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Frequently asked questions (FAQ)

We have collected many frequently asked questions and answer them here.


General questions

01 - The PUK principle

  • The PUK is a precision welding device that is based on TIG welding technology.
  • It generates an electric arc (also known as plasma) for a brief moment, which generates a welding point.
  • The welding points have a diameter of approximately 0.2 - 3.7 mm.
  • An electrode made of wolfram is clamped in the PUK's hand piece; the electric arc is triggered from its tip.
  • Tungsten is the metal with the highest melting point (3422°C) – the electrode itself does not melt.
  • Working with the PUK is very easy: You look at the electrode through a microscope equipped with an eye protection filter, and introduce the workpieces to the electrode by hand.
  • The welding point is triggered automatically.
  • The output (%), pulse duration (ms) and various welding pulse curves can be adjusted easily and clearly on the PUK.

03 - Microscope function

The microscope is equipped with an eye protection filter that is controlled electronically and is DIN-certified. This ensures triple protection for the eyes. Permanent protection against dazzling by UV and IR light and an LCD eye protection filter that is controlled electronically.

05 - How important is the angle that the electrode has to the workpiece?

The angle is extremely important.
You can achieve the greatest depth of penetration at a 90° angle to the workpiece.
If the electrode is at an angle, the metal tends to flow towards the angled electrode. This means that the metal (e.g. applied wire) follows the electrode's direction of movement; it is pulled towards the hand piece.
One exception to this rule is silver. (Also see point 17)

07 - Which metals can be welded?

The basic rule is that all precious metals and precious metal alloys made from gold, silver, platinum and palladium can be welded. In addition, all metals that can also be welded using the laser welding process or the common TIG welding process can be welded.

This includes: Numerous types of stainless steel, titanium and many titanium alloys, steels, and non-ferrous metals and alloys.

09 - Can I weld different metals or alloys to each other?

Yes. Even metals with very different properties can be welded; e.g. gold to titanium.
However, welding is not possible if the physical differences are too great, as with titanium and steel for example.


02 - What does "welding" mean?

  • Workpieces are melted punctiformly and are fused in this way.
  • The welding material always has ideally the same melting temperature as the workpiece itself (solder is always used when soldering; this has a lower melting temperature than the workpiece. The risk of solder "flowing back" is reduced).
  • The material does not anneal; therefore work can even be carried out on mechanisms and thin sheets without affecting the solidity.
  • No changes to colour or durability using the same material.

04 - Are there running or maintenance costs?

Maintenance is not required!
In normal operation, there are only minor costs for shielding gas, and wear and tear on the electrodes.

06 - How do I learn PUK welding?

The technique of PUK welding is easy to learn. However, you should take enough time to familiarise yourself with the device. The PUK course that is included with the device may be of help here. You can use the supplied stainless steel plates to practice material application, play with the power and welding time regulators or weld a clean joint. Change the electrode's angle to the workpiece and see what happens. With a little practice, you will achieve very good results very quickly. In addition, it may be sensible to attend a PUK welding seminar to refine the techniques further.

08 - Can I weld brass?

There is a brass mode in the current model; it can be used to weld brass alloys with a low zinc content well.

10 - Can I weld aluminium?

There is a special aluminium mode in the current PUK model. This mode can be used to weld suitable aluminium alloys particularly well by adding welding wire. It is important to ensure that you select suitable welding wire here.

11 - What about the development of heat when welding with the PUK?

The development of heat is very low.
In heat-sensitive areas such as near to gemstones, we recommend working with as short a pulse time as possible (on the PUK04, a pre-setting is already stored within metal mode for this).



Technical questions

12 - How long does a 10 litre argon gas cylinder last?

In the average goldsmith's workshop, one fill of a 10 litre cylinder lasts around 6 to 12 months, depending on the frequency of use.

14 - How long is the period between two welding points?

The period between two welding points is between 0.8 and 2.0 seconds. It is automatically adjusted to the operator's working speed. If the welding sequence is fast, the period automatically reduces to 0.8 seconds.

16 - How do the welding points change if I change the power?

In general, you can say that the power controls the diameter of the welding point to be achieved.
As the energy increases, the penetration depth does increase but the welds remain comparatively flat.

18 - Soldering or welding?

The basic rule in jewellery manufacturing is that soldering is more often than not the ideal joining technique, where it makes sense. However, there are numerous applications in which soldering is not possible or does not make sense in jewellery manufacturing and repair. These applications are normally situations where excessive heat must be avoided or the retouching tasks required by soldering must or should be avoided.
In these situations, the PUK precision welding device is the perfect solution. It can be used to create local weld joins with minimum heat input or to apply metal with the same alloy using welding wire. Time-consuming surface treatment for the entire workpiece or damage to heat-sensitive areas can be easily avoided.

