Re: FDM Tips

From: Pradeep Nair (
Date: Tue May 13 1997 - 12:28:48 EEST

Atif Mehmet Yardimci wrote:
> Dear List Members:
> We've a FDM1650 in house, and have been RP'ing happily since December '96
> with ABS/T12.
> Recently 1650 gave 'torque limiting error'. A torque
> check revealed that the ABS modeling side has been running between
> 280-390. Hand feeding small lengths of filament, and cleaning liquefier
> entrance ruled out filament delivery errors before the liquefier.
> It looks like we have plugging, either in tips or in liquefier.
> How do you deal with plugging? How frequent does it occur in your
> operations? Are there guidelines for preventive maintenance?
> Best Regards,
> Atif Yardimci
> Manufacturing Processes Laboratory +1-312-355-0478 / +1-312-413-7408 [voice]
> Mechanical Engineering Department +1-312-413-0447 [fax]
> University of Illinois at Chicago e-mail:
Dear Atif Yardimci,

There are few things I recommend checking on the FDM head:

a)Remove head from machine and check the entrance to make
sure there is no debry. Over time the entrance can collect
debry and create high torque read outs. To remove debry use a long
pick to reach between the motor and entrance.

b)Look at the tips under a magnifying glass to make sure the tips
have not been damaged (nicks or dents). This can sometime restrict
proper flow and affect the amount of torque.

c)Check the tension screws in the back of the head mount. These
tensions screws are sometime adjusted to tight and can restrict proper
flow. I recommend the tension screws to be adjust so that when
pulling the material through you feel a sight resistance.

d)Check the rolls of material in the back of the machine. Sometime
the center of the rolls are not dimensionally correct and can rub
against the shaft creating a restriction of material flow.

e)If you check all the above then it could possible be that your
motor in the head has bad bearings. When the bearings go it will not
stop, it will just run at high torque levels. This problem is common
with the bearings in the early head design. Fortunately, Stratasys
has redesigned the bearing for loner life. How long I don't know
but, I have not had any torque problem since I replaced my head in
my FDM1650 machine.

g)If you still have any doubts then call Stratasys at
1(612)937-3000. They will help you with any problem hassle free and
take you step-by-step to come to a solution to your problem.

Let me know how things turn out for you.

                                             GOOD LUCK,

                                             Jonathan E. mcCray
                                    [Applied Research Dept. RPC]


                           AT THE:Milwaukee School of Engineering

Hello List Menbers,

Thanks to Mr mcCray for the reply sent in.
The point (e) regarding "the gear being bad" this problem has been identified
and rectified long ago. This problem should not be seen in systems sold and
installed after AUG 96.

To address your issue of Torque error sent in by Mr Ytif.

It seems you have already identified that the torque error is due to clogging of
the tip or lequifier. Clogging of tip might happen ones in a while.Have never
seen the lequifier to clog myself. Our experience with Indian customers are, may
be one tip clog every two systems in a year. It is advised that customers keep
at least one set of extra tips. The tips are an consumable item and may be
obtained from stratasys.

However let me give you more details about torque error. Torque error can be
caused due to various reasons and the symptoms may be different.

Symptoms :-

a) Torque error only on one side either the model side or the support side.
b)Torque error on both side model as well as support and behaving randomly.

Case 1 - Only on one side.

The likely cause is that the material is not being fed into the leqifier and
pushed out properly. This could be caused due to :-
1) The spool is not moving freely at the back of the system.
2) The strands of spool could be entangled and obstructing movement of the
3) The filament seal behind the head may be too tight.

4) Material could be clogging behind the drive motors. Clean the drive motors
and the lequifer entrance.
5) The lequifier temperature may be too low to melt the material.
6) The FDM tip could be clogged. If you suspect this a good way to confirm this
is to swap the support and the model tip. After the swap the problem of torque
error should shift to the other side( in your case the support)

b) Case 2- Torque error on both side , and erratically.

Problem that need to be checked by Stratasys customer service.
Please call them they will be glad to help (612.937.3000) ask for customer

Best regards
Sujit Pal
Stratasys Inc. (India)
Technical Support Manager(Asia/Pacific)

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