFBE BOHMF HFPNFUSZ XJUI UIF NBJO r 3PCVTU GBTUFOFS XIJDI DBO USBOTGFS 20°
angle of thread of 20° favours the more preload.
140°
working of the plastic r 5IF %&-5" 15 prognosis programme
®
r 6Q UP NPSF UFOTJPOBM BOE UPS DELTACALC allows a design based
®
sional strength for the same nominal on preload oriented engineering (~VDI
Ø d1, thanks to the increased cross- 2230).
section of the core
Cost-effective connections be calculated from the given depth of
AFL P d te
The following example shows that, for thread engagement AFL.
mm 2 mm mm mm
the same depth of thread engagement A comparison of the Delta PT with the PT K50 35 2,24 4 13,24
®
®
AFL, thanks to the smaller thread pitch P it PT screw shows that: Delta PT 50 35 1,8 4 10,42
®
®
®
is possible to design for a smaller length Use of the DELTA PT allows you to Delta PT 40 35 1,46 3,2 11,75
®
of thread engagement te. The required use a shorter and so more cost-effec-
screw depth for the Delta PT screw can tive screw.
te
®
2
AFL = (d1 - d ) x x
2
4 P
Construction recommendations creases the safety of the process dur- r "WPJE VTJOH FMPOHBUFE IPMFT JO DMBNQ
r 'PS TJNQMF GBTUFOJOHT UIF SFDPNNFO ing assembly, a smaller surface pres- ing parts made from plastic. Lack of
dations published here are quite ad- sure results in less relaxation and so in bearing surface can lead to the form-
equate greater residual locking forces. ing torque being greater than the head
r We would be pleased to help you with r "WPJE VTJOH DPVOUFSTVOL TDSFXT GPS friction torque and this can make it
the design of fastenings under opera- clamping parts made from plastic. The impossible to construct a mounting
tional loadings, and can also provide 90° angle results in radial as well as process secured.
support through the use of DELTA- axial relaxation, and where the edge r 5SBOTWFSTF GPSDFT TIPVME CF UBLFO
CALC ® distance is small this can lead to large up by the engagement between the
r 4FMFDU MBSHFS IFBE EJBNFUFST #/ losses in preload, and so to a break in components.
20040) for fastening together parts the part being clamped. r Provide a pressure relief hole d e (avoids
made of plastic. The head friction in- stress cracks)
Shape of the hole are subject to stress cracking. It also en-
D = 2 x d 1
The maximum achievable preload when sures the even support of the clamping
d e
overtightening is the criteria for deter- part. Bulging of the plastic when forming
mining the optimum hole Ø d. It is less the first turn of the thread. To optimise
dependent on the tube material and the the fastening the hole diameter should 0,3 - 0,4 x d 1
length of engaged thread te, and more not exceed Ø d = 0,88 x d1.
dependent on the thread pitch P and the t e = 2 x d 1
nominal diameter Ø d1 of the screw. The In practice deviations from these recom-
design applies to all conventional plas- mendations may arise, for the following d = 0,8 x d 1
tics with a modulus of elasticity of up to reasons: 0,5 x d 1
E = 15000 N/mm (hole-Ø d for special r 1SPDFTTJOH DPOEJUJPOT EVSJOH NBOV
2
plastics available on request): facture of the plastic D outside Ø
r %FTJHO PG UIF JOKFDUJPO NPVMEJOH
d pilot holed Ø
d = 0,8 x d1 equipment
t e length of thread engagement
d e = d1 + 0,2 mm r 1PTJUJPO PG UIF JOKFDUJPO QPJOU
d e edge relief
r $SFBUJPO PG GMPX TFBNT
d 1 nominal Ø of the screw thread
The pressure relief hole de is particularly r -PDBM UFYUVSF F H UISPVHI VTF PG BE
important, since it gives a favourable dis- ditives and fillers such as colour pig-
tribution of edge stresses and so prevents ments and fibres. We recommend that control assem-
the tube from shattering, particularly with r The plastics can be modified in different bly runs be made using the first avail-
able parts.
plastics such as polycarbonates which ways, depending on the manufacturer.
Ask for informationon our «BossAna-
lytik» service.