20 - Can I use solder as a filler material?

Solder tends to burn during welding due to its additives; it is therefore not suitable as a filler material. If possible, you should not weld at solder points. Alternatively, remove the solder beforehand. In specific exceptional cases (e.g. when carrying out difficult repairs or if using alloys that are difficult to weld), it may be helpful to add one piece of solder with the highest possible melting range. If used at the right time and with enough experience, this can certainly produce a good result.

21 - Applications in the silversmith area

Visit the website of our "PUK master", Jeffrey Herman, at http://www.hermansilver.com and his new blog at http://www.silversmithing.com/puk.htm. You can find numerous applications in the silversmith area here.


13 - Is argon poisonous?

It is an inert gas and is naturally present in the atmosphere. As with all inert gases, it does not react: It cannot burn and is not poisonous.
However, there must still be sufficient ventilation in small rooms. For more information, contact your gas dealer.


(The gas consumption is very low: A flow rate of approx. 2 - 3 litres per minute is optimal. This corresponds to a pressure of approx. 0.4 bar.)

15 - What is the maximum metal thickness for workpieces to be welded? Maximum penetration depth

If the workpiece's material thickness at the point of break is greater than 1.0 mm, the welding device's penetration depth is not sufficient. The point of break must be prepared specially for welding: The edges are filed into a V shape and only the remaining material that is directly touching is welded together. The joint that results from this is continually filled with filler material (welding wire).

17 - How does the welding point change if I change the time?

The pulse time is mainly responsible for the welding point's penetration depth. The longer the time, the deeper the point, the work piece is heated up at the same time.
If the material is very thin, always use the shortest possible pulse time to reduce the risk of melting a hole through it! Always use the shortest possible pulse time close to stones, in order to control the weld.

19 - Welding silver: What must I pay attention to?

Metals with a high thermal conductivity do not generally weld well; however:
The thermal conductivity of silver reduces as the temperature increases.
Therefore: Silver welds better when it is warm!


  • Weld the same place several times to increase the temperature.
  • A continuous welding sequence keeps the workpiece warm!
  • The workpiece can heat up to 100°C; this does not damage any stones but cannot be held with bare hands!


Hold the workpiece with tongs, finger stalls, etc.!

In contrast to most other metals, silver has a lower viscosity welding behaviour; therefore, it is pushed away by the electric arc and not pulled towards the electrode.





22 - How can I set the flow regulator correctly?

  • In order to set the correct flow rate, switch the PUK on and open the valve of the gas tank carefully. For the PUK3, press the power regulator on the device and for the PUK04, activate the gas test in the operating level "Settings".
  • This opens the gas valve in the device and the right gauge of the flow regulator displays the actual flow rate. A flow rate of approx. 2 - 3 litres per minute is optimal. This corresponds to a pressure of approx. 0.4 bar.
  • You can now set the required value by turning the large regulator underneath. (Please note the right rotation direction, see figure.) If no gas flows, the right manometer display shows a higher value compared to the value being shown when the gas valve is opened.

23 - What might be the reason for black coloured welding spots?

  • The flow rate of the shielding gas is set too high:
    Ensure that the flow rate is set correctly. 2 - 3 litres per minute are sufficient (appoximately 0.4 bar)!

  • The electrode protrudes too long from the argon nozzle:
    The less the electrode protrudes out of the hand piece, the better the protection by the argon.

  • Incorrect shielding gas, insufficient quality:
    We recommend pure argon (Ar 4.6), with a purity of at least 99.996%, without additives.

  • Soiled surface of the workpiece:
    Any type of dirt, polish, paint, galvanised coating, etc. burns during welding and often leaves large quantities of soot. Clean the workpiece thoroughly before welding.

  • The alloy the workpiece is made from is contaminated:
    If the metal the workpiece is made from has inclusions or the alloy contains metals that tend to burn at low temperatures (zinc, lead, tin, etc.), soot can be formed.

24 - What might be the reason for the electrode splitting or breaking?

The electrodes used are made from a special alloy of wolfram and metal oxides.
These electrodes were designed especially for use in conjunction with Lampert precision welding devices. The electrodes have excellent welding properties but are hard and brittle.
If the electrode is bent, e.g. after it has got stuck accidentally to the workpiece  and then "broken off", it may become split.
The extreme temperature differences between the electrode tip and the electrode shank which occur during welding also cause great mechanical stress in the electrode. We cannot therefore guarantee that the electrode will not break or fan out (split) in individual cases.


Lampert Werktechnik GmbH
Ettlebener Strasse 27 · 97440 Werneck · Germany
Tel. +49 9722 94 59 - 0 · Fax +49 9722 94 59 - 100 · mail@lampert.